Absolute Quantum Efficiency Measurements Using Correlated Photons: Toward a Measurement
Alan L. Migdall
2001-01-01
Abstract—Correlated photons can be used to measure the quantum,efficiency of photon counting photodetectors without ties to any externally calibrated standards. We present a study of measurement,systematics aimed at reducing the measurement uncertainties to the 0.1% level, and developing a robust measure- ment protocol. Index Terms—Photodetectors, quantum efficiency, radiometry.
Absolute quantum efficiency measurements using: toward a measurement protocol
Alan L. Migdall
2001-01-01
Correlated photons can be used to measure the quantum efficiency of photon counting photodetectors without ties to any externally calibrated standards. We present a study of measurement systematics aimed at reducing the measurement uncertainties to the 0.1% level, and developing a robust measurement protocol
Accurate measurement of external quantum efficiency of semiconductors for thermophotonics
K. R. Catchpole; K. L. Lin; O. Breitenstein
2003-01-01
To achieve net conversion of heat to electricity with thermophotonics, a LED with high external quantum efficiency (EQE) is required. As part of the initial stages of making a thermophotonic device, we have developed a system for accurately measuring the external quantum efficiency of highly radiatively efficient structures. The technique involves measuring uncalibrated photoluminescence and thermal signals from an optically
Quantum Efficiency measurement setup for the near-infrared range
A. C. Pan; C. del Canizo; J. Hofstetter; A. Luque
2009-01-01
The quantum efficiency measurement provides an important information of the solar cell performance. In this paper we report on the extension of the external quantum efficiency measurement to near-infrared range. It is necessary to characterize the effect of up-converter layers on the rear of bifacial silicon solar cells, which can enhance the performance of solar cells as they have the
Simple Measurement of Quantum Efficiency in Organic Electroluminescent Devices
Shinji Okamoto; Katsu Tanaka; Yoshitaka Izumi; Hironori Adachi; Takayuki Yamaji; Takeo Suzuki
2001-01-01
A simple method of measuring the external quantum efficiency of organic electroluminescent (EL) devices has been investigated. Assuming a perfectly diffusive EL emission surface, this method enables the external quantum efficiency to be calculated from the conventionally measured parameters: luminance, EL spectrum, and current. Its use is limited to EL emission in the visible wavelength range.
Flash quantum efficiency measurements for multi-junction solar cells
G. S. Horner; L. A. Vasilyev; J. Schmidt; J. E. Hudson; M. Arbore; M. Dybiec; E. A. Good
2011-01-01
Flash Quantum Efficiency — a technique used to simultaneously measure full spectrum external quantum efficiency (EQE), Reflectance (R), and Transmittance (T), has been introduced in two prior publications [1,2]. The method uses a novel architecture to simultaneously modulate a bank of solid state lightsources and measure, in real time, the cell response to each wavelength. In this work we extend
Low temperature quantum efficiency measurements on irradiated multijunction solar cells
S. R. Messenger; J. H. Warner; P. P. Jenkins; R. J. Walters; J. R. Lorentzen
2008-01-01
This paper presents quantum efficiency (QE) measurements and analyses on monolithic triple junction (3J) InGaP\\/GaAs\\/Ge solar cells under both room (300K) and low temperature (130K) conditions. In measuring the quantum efficiency of multijunction solar cells, one must be careful to use the proper bias conditions to isolate the subcell of interest. This may be achieved by using external light sources
Elison Matioli; Claude Weisbuch
2011-01-01
A method is presented for the direct measurement of the internal quantum efficiency in light emitting diodes (LEDs), based on the ratio of the measured external quantum efficiency and the calculated light extraction efficiency. The external quantum efficiency is measured from a single facet of the device in a simple, well-defined geometry, for which the light extraction efficiency can be
Efficient measurement of quantum dynamics via compressive sensing.
Shabani, A; Kosut, R L; Mohseni, M; Rabitz, H; Broome, M A; Almeida, M P; Fedrizzi, A; White, A G
2011-03-11
The resources required to characterize the dynamics of engineered quantum systems--such as quantum computers and quantum sensors--grow exponentially with system size. Here we adapt techniques from compressive sensing to exponentially reduce the experimental configurations required for quantum process tomography. Our method is applicable to processes that are nearly sparse in a certain basis and can be implemented using only single-body preparations and measurements. We perform efficient, high-fidelity estimation of process matrices of a photonic two-qubit logic gate. The database is obtained under various decoherence strengths. Our technique is both accurate and noise robust, thus removing a key roadblock to the development and scaling of quantum technologies. PMID:21469772
Precision, all-optical measurement of external quantum efficiency in semiconductors
Sheik-Bahae, Mansoor
Precision, all-optical measurement of external quantum efficiency in semiconductors Chengao Wang) External quantum efficiency of semiconductor photonic devices is directly measured by wavelength- dependent is discussed. VC 2011 American Institute of Physics. [doi:10.1063/1.3580259] External quantum efficiency (EQE
Internal quantum efficiency measurements for GaAs light-emitting diodes
A. Lastras-Martínez
1978-01-01
Internal quantum efficiency values at room temperature are given for single-heterojunction Zn-diffused GaAs diodes with substrate doping concentrations of ~1×1018 and (2-3) ×1017\\/cm3. The internal quantum efficiency temperature dependence for diodes with a substrate doping concentration of (2-3) ×1017\\/cm3 is also given in the range 200-323 K. Internal quantum efficiency values have been calculated from external quantum efficiency measurements. The
Internal quantum efficiency measurements for GaAs light-emitting diodes
A. Lastras-Marti´nez
1978-01-01
Internal quantum efficiency values at room temperature are given for single-heterojunction Zn-diffused GaAs diodes with substrate doping concentrations of ?1×1018 and (2–3) ×1017\\/cm3. The internal quantum efficiency temperature dependence for diodes with a substrate doping concentration of (2–3) ×1017\\/cm3 is also given in the range 200–323 K. Internal quantum efficiency values have been calculated from external quantum efficiency measurements. The
Single light path quantum efficiency measurement system used for multi-junction solar cells
Suoliang Zhang; Lei Liu; Yongqing Wang; Tianshu Zhang; Zhipeng Zhang
2009-01-01
A single light path quantum efficiency measurement system, which has the properties of high test speed, high precision and good repetition, has been designed and successfully developed basing the monolithic structure of the multi-junction solar cell in order to realize its spectrum responses measurement. The principle of the quantum efficiency measurement was expatiated, and the structure of the measurement system
Measurement of internal quantum efficiency and surface recombination velocity in InGaN structures
M. Jackson; M. Boroditsky; E. Yablonovitch; S. Keller; B. Keller; S. DenBaars
1997-01-01
We report the first measurements of the spectrally resolved absolute internal luminescence quantum efficiency and surface recombination velocity of an InGaN-GaN multiquantum well (MQW) structures. The absolute external quantum efficiency is measured by referencing the measured photoluminescence (PL) from the sample with the reading measured from the laser off of the perfect 100% white lambertian reflector
Gerald Siefer; Carsten Baur; Andreas W. Bett
2010-01-01
The measurement procedures for the determination of the external quantum efficiency (EQE) of individual subcells in a monolithic, series connected stack of solar cells are known since the 1980s [1]. There, the importance of the choice of appropriate bias light spectrum and bias voltage was already addressed. However, especially when measuring the EQE of Germanium bottom subcells in monolithic III-V
A. W. Walker; J. F. Wheeldon; O. Theriault; M. D. Yandt; K. Hinzer
2011-01-01
The external quantum efficiency (EQE) of a high efficiency lattice matched multi-junction solar cell (MJSC) and a quantum dot enhanced MJSC are numerically simulated. An effective medium is developed and integrated into the model to simulate the absorption characteristics of the quantum dots in the latter device. A calibration of the model is carried out using room temperature EQE measurements
Measuring external photoluminescence quantum efficiency of organic solid films
Hua Zheng; Chan Luo; Qing Wang; Sha Wu; Hongbin Wu; Lei Wang; Diangang Hu; Yong Cao; Jian Wang
2011-01-01
An algorithm with high reliability to obtain the photoluminescence quantum efficiency (PLQE) of the organic solid materials was developed by directly calculating the number of the absorbed photons and the emitted photons. By eliminating the step to determine the sample’s absorbance, not only is the experiment simplified, but also the PLQE value is less error-prone. Moreover, our developed method could
Quantum efficiency measurements in the swept charge device CCD236
NASA Astrophysics Data System (ADS)
Smith, P. H.; Gow, J. P. D.; Murray, N. J.; Tutt, J. H.; Soman, M. R.; Holland, A. D.
2014-04-01
The e2v technologies plc. CCD236 is a Swept Charge Device (SCD) designed as a large area (20 mm × 20 mm) soft X-ray detector for spectroscopy in the range 0.8 keV to 10 keV. It benefits from improvements in design over the previous generation, the e2v CCD54, such as: a 4 times increased detector area, a reduction in split X-ray events due to the 100 ?m × 100 ?m `pixel' size, and improvements to radiation hardness. The CCD236 will be used in India's Chandrayaan-2 Large Soft X-ray Spectrometer (CLASS) instrument and China's Hard X-ray Modulation Telescope (HXMT). Measurements of the Quantum Efficiency (QE) have been obtained relative to a NIST calibrated photodiode over the energy range 0.2 keV to 1.9 keV, using the BESSY II X-ray synchrotron in Berlin. Two X-ray event counting methods are described and compared, and QE for soft X-ray interaction is reported. Uniformity of QE across the device is also investigated at energies between 0.52 keV and 1.5 keV in different areas of the detector. This work will enable the actual number of photons incident on the detectors to be calculated, thus ensuring that the CCD236 detectors provide valuable scientific data during use. By comparing the QE methods in this paper with the event processing techniques to be used with CLASS, an estimate of the instrument-specific QE for CLASS can be provided.
Absolute detector quantum-efficiency measurements using correlated photons
A. L. Migdall; R. U. Datla; A. Sergienko; J. S. Orszak; Y. H. Shih
1995-01-01
An experimental system using correlated photons for radiometric purposes has been set up at the National Institute of Standards and Technology (NIST). We use pairs of correlated photons to produce spatial maps of the absolute efficiency of a photomultiplier photocathode at four wavelengths. We also compare this technique with measurements carried out by conventional means tied to existing radiometric standards.
Tomas Zimmermann; Jiri Vanicek
2011-12-01
We propose to measure nonadiabaticity of molecular quantum dynamics rigorously with the quantum fidelity between the Born-Oppenheimer and fully nonadiabatic dynamics. It is shown that this measure of nonadiabaticity applies in situations where other criteria, such as the energy gap criterion or the extent of population transfer, fail. We further propose to estimate this quantum fidelity efficiently with a generalization of the dephasing representation to multiple surfaces. Two variants of the multiple-surface dephasing representation (MSDR) are introduced, in which the nuclei are propagated either with the fewest-switches surface hopping (FSSH) or with the locally mean field dynamics (LMFD). The LMFD can be interpreted as the Ehrenfest dynamics of an ensemble of nuclear trajectories, and has been used previously in the nonadiabatic semiclassical initial value representation. In addition to propagating an ensemble of classical trajectories, the MSDR requires evaluating nonadiabatic couplings and solving the Schr\\"{o}dinger (or more generally, the quantum Liouville-von Neumann) equation for a single discrete degree of freedom. The MSDR can be also used to measure the importance of other terms present in the molecular Hamiltonian, such as diabatic couplings, spin-orbit couplings, or couplings to external fields, and to evaluate the accuracy of quantum dynamics with an approximate nonadiabatic Hamiltonian. The method is tested on three model problems introduced by Tully, on a two-surface model of dissociation of NaI, and a three-surface model including spin-orbit interactions. An example is presented that demonstrates the importance of often-neglected second-order nonadiabatic couplings.
Precise Measurement of External Quantum Efficiency of Organic Light-Emitting Devices
Isao Tanaka; Shizuo Tokito
2004-01-01
We report on the direct measurement of the external quantum efficiency of electroluminescence of organic light-emitting devices with different emission colors and patterns using an integrating sphere and a highly sensitive charge-coupled device spectral analyzer. Using this direct-measurement method, precise external quantum efficiency can be obtained more easily and more quickly than using the conventional luminance-conversion method. This method is
K. R. Catchpole
2004-01-01
A high photoluminescence external quantum efficiency (EQE) of 3.1% has been measured for a passivated, textured silicon wafer using a combined thermal and photoluminescence technique. This result shows that the high photoluminescence EQEs reported recently, which were achieved using calibrated photoluminescence measurements, are confirmed with an entirely independent measurement technique. The technique involves measuring uncalibrated photoluminescence and thermal signals from
Absolute quantum efficiency measurements using correlated photons: A study of systematics
A. L. Migdall
2000-01-01
Correlated photons can be used to measure the quantum efficiency of photon counting photodetectors without ties to any externally calibrated standards. We present a study of the measurement systematics for the purpose of reducing the measurement uncertainties to the 0.1% level and developing a robust measurement protocol
Quantum efficiency measurements for several waveshifter coatings in the extreme vacuum ultraviolet
NASA Astrophysics Data System (ADS)
Butner, C. L.; Viehmann, W.
1984-07-01
Quantum efficiency measurements are given for coronene and liumogen coatings designed to enhance UV sensitivity for silicon charge coupled device imaging detectors. Coatings on quartz and on UDT PIN 10DP photodiodes were tested. The wavelength range extended from 153.7 to 50.0 nm in the vacuum ultraviolet. Similar measurements were made for coronene, liumogen, and stilbene-3 laser dye films on quartz disks relative to sodium salicylate. Sodium salicylate and coronene are the most efficient waveshifters down to 50 nm so far observed. Coronene's fairly constant quantum efficiency over such a wide wavelength range into the far VUV makes it a useful waveshifter for UV and VUV applications.
Precision, all-optical measurement of external quantum efficiency in semiconductors
Chengao Wang; Chia-Yeh Li; Michael P. Hasselbeck; Babak Imangholi; Mansoor Sheik-Bahae
2011-01-01
External quantum efficiency of semiconductor photonic devices is directly measured by wavelength-dependent laser-induced temperature change (scanning laser calorimetry) with very high accuracy. Maximum efficiency is attained at an optimum photo-excitation level that can be determined with an independent measurement of power-dependent temperature or power-dependent photoluminescence. Time-resolved photoluminescence lifetime and power-dependent photoluminescence measurements are used to evaluate unprocessed heterostructures for critical
Measurement of InGaAs single photon detector quantum efficiency at 1550nm
NASA Astrophysics Data System (ADS)
Zhao, Kun; Liu, Changming; Chen, Haidong; Shi, Xueshun
2015-02-01
Single photon detectors nowadays are widely used in numerous applications such as quantum cryptography, laser ranging, single molecule spectroscopy and so on. And the calibration of the detection efficiency is quite important for some of the applications. In recent years, researchers find that correlated photon pairs can be employed to calibrate the detection efficiency of single-photon detectors with quite high precision. Firstly, we calibrated the InGaAs single photon detector quantum efficiency at 1550nm by correlated photon pairs. Consistency between the measurement result using correlated photon pairs and the reference value is better than 0.8%. Secondly, the detectors are calibrated with an attenuated laser source. Thirdly, the two methods for measuring the quantum efficiency of single photon detectors, correlated photon pairs and laser attenuation, respectively, are discussed and analyzed in detail. Finally, results derived from the two methods have been compared with each other.
Schmidt, Tobias D., E-mail: Tobias.Schmidt@physik.uni-augsburg.de; Reichardt, Lukas J.; Wehrmeister, Sebastian; Scholz, Bert J.; Mayr, Christian; Brütting, Wolfgang, E-mail: Wolfgang.Bruetting@physik.uni-augsburg.de [Institute of Physics, University of Augsburg, 86135 Augsburg (Germany); Rausch, Andreas F.; Wehlus, Thomas; Reusch, Thilo C. G. [OSRAM OLED GmbH, Wernerwerkstrasse 2, 93049 Regensburg (Germany); Ciarnáin, Rossá Mac; Danz, Norbert [Fraunhofer Institute for Applied Optics and Precision Engineering, 07745 Jena (Germany)
2014-07-28
Emitter orientation will play a major role in future applications of organic light-emitting diodes due to its strong impact on the efficiency of the devices. Up to now, determining the orientation of transition dipole moments required elaborate angular-dependent measurements of the light emission pattern. In this paper, we present a simplified and straightforward method to extract the emitter orientation from external quantum efficiency measurements. We demonstrate the validity of the method on three different dye-doped emitting systems.
Jing-Jing Li; Swee Hoe Lim; Charles R. Allen; Ding Ding; Yong-Hang Zhang
2011-01-01
The combined effects of shunt and luminescence coupling on the measurement artifact of external quantum efficiency (EQE) of multi-junction solar cells are studied. The EQE measurement artifact is modeled using DC and small-signal equivalent circuits under voltage and light bias conditions. The modeling results are verified with EQE measurements of a Ge bottom cell of a triple-junction solar cell. It
M. Schädel; J. Isenberg; J. Suthues; C. Ballif; G. Gobsch
This paper presents an improvement for the measurement of the external quantum efficiency (EQE) of large area crystalline silicon solar cells. The main concept is to replace the standard white light source for the bias illumination by infrared light emitting diodes (LED). We show that, even for strongly injection dependent lifetime or back surface recombination velocity, similar carrier injection can
Measurement-based Formulation of Quantum Heat Engine and Optimal Efficiency with Finite-Size Effect
Hiroyasu Tajima; Masahito Hayashi
2015-04-23
There exist two formulations for quantum heat engine. One is semi-classical scenario, and the other is full quantum scenario. The former is formulated as a unitary evolution for the internal system, and is adopted by the community of statistical mechanics. In the latter, the whole process is formulated as unitary. It was adopted by the community of quantum information. However, their formulation does not consider measurement process. In particular, the former formulation does not work when the amount of extracted work is observed. In this paper, we formulate the quantum heat engine as the measurement process because the amount of extracted work should be observed in a practical situation. Then, we clarify the contradiction of the former formulation by using a novel trade-off relation. Next, based on our formulation, we derive the optimal efficiency of quantum heat engines with the finite-size heat baths, without assuming the existence of quasi-static processes. That is, we asymptotically expand the optimal efficiency up to the third order when we extract work from the pair of hot and cold baths. The first term is shown to be Carnot efficiency. We also investigate the effect by finiteness of the resources by classifying it into two types.
Dave Bacon; Andrew M. Childs; Wim van Dam
2005-04-26
We approach the hidden subgroup problem by performing the so-called pretty good measurement on hidden subgroup states. For various groups that can be expressed as the semidirect product of an abelian group and a cyclic group, we show that the pretty good measurement is optimal and that its probability of success and unitary implementation are closely related to an average-case algebraic problem. By solving this problem, we find efficient quantum algorithms for a number of nonabelian hidden subgroup problems, including some for which no efficient algorithm was previously known: certain metacyclic groups as well as all groups of the form (Z_p)^r X| Z_p for fixed r (including the Heisenberg group, r=2). In particular, our results show that entangled measurements across multiple copies of hidden subgroup states can be useful for efficiently solving the nonabelian HSP.
Satoshi Inada; Masahiro Yoshita; Makoto Okano; Toshiyuki Ihara; Hidefumi Akiyama; Liming Zhang
2008-01-01
We measured the cavity length dependence of the internal differential quantum efficiency etaint and the internal optical loss alphaint in 1500-nm-wavelength laser diodes (LDs). By evaluating alphaint directly from gain\\/absorption spectra for various injection current densities and measuring the external differential quantum efficiency etaext, we obtained the etaint and alphaint values of all the LDs with different cavity lengths. The
Measuring the X-ray quantum efficiency of a hybrid CMOS detector with 55Fe
NASA Astrophysics Data System (ADS)
Bongiorno, S. D.; Falcone, A. D.; Prieskorn, Z.; Griffith, C.; Burrows, D. N.
2015-06-01
Charge coupled devices (CCDs) are currently the workhorse focal plane arrays operating aboard many orbiting astrophysics X-ray telescopes, e.g. Chandra, XMM-Newton, Swift, and Suzaku. In order to meet the count rate, power, and mission duration requirements defined by next-generation X-ray telescopes, future detectors will need to be read out faster, consume less power, and be more resistant to radiation and micrometeoroid damage than current-generation devices. The hybrid CMOS detector (HCD), a type of active pixel sensor, is currently being developed to meet these requirements. With a design architecture that involves bump bonding two semiconductor substrates together at the pixel level, these devices exhibit both the high read speed and low power consumption of CMOS readout circuitry and the high quantum efficiency (QE) of a deeply depleted silicon absorber. These devices are expected to exhibit the same excellent, high-energy quantum efficiency (QE) as deep-depletion CCDs (QE > 0.9 at 6 keV), while at the same time exhibiting superior readout flexibility, power consumption, and radiation hardness than CCDs. In this work we present a QE model for a Teledyne Imaging Sensors HyViSI HCD, which predicts QE=96% at 55Fe source energies (5.89 and 6.49 keV). We then present a QE measurement of the modeled device at the same energies, which shows QE=97±5% and is in good agreement with the model.
Efficient Quantum-State Estimation by Continuous Weak Measurement and Dynamical Control
Smith, Greg A.; Jessen, Poul S. [College of Optical Sciences, University of Arizona, Tucson, Arizona 85721 (United States); Silberfarb, Andrew; Deutsch, Ivan H. [Department of Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico 87131 (United States)
2006-11-03
We demonstrate a fast, robust, and nondestructive protocol for quantum-state estimation based on continuous weak measurement in the presence of a controlled dynamical evolution. Our experiment uses optically probed atomic spins as a test bed and successfully reconstructs a range of trial states with fidelities of {approx}90%. The procedure holds promise as a practical diagnostic tool for the study of complex quantum dynamics, the testing of quantum hardware, and as a starting point for new types of quantum feedback control.
Jing-Jing Li; Swee H. Lim; Charles R. Allen; Yong-Hang Zhang
2011-01-01
The combined effects of shunt and luminescence coupling on the measurement artifacts of external quantum efficiency (EQE) are modeled and analyzed for the top, middle and bottom subcells of multi-junction solar cells. The measurement artifacts of a Ge bottom cell caused by the combined effects are explained with the models.
Quantum efficiency characterization of back-illuminated CCDs Part2: reflectivity measurements
Fabricius, Maximilian H.; Bebek, Chris J.; Groom, Donald E.; Karcher, Armin; Roe, Natalie A.
2006-01-19
The usual quantum efficiency (QE) measurement heavily relies on a calibrated photodiode (PD) and the knowledge of the CCDs gain. Either can introduce significant systematic errors. But reflectivity can also be used to verify QE measurements. 1 - R > QE, where R is the reflectivity, and over a significant wavelength range, 1 - R = QE. An unconventional reflectometer has been developed to make this measurement. R is measured in two steps, using light from the lateral monochromator port via an optical fiber. The beam intensity is measured directly with aPD, then both the PD and CCD are moved so that the optical path length is unchanged and the light reflects once from the CCD; the PD current ratio gives R. Unlike traditional schemes this approach makes only one reflection from the CCD surface. Since the reflectivity of the LBNL CCDs might be as low as 2 percent this increases the signal to noise ratio dramatically. The goal is a 1 percent accuracy. We obtain good agreement between 1 - R and the direct QE results.
Synchrotron measurements of the absolute x-ray quantum efficiency of CsI-coated microchannel plates
NASA Astrophysics Data System (ADS)
Rideout, Rob M.; Pearson, James F.; Fraser, George W.; Lees, John E.; Brunton, Adam N.; Bannister, N. P.; Kenter, Almus T.; Kraft, Ralph P.
1998-11-01
Two identical CsI-coated, low noise microchannel plate (MCP) detectors were taken to the Daresbury Synchrotron Radiation Source (SRS) to measure their quantum efficiencies over two different energy ranges - 450 eV to 1200 eV and 4.5 eV to 9.5 eV. The SRS was run in low ring current with the beam flux monitored using single wire gas proportional counters. We present accurate measurements of edge-related absolute quantum efficiency features due to the CsI photocathodes. This data will be incorporated into the calibration program of the Advanced X-ray Astrophysical Facility High Resolution Camera.
NASA Astrophysics Data System (ADS)
McDonald, Michael C.; Kim, H. K.; Henry, J. R.; Cunningham, I. A.
2012-03-01
The detective quantum efficiency (DQE) is widely accepted as a primary measure of x-ray detector performance in the scientific community. A standard method for measuring the DQE, based on IEC 62220-1, requires the system to have a linear response meaning that the detector output signals are proportional to the incident x-ray exposure. However, many systems have a non-linear response due to characteristics of the detector, or post processing of the detector signals, that cannot be disabled and may involve unknown algorithms considered proprietary by the manufacturer. For these reasons, the DQE has not been considered as a practical candidate for routine quality assurance testing in a clinical setting. In this article we described a method that can be used to measure the DQE of both linear and non-linear systems that employ only linear image processing algorithms. The method was validated on a Cesium Iodide based flat panel system that simultaneously stores a raw (linear) and processed (non-linear) image for each exposure. It was found that the resulting DQE was equivalent to a conventional standards-compliant DQE with measurement precision, and the gray-scale inversion and linear edge enhancement did not affect the DQE result. While not IEC 62220-1 compliant, it may be adequate for QA programs.
Efficient Quantum Filtering for Quantum Feedback Control
Pierre Rouchon; Jason F. Ralph
2015-01-06
We discuss an efficient numerical scheme for the recursive filtering of diffusive quantum stochastic master equations. We show that the resultant quantum trajectory is robust and may be used for feedback based on inefficient measurements. The proposed numerical scheme is amenable to approximation, which can be used to further reduce the computational burden associated with calculating quantum trajectories and may allow real-time quantum filtering. We provide a two-qubit example where feedback control of entanglement may be within the scope of current experimental systems.
Precision quantum efficiency measurements on 1.7 micron near infrared devices
NASA Astrophysics Data System (ADS)
Schubnell, M.; Brown, M. G.; Karabina, A.; Lorenzon, W.; Mostek, N.; Mufson, S.; Tarlé, G.; Weaverdyck, C.
2008-07-01
High detector quantum efficiency (QE) can greatly improve speed and performance of wide field instruments that strive for fast precision photometry. SNAP, a proposed satellite mission dedicated to exploring the nature of the dark energy will employ a very large focal plane instrumented with about equal number of CCD and NIR sensors totaling more than 600 million pixels covering roughly 0.7 square degrees on the sky. To precisely characterize the NIR detector QE, the SNAP project has put in place a test set-up capable of measuring absolute QE at the 5% level with the goal of ultimately reaching a precision better than 2%. Illumination of the NIR detectors is provided by either a quartz tungsten halogen lamp combined with a set of narrow band filters or a manually tunable monochromator. The two light sources feed an integrating sphere at a distance of roughly 60 cm from the detector to be tested and a calibrated InGaAs photodiode, mounted adjacent to the NIR detector provides absolute photon flux measurements. This paper describes instrumentation, performance and measurement procedures and summarizes results of detailed characterization of the QE on several SNAP devices as a function of wavelength.
Schiff, Eric A.
Plasmonic Light-trapping and Quantum Efficiency Measurements on Nanocrystalline Silicon Solar Cells alternative to texturing is "plasmonic" light-trapping based on non-textured cells and using an overlayer (about 50 for Si) as predicted by Yablonovitch [1]. Plasmonic light trapping is an emerging alternative
Salvagnini, Elena [UZ Gasthuisberg, Medical Imaging Research Center and Department of Radiology, Herestraat 49, B-3000 Leuven, Belgium and SCK-CEN, Boeretang 200, B-2400 Mol (Belgium)] [UZ Gasthuisberg, Medical Imaging Research Center and Department of Radiology, Herestraat 49, B-3000 Leuven, Belgium and SCK-CEN, Boeretang 200, B-2400 Mol (Belgium); Bosmans, Hilde; Marshall, Nicholas W. [UZ Gasthuisberg, Medical Imaging Research Center and Department of Radiology, Herestraat 49, B-3000 Leuven (Belgium)] [UZ Gasthuisberg, Medical Imaging Research Center and Department of Radiology, Herestraat 49, B-3000 Leuven (Belgium); Struelens, Lara [SCK-CEN, Boeretang 200, B-2400 Mol (Belgium)] [SCK-CEN, Boeretang 200, B-2400 Mol (Belgium)
2013-10-15
Purpose: The aim of this paper was to illustrate the value of the new metric effective detective quantum efficiency (eDQE) in relation to more established measures in the optimization process of two digital mammography systems. The following metrics were included for comparison against eDQE: detective quantum efficiency (DQE) of the detector, signal difference to noise ratio (SdNR), and detectability index (d?) calculated using a standard nonprewhitened observer with eye filter.Methods: The two systems investigated were the Siemens MAMMOMAT Inspiration and the Hologic Selenia Dimensions. The presampling modulation transfer function (MTF) required for the eDQE was measured using two geometries: a geometry containing scattered radiation and a low scatter geometry. The eDQE, SdNR, and d? were measured for poly(methyl methacrylate) (PMMA) thicknesses of 20, 40, 60, and 70 mm, with and without the antiscatter grid and for a selection of clinically relevant target/filter (T/F) combinations. Figures of merit (FOMs) were then formed from SdNR and d? using the mean glandular dose as the factor to express detriment. Detector DQE was measured at energies covering the range of typical clinically used spectra.Results: The MTF measured in the presence of scattered radiation showed a large drop at low spatial frequency compared to the low scatter method and led to a corresponding reduction in eDQE. The eDQE for the Siemens system at 1 mm{sup ?1} ranged between 0.15 and 0.27, depending on T/F and grid setting. For the Hologic system, eDQE at 1 mm{sup ?1} varied from 0.15 to 0.32, again depending on T/F and grid setting. The eDQE results for both systems showed that the grid increased the system efficiency for PMMA thicknesses of 40 mm and above but showed only small sensitivity to T/F setting. While results of the SdNR and d? based FOMs confirmed the eDQE grid position results, they were also more specific in terms of T/F selection. For the Siemens system at 20 mm PMMA, the FOMs indicated Mo/Mo (grid out) as optimal while W/Rh (grid in) was the optimal configuration at 40, 60, and 70 mm PMMA. For the Hologic, the FOMs pointed to W/Rh (grid in) at 20 and 40 mm of PMMA while W/Ag (grid in) gave the highest FOM at 60 and 70 mm PMMA. Finally, DQE at 1 mm{sup ?1} averaged for the four beam qualities studied was 0.44 ± 0.02 and 0.55 ± 0.03 for the Siemens and Hologic detectors, respectively, indicating only a small influence of energy on detector DQE.Conclusions: Both the DQE and eDQE data showed only a small sensitivity to T/F setting for these two systems. The eDQE showed clear preferences in terms of scatter reduction, being highest for the grid-in geometry for PMMA thicknesses of 40 mm and above. The SdNR and d? based figures of merit, which contain additional weighting for contrast and dose, pointed to specific T/F settings for both systems.
R. Westphäling; P. Ullrich; J. Hoffmann; H. Kalt; C. Klingshirn; K. Ohkawa; D. Hommel
1998-01-01
We report on a novel experimental setup using a miniature integrating sphere fitted into a cryostat to measure spectrally resolved the absolute external photoluminescence quantum efficiency ?lum in the temperature range from 6 K to beyond room temperature. Direct access to ?lum is achieved by an uncomplicated method to calibrate the spatially integrated emission spectra absolutely. The fraction of light
Efficient Distributed Quantum Computing
Robert Beals; Stephen Brierley; Oliver Gray; Aram Harrow; Samuel Kutin; Noah Linden; Dan Shepherd; Mark Stather
2012-11-16
We provide algorithms for efficiently addressing quantum memory in parallel. These imply that the standard circuit model can be simulated with low overhead by the more realistic model of a distributed quantum computer. As a result, the circuit model can be used by algorithm designers without worrying whether the underlying architecture supports the connectivity of the circuit. In addition, we apply our results to existing memory intensive quantum algorithms. We present a parallel quantum search algorithm and improve the time-space trade-off for the Element Distinctness and Collision problems.
NASA Astrophysics Data System (ADS)
Maxson, Jared; Cultrera, Luca; Gulliford, Colwyn; Bazarov, Ivan
2015-06-01
We measure the tradeoff between the quantum efficiency and intrinsic emittance from a NaKSb photocathode at three increasing wavelengths (635, 650, and 690 nm) at or below the energy of the bandgap plus the electron affinity, h ??Eg+Ea . These measurements were performed using a high voltage dc gun for varied photocathode surface fields of 1.4 -4.4 MV/m. Measurements of intrinsic emittance are performed using two different methods and were found to agree. At the longest wavelength available, 690 nm, the intrinsic emittance was 0.26 ?m/mm-rms with a quantum efficiency of ˜10-4 . The suitability of NaKSb emitting at threshold for various low emittance applications is discussed.
Energy Efficiency Measurement Discussion
2000-01-01
Energy efficiency measurement, energy efficiency measures, policy issues, and energy intensity provides information on indices as a measure of relative changes and other approaches and measurement Issues.
NASA Astrophysics Data System (ADS)
Jacquot, Blake C.; Monacos, Steve P.; Hoenk, Michael E.; Greer, Frank; Jones, Todd J.; Nikzad, Shouleh
2011-04-01
In this paper we present our system design and methodology for making absolute quantum efficiency (QE) measurements through the vacuum ultraviolet (VUV) and verify the system with delta-doped silicon CCDs. Delta-doped detectors provide an excellent platform to validate measurements through the VUV due to their enhanced UV response. The requirements for measuring QE through the VUV are more strenuous than measurements in the near UV and necessitate, among other things, the use of a vacuum monochromator, good dewar chamber vacuum to prevent on-chip condensation, and more stringent handling requirements.
Efficient quantum circuit implementation of quantum walks
Douglas, B. L.; Wang, J. B. [School of Physics, University of Western Australia, 6009 Perth (Australia)
2009-05-15
Quantum walks, being the quantum analog of classical random walks, are expected to provide a fruitful source of quantum algorithms. A few such algorithms have already been developed, including the 'glued trees' algorithm, which provides an exponential speedup over classical methods, relative to a particular quantum oracle. Here, we discuss the possibility of a quantum walk algorithm yielding such an exponential speedup over possible classical algorithms, without the use of an oracle. We provide examples of some highly symmetric graphs on which efficient quantum circuits implementing quantum walks can be constructed and discuss potential applications to quantum search for marked vertices along these graphs.
Quantum Mechanics Measurements, Mutually
Gruner, Daniel S.
Quantum Mechanics Measurements, Mutually Unbiased Bases and Finite Geometry Or why six is the first) #12;Quantum Mechanics for Dummies Finite dimensional quantum states are represented by trace one,1 -icS1,1[ ] #12;Quantum systems evolve and are measured. The evolution of a quantum system using
Photovoltaic efficiency measurements
Keith Emery
2004-01-01
Photovoltaic power conversion efficiency is the single most important performance indicator. This paper gives an overview of procedures to determine the efficiency with respect to standard conditions. The measurement theory and general procedures for determining the efficiency with respect to reference conditions are well understood. The engineering challenge of commercial or custom equipment to perform accurate efficiency measurements for all
Quantum efficiency of SiGe LEDs
T. Stoica; L. Vescan
2003-01-01
The quantum efficiency of p-i-n light emitting diodes with thick fully strained Si0.80Ge0.20\\/Si(001) has been studied with the aim to optimize light emission from SiGe. Electroluminescence spectra and external quantum efficiency were measured in a wide range of temperature and injection current for diodes with different thicknesses of the SiGe layer. From the detailed analysis of thickness and injection current
NASA Technical Reports Server (NTRS)
Emery, Keith; Osterwald, Carl
1989-01-01
Procedures for measuring the air mass zero (AM0) current versus voltage characteristics and calculating the efficiency are discussed. The various factors influencing the determination of the efficiency include the I-V measurement system, reference cell calibration, standard reporting conditions, area measurement, light source characteristics, temperature measurement and control, and the measurement procedures. Each of these sources contributes to the precision index and bias limit which is combined to obtain the total uncertainty in the efficiency. These factors are discussed as well as how to minimize differences in the reported AM0 efficiency of a given PV cell between various laboratories.
Direct modeling of external quantum efficiency of silicon trap detectors
Thiago Menegotto; Maurício S. Lima; Giovanna B. Almeida; Iakyra B. Couceiro; Hans Peter Grieneisen
2011-01-01
It is shown the feasibility of direct fitting of external quantum efficiency for silicon trap detectors which are applied as radiometric transfer standards at several National Institutes of Metrology. The model considers the internal quantum efficiency and the reflectance of the detector, whose parameters are fitted in the measured data of external quantum efficiency. The advantage of the suggested approach
High quantum efficiency photoluminescence from localized excitons in Si, -,Ge,
measured an external photoluminescence quantum efficiency of 11.5 *2%. Recent progress in the epitaxialHigh quantum efficiency photoluminescence from localized excitons in Si, -,Ge, L. C. Lenchyshyn-*), very long decay times ( > 1 ms), and high quantum efficiency at low excitation. We have directly
External quantum efficiency of heterojunction lasers
A. Halak
1975-01-01
External quantum efficiency is understood to mean the ratio of the number of photons emitted from the resonant cavity to the number of injected carriers. Measurement of this ratio is closely associated with the measurement of the threshold current of a junction laser. Optical and electric methods of measuring the threshold current are reviewed, along with a method based on
Property Testing of Quantum Measurements
Guoming Wang
2012-05-03
In this paper, we study the following question: given a black box performing some unknown quantum measurement on a multi-qudit system, how do we test whether this measurement has certain property or is far away from having this property. We call this task \\textit{property testing} of quantum measurement. We first introduce a metric for quantum measurements, and show that it possesses many nice features. Then we show that, with respect to this metric, the following classes of measurements can be efficiently tested: 1. the stabilizer measurements, which play a crucial role for quantum error correction; 2. the $k$-local measurements, i.e. measurements whose outcomes depend on a subsystem of at most $k$ qudits; 3. the permutation-invariant measurements, which include those measurements used in quantum data compression, state estimation and entanglement concentration. In fact, all of them can be tested with query complexity independent of the system's dimension. Furthermore, we also present an algorithm that can test any finite set of measurements. Finally, we consider the following natural question: given two black-box measurement devices, how do we estimate their distance? We give an efficient algorithm for this task, and its query complexity is also independent of the system's dimension. As a consequence, we can easily test whether two unknown measurements are identical or very different.
Voltage-dependent quantum efficiency measurements of amorphous silicon multi-junction mini-modules
C. J. Hibberd; F. Plyta; C. Monokroussos; M. Bliss; T. R. Betts; R. Gottschalg
2011-01-01
Multi-junction solar cells have the potential to provide higher efficiencies than single junction devices and to reduce the impact of Staebler–Wronski degradation on amorphous silicon (a-Si) devices. They could, therefore, reduce the cost of solar electricity. However, their characterization presents additional challenges over that of single junction devices. Achieving acceptable accuracy of any current–voltage calibration requires correction of the current–voltage
Photoreceiver efficiency measurements
NASA Technical Reports Server (NTRS)
Lehr, C. G.
1975-01-01
The efficiency and other related parameters of Smithsonian Astrophysical Observatory's four laser receivers were measured at the observing stations by oscilloscope photography. If the efficiency is defined as the number of photoelectrons generated by the photomultiplier tube divided by the number of photons entering the aperture of the receiver, its measured value is about 1% for the laser wavelength of 694 nm. This value is consistent with the efficiency computed from the specified characteristics of the photoreceiver's optical components.
Efficient Toffoli Gate in Circuit Quantum Electrodynamics
NASA Astrophysics Data System (ADS)
Reed, Matthew; Dicarlo, Leonardo; Sun, Luyan; Frunzio, Luigi; Schoelkopf, Robert
2011-03-01
The fidelity of quantum gates in circuit quantum electrodynamics is typically limited by qubit decoherence. As such, significant improvements can be realized by shortening gate duration. The three-qubit Toffoli gate, also called the controlled-controlled NOT, is an important operation in basic quantum error correction. We report a scheme for a Toffoli gate that exploits interactions with non-computational excited states of transmon qubits which can be executed faster than an equivalent construction using one- and two-qubit gates. The application of this gate to efficient measurement-free quantum error correction will be discussed. Research supported by NSF, NSA, and ARO.
Quantum efficiency measurements of a copper photocathode in an RF electron gun
P. Davis; G. Hairapetian; C. Clayton; C. Joshi; S. Hartman; C. Pellegrini; J. Rosenzweig
1993-01-01
A 4.5 MeV photocathode RF gun has been commissioned at UCLA. A photo-injector drive laser produces sub 2 ps pulses of UV (?=266 nm) light with up to 200 ?J\\/pulse, and illuminates a copper cathode. The photoelectrons are accelerated to an energy of 3.5 MeV within the gun. The electron beam charge is measured as a function of laser energy
NASA Astrophysics Data System (ADS)
Lyashenko, A.; Nguyen, T.; Snyder, A.; Wang, H.; Arisaka, K.
2014-11-01
We report on the measurements of the absolute Quantum Efficiency(QE) for Hamamatsu model R11410-10 PMTs specially designed for the use in low background liquid xenon detectors. QE was measured for five PMTs in a spectral range between 154.5 nm to 400 nm at low temperatures down to -110°C. It was shown that during the PMT cooldown from room temperature to -110°C (a typical PMT operation temperature in liquid xenon detectors), the absolute QE increases by a factor of 1.1–1.15 at 175 nm. The QE growth rate with respect to temperature is wavelength dependent peaking at about 165 nm corresponding to the fastest growth of about -0.07%QE/°C and at about 200 nm corresponding to slowest growth of below -0.01%QE/°C. A dedicated setup and methods for PMT Quantum Efficiency measurement at low temperatures are described in details.
Lyashenko, Alexey; Snyder, Adam; Wang, Hanguo; Arisaka, Katsushi
2014-01-01
We report on the measurements of the absolute Quantum Efficiency(QE) for Hamamatsu model R11410-10 PMTs specially designed for the use in low background liquid xenon detectors. QE was measured for five PMTs in a spectral range between 154.5 nm to 400 nm at low temperatures down to -110$^0$C. It was shown that during the PMT cooldown from room temperature to -110 $^0$C (a typical PMT operation temperature in liquid xenon detectors), the absolute QE increases by a factor of 1.1 - 1.15 at 175 nm. The QE growth rate with respect to temperature is wavelength dependent peaking at about 165 nm corresponding to the fastest growth of about -0.07 %QE/$^{0}C$ and at about 200 nm corresponding to slowest growth of below -0.01 %QE/$^{0}C$. A dedicated setup and methods for PMT Quantum Efficiency measurement at low temperatures are described in details.
Xuan-Dung Dang; Alexander Mikhailovsky; Thuc-Quyen Nguyen
2010-01-01
Photoconductive atomic force microscopy is used to investigate nanoscale incident photon-to-current efficiency spectra of polymer bulk heterojunction solar cells based on poly[2-methoxy-5-(3,7-dimethyloctyloxy)]-1,4-phenylenevinylene (MDMO-PPV) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM). Nanoscale external quantum efficiency reveals the complex morphology of MDMO-PPV:PC71BM films cast from toluene solution. Not only electron transfer from the photoexcited donor to the fullerene but also hole transfer process
High external quantum efficiency of planar semiconductor structures
K. R. Catchpole; K. L. Lin; P. Campbell; M. A. Green; A. W. Bett; F. Dimroth
2004-01-01
We have measured a very high photoluminescence external quantum efficiency (EQE) of 92% for a GaAs\\/GaInP double heterostructure mounted on a planar substrate. The measurement was made using a system we developed for accurately measuring the external quantum efficiency of highly radiatively efficient structures. The technique involves measuring uncalibrated photoluminescence and thermal signals from an optically pumped structure, as a
Robert A. Stern; L. Shing; N. Waltham; H. Mapson-Menard; A. Harris; P. Pool
2010-01-01
We report first absolute effective quantum efficiency (e-h pairs collected\\/predicted) measurements of a monolithic, thinned, back-illuminated CMOS Active Pixel Sensor (APS) in the EUV and soft X-ray region (13-600 Å). The sensor was designed and fabricated under a joint RAL\\/e2v research program, and characterized in the Lockheed Martin Solar and Astrophysics (LMSAL) XUV calibration facility. We compare our QE results
Efficient Algorithms for Universal Quantum Simulation
Barry C. Sanders
2013-07-04
A universal quantum simulator would enable efficient simulation of quantum dynamics by implementing quantum-simulation algorithms on a quantum computer. Specifically the quantum simulator would efficiently generate qubit-string states that closely approximate physical states obtained from a broad class of dynamical evolutions. I provide an overview of theoretical research into universal quantum simulators and the strategies for minimizing computational space and time costs. Applications to simulating many-body quantum simulation and solving linear equations are discussed.
Absolute external luminescence quantum efficiency of zinc oxide
Mario Hauser; Alexander Hepting; Robert Hauschild; Huijuan Zhou; Johannes Fallert; Heinz Kalt; Claus Klingshirn
2008-01-01
We report on the measurement of the absolute external luminescence quantum efficiency of various ZnO samples using a miniature integrating sphere fitted into a cryostat. Even the absolute luminescence quantum efficiencies per spectral interval are directly accessible. Measurements have been carried out on high quality bulk samples and different commercially available ZnO powders from 8 K up to room temperature.
Temperature-dependent quantum efficiency of Ga(N,As,P) quantum wells
NASA Astrophysics Data System (ADS)
Rosemann, N. W.; Metzger, B.; Kunert, B.; Volz, K.; Stolz, W.; Chatterjee, S.
2013-12-01
The photoluminescence quantum efficiencies of a series of Ga(N,As,P)/GaP multiple quantum wells are analyzed. The external quantum efficiencies are derived from the absorbed and the emitted light intensities measured using an integrating sphere mounted inside a closed-cycle helium cryostat. By taking into account the device layer sequences as well as internal reflections and reabsorption, the internal quantum efficiencies yield values above 90% for all samples at cryogenic temperatures. The temperature-dependence of the quantum efficiencies as a function of active quantum well layer design reveal the internal interfaces as remaining growth challenge in these heterostructures.
Wai, Ping-kong Alexander
directly. The internal quantum efficiency can thus be estimated easily through the measurement quantum efficiency int , external quantum efficiency, exciton lifetime, and angular dependenceModifications of the exciton lifetime and internal quantum efficiency for organic light
Efficiencies of Quantum Optical Detectors
Daniel Hogg; Dominic W. Berry; A. I. Lvovsky
2014-12-15
We propose a definition for the efficiency that can be universally applied to all classes of quantum optical detectors. This definition is based on the maximum amount of optical loss that a physically plausible device can experience while still replicating the properties of a given detector. We prove that detector efficiency cannot be increased using linear optical processing. That is, given a set of detectors, as well as arbitrary linear optical elements and ancillary light sources, it is impossible to construct detection devices that would exhibit higher efficiencies than the initial set.
Chiao, R Y; Speliotopoulos, A D
2003-01-01
A minimal coupling rule for the coupling of the electron spin to curved spacetime in general relativity suggests the possibility of a coupling between electromagnetic and gravitational radiation mediated by means of a quantum fluid. Thus quantum transducers between these two kinds of radiation fields might exist. We report here on the first attempt at a Hertz-type experiment, in which a high-$\\rm{T_c}$ superconductor (YBCO) was the sample material used as a possible quantum transducer to convert EM into GR microwaves, and a second piece of YBCO in a separate apparatus was used to back-convert GR into EM microwaves. An upper limit on the conversion efficiency of YBCO was measured to be $1.6\\times10^{-5}$ at liquid nitrogen temperature.
Efficiency and formalism of quantum games
Chiu Fan Lee; Neil Johnson
2008-09-19
We pursue a general theory of quantum games. We show that quantum games are more efficient than classical games, and provide a saturated upper bound for this efficiency. We demonstrate that the set of finite classical games is a strict subset of the set of finite quantum games. We also deduce the quantum version of the Minimax Theorem and the Nash Equilibrium Theorem.
High internal and external quantum efficiency InGaN\\/GaN solar cells
Elison Matioli; Carl Neufeld; Michael Iza; Samantha C. Cruz; Ali A. Al-Heji; Xu Chen; Robert M. Farrell; Stacia Keller; Steven Denbaars; Umesh Mishra; Shuji Nakamura; James Speck; Claude Weisbuch
2011-01-01
High internal and external quantum efficiency GaN\\/InGaN solar cells are demonstrated. The internal quantum efficiency was assessed through the combination of absorption and external quantum efficiency measurements. The measured internal quantum efficiency, as high as 97%, revealed an efficient conversion of absorbed photons into electrons and holes and an efficient transport of these carriers outside the device. Improved light incoupling
NASA Astrophysics Data System (ADS)
Boscolo, A.; Placentino, L.; Poletto, L.
1998-07-01
The quantum efficiency of an uncoated channel electron multiplier (CEM) working in the photon-counting regime has been evaluated over a wide spectral range, which comprises the EUV and soft x-ray regions. Three different experimental set-ups have been used: a Johnson - Onaka monochromator for the 30 - 160 nm region, a grazing incidence monochromator for the 0.3 - 30 nm region and a test facility mounting filters for the 0.14 - 0.3 nm region. As a secondary standard, both silicon and aluminium photodiodes have been used. The efficiency has been evaluated at normal incidence angle. The measured values range from 2% to 15% in the range 0.14 - 100 nm, while a rapid decrease is present over 120 nm. Changes in the efficiency due to carbon contamination in the vacuum system are discussed, and also effects due to variations of the illuminated area on the CEM entrance cone.
NASA Astrophysics Data System (ADS)
Stern, Robert A.; Shing, L.; Waltham, N.; Mapson-Menard, H.; Harris, A.; Pool, P.
2010-05-01
We report first absolute effective quantum efficiency (e-h pairs collected/predicted) measurements of a monolithic, thinned, back-illuminated CMOS Active Pixel Sensor (APS) in the EUV and soft X-ray region (13-600 Å). The sensor was designed and fabricated under a joint RAL/e2v research program, and characterized in the Lockheed Martin Solar and Astrophysics (LMSAL) XUV calibration facility. We compare our QE results to data and models developed for thinned CCDs with similar back surface passivation. Our results demonstrate that CMOS APS arrays show significant promise for use in space-based solar physics missions.
Quantum discord with weak measurements
Singh, Uttam, E-mail: uttamsingh@hri.res.in; Pati, Arun Kumar, E-mail: akpati@hri.res.in
2014-04-15
Weak measurements cause small change to quantum states, thereby opening up the possibility of new ways of manipulating and controlling quantum systems. We ask, can weak measurements reveal more quantum correlation in a composite quantum state? We prove that the weak measurement induced quantum discord, called as the “super quantum discord”, is always larger than the quantum discord captured by the strong measurement. Moreover, we prove the monotonicity of the super quantum discord as a function of the measurement strength and in the limit of strong projective measurement the super quantum discord becomes the normal quantum discord. We find that unlike the normal discord, for pure entangled states, the super quantum discord can exceed the quantum entanglement. Our results provide new insights on the nature of quantum correlation and suggest that the notion of quantum correlation is not only observer dependent but also depends on how weakly one perturbs the composite system. We illustrate the key results for pure as well as mixed entangled states. -- Highlights: •Introduced the role of weak measurements in quantifying quantum correlation. •We have introduced the notion of the super quantum discord (SQD). •For pure entangled state, we show that the SQD exceeds the entanglement entropy. •This shows that quantum correlation depends not only on observer but also on measurement strength.
Internal quantum efficiency modeling of silicon photodiodes.
Gentile, T R; Brown, S W; Lykke, K R; Shaw, P S; Woodward, J T
2010-04-01
Results are presented for modeling of the shape of the internal quantum efficiency (IQE) versus wavelength for silicon photodiodes in the 400 nm to 900 nm wavelength range. The IQE data are based on measurements of the external quantum efficiencies of three transmission optical trap detectors using an extensive set of laser wavelengths, along with the transmittance of the traps. We find that a simplified version of a previously reported IQE model fits the data with an accuracy of better than 0.01%. These results provide an important validation of the National Institute of Standards and Technology (NIST) spectral radiant power responsivity scale disseminated through the NIST Spectral Comparator Facility, as well as those scales disseminated by other National Metrology Institutes who have employed the same model. PMID:20357870
Efficiency and formalism of quantum games
Lee, C.F.; Johnson, Neil F. [Centre for Quantum Computation and Physics Department, Clarendon Laboratory, Oxford University, Parks Road, Oxford OX1 3PU (United Kingdom)
2003-02-01
We show that quantum games are more efficient than classical games and provide a saturated upper bound for this efficiency. We also demonstrate that the set of finite classical games is a strict subset of the set of finite quantum games. Our analysis is based on a rigorous formulation of quantum games, from which quantum versions of the minimax theorem and the Nash equilibrium theorem can be deduced.
Duality quantum computer and the efficient quantum simulations
Shi-Jie Wei; Gui-Lu Long
2015-07-12
In this paper, we firstly briefly review the duality quantum computer. Distinctly, the generalized quantum gates, the basic evolution operators in a duality quantum computer are no longer unitary, and they can be expressed in terms of linear combinations of unitary operators. All linear bounded operators can be realized in a duality quantum computer, and unitary operators are just the extreme points of the set of generalized quantum gates. A d-slits duality quantum computer can be realized in an ordinary quantum computer with an additional qudit using the duality quantum computing mode. Duality quantum computer provides flexibility and clear physical picture in designing quantum algorithms, serving as a useful bridge between quantum and classical algorithms. In this review, we will show that duality quantum computer can simulate quantum systems more efficiently than ordinary quantum computers by providing descriptions of the recent efficient quantum simulation algorithms of Childs et al [Quantum Information & Computation, 12(11-12): 901-924 (2012)] for the fast simulation of quantum systems with a sparse Hamiltonian, and the quantum simulation algorithm by Berry et al [Phys. Rev. Lett. 114, 090502 (2015)], which provides exponential improvement in precision for simulating systems with a sparse Hamiltonian.
Beginner's Guide to Efficiency Measurement.
ERIC Educational Resources Information Center
Easun, Sue
1994-01-01
Explains traditional notions of efficient behavior; applies them to libraries and information centers; discusses how we measure efficiency; describes data envelopment analysis, a mathematical model designed for use with nonprofit organizations to measure efficiency through a weighting scheme; and discusses its use in school media centers.…
Universal Quantum Measurements
NASA Astrophysics Data System (ADS)
Brody, Dorje C.; Hughston, Lane P.
2015-06-01
We introduce a family of operations in quantum mechanics that one can regard as “universal quantum measurements” (UQMs). These measurements are applicable to all finite dimensional quantum systems and entail the specification of only a minimal amount of structure. The first class of UQM that we consider involves the specification of the initial state of the system—no further structure is brought into play. We call operations of this type “tomographic measurements”, since given the statistics of the outcomes one can deduce the original state of the system. Next, we construct a disentangling operation, the outcome of which, when the procedure is applied to a general mixed state of an entangled composite system, is a disentangled product of pure constituent states. This operation exists whenever the dimension of the Hilbert space is not a prime, and can be used to model the decay of a composite system. As another example, we show how one can make a measurement of the direction along which the spin of a particle of spin s is oriented (s = 1/2, 1,...). The required additional structure in this case involves the embedding of CP1 as a rational curve of degree 2s in CP2s.
Quantum entanglement helps in improving economic efficiency
NASA Astrophysics Data System (ADS)
Du, Jiangfeng; Ju, Chenyong; Li, Hui
2005-02-01
We propose an economic regulation approach based on quantum game theory for the government to reduce the abuses of oligopolistic competition. Theoretical analysis shows that this approach can help government improve the economic efficiency of the oligopolistic market, and help prevent monopoly due to incorrect information. These advantages are completely attributed to the quantum entanglement, a unique quantum mechanical character.
Quantum effects improve the energy efficiency of feedback control
NASA Astrophysics Data System (ADS)
Horowitz, Jordan M.; Jacobs, Kurt
2014-04-01
The laws of thermodynamics apply equally well to quantum systems as to classical systems, and because of this, quantum effects do not change the fundamental thermodynamic efficiency of isothermal refrigerators or engines. We show that, despite this fact, quantum mechanics permits measurement-based feedback control protocols that are more thermodynamically efficient than their classical counterparts. As part of our analysis, we perform a detailed accounting of the thermodynamics of unitary feedback control and elucidate the sources of inefficiency in measurement-based and coherent feedback.
Direct determination of quantum efficiency of semiconducting films
Faughnan, Brian W. (Princeton, NJ); Hanak, Joseph J. (Lawrenceville, NJ)
1986-01-01
Photovoltaic quantum efficiency of semiconductor samples is determined directly, without requiring that a built-in photovoltage be generated by the sample. Electrodes are attached to the sample so as to form at least one Schottky barrier therewith. When illuminated, the generated photocurrent carriers are collected by an external bias voltage impressed across the electrodes. The generated photocurrent is measured, and photovoltaic quantum efficiency is calculated therefrom.
Mid-infrared interband cascade lasers with quantum efficiencies >200%
B. H. Yang; D. Zhang; Rui Q. Yang; C.-H. Lin; S. J. Murry; S. S. Pei
1998-01-01
An external differential quantum efficiency exceeding 200% has been observed from 4 ?m InAs\\/InGaSb\\/AlSb interband cascade lasers under 1 ?s pulses and 0.1% duty cycle at 80 K. By increasing the pulse lengths and the repetition rates, average powers >16 mW have been measured with 5 ?s pulses at 10% duty cycle, the internal quantum efficiency and the internal loss
Mid-infrared interband cascade lasers with quantum efficiencies >200%
B. H. Yang; D. Zhang; Rui Q. Yang; C.-H. Lin; S. J. Murry; S. S. Pei
1998-01-01
An external differential quantum efficiency exceeding 200% has been observed from 4 mum InAs\\/InGaSb\\/AlSb interband cascade lasers under 1 mus pulses and 0.1% duty cycle at 80 K. By increasing the pulse lengths and the repetition rates, average powers >16 mW have been measured with 5 mus pulses at 10% duty cycle, the internal quantum efficiency and the internal loss
Quantum efficiency of ZnO nanowire nanolasers
Yanfeng Zhang; Richard E. Russo; Samuel S. Mao
2005-01-01
Crystalline ZnO nanowires were grown on sapphire and silicon substrates using pulsed-laser deposition. The optical properties of nanowire nanolasers, including their absolute light emission intensity and external and internal quantum efficiencies were experimentally determined. The external differential quantum efficiency was measured to be as high as 60% for lasing ZnO nanowires of 7.5 mum in length, compared to a value
Simulation of n-qubit quantum systems. V. Quantum measurements
NASA Astrophysics Data System (ADS)
Radtke, T.; Fritzsche, S.
2010-02-01
The FEYNMAN program has been developed during the last years to support case studies on the dynamics and entanglement of n-qubit quantum registers. Apart from basic transformations and (gate) operations, it currently supports a good number of separability criteria and entanglement measures, quantum channels as well as the parametrizations of various frequently applied objects in quantum information theory, such as (pure and mixed) quantum states, hermitian and unitary matrices or classical probability distributions. With the present update of the FEYNMAN program, we provide a simple access to (the simulation of) quantum measurements. This includes not only the widely-applied projective measurements upon the eigenspaces of some given operator but also single-qubit measurements in various pre- and user-defined bases as well as the support for two-qubit Bell measurements. In addition, we help perform generalized and POVM measurements. Knowing the importance of measurements for many quantum information protocols, e.g., one-way computing, we hope that this update makes the FEYNMAN code an attractive and versatile tool for both, research and education. New version program summaryProgram title: FEYNMAN Catalogue identifier: ADWE_v5_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADWE_v5_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 27 210 No. of bytes in distributed program, including test data, etc.: 1 960 471 Distribution format: tar.gz Programming language: Maple 12 Computer: Any computer with Maple software installed Operating system: Any system that supports Maple; the program has been tested under Microsoft Windows XP and Linux Classification: 4.15 Catalogue identifier of previous version: ADWE_v4_0 Journal reference of previous version: Comput. Phys. Commun. 179 (2008) 647 Does the new version supersede the previous version?: Yes Nature of problem: During the last decade, the field of quantum information science has largely contributed to our understanding of quantum mechanics, and has provided also new and efficient protocols that are used on quantum entanglement. To further analyze the amount and transfer of entanglement in n-qubit quantum protocols, symbolic and numerical simulations need to be handled efficiently. Solution method: Using the computer algebra system Maple, we developed a set of procedures in order to support the definition, manipulation and analysis of n-qubit quantum registers. These procedures also help to deal with (unitary) logic gates and (nonunitary) quantum operations and measurements that act upon the quantum registers. All commands are organized in a hierarchical order and can be used interactively in order to simulate and analyze the evolution of n-qubit quantum systems, both in ideal and noisy quantum circuits. Reasons for new version: Until the present, the FEYNMAN program supported the basic data structures and operations of n-qubit quantum registers [1], a good number of separability and entanglement measures [2], quantum operations (noisy channels) [3] as well as the parametrizations of various frequently applied objects, such as (pure and mixed) quantum states, hermitian and unitary matrices or classical probability distributions [4]. With the current extension, we here add all necessary features to simulate quantum measurements, including the projective measurements in various single-qubit and the two-qubit Bell basis, and POVM measurements. Together with the previously implemented functionality, this greatly enhances the possibilities of analyzing quantum information protocols in which measurements play a central role, e.g., one-way computation. Running time: Most commands require ?10 seconds of processor time on a Pentium 4 processor with ?2 GHz RAM or newer, if they work with quantum registers with five or less qubits. Moreover, about 5-20 MB of working memory is typically n
Efficiency of quantum and classical transport on graphs.
Mülken, Oliver; Blumen, Alexander
2006-06-01
We propose a measure to quantify the efficiency of classical and quantum mechanical transport processes on graphs. The measure only depends on the density of states (DOS), which contains all the necessary information about the graph. For some given (continuous) DOS, the measure shows a power law behavior, where the exponent for the quantum transport is twice the exponent of its classical counterpart. For small-world networks, however, the measure shows rather a stretched exponential law but still the quantum transport outperforms the classical one. Some finite tree graphs have a few highly degenerate eigenvalues, such that, on the other hand, on them the classical transport may be more efficient than the quantum one. PMID:16906924
Measurement-based quantum computation
H. J. Briegel; D. E. Browne; W. Dür; R. Raussendorf; M. Van den Nest
2009-10-09
Quantum computation offers a promising new kind of information processing, where the non-classical features of quantum mechanics can be harnessed and exploited. A number of models of quantum computation exist, including the now well-studied quantum circuit model. Although these models have been shown to be formally equivalent, their underlying elementary concepts and the requirements for their practical realization can differ significantly. The new paradigm of measurement-based quantum computation, where the processing of quantum information takes place by rounds of simple measurements on qubits prepared in a highly entangled state, is particularly exciting in this regard. In this article we discuss a number of recent developments in measurement-based quantum computation in both fundamental and practical issues, in particular regarding the power of quantum computation, the protection against noise (fault tolerance) and steps toward experimental realization. Moreover, we highlight a number of surprising connections between this field and other branches of physics and mathematics.
Coherent measurements in quantum metrology
NASA Astrophysics Data System (ADS)
Micadei, K.; Rowlands, D. A.; Pollock, F. A.; Céleri, L. C.; Serra, R. M.; Modi, K.
2015-02-01
It is well known that a quantum correlated probe can yield better precision in estimating an unknown parameter than classically possible. However, how such a quantum probe should be measured remains somewhat elusive. We examine the role of measurements in quantum metrology by considering two types of readout strategies: coherent, where all probes are measured simultaneously in an entangled basis; and adaptive, where probes are measured sequentially, with each measurement one way conditioned on the prior outcomes. Here we firstly show that for classically correlated probes the two readout strategies yield the same precision. Secondly, we construct an example of a noisy multipartite quantum system where coherent readout yields considerably better precision than adaptive readout. This highlights a fundamental difference between classical and quantum parameter estimation. From the practical point of view, our findings are relevant for the optimal design of precision-measurement quantum devices.
Robust and efficient in situ quantum control
NASA Astrophysics Data System (ADS)
Ferrie, Christopher; Moussa, Osama
2015-05-01
Precision control of quantum systems is the driving force for both quantum technology and the probing of physics at the quantum and nanoscale levels. We propose an implementation-independent method for in situ quantum control that leverages recent advances in the direct estimation of quantum gate fidelity. Our algorithm takes account of the stochasticity of the problem, is suitable for closed-loop control, and requires only a constant number of fidelity-estimating experiments per iteration independent of the dimension of the control space. It is efficient and robust to both statistical and technical noise.
Robust and efficient in situ quantum control
Christopher Ferrie; Osama Moussa
2014-09-10
Precision control of quantum systems is the driving force for both quantum technology and the probing of physics at the quantum and nano-scale. We propose an implementation independent method for in situ quantum control that leverages recent advances in the direct estimation of quantum gate fidelity. Our algorithm takes account of the stochasticity of the problem and is suitable for closed-loop control and requires only a constant number of fidelity estimating experiments per iteration independent of the dimension of the control space. It is efficient and robust to both statistical and technical noise.
Robust and efficient in situ quantum control
Christopher Ferrie; Osama Moussa
2015-07-12
Precision control of quantum systems is the driving force for both quantum technology and the probing of physics at the quantum and nano-scale. We propose an implementation independent method for in situ quantum control that leverages recent advances in the direct estimation of quantum gate fidelity. Our algorithm takes account of the stochasticity of the problem and is suitable for closed-loop control and requires only a constant number of fidelity estimating experiments per iteration independent of the dimension of the control space. It is efficient and robust to both statistical and technical noise.
An intuition behind quantum measurement
Witas, Piotr
2014-01-01
An attempt is made to give a heuristic explanation of the distinguished role of measurement in the quantum theory. We question the notion of "naive" reductionism by stressing the difference between an isolated quantum and classical object. It is argued that the transition from the micro- to the macroscopic description should be made along some parameters not characterized by the quantum theory.
Highly power-efficient quantum cascade lasers
Peter Q. Liu; Anthony J. Hoffman; Matthew D. Escarra; Kale J. Franz; Jacob B. Khurgin; Yamac Dikmelik; Xiaojun Wang; Jen-Yu Fan; Claire F. Gmachl
2010-01-01
Quantum cascade lasers are promising mid-infrared semiconductor light sources for molecular detection in applications such as environmental sensing or medical diagnostics. For such applications, researchers have been striving to improve device performance. Recently, improvements in wall plug efficiency have been pursued with a view to realizing compact, portable, power-efficient and high-power quantum cascade laser systems. However, advances have largely been
Accurate Measurement of Organic Solar Cell Efficiency
Emery, K.; Moriarty, T.
2008-01-01
We discuss the measurement and analysis of current vs. voltage (I-V) characteristics of organic and dye-sensitized photovoltaic cells and modules. A brief discussion of the history of photovoltaic efficiency measurements and procedures will be presented. We discuss both the error sources in the measurements and the strategies to minimize their influence. These error sources include the sample area, spectral errors, temperature fluctuations, current and voltage response time, contacting, and degradation during testing. Information that can be extracted from light and dark I-V measurement includes peak power, open-circuit voltage, short-circuit current, series and shunt resistance, diode quality factor, dark current, and photo-current. The quantum efficiency provides information on photo-current nonlinearities, current generation, and recombination mechanisms.
Informational power of quantum measurements
Dall'Arno, Michele; D'Ariano, Giacomo Mauro [Quit Group, Dipartimento di Fisica 'A. Volta', via A. Bassi 6, I-27100 Pavia (Italy); Istituto Nazionale di Fisica Nucleare, Gruppo IV, via A. Bassi 6, I-27100 Pavia (Italy); Sacchi, Massimiliano F. [Quit Group, Dipartimento di Fisica 'A. Volta', via A. Bassi 6, I-27100 Pavia (Italy); Istituto di Fotonica e Nanotecnologie (INF-CNR), Piazza Leonardo da Vinci 32, I-20133, Milano (Italy)
2011-06-15
We introduce the informational power of a quantum measurement as the maximum amount of classical information that the measurement can extract from any ensemble of quantum states. We prove the additivity by showing that the informational power corresponds to the classical capacity of a quantum-classical channel. We restate the problem of evaluating the informational power as the maximization of the accessible information of a suitable ensemble. We provide a numerical algorithm to find an optimal ensemble and quantify the informational power.
Efficiency vs. multi-photon contribution test for quantum dots
Ana Predojevic; Miroslav Jezek; Tobias Huber; Harishankar Jayakumar; Thomas Kauten; Glenn S. Solomon; Radim Filip; Gregor Weihs
2014-03-19
The development of linear quantum computing within integrated circuits demands high quality semiconductor single photon sources. In particular, for a reliable single photon source it is not sufficient to have a low multi-photon component, but also to possess high efficiency. We investigate the photon statistics of the emission from a single quantum dot with a method that is able to sensitively detect the trade-off between the efficiency and the multi-photon contribution. Our measurements show, that the light emitted from the quantum dot when it is resonantly excited possess a very low multi-photon content. Additionally, we demonstrated, for the first time, the non-Gaussian nature of the quantum state emitted from a single quantum dot.
Universality of sequential quantum measurements
NASA Astrophysics Data System (ADS)
Heinosaari, Teiko; Miyadera, Takayuki
2015-02-01
We show that any jointly measurable pair of quantum observables can be obtained in a sequential measurement scheme, even if the second observable will be decided after the first measurement. This means that it is possible to perform a measurement of any quantum observable in a way that does not disturb the subsequent measurements more than is dictated by joint measurability. Only measurements with a specific structure have this universality feature. As a supplementing result, we provide a characterization of all possible joint measurements obtained from a sequential measurement lacking universality.
National Residential Efficiency Measures Database
The National Residential Efficiency Measures Database is a publicly available, centralized resource of residential building retrofit measures and costs for the U.S. building industry. With support from the U.S. Department of Energy, NREL developed this tool to help users determine the most cost-effective retrofit measures for improving energy efficiency of existing homes. Software developers who require residential retrofit performance and cost data for applications that evaluate residential efficiency measures are the primary audience for this database. In addition, home performance contractors and manufacturers of residential materials and equipment may find this information useful. The database offers the following types of retrofit measures: 1) Appliances, 2) Domestic Hot Water, 3) Enclosure, 4) Heating, Ventilating, and Air Conditioning (HVAC), 5) Lighting, 6) Miscellaneous.
Gilchrist, James F.
) and external differential quantum efficiencies of 52% [3]. Interestingly, even with such high performance Efficiency and Gain Characteristics of Strained-Layer InGaAsGaAs Quantum-Well Lasers Gene Tsvid, Student-emitting aluminum-free InGaAsInGaAsPGaAs quantum-well (QW) laser diode. These measurements provide a baseline
Investigation of the quantum efficiency of optical heterodyne detectors
NASA Technical Reports Server (NTRS)
Batchman, T. E.
1984-01-01
The frequency response and quantum efficiency of optical photodetectors for heterodyne receivers is investigated. The measurements utilized two spectral lines from the output of two lasers as input to the photodetectors. These lines are easily measurable in power and frequency and hence serve as known inputs. By measuring the output current of the photodetector the quantum efficiency is determined as a function of frequency separation between the two input signals. An investigation of the theoretical basis and accuracy of this type of measurement relative to similar measurements utilizing risetime is undertaken. A theoretical study of the heterodyne process in photodetectors based on semiconductor physics is included so that higher bandwidth detectors may be designed. All measurements are made on commercially available detectors and manufacturers' specifications for normal photodetector operation are compared to the measured heterodyne characteristics.
Tight informationally complete quantum measurements
A. J. Scott
2006-10-11
We introduce a class of informationally complete positive-operator-valued measures which are, in analogy with a tight frame, "as close as possible" to orthonormal bases for the space of quantum states. These measures are distinguished by an exceptionally simple state-reconstruction formula which allows "painless" quantum state tomography. Complete sets of mutually unbiased bases and symmetric informationally complete positive-operator-valued measures are both members of this class, the latter being the unique minimal rank-one members. Recast as ensembles of pure quantum states, the rank-one members are in fact equivalent to weighted 2-designs in complex projective space. These measures are shown to be optimal for quantum cloning and linear quantum state tomography.
Circuit analysis of quantum measurement
Yuji Kurotani; Masahito Ueda
2006-09-08
We develop a circuit theory that enables us to analyze quantum measurements on a two-level system and on a continuous-variable system on an equal footing. As a measurement scheme applicable to both systems, we discuss a swapping state measurement which exchanges quantum states between the system and the measuring apparatus before the apparatus meter is read out. This swapping state measurement has an advantage in gravitational-wave detection over contractive state measurement in that the postmeasurement state of the system can be set to a prescribed one, regardless of the outcome of the measurement.
and holes to the tiny space of a quantum dot can lead to increased PV efficiency in solar cells. Result efficiency and could lead to a doubling of third-generation solar cell efficiencies. Tiny quantum dots quantum dot solar cell performance for an initial efficiency measurement along with good stability
Efficient networks for quantum factoring
Beckman, D.; Chari, A.N.; Devabhaktuni, S.; Preskill, J. [California Institute of Technology, Pasadena, California 91125 (United States)] [California Institute of Technology, Pasadena, California 91125 (United States)
1996-08-01
We consider how to optimize memory use and computation time in operating a quantum computer. In particular, we estimate the number of memory quantum bits (qubits) and the number of operations required to perform factorization, using the algorithm suggested by Shor [in {ital Proceedings} {ital of} {ital the} 35{ital th} {ital Annual} {ital Symposium} {ital on} {ital Foundations} {ital of} {ital Computer} {ital Science}, edited by S. Goldwasser (IEEE Computer Society, Los Alamitos, CA, 1994), p. 124]. A {ital K}-bit number can be factored in time of order {ital K}{sup 3} using a machine capable of storing 5{ital K}+1 qubits. Evaluation of the modular exponential function (the bottleneck of Shor{close_quote}s algorithm) could be achieved with about 72{ital K}{sup 3} elementary quantum gates; implementation using a linear ion trap would require about 396{ital K}{sup 3} laser pulses. A proof-of-principle demonstration of quantum factoring (factorization of 15) could be performed with only 6 trapped ions and 38 laser pulses. Though the ion trap may never be a useful computer, it will be a powerful device for exploring experimentally the properties of entangled quantum states. {copyright} {ital 1996 The American Physical Society.}
Observable measure of quantum coherence in finite dimensional systems.
Girolami, Davide
2014-10-24
Quantum coherence is the key resource for quantum technology, with applications in quantum optics, information processing, metrology, and cryptography. Yet, there is no universally efficient method for quantifying coherence either in theoretical or in experimental practice. I introduce a framework for measuring quantum coherence in finite dimensional systems. I define a theoretical measure which satisfies the reliability criteria established in the context of quantum resource theories. Then, I present an experimental scheme implementable with current technology which evaluates the quantum coherence of an unknown state of a d-dimensional system by performing two programmable measurements on an ancillary qubit, in place of the O(d2) direct measurements required by full state reconstruction. The result yields a benchmark for monitoring quantum effects in complex systems, e.g., certifying nonclassicality in quantum protocols and probing the quantum behavior of biological complexes. PMID:25379903
Quantum Mechanics (QM) Measurement Package
NSDL National Science Digital Library
Belloni, Mario
This set of tutorial worksheets, based on the OSP Quantum Mechanics Simulations, help students explore the effects of position, momentum, and energy measurements on quantum state wavepackets. The probabilistic change in the wavefunction upon measurements and the time propagation of the states are illustrated. Similar worksheets are available for measurements of single and superpositions of energy eigenstates. The worksheets can be run online or downloaded as a pdf (attached).
Tight informationally complete quantum measurements
A. J. Scott
2006-01-01
We introduce a class of informationally complete positive-operator-valued measures which are, in analogy with a tight frame, ‘as close as possible’ to orthonormal bases for the space of quantum states. These measures are distinguished by an exceptionally simple state-reconstruction formula which allows ‘painless’ quantum state tomography. Complete sets of mutually unbiased bases and symmetric informationally complete positive-operator-valued measures are both
Operational measurements in quantum mechanics
NASA Astrophysics Data System (ADS)
Kocha?ski, Piotr; Wódkiewicz, Krzysztof
1997-10-01
The operational approach to quantum measurements is formulated in terms of a phase space propensity and the corresponding positive operator-valued measure. This general approach is illustrated by an operational measurement of the position and momentum of a particle, and by an operational Malus measurement of spin phases.
Quantum measurements and finite geometry
William K. Wootters
2004-08-12
A complete set of mutually unbiased bases for a Hilbert space of dimension N is analogous in some respects to a certain finite geometric structure, namely, an affine plane. Another kind of quantum measurement, known as a symmetric informationally complete positive-operator-valued measure, is, remarkably, also analogous to an affine plane, but with the roles of points and lines interchanged. In this paper I present these analogies and ask whether they shed any light on the existence or non-existence of such symmetric quantum measurements for a general quantum system with a finite-dimensional state space.
Supporting Information High Quantum Efficiency of Band-Edge Emission from
Yang, Peidong
were normalized to = 470nm. #12;3 Figure S3. Calculation of External Quantum Efficiency (EQE). EQE1 Supporting Information High Quantum Efficiency of Band-Edge Emission from ZnO Nanowires Daniel J efficiency (IQE) measurement of single ZnO nanowires. A) Diagram of IQE experimental setup. B) PL spectra
Quantum state estimation with informationally overcomplete measurements
Huangjun Zhu
2014-08-05
We study informationally overcomplete measurements for quantum state estimation so as to clarify their tomographic significance as compared with minimal informationally complete measurements. We show that informationally overcomplete measurements can improve the tomographic efficiency significantly over minimal measurements when the states of interest have high purities. Nevertheless, the efficiency is still too limited to be satisfactory with respect to figures of merit based on monotone Riemannian metrics, such as the Bures metric and quantum Chernoff metric. In this way, we also pinpoint the limitation of nonadaptive measurements and motivate the study of more sophisticated measurement schemes. In the course of our study, we introduce the best linear unbiased estimator and show that it is equally efficient as the maximum likelihood estimator in the large-sample limit. This estimator may significantly outperform the canonical linear estimator for states with high purities. It is expected to play an important role in experimental designs and adaptive quantum state tomography besides its significance to the current study.
The quantum measurement of time
NASA Technical Reports Server (NTRS)
Shepard, Scott R.
1994-01-01
Traditionally, in non-relativistic Quantum Mechanics, time is considered to be a parameter, rather than an observable quantity like space. In relativistic Quantum Field Theory, space and time are treated equally by reducing space to also be a parameter. Herein, after a brief review of other measurements, we describe a third possibility, which is to treat time as a directly observable quantity.
Quantum nondemolition measurements via quantum counting
Milburn, G.J.; Walls, D.F.
1983-11-01
For a harmonic-oscillator gravitational-wave detector, we show that a quantum nondemolition measurement of the square of the number operator may be made by coupling the detector to an oscillator readout via a quadratic interaction, as in optical four-wave mixing. Explicit evaluation of the effect of a meter readout on the detector demonstrates the possibility of arbitrarily accurate instantaneous measurements for sufficiently large coupling strength.
External quantum efficiency of single porous silicon nanoparticles
G. M. Credo; M. D. Mason; S. K. Buratto
1999-01-01
We use a combination of single nanoparticle luminescence and scanning force microscopy to determine the quantum efficiency (QE) of single porous Si nanoparticles and to determine the ratio of luminescent nanoparticles deposited on a silica surface to the total nanoparticles. An estimate of the QE of bulk porous Si based on these data compares favorably to the QE measured experimentally.
Carotenoid-sensitized photosynthesis: Quantum efficiency, fluorescence and energy transfer
Herbert J. Dutton
1997-01-01
The observation in the early 1940s that the quantum efficiency of photosynthesis in a diatom was almost the same whether incident light was absorbed by chlorophyll a or by fucoxanthol sparked subsequent investigations of the variety of chloroplast pigments and in a diversity of photosynthetic organisms. Subsequent fluorimetric measurements provided the first relevant observation on the existence of excitation energy
UV detective quantum efficiency measurements
NASA Astrophysics Data System (ADS)
Joseph, Charles L.
1999-11-01
We have been testing the vacuum ultraviolet (UV) response of several types of detectors, supporting investigators developing photodiodes made of GaN, near UV photocathodes, and Electron-Bombarded CCDs (EBCCDs). We are currently supporting 4 independent research groups developing GaN most of which have produced devices with significant sensitivity down to 1200 Angstroms. Over the past year, we have also tested bare CCDs with coatings to enhance ultraviolet response. Detectors based on microchannel plate (MCP) have been used extensively for a wide variety of NASA mission and continue to be the standard to beat. Two particularly promising detector technologies are (1) EBCCDs which offer an immediate factor of 3 - 4 improvement in sensitivity and (2) devices made of GaN or GaAlN which may eventually offer factors of 6 - 8 increased sensitivity, both compared to MCPs for wavelengths between 1200 to 3000 Angstroms. We present latest results and plans to expand our vacuum UV testing.
Cloning of a quantum measurement
Bisio, Alessandro; D'Ariano, Giacomo Mauro; Perinotti, Paolo; Sedlak, Michal [QUIT Group, Dipartimento di Fisica ''A. Volta'' and INFN, via Bassi 6, I-27100 Pavia (Italy); QUIT Group, Dipartimento di Fisica ''A. Volta'' via Bassi 6, I-27100 Pavia (Italy) and Institute of Physics, Slovak Academy of Sciences, Dubravska cesta 9, SK-845 11 Bratislava (Slovakia)
2011-10-15
We analyze quantum algorithms for cloning of a quantum measurement. Our aim is to mimic two uses of a device performing an unknown von Neumann measurement with a single use of the device. When the unknown device has to be used before the bipartite state to be measured is available we talk about 1{yields}2 learning of the measurement, otherwise the task is called 1{yields}2 cloning of a measurement. We perform the optimization for both learning and cloning for arbitrary dimension d of the Hilbert space. For 1{yields}2 cloning we also propose a simple quantum network that achieves the optimal fidelity. The optimal fidelity for 1{yields}2 learning just slightly outperforms the estimate and prepare strategy in which one first estimates the unknown measurement and depending on the result suitably prepares the duplicate.
Satoshi Watanabe; Norihide Yamada; Masakazu Nagashima; Yusuke Ueki; Chiharu Sasaki; Yoichi Yamada; Tsunemasa Taguchi; Kazuyuki Tadatomo; Hiroaki Okagawa; Hiromitsu Kudo
2003-01-01
The internal quantum efficiency (IQE) of highly-efficient near-UV light-emitting diodes, which shows an external quantum efficiency of 43% at 406 nm, has been measured by excitation power and temperature-dependent photoluminescence (PL). Assuming peak PL quantum efficiency at 8 K is 100%, peak IQE at 300 K was measured to be as high as 63%. At the injected carrier density, which
Efficient ML Decoding for Quantum Convolutional Codes
Peiyu Tan; Jing Li
2010-04-01
A novel decoding algorithm is developed for general quantum convolutional codes. Exploiting useful ideas from classical coding theory, the new decoder introduces two innovations that drastically reduce the decoding complexity compared to the existing quantum Viterbi decoder. First, the new decoder uses an efficient linear-circuits-based mechanism to map a syndrome to a candidate vector, whereas the existing algorithm relies on a non-trivial lookup table. Second, the new algorithm is cleverly engineered such that only one run of the Viterbi algorithm suffices to locate the most-likely error pattern, whereas the existing algorithm must run the Viterbi algorithm many times. The efficiency of the proposed algorithm allows us to simulate and present the first performance curve of a general quantum convolutional code.
Fast, efficient error reconciliation for quantum cryptography
W. T. Buttler; S. K. Lamoreaux; J. R. Torgerson; G. H. Nickel; C. H. Donahue; C. G. Peterson
2003-01-22
We describe a new error reconciliation protocol {\\it Winnow} based on the exchange of parity and Hamming's ``syndrome'' for $N-$bit subunits of a large data set. {\\it Winnow} was developed in the context of quantum key distribution and offers significant advantages and net higher efficiency compared to other widely used protocols within the quantum cryptography community. A detailed mathematical analysis of Winnow is presented in the context of practical implementations of quantum key distribution; in particular, the information overhead required for secure implementation is one of the most important criteria in the evaluation of a particular error reconciliation protocol. The increase in efficiency for Winnow is due largely to the reduction in authenticated public communication required for its implementation.
Quantum Behavior of Measurement Apparatus
Taoufik Amri
2010-05-31
We precise for the first time the quantum behavior of a measurement apparatus in the framework of the usual interpretation of quantum physics. We show how such a behavior can also be studied by the retrodiction of pre-measurement states corresponding to its responses. We translate in terms of these states some interesting properties of the behavior of an apparatus, such as the projectivity, the fidelity, the non-Gaussian character, or the non-classicality of measurements performed by this one. We also propose an experimental procedure allowing the tomography of these pre-measurement states for optical detectors. We illustrate the relevance of these new notions for measurements, by evaluating them for two detectors widely used in quantum optics: the avalanche photodiode and the homodyne detection.
QAM Adaptive Measurements Feedback Quantum Receiver Performance
Tian Chen; Ke Li; Yuan Zuo; Bing Zhu
2015-04-11
We theoretically study the quantum receivers with adaptive measurements feedback for discriminating quadrature amplitude modulation (QAM) coherent states in terms of average symbol error rate. For rectangular 16-QAM signal set, with different stages of adaptive measurements, the effects of realistic imperfection parameters including the sub-unity quantum efficiency and the dark counts of on-off detectors, as well as the transmittance of beam splitters and the mode mismatch factor between the signal and local oscillating fields on the symbol error rate are separately investigated through Monte Carlo simulations. Using photon-number-resolving detectors (PNRD) instead of on-off detectors, all the effects on the symbol error rate due to the above four imperfections can be suppressed in a certain degree. The finite resolution and PNR capability of PNRDs are also considered. We find that for currently available technology, the receiver shows a reasonable gain from the standard quantum limit (SQL) with moderate stages.
Coherence-enhanced efficiency of feedback-driven quantum engines
NASA Astrophysics Data System (ADS)
Brandner, Kay; Bauer, Michael; Schmid, Michael T.; Seifert, Udo
2015-06-01
A genuine feature of projective quantum measurements is that they inevitably alter the mean energy of the observed system if the measured quantity does not commute with the Hamiltonian. Compared to the classical case, Jacobs proved that this additional energetic cost leads to a stronger bound on the work extractable after a single measurement from a system initially in thermal equilibrium (2009 Phys. Rev. A 80 012322). Here, we extend this bound to a large class of feedback-driven quantum engines operating periodically and in finite time. The bound thus implies a natural definition for the efficiency of information to work conversion in such devices. For a simple model consisting of a laser-driven two-level system, we maximize the efficiency with respect to the observable whose measurement is used to control the feedback operations. We find that the optimal observable typically does not commute with the Hamiltonian and hence would not be available in a classical two level system. This result reveals that periodic feedback engines operating in the quantum realm can exploit quantum coherences to enhance efficiency.
High internal and external quantum efficiency InGaN/GaN solar cells
Matioli, Elison; Neufeld, C. J.; Iza, Michael; Cruz, S. C.; Al-Heji, Ali A.; Chen, Xu; Farrell, Rober M.; Keller, Stacia; DenBaars, Steven; Mishra, U. K.; Nakamura, Shuji; Speck, J. S.; Weisbuch, Claude
2011-01-01
High internal and external quantum efficiency GaN/InGaN solar cells are demonstrated. The internal quantum efficiency was assessed through the combination of absorption and external quantum efficiency measurements. The measured internal quantum efficiency, as high as 97%, revealed an efficient conversion of absorbed photons into electrons and holes and an efficient transport of these carriers outside the device. Improved light incoupling into the solar cells was achieved by texturing the surface. A peak external quantum efficiency of 72%, a fill factor of 79%, a short-circuit current density of 1.06?mA/cm{sup 2} , and an open circuit voltage of 1.89 V were achieved under 1 sun air-mass 1.5 global spectrumillumination conditions.
Peak external photocurrent quantum efficiency exceeding 100% via MEG in a quantum dot solar cell.
Semonin, Octavi E; Luther, Joseph M; Choi, Sukgeun; Chen, Hsiang-Yu; Gao, Jianbo; Nozik, Arthur J; Beard, Matthew C
2011-12-16
Multiple exciton generation (MEG) is a process that can occur in semiconductor nanocrystals, or quantum dots (QDs), whereby absorption of a photon bearing at least twice the bandgap energy produces two or more electron-hole pairs. Here, we report on photocurrent enhancement arising from MEG in lead selenide (PbSe) QD-based solar cells, as manifested by an external quantum efficiency (the spectrally resolved ratio of collected charge carriers to incident photons) that peaked at 114 ± 1% in the best device measured. The associated internal quantum efficiency (corrected for reflection and absorption losses) was 130%. We compare our results with transient absorption measurements of MEG in isolated PbSe QDs and find reasonable agreement. Our findings demonstrate that MEG charge carriers can be collected in suitably designed QD solar cells, providing ample incentive to better understand MEG within isolated and coupled QDs as a research path to enhancing the efficiency of solar light harvesting technologies. PMID:22174246
Quantum algorithm for universal implementation of projective measurement of energy
Shojun Nakayama; Akihito Soeda; Mio Murao
2015-04-14
A projective measurement of energy (PME) on a quantum system is a quantum measurement, determined by the Hamiltonian of the system. PME protocols exist when the Hamiltonian is given in advance. Unknown Hamiltonians can be identified by quantum tomography, but the time cost to achieve a given accuracy increases exponentially with the size of the quantum system. In this letter, we improve the time cost by adapting quantum phase estimation, an algorithm designed for computational problems, to measurements on physical systems. We present a PME protocol without quantum tomography for Hamiltonians whose dimension and energy scale are given but otherwise unknown. Our protocol implements a PME to arbitrary accuracy without any dimension dependence on its time cost. We also show that another computational quantum algorithm may be used for efficient estimation of the energy scale. These algorithms show that computational quantum algorithms have applications beyond their original context with suitable modifications.
On quantum subsystem measurement
Fedor Herbut
2013-02-09
It is assumed that an arbitrary composite bipartite pure state in which the two subsystems are entangled is given, and it is investigated how the entanglement transmits the influence of measurement on only one of the subsystems to the state of the opposite subsystem. It is shown that any exact subsystem measurement has the same influence as ideal measurement on the opposite subsystem. In particular, the distant effect of subsystem measurement of a twin observable, i. e., so-called 'distant measurement', is always ideal measurement on the distant subsystem no matter how intricate the direct exact measurement on the opposite subsystem is.
NASA Astrophysics Data System (ADS)
Sasaki, Tomotake; Hara, Shinji; Tsumura, Koji
In this paper, we analyze local state transition of controlled quantum systems under continuous quantum measurement, which is described by a matrix-valued nonlinear stochastic differential equation. To this end, we utilize the method of differential geometric analysis for systems with matrix-valued states developed in the first part of this series. The method provides us a direct and efficient way of analysis with a clear perspective. We study local state transition of the controlled quantum systems with imperfect detector efficiency which has not been studied enough in previous works. The controlled quantum system with perfect detector efficiency is also investigated as a special case. Sufficient conditions for the measurement operator and the control Hamiltonian are derived, under which the local state transition is quite limited. We also show that the conditions are satisfied in many typical situations. The results reveal fundamental nature of the controlled quantum systems under continuous quantum measurement.
Symmetric informationally complete quantum measurements
Joseph M. Renes; Robin Blume-Kohout; A. J. Scott; Carlton M. Caves
2004-01-01
We consider the existence in arbitrary finite dimensions d of a positive operator valued measure (POVM) comprised of d2 rank-one operators all of whose operator inner products are equal. Such a set is called a “symmetric, informationally complete” POVM (SIC–POVM) and is equivalent to a set of d2 equiangular lines in Cd. SIC–POVMs are relevant for quantum state tomography, quantum
Enhanced quantum efficiency bialkali photo multiplier tubes
NASA Astrophysics Data System (ADS)
Mirzoyan, Razmick; Goebel, Florian; Hose, Juergen; Hsu, Ching Cheng; Ninkovi?, Jelena; Paneque, David; Rudert, Agnes; Teshima, Masahiro
2007-03-01
Currently, the classical PMTs with semitransparent bialkali photo cathode show peak quantum efficiency (QE) of ˜25-27%. Although the above-mentioned peak QE was achieved already ˜40 years ago, nevertheless one cannot report any significant increase since then. A couple of years ago we started a development program with the main PMT manufacturers Photonis, Electron Tubes and Hamamatsu, aiming to boost-up the peak QE of the (1-2)? size bialkali PMTs. Today we want to report that our efforts were successful: all of the three above-mentioned companies succeeded to boost the peak QE of bialkali PMTs to the level of 30-35%. In this report, we want to show the QE measurements of different tubes and discuss the future prospects. For example, it shall be possible to use the diffuse-scattering matt lacquer coating technique in order to enhance further the QE. In our previous experience application of that coating provided ˜15% increase in QE for 1-1.5? hemispherical tubes.
Measuring quantumness: from theory to observability in interferometric setups
Leonardo Ferro; Paolo Facchi; Rosario Fazio; Fabrizio Illuminati; Giuseppe Marmo; Vlatko Vedral; Saverio Pascazio
2015-01-13
We investigate the notion of quantumness based on the non-commutativity of the algebra of observables and introduce a measure of quantumness based on the mutual incompatibility of quantum states. Since it relies on the full algebra of observables, our measure for composed systems is partition independent and witnesses the global quantum nature of a state. We show that such quantity can be experimentally measured with an interferometric setup and that, when an arbitrary bipartition is introduced, it detects the one-way quantum correlations restricted to one of the two subsystems. We finally show that, by combining only two projective measurements and carrying out the interference procedure, our measure becomes an efficient universal witness of quantum discord and non-classical correlations.
Factors determining the external quantum efficiency of AlGaInP microcavity light-emitting diodes
P. Royo; R. P. Stanley; M. Ilegems; K. Streubel; K. H. Gulden
2000-01-01
A detailed study of external quantum efficiency is reported for AlGaInP-based microcavity light-emitting diodes. By comparing numerical simulations with angle-resolved spectral measurements, the extraction efficiency could be accurately determined. This allowed precise calculation of the internal quantum efficiency. By using a simple model, we could identify the contributions of radiative and injection efficiencies to the internal quantum efficiency. We showed
Internal quantum efficiency analysis of solar cell by genetic algorithm
Xiong, Kanglin; Yang, Hui [Institute of Semiconductors, CAS, No. A35, Qing Hua East Road, Beijing 100083 (China); Suzhou Institute of Nano-tech and Nano-bionics, CAS, Ruoshui Road 398, Suzhou 215125 (China); Lu, Shulong; Zhou, Taofei; Wang, Rongxin; Qiu, Kai; Dong, Jianrong [Suzhou Institute of Nano-tech and Nano-bionics, CAS, Ruoshui Road 398, Suzhou 215125 (China); Jiang, Desheng [Institute of Semiconductors, CAS, No. A35, Qing Hua East Road, Beijing 100083 (China)
2010-11-15
To investigate factors limiting the performance of a GaAs solar cell, genetic algorithm is employed to fit the experimentally measured internal quantum efficiency (IQE) in the full spectra range. The device parameters such as diffusion lengths and surface recombination velocities are extracted. Electron beam induced current (EBIC) is performed in the base region of the cell with obtained diffusion length agreeing with the fit result. The advantage of genetic algorithm is illustrated. (author)
Efficient estimation of resonant coupling between quantum systems
Markku P. V. Stenberg; Yuval R. Sanders; Frank K. Wilhelm
2014-11-04
We present an efficient method for the characterization of two coupled discrete quantum systems, one of which can be controlled and measured. For two systems with transition frequencies $\\omega_q$, $\\omega_r$, and coupling strength $g$ we show how to obtain estimates of $g$ and $\\omega_r$ whose error decreases exponentially in the number of measurement shots rather than as a power law expected in simple approaches. Our algorithm can thereby identify $g$ and $\\omega_r$ simultaneously with high precision in a few hundred measurement shots. This is achieved by adapting measurement settings upon data as it is collected. We also introduce a method to eliminate erroneous estimates with small overhead. Our algorithm is robust against the presence of relaxation and typical noise. Our results are applicable to many candidate technologies for quantum computation, in particular, for the characterization of spurious two-level systems in superconducting qubits or stripline resonators.
Quantum Cloning using Protective Measurement
C. S. Sudheer Kumar
2015-04-23
Here we show that, in principle it is possible to clone (measure) a single arbitrary unknown quantum state of a spin-$\\frac{1}{2}$ particle (an electron) with arbitrary precision and with success probability tending to one, using protective measurement. We first transfer the information from spin to spatial degree of freedom (d.o.f) of system electron, then trap it in a double well potential, and finally measure it protectively using a probe electron (which donot get entangled with system electron, but still extracts expectation value of an observable from a single quantum system (system electron)) to obtain information about the unknown spin polarization. Nonorthogonal state discrimination being a subclass of cloning, part of the paper (till finding out $\\theta_{m}$, polar angle corresponding to the unknown spin polarization) is sufficient for discrimination.
Optimal Control of Quantum Measurement
Daniel J. Egger; Frank K. Wilhelm
2014-08-26
Pulses to steer the time evolution of quantum systems can be designed with optimal control theory. In most cases it is the coherent processes that can be controlled and one optimizes the time evolution towards a target unitary process, sometimes also in the presence of non-controllable incoherent processes. Here we show how to extend the GRAPE algorithm in the case where the incoherent processes are controllable and the target time evolution is a non-unitary quantum channel. We perform a gradient search on a fidelity measure based on Choi matrices. We illustrate our algorithm by optimizing a phase qubit measurement pulse. We show how this technique can lead to large measurement contrast close to 99%. We also show, within the validity of our model, that this algorithm can produce short 1.4 ns pulses with 98.2% contrast.
Quantum Confined Semiconductors for High Efficiency Photovoltaics
NASA Astrophysics Data System (ADS)
Beard, Matthew
2014-03-01
Semiconductor nanostructures, where at least one dimension is small enough to produce quantum confinement effects, provide new pathways for controlling energy flow and therefore have the potential to increase the efficiency of the primary photon-to-free energy conversion step. In this discussion, I will present the current status of research efforts towards utilizing the unique properties of colloidal quantum dots (NCs confined in three dimensions) in prototype solar cells and demonstrate that these unique systems have the potential to bypass the Shockley-Queisser single-junction limit for solar photon conversion. The solar cells are constructed using a low temperature solution based deposition of PbS or PbSe QDs as the absorber layer. Different chemical treatments of the QD layer are employed in order to obtain good electrical communication while maintaining the quantum-confined properties of the QDs. We have characterized the transport and carrier dynamics using a transient absorption, time-resolved THz, and temperature-dependent photoluminescence. I will discuss the interplay between carrier generation, recombination, and mobility within the QD layers. A unique aspect of our devices is that the QDs exhibit multiple exciton generation with an efficiency that is ~ 2 to 3 times greater than the parental bulk semiconductor.
Continuous Measurement Quantum State Tomography of Atomic Ensembles
Riofrío, Carlos A
2011-01-01
Quantum state tomography is a fundamental tool in quantum information processing. It allows us to estimate the state of a quantum system by measuring different observables on many identically prepared copies of the system. This is, in general, a very time-consuming task that requires a large number of measurements. There are, however, systems in which the data acquisition can be done more efficiently. In fact, an ensemble of quantum systems can be prepared and manipulated by external fields while being continuously and collectively probed, producing enough information to estimate its state. This provides a basis for continuous measurement quantum tomography. In this protocol, an ensemble of identically prepared systems is collectively probed and controlled in a time-dependent manner to create an informationally complete continuous measurement record. The measurement history is then inverted to determine the state at the initial time. We use two different estimation methods: maximum likelihood and compressed s...
Deep ultraviolet emitting AlGaN quantum wells with high internal quantum efficiency
Deep ultraviolet emitting AlGaN quantum wells with high internal quantum efficiency A 2009 We report the development of Al0.7Ga0.3N/AlN quantum wells with high internal quantum efficiency. All samples had identical well and barrier thickness but the III/V flux ratio was varied during growth
Symmetrization, quantum images and measurement
Fariel Shafee
2005-07-11
We argue that symmetrization of an incoming microstate with similar states in a sea of microstates contained in a macroscopic detector can produce an effective image, which does not contradict the no-cloning theorem, and such a combinatorial set can then be used with first passage random walk interactions suggested in an earlier work to give the right quantum mechanical weight for measured eigenvalues.
An enhanced DEA Russell graph efficiency measure
Jesús T. Pastor; José L. Ruiz; Inmaculada Sirvent
1999-01-01
The measurement of productive efficiency is an issue of great interest. Since Farrell (Farrell, M.J., 1957. Journal of Royal Statistical Society, Series A 120, 253) implemented the first measure of technical efficiency, many researchers have developed new measures or have extended the already existing ones. The beginning of Data Envelopment Analysis (DEA) meant a new way of empirically measuring productive
99% External quantum efficiency from a GaAs heterostructure at 100 K
B. Imangholi; C. Wang; M. P. Hasselbeck; M. Sheik-Bahae; R. Epstein; S. Kurtz
2006-01-01
Record external quantum efficiency (99%) is obtained for a GaAs\\/InGaP heterostructure bonded to a dome lens at 100 K. This was measured using a differential luminescence thermometry technique with temperature resolution ~ 30 muK.
Evolution equation for geometric quantum correlation measures
NASA Astrophysics Data System (ADS)
Hu, Ming-Liang; Fan, Heng
2015-05-01
A simple relation is established for the evolution equation of quantum-information-processing protocols such as quantum teleportation, remote state preparation, Bell-inequality violation, and particularly the dynamics of geometric quantum correlation measures. This relation shows that when the system traverses the local quantum channel, various figures of merit of the quantum correlations for different protocols demonstrate a factorization decay behavior for dynamics. We identified the family of quantum states for different kinds of quantum channels under the action of which the relation holds. This relation simplifies the assessment of many quantum tasks.
Quantum efficiency of the photochemical cycle of bacteriorhodopsin
Govindjee, R.; Balashov, S. P.; Ebrey, T. G.
1990-01-01
Values in the literature for the quantum efficiency of the photochemical cycle of bacteriorhodopsin (bR) range from 0.25 to 0.79 and the sum of the quantum yields of the forward and back photoreactions [Formula: see text] has been proposed to be 1. In the present work, low intensity laser flashes (532 nm) and kinetic spectroscopy were used to determine the quantum efficiency of bR photoconversion, [UNK]bR, by measuring transient bleaching of bR at 610 nm in the millisecond time scale. Bovine rhodopsin (R) in 2% ammonyx LO was used as a photon counter. We find that the ratio of the quantum yields of bacteriorhodopsin photoconversion and bleaching of rhodopsin, [UNK]bR/[UNK]R, is 0.96 ± 0.04. Based on the quantum yield of the photobleaching of rhodopsin, 0.67, the quantum efficiency of bR photoconversion was determined to be 0.64 ± 0.04. The quantum yield of M formation was found to be 0.65 ± 0.06. From the transient bleaching of bR at 610 nm with a saturating laser flash (28 mJ/cm2) the maximum amount of bR cycling was estimated to be 47 ± 3%. From this value and the spectrum of K published in the literature, the ratio of the efficiencies of the forward and back light reactions, [UNK]1/[UNK]2, was estimated to be 0.67 ± 0.06 and so [UNK]2 ? 1 (0.94 ± 0.06). The sum of [UNK]1 + [UNK]2 ? 1.6. It was found that repeated high-intensity laser flashes (>20 mJ/cm2) irreversibly transformed bR into two stable photoproducts. One has its absorption maximum at 605 nm and the other has a well-resolved vibronic spectrum with maxima at 342, 359 (main peak), and 379 nm. The quantum yield of the formation of the photoproducts is ? 10-4. PMID:19431766
Machine Learning for Precise Quantum Measurement
NASA Astrophysics Data System (ADS)
Hentschel, Alexander; Sanders, Barry C.
2010-02-01
Adaptive feedback schemes are promising for quantum-enhanced measurements yet are complicated to design. Machine learning can autonomously generate algorithms in a classical setting. Here we adapt machine learning for quantum information and use our framework to generate autonomous adaptive feedback schemes for quantum measurement. In particular, our approach replaces guesswork in quantum measurement by a logical, fully automatic, programable routine. We show that our method yields schemes that outperform the best known adaptive scheme for interferometric phase estimation.
Machine Learning for Precise Quantum Measurement
Alexander Hentschel; Barry C. Sanders
2010-02-25
Adaptive feedback schemes are promising for quantum-enhanced measurements yet are complicated to design. Machine learning can autonomously generate algorithms in a classical setting. Here we adapt machine learning for quantum information and use our framework to generate autonomous adaptive feedback schemes for quantum measurement. In particular our approach replaces guesswork in quantum measurement by a logical, fully-automatic, programmable routine. We show that our method yields schemes that outperform the best known adaptive scheme for interferometric phase estimation.
Hardware-efficient quantum memory protection
NASA Astrophysics Data System (ADS)
Leghtas, Zaki; Kirchmair, Gerhard; Vlastakis, Brian; Schoelkopf, Robert; Devoret, Michel; Mirrahimi, Mazyar
2013-03-01
We propose a new method to autonomously correct for errors of a logical qubit induced by energy relaxation. This scheme encodes the logical qubit as a multi-component superposition of coherent states in a harmonic oscillator, more specifically a single cavity mode. The sequences of encoding, decoding and correction operations employ the non-linearity provided by a single physical qubit coupled to the cavity. We layout in detail how to implement these operations in a circuit QED architecture. This proposal directly addresses the task of building a hardware-efficient and technically realizable quantum memory. We propose a new method to autonomously correct for errors of a logical qubit induced by energy relaxation. This scheme encodes the logical qubit as a multi-component superposition of coherent states in a harmonic oscillator, more specifically a single cavity mode. The sequences of encoding, decoding and correction operations employ the non-linearity provided by a single physical qubit coupled to the cavity. We layout in detail how to implement these operations in a circuit QED architecture. This proposal directly addresses the task of building a hardware-efficient and technically realizable quantum memory. This work was partially supported by the French ``Agence Nationale de la Recherche'' under the project EPOQ2 number ANR-09-JCJC-0070 and the Army Research Office (ARO) under the project number ARO - W911NF-09-1-0514.
Continuous quantum measurement of a light-matter system
Zhao, R.; Jenkins, S. D.; Campbell, C. J.; Kennedy, T. A. B.; Kuzmich, A. [School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430 (United States); Matsukevich, D. N. [JQI and Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Chaneliere, T. [Laboratoire Aime Cotton, CNRS-UPR 3321, Batiment 505, Campus Universitaire, F-91405 Orsay Cedex (France)
2010-03-15
Continuous measurements on correlated quantum systems, in addition to providing information on the state vector of the system in question, induce evolution in the unmeasured degrees of freedom conditioned on the measurement outcome. However, experimentally accessing these nontrivial regimes requires high-efficiency measurements over time scales much longer than the temporal resolution of the measurement apparatus. We report the observation of such a continuous conditioned evolution in the state of a light-collective atomic excitation system undergoing photoelectric measurement.
Improving Students' Understanding of Quantum Measurement
Zhu Guangtian; Singh, Chandralekha [Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260 (United States)
2010-10-24
We describe the difficulties advanced undergraduate and graduate students have with quantum measurement. To reduce these difficulties, we have developed research-based learning tools such as the Quantum Interactive Learning Tutorial (QuILT) and peer instruction tools. A preliminary evaluation shows that these learning tools are effective in improving students' understanding of concepts related to quantum measurement.
Improving Students' Understanding of Quantum Measurement
NASA Astrophysics Data System (ADS)
Zhu, Guangtian; Singh, Chandralekha
2010-10-01
We describe the difficulties advanced undergraduate and graduate students have with quantum measurement. To reduce these difficulties, we have developed research-based learning tools such as the Quantum Interactive Learning Tutorial (QuILT) and peer instruction tools. A preliminary evaluation shows that these learning tools are effective in improving students' understanding of concepts related to quantum measurement.
GBES Antenna Efficiency Measurements Glen Langston
Groppi, Christopher
1 GBES Antenna Efficiency Measurements Glen Langston Draft -- 94 April 28 Overview This document describes a set of measurements and calculations of the OVLBI GBES antenna gain. The antenna efficiency was measured by observations of radio sources of known brightness and small angular size. The antenna
Absolute external luminescence quantum efficiency of GaAs\\/Al0.3Ga0.7As multiple quantum wells
T. Fleck; M. Schmidt; C. Klingshirn
2003-01-01
We use a spatially integrating sphere to measure the absolute external luminescence quantum efficiency of GaAs\\/Al0.3Ga0.7As multiple quantum well (MQW) structures with and without GaAs substrate. The substrate reduces the external quantum efficiency by a huge amount depending on structure design and absorption coefficients, thus making it impossible to obtain information about the internal efficiency of the structures with substrate.
Quantum theory of measurements as quantum decision theory
NASA Astrophysics Data System (ADS)
Yukalov, V. I.; Sornette, D.
2015-03-01
Theory of quantum measurements is often classified as decision theory. An event in decision theory corresponds to the measurement of an observable. This analogy looks clear for operationally testable simple events. However, the situation is essentially more complicated in the case of composite events. The most difficult point is the relation between decisions under uncertainty and measurements under uncertainty. We suggest a unified language for describing the processes of quantum decision making and quantum measurements. The notion of quantum measurements under uncertainty is introduced. We show that the correct mathematical foundation for the theory of measurements under uncertainty, as well as for quantum decision theory dealing with uncertain events, requires the use of positive operator-valued measure that is a generalization of projection-valued measure. The latter is appropriate for operationally testable events, while the former is necessary for characterizing operationally uncertain events. In both decision making and quantum measurements, one has to distinguish composite nonentangled events from composite entangled events. Quantum probability can be essentially different from classical probability only for entangled events. The necessary condition for the appearance of an interference term in the quantum probability is the occurrence of entangled prospects and the existence of an entangled strategic state of a decision maker or of an entangled statistical state of a measuring device.
Quantum efficiency of energy transfer in non-covalent carbon nanotube/porphyrin compounds
Paris-Sud XI, Université de
Quantum efficiency of energy transfer in non-covalent carbon nanotube/porphyrin compounds C) Abstract We report on the quantum yield of excitation energy transfer in non-covalently bound nan- otube/porphyrin of the donor (porphyrin) and ultrafast transient absorption measurements. The latter shows a tremendous
Benítez, Ricardo Betancourt; Ning, Ruola; Conover, David; Liu, Shaohua
2009-01-01
The physical performance of two Flat Panel Detectors has been evaluated. The first Flat Panel Detector is for Fluoroscopic applications, Varian PaxScan 2520, and the second is for Cone Beam Computer Tomography applications, Varian PaxScan 4030CB. First, the spectrum of the X-ray source was measured. Second, the linearity of the detectors was investigated by using an ionization chamber and the average ADU values of the detectors. Third, the temporal resolution was characterized by evaluating their image lag. Fourth, their spatial resolution was characterized by the pre-sampling Modulation Transfer Function. Fifth, the Normalized Noise Power Spectrum was calculated for various exposures levels. Finally, the Detective Quantum Efficiency was obtained as a function of spatial frequency and entrance exposure. The results illustrate that the physical performance in Detective Quantum Efficiency and Normalized Noise Power Spectrum of the Cone Beam Computer Tomography detector is superior to that of the fluoroscopic detector whereas the latter detector has a higher spatial resolution as demonstrated by larger values of its Modulation Transfer Function at large spatial frequencies. PMID:19923685
Irrigation Performance Measures: Efficiency and Uniformity
Charles M. Burt; Albert J. Clemmens; Theodor S. Strelkoff; Kenneth H. Solomon; Ronald D. Bliesner; Leland A. Hardy; Terry A. Howell; Dean E. Eisenhauer
1997-01-01
It is essential to standardize the definitions and approaches to quantifying various irrigation performance measures. The ASCE Task Committee on Defining Irrigation Efficiency and Uniformity provides a comprehensive examination of various performance indices such as irrigation efficiency, application efficiency, irrigation sagacity, distribution uniformity, and others. Consistency is provided among different irrigation methods and different scales. Clarification of common points of
Pulsed homodyne Gaussian quantum tomography with low detection efficiency
Martina Esposito; Fabio Benatti; Roberto Floreanini; Stefano Olivares; Francesco Randi; Kelvin Titimbo; Marco Pividori; Fabio Novelli; Federico Cilento; Fulvio Parmigiani; Daniele Fausti
2014-02-19
Pulsed homodyne quantum tomography usually requires a high detection efficiency limiting its applicability in quantum optics. Here, it is shown that the presence of low detection efficiency ($adaptive reconstruction of the Wigner function to pulsed homodyne detection. In particular, we prove, by both numerical and real experiments, that an effective discrimination of different Gaussian quantum states can be achieved. Our finding paves the way to a more extensive use of quantum tomographic methods, even in physical situations in which high detection efficiency is unattainable.
Quantum Efficiency of a Backilluminated CCD Imager: An Optical Approach
Quantum Efficiency of a Backilluminated CCD Imager: An Optical Approach D. E. Groom, a S. E for modeling the quantum efficiency (QE) of backilluminated CCD optical imagers for astronomy. Beyond itsaperture) system. Standard thinfilm calculations are extended by (a) considering the CCD itself as a thin film
Surface and bulk contribution to Cu(111) quantum efficiency
Pedersoli, Emanuele; Greaves, Corin Michael Ricardo; Wan, Weishi; Coleman-Smith, Christopher; Padmore, Howard A.; Pagliara, Stefania; Cartella, Andrea; Lamarca, Fabrizio; Ferrini, Gabriele; Galimberti, Gianluca; Montagnese, Matteo; dal Conte, Stefano; Parmigiani, Fulvio
2008-11-04
The quantum efficiency (QE) of Cu(111) is measured for different impinging light angles with photon energies just above the work function. We observe that the vectorial photoelectric effect, an enhancement of the QE due to illumination with light with an electric vector perpendicular to the sample surface, is stronger in the more surface sensitive regime. This can be explained by a contribution to photoemission due to the variation in the electromagnetic potential at the surface. The contributions of bulk and surface electrons can then be determined.
Deterministic and efficient quantum cryptography based on Bell's theorem
Chen Zengbing; Pan Jianwei [Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Physikalisches Institut, Universitaet Heidelberg, Philosophenweg 12, 69120 Heidelberg (Germany); Zhang Qiang; Bao Xiaohui [Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Schmiedmayer, Joerg [Physikalisches Institut, Universitaet Heidelberg, Philosophenweg 12, 69120 Heidelberg (Germany)
2006-05-15
We propose a double-entanglement-based quantum cryptography protocol that is both efficient and deterministic. The proposal uses photon pairs with entanglement both in polarization and in time degrees of freedom; each measurement in which both of the two communicating parties register a photon can establish one and only one perfect correlation, and thus deterministically create a key bit. Eavesdropping can be detected by violation of local realism. A variation of the protocol shows a higher security, similar to the six-state protocol, under individual attacks. Our scheme allows a robust implementation under the current technology.
Measurement analysis and quantum gravity
Albers, Mark; Kiefer, Claus; Reginatto, Marcel [Institut fuer Theoretische Physik, Universitaet zu Koeln, Zuelpicher Strasse 77, 50937 Koeln (Germany); Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig (Germany)
2008-09-15
We consider the question of whether consistency arguments based on measurement theory show that the gravitational field must be quantized. Motivated by the argument of Eppley and Hannah, we apply a DeWitt-type measurement analysis to a coupled system that consists of a gravitational wave interacting with a mass cube. We also review the arguments of Eppley and Hannah and of DeWitt, and investigate a second model in which a gravitational wave interacts with a quantized scalar field. We argue that one cannot conclude from the existing gedanken experiments that gravity has to be quantized. Despite the many physical arguments which speak in favor of a quantum theory of gravity, it appears that the justification for such a theory must be based on empirical tests and does not follow from logical arguments alone.
Fuzzy efficiency measures in data envelopment analysis
Chiang Kao; Shiang-Tai Liu
2000-01-01
The existing data envelopment analysis (DEA) models for measuring the relative efficiencies of a set of decision making units (DMUs) using various inputs to produce various outputs are limited to crisp data. To deal with imprecise data, the notion of fuzziness has been introduced. This paper develops a procedure to measure the efficiencies of DMUs with fuzzy observations. The basic
An Efficient User-Side Nulling Calibration for Quantum Annealing Computers
Randall R. Correll
2015-04-02
(Withdrawn) This work describes an efficient user-side method of calibrating and correcting quantum annealing computers. For quantum annealing computers based on the Ising model, the method measures the residual bias of the h and J coefficients. Once measured, these biases can then be nulled in subsequent runs for any problem of interest. This method also returns a temperature for each qubit based on the measured versus the expected qubit distributions computed from a Boltzmann distribution model.
Optically Measuring Force near the Standard Quantum Limit
Schreppler, Sydney; Brahms, Nathan; Botter, Thierry; Barrios, Maryrose; Stamper-Kurn, Dan M
2013-01-01
The Heisenberg uncertainty principle sets a lower bound on the sensitivity of continuous optical measurements of force. This bound, the standard quantum limit, can only be reached when a mechanical oscillator subjected to the force is unperturbed by its environment, and when measurement imprecision from photon shot-noise is balanced against disturbance from measurement backaction. We apply an external force to the center-of-mass motion of an ultracold atom cloud in a high-finesse optical cavity. The optomechanically transduced response clearly demonstrates the trade-off between measurement imprecision and back-action noise. We achieve a sensitivity that is consistent with theoretical predictions for the quantum limit given the atoms' slight residual thermal disturbance and the photodetection quantum efficiency, and is a factor of 4 above the absolute standard quantum limit.
Optically Measuring Force near the Standard Quantum Limit
Sydney Schreppler; Nicolas Spethmann; Nathan Brahms; Thierry Botter; Maryrose Barrios; Dan M. Stamper-Kurn
2013-12-17
The Heisenberg uncertainty principle sets a lower bound on the sensitivity of continuous optical measurements of force. This bound, the standard quantum limit, can only be reached when a mechanical oscillator subjected to the force is unperturbed by its environment, and when measurement imprecision from photon shot-noise is balanced against disturbance from measurement backaction. We apply an external force to the center-of-mass motion of an ultracold atom cloud in a high-finesse optical cavity. The optomechanically transduced response clearly demonstrates the trade-off between measurement imprecision and back-action noise. We achieve a sensitivity that is consistent with theoretical predictions for the quantum limit given the atoms' slight residual thermal disturbance and the photodetection quantum efficiency, and is a factor of 4 above the absolute standard quantum limit.
Minority-carrier lifetimes and internal quantum efficiency of surface-free GaAs
R. J. Nelson; R. G. Sobers
1978-01-01
Minority-carrier lifetimes, internal quantum efficiencies, and values of the radiative recombination coefficient B are determined from photoluminescence time-decay and external quantum efficiency data taken for LPE GaAs samples (germanium doped or undoped) in the doping range 1.9×1015?p0 ?1×1019 cm?3 at 300 °K. Measurements are made on isotype double heterostructure samples where the optically exicted GaAs layer is bounded by wider-band-gap
Influence of reflectivity on the external quantum efficiency of GaAs injection lasers
R. Ulbrich; M. Pilkuhn
1970-01-01
The differential external quantum efficiency ?extof Fabry-Perot-type GaAs injection lasers has been measured as a function of the mean reflectivityR. By evaporation of antireflective films,Rhas been varied between 0.25 and 0.06. The observed increase of ?extwith decreasingRis interpreted in terms of a simple model. Values for the optical losses ?, the gain factor ?, and the internal quantum efficiency at
Spectral quantum efficiencies of semiconductor photodiodes in the far ultraviolet region
T. Saito; K. Katori; M. Nishi; H. Onuki
1989-01-01
The spectral quantum efficiencies and reflectances of p-i-n-type Si photodiodes and a Schottky-type GaAsP photodiode were measured in the wavelength region between 105 to 300 nm. These results are compared with an optical model using complex refractive indices. The spectral relative external quantum efficiencies are well interpreted within the model by assuming that the production energy of an electron-hole pair,
Long wavelength characterization of internal quantum efficiency in LT--GaAs MSM photodiodes
J. D. Morse; R. P. Jr. Mariella
1991-01-01
Metal-Semiconductor-Metal (MSM) photodiodes fabricated from low temperature all grown GaAs by molecular beam epitaxy have been characterized for wavelengths extending out to 1.5Î¼m. External quantum efficiencies on the order of 0.5 % have been measured for subbandgap wavelengths, which translates to internal quantum efficiencies of 2--4 % for the interdigitated electrode structure with 1Î¼m finger spacing and width. Although the
Simulation of the external quantum efficiency for bilayer organic light-emitting diodes
Matthew A. Webster; James Auld; Simon J. Martin; Alison B. Walker
2004-01-01
Changes in the external quantum efficiency of bilayer organic light emitting devices with layer length have been measured for devices of configuration ITO\\\\TPD\\\\Alq\\\\Mg:Ag with the Alq length varying between 25-200nm. It has been independently concluded for similar devices that the thickness of the Alq layer can be optimised with regard to the external quantum efficiency. However, our simulations of the
Minority-carrier lifetimes and internal quantum efficiency of surface-free GaAs
R. J. Nelson; R. G. Sobers
1978-01-01
Minority-carrier lifetimes, internal quantum efficiencies, and values of the radiative recombination coefficient B are determined from photoluminescence time-decay and external quantum efficiency data taken for LPE GaAs samples (germanium doped or undoped) in the doping range 1.9×1015?p0 ?1×1019 cm-3 at 300 °K. Measurements are made on isotype double heterostructure samples where the optically exicted GaAs layer is bounded by wider-band-gap
Raymond Y. Chiao; Walter J. Fitelson; Achilles D. Speliotopoulos
2003-01-01
A minimal coupling rule for the coupling of the electron spin to curved\\u000aspacetime in general relativity suggests the possibility of a coupling between\\u000aelectromagnetic and gravitational radiation mediated by means of a quantum\\u000afluid. Thus quantum transducers between these two kinds of radiation fields\\u000amight exist. We report here on the first attempt at a Hertz-type experiment, in\\u000awhich
Most efficient quantum thermoelectric at finite power output.
Whitney, Robert S
2014-04-01
Machines are only Carnot efficient if they are reversible, but then their power output is vanishingly small. Here we ask, what is the maximum efficiency of an irreversible device with finite power output? We use a nonlinear scattering theory to answer this question for thermoelectric quantum systems, heat engines or refrigerators consisting of nanostructures or molecules that exhibit a Peltier effect. We find that quantum mechanics places an upper bound on both power output and on the efficiency at any finite power. The upper bound on efficiency equals Carnot efficiency at zero power output but decays with increasing power output. It is intrinsically quantum (wavelength dependent), unlike Carnot efficiency. This maximum efficiency occurs when the system lets through all particles in a certain energy window, but none at other energies. A physical implementation of this is discussed, as is the suppression of efficiency by a phonon heat flow. PMID:24745399
Most efficient quantum thermoelectric at finite power output
Robert S. Whitney
2014-03-13
Machines are only Carnot efficient if they are reversible, but then their power output is vanishingly small. Here we ask, what is the maximum efficiency of an irreversible device with finite power output? We use a nonlinear scattering theory to answer this question for thermoelectric quantum systems; heat engines or refrigerators consisting of nanostructures or molecules that exhibit a Peltier effect. We find that quantum mechanics places an upper bound on both power output, and on the efficiency at any finite power. The upper bound on efficiency equals Carnot efficiency at zero power output, but decays with increasing power output. It is intrinsically quantum (wavelength dependent), unlike Carnot efficiency. This maximum efficiency occurs when the system lets through all particles in a certain energy window, but none at other energies. A physical implementation of this is discussed, as is the suppression of efficiency by a phonon heat flow.
Most Efficient Quantum Thermoelectric at Finite Power Output
NASA Astrophysics Data System (ADS)
Whitney, Robert S.
2014-04-01
Machines are only Carnot efficient if they are reversible, but then their power output is vanishingly small. Here we ask, what is the maximum efficiency of an irreversible device with finite power output? We use a nonlinear scattering theory to answer this question for thermoelectric quantum systems, heat engines or refrigerators consisting of nanostructures or molecules that exhibit a Peltier effect. We find that quantum mechanics places an upper bound on both power output and on the efficiency at any finite power. The upper bound on efficiency equals Carnot efficiency at zero power output but decays with increasing power output. It is intrinsically quantum (wavelength dependent), unlike Carnot efficiency. This maximum efficiency occurs when the system lets through all particles in a certain energy window, but none at other energies. A physical implementation of this is discussed, as is the suppression of efficiency by a phonon heat flow.
Radiated microwave power transmission system efficiency measurements
NASA Technical Reports Server (NTRS)
Dickinson, R. M.; Brown, W. C.
1975-01-01
The measured and calculated results from determining the operating efficiencies of a laboratory version of a system for transporting electric power from one point to another via a wireless free space radiated microwave beam are reported. The system's overall end-to-end efficiency as well as intermediated conversion efficiencies were measured. The maximum achieved end-to-end dc-to-ac system efficiency was 54.18% with a probable error of + or - 0.94%. The dc-to-RF conversion efficiency was measured to be 68.87% + or - 1.0% and the RF-to-dc conversion efficiency was 78.67 + or - 1.1%. Under these conditions a dc power of 495.62 + or - 3.57 W was received with a free space transmitter antenna receiver antenna separation of 170.2 cm (67 in).
The Quantum Schur Transform: I. Efficient Qudit Circuits
Dave Bacon; Isaac L. Chuang; Aram W. Harrow
2005-12-30
We present an efficient family of quantum circuits for a fundamental primitive in quantum information theory, the Schur transform. The Schur transform on n d-dimensional quantum systems is a transform between a standard computational basis to a labelling related to the representation theory of the symmetric and unitary groups. If we desire to implement the Schur transform to an accuracy of epsilon, then our circuit construction uses a number of gates which is polynomial in n, d and log(1/epsilon). The important insights we use to perform this construction are the selection of the appropriate subgroup adapted basis and the Wigner-Eckart theorem. Our efficient circuit construction renders numerous protocols in quantum information theory computationally tractable and is an important new efficient quantum circuit family which goes significantly beyond the standard paradigm of the quantum Fourier transform.
Absolute external photoluminescence quantum efficiency of the 1s orthoexciton in Cu2O
M. Jörger; M. Schmidt; A. Jolk; R. Westphäling; C. Klingshirn
2001-01-01
The photoluminescence quantum efficiency of the yellow series 1s orthoexciton in Cu2O, including its phonon sidebands, was measured in an Ulbricht sphere. The obtained efficiency values between 10-4 and 10-6 are remarkably low. The nonmonotonous temperature dependence is analyzed.
Highly Efficient Quantum Key Distribution Immune to All Detector Attacks
Wen-Fei Cao; Yi-Zheng Zhen; Yu-Lin Zheng; Zeng-Bing Chen; Nai-Le Liu; Kai Chen; Jian-Wei Pan
2014-10-10
Vulnerabilities and imperfections of single-photon detectors have been shown to compromise security for quantum key distribution (QKD). The measurement-device-independent QKD (MDI-QKD) appears to be the most appealing solution to solve the issues. However, in practice one faces severe obstacles of having significantly lower key generation rate, difficult two photon interferences, and remote synchronization etc. In this letter, we propose a highly efficient and simple quantum key distribution scheme to remove all of these drawbacks. Our proposal can be implemented with only small modifications over the standard decoy BB84 system. Remarkably it enjoys both the advantages of high key generation rate (being almost two orders of magnitude higher than that based on conventional MDI-QKD) comparable to the normal decoy system, and security against any detector side channel attacks. Most favorably one can achieve complete Bell state measurements with resort to single photon interference, which reduces significantly experimental costs. Our approach enables utilization of high speed and efficient secure communication, particularly in real-life scenario of both metropolitan and intercity QKD network, with an attack free fashion from arbitrary detector side channels.
Efficient Quantum Transmission in Multiple-Source Networks
Luo, Ming-Xing; Xu, Gang; Chen, Xiu-Bo; Yang, Yi-Xian; Wang, Xiaojun
2014-01-01
A difficult problem in quantum network communications is how to efficiently transmit quantum information over large-scale networks with common channels. We propose a solution by developing a quantum encoding approach. Different quantum states are encoded into a coherent superposition state using quantum linear optics. The transmission congestion in the common channel may be avoided by transmitting the superposition state. For further decoding and continued transmission, special phase transformations are applied to incoming quantum states using phase shifters such that decoders can distinguish outgoing quantum states. These phase shifters may be precisely controlled using classical chaos synchronization via additional classical channels. Based on this design and the reduction of multiple-source network under the assumption of restricted maximum-flow, the optimal scheme is proposed for specially quantized multiple-source network. In comparison with previous schemes, our scheme can greatly increase the transmission efficiency. PMID:24691590
Efficient Quantum Dot-Quantum Dot and Quantum Dot-Dye Energy Transfer in Biotemplated Assemblies
Achermann, Marc; Jeong, Sohee; Balet, Laurent; Montano, Gabriel A.; Hollingsworth, Jennifer A.
2011-01-01
CdSe semiconductor nanocrystal quantum dots are assembled into nanowire-like arrays employing microtubule fibers as nanoscale molecular “scaffolds.” Spectrally and time-resolved energy-transfer analysis is used to assess the assembly of the nanoparticles into the hybrid inorganic-biomolecular structure. Specifically, we demonstrate that a comprehensive study of energy transfer between quantum-dot pairs on the biotemplate, and, alternatively, between quantum dots and molecular dyes embedded in the microtubule scaffold, comprises a powerful spectroscopic tool for evaluating the assembly process. In addition to revealing the extent to which assembly has occurred, the approach allows determination of particle-to-particle (and particle-to-dye) distances within the bio-mediated array. Significantly, the characterization is realized in situ, without need for further sample workup or risk of disturbing the solution-phase constructs. Furthermore, we find that the assemblies prepared in this way exhibit efficient quantum dot-quantum dot and quantum dot-dye energy transfer that affords faster energy-transfer rates compared to densely packed quantum dot arrays on planar substrates and small-molecule-mediated quantum dot/dye couples, respectively. PMID:21314178
Control of the quantum open system via quantum generalized measurement
Zhang Ming; Zhu Xiaocai; Li Xingwei; Hu Dewen [College of Mechatronics and Automation, National University of Defense Technology, Changsha, Hunan 410073 (China); Dai Hongyi [College of Science, National University of Defense Technology, Changsha, Hunan 410073 (China)
2006-03-15
For any specified pure state of quantum open system, we can construct a kind of quantum generalized measurement (QGM) that the state of the system after measurement will be deterministically collapsed into the specified pure state from any initial state. In other words, any pure state of quantum open system is reachable by QGM. Subsequently, whether the qubit is density matrix controllable is discussed in the case of pure dephasing. Our results reveal that combining QGM with coherent control will enhance the ability of controlling the quantum open system. Furthermore, it is found that the ability to perform QGM on the quantum open system, combined with the ability of coherence control and conditions of decoherence-free subspace, allows us to suppress quantum decoherence.
Measurement-based quantum computation
D. E. Browne; R. Raussendorf; M. Van den Nest; H. J. Briegel
2009-01-01
Quantum computation offers a promising new kind of information processing, where the non-classical features of quantum mechanics are harnessed and exploited. A number of models of quantum computation exist. These models have been shown to be formally equivalent, but their underlying elementary concepts and the requirements for their practical realization can differ significantly. A particularly exciting paradigm is that of
Quantum Reality and Measurement: A Quantum Logical Approach
Masanao Ozawa
2010-05-03
The recently established universal uncertainty principle revealed that two nowhere commuting observables can be measured simultaneously in some state, whereas they have no joint probability distribution in any state. Thus, one measuring apparatus can simultaneously measure two observables that have no simultaneous reality. In order to reconcile this discrepancy, an approach based on quantum logic is proposed to establish the relation between quantum reality and measurement. We provide a language speaking of values of observables independent of measurement based on quantum logic and we construct in this language the state-dependent notions of joint determinateness, value identity, and simultaneous measurability. This naturally provides a contextual interpretation, in which we can safely claim such a statement that one measuring apparatus measures one observable in one context and simultaneously it measures another nowhere commuting observable in another incompatible context.
P. Royo; R. P. Stanley; R. Houdré; M. Ilegems; M. Moser; R. Hövel; H. P. Schweizer; K. H. Gulden
1999-01-01
We present results on visible red top-emission microcavity light-emitting diodes grown by metal organic chemical vapor deposition. The emission characteristics dependence with respect to the detuning between the quantum well emission and the cavity mode was experimentally investigated. The detuning was varied during growth by 60 nm across a 2 in. wafer radius according to a parabolic and reproducible dependence
Quantum State Reconstruction via Continuous Measurement
Silberfarb, Andrew; Deutsch, Ivan H. [Department of Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico 87131 (United States); Jessen, Poul S. [Optical Sciences Center, University of Arizona, Tucson, Arizona 85721 (United States)
2005-07-15
We present a new procedure for quantum state reconstruction based on weak continuous measurement of an ensemble average. By applying controlled evolution to the initial state, new information is continually mapped onto the measured observable. A Bayesian filter is then used to update the state estimate in accordance with the measurement record. This generalizes the standard paradigm for quantum tomography based on strong, destructive measurements on separate ensembles. This approach to state estimation induces minimal perturbation of the measured system, giving information about observables whose evolution cannot be described classically in real time and opening the door to new types of quantum feedback control.
The Role of Measurement in Quantum Games
Ahmad Nawaz; A. H. Toor
2006-03-02
The game of Prisoner Dilemma is analyzed to study the role of measurement basis in quantum games. Four different types of payoffs for quantum games are identified on the basis of different combinations of initial state and measurement basis. A relation among these different payoffs is established.
Practical attacks on decoy-state quantum-key-distribution systems with detector efficiency mismatch
NASA Astrophysics Data System (ADS)
Fei, Yangyang; Gao, Ming; Wang, Weilong; Li, Chaobo; Ma, Zhi
2015-05-01
To the active-basis-choice decoy-state quantum-key-distribution systems with detector efficiency mismatch, we present a modified attack strategy, which is based on the faked states attack, with quantum nondemolition measurement ability to restress the threat of detector efficiency mismatch. Considering that perfect quantum nondemolition measurement ability doesn't exist in real life, we also propose a practical attack strategy using photon number resolving detectors. Theoretical analysis and numerical simulation results show that, without changing the channel, our attack strategies are serious threats to decoy-state quantum-key-distribution systems. The eavesdropper may get some information about the secret key without causing any alarms. Besides, the lower bound of detector efficiency mismatch to run our modified faked states attack successfully with perfect quantum nondemolition measurement ability is also given out, which provides the producers of quantum-key-distribution systems with a reference and can be treated as the approximate secure bound of detector efficiency mismatch in decoy-state quantum-key-distribution systems.
Improved quantum state transfer via quantum partially collapsing measurements
NASA Astrophysics Data System (ADS)
Man, Zhong-Xiao; Ba An, Nguyen; Xia, Yun-Jie
2014-10-01
In this work, we present a general scheme to improve quantum state transfer (QST) by taking advantage of quantum partially collapsing measurements. The scheme consists of a weak measurement performed at the initial time on the qubit encoding the state of concern and a subsequent quantum reversal measurement at a desired time on the destined qubit. We determine the strength qr of the post quantum reversal measurement as a function of the strength p of the prior weak measurement and the evolution time t so that near-perfect QST can be achieved by choosing p close enough to 1, with a finite success probability, regardless of the evolution time and the distance over which the QST takes place. The merit of our scheme is twofold: it not only improves QST, but also suppresses the energy dissipation, if any.
Matt Law; Matthew C. Beard; Sukgeun Choi; Joseph M. Luther; Mark C. Hanna; Arthur J. Nozik
2008-01-01
We determine the internal quantum efficiency (IQE) of the active layer of PbSe nanocrystal (NC) back-contact Schottky solar cells by combining external quantum efficiency (EQE) and total reflectance measurements with an optical model of the device stack. The model is parameterized with the complex index of refraction of each layer in the stack as calculated from ellipsometry data. Good agreement
Architectures for measurement-based quantum computation
NASA Astrophysics Data System (ADS)
Raussendorf, Robert
2014-03-01
As our experience so far shows, building a quantum computer is not going to be easy. There are fundamental difficulties to overcome, such as decoherence, and suitable technologies and materials need to be identified. In between those two extremes lies the challenge of quantum computer architecture. Shall or shall we not envision a quantum computer as a von-Neumann type device, with CPU here and memory there? How are the qubits supposed to be wired? How do realistic physical constraints such translation invariance, planarity or bounded degree of the qubit connectivity graph affect quantum computer architecture? I will discuss these questions from the angle of measurement-based quantum computation.
State reduction in quantum-counting quantum nondemolition measurements
Milburn, G.J.; Walls, D.F.
1984-07-01
We show how quantum-counting quantum nondemolition measurements may be made using standard demolition counting techniques (e.g., photoelectron counting) for two oscillators coupled via a four-wave-mixing interaction. The analysis reveals how the state of one oscillator is reduced to a number eigenstate during the irreversible demolition counting process occurring in another coupled oscillator.
Yu Zhi-Guo; Chen Peng; Yang Guo-Feng; Liu Bin; Xie Zi-Li; Xiu Xiang-Qian; Wu Zhen-Long; Xu Feng; Xu Zhou; Hua Xue-Mei; Han Ping; Shi Yi; Zhang Rong; Zheng You-Dou
2012-01-01
The influence of dry etching damage on the internal quantum efficiency of InGaN\\/GaN nanorod multiple quantum wells (MQWs) is studied. The samples were etched by inductively coupled plasma (ICP) etching via a self-assembled nickel nanomask, and examined by room-temperature photoluminescence measurement. The key parameters in the etching process are rf power and ICP power. The internal quantum efficiency of nanorod
Choquette, Kent
I) characteristic in excess of 400% external quantum efficiency from a monolithic dual resonator verticalIEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 18, NO. 9, MAY 1, 2006 1019 High Slope Efficiency Measured% quantum efficiency at 850 nm) near threshold from a single VCSEL with two electrically indepen- dent
Quantum nondemolition measurements. [by gravitational wave antennas
NASA Technical Reports Server (NTRS)
Braginskii, V. B.; Vorontsov, Iu. I.; Thorne, K. S.
1980-01-01
The article describes new electronic techniques required for quantum nondemolition measurements and the theory underlying them. Consideration is given to resonant-bar gravitational-wave antennas. Position measurements are discussed along with energy measurements and back-action-evading measurements. Thermal noise in oscillators and amplifiers is outlined. Prospects for stroboscopic measurements are emphasized.
Efficiency of quantum energy teleportation within spin-1/2 particle pairs
NASA Astrophysics Data System (ADS)
Frey, Michael R.
2015-03-01
A protocol for quantum energy teleportation (QET) is known for a so-called minimal spin-1/2 particle pair model. We extend this protocol to explicitly admit quantum weak measurements at its first stage. The extended protocol is applied beyond the minimal model to spin-1/2 particle pairs whose Hamiltonians are of a general class characterized by orthogonal pairs of entangled eigenstates. The energy transfer efficiency of the extended QET protocol is derived for this setting, and we show that weaker measurement yields greater efficiency. In the minimal particle pair model, for example, the efficiency can be doubled by this means. We also show that the QET protocol's transfer efficiency never exceeds 100 %, supporting the understanding that quantum energy teleportation is, indeed, an energy transfer protocol, rather than a protocol for remotely catalyzing local extraction of system energy already present.
Hussain Anwar; Sania Jevtic; Oliver Rudolph; Shashank Virmani
2014-12-17
An important problem in quantum information theory is to understand what makes entangled quantum systems non-local or hard to simulate efficiently. In this work we consider situations in which various parties have access to a restricted set of measurements on their particles, and construct entangled quantum states that are essentially classical for those measurements. In particular, given any set of local measurements on a large enough Hilbert space whose dual strictly contains (i.e. contains an open neighborhood of) a pure state, we use the PEPS formalism and ideas from generalized probabilistic theories to construct pure multiparty entangled states that have (a) local hidden variable models, and (b) can be efficiently simulated classically. We believe that the examples we construct cannot be efficiently classically simulated using previous techniques. Without the restriction on the measurements, the states that we construct are non-local, and in some proof-of-principle cases are universal for measurement based quantum computation.
An efficient and accurate quantum algorithm for the Dirac equation
Jeffrey Yepez
2002-10-11
An efficient quantum algorithm for the many-body three-dimensional Dirac equation is presented. Its computational complexity is dominantly linear in the number of qubits used to spatially resolve the 4-spinor wave function.
An efficient and accurate quantum algorithm for the Dirac equation
Jeffrey Yepez
2002-01-01
An efficient quantum algorithm for the many-body three-dimensional Dirac equation is presented. Its computational complexity is dominantly linear in the number of qubits used to spatially resolve the 4-spinor wave function.
Chapter 20: Data Center IT Efficiency Measures
Huang, R.; Masanet, E.
2015-01-01
Data centers use about 2% of the electricity in the United States; a typical data center has 100 to 200 times the energy use intensity of a commercial building. Data centers present tremendous opportunities--energy use can be reduced as much as 80% between inefficient and efficient data centers. Data center efficiency measures generally fall into the following categories: power infrastructure (e.g., more efficient uninterruptible power supplies, power distribution units); cooling (e.g., free cooling, variable-speed drives, temperature and humidity set points); airflow management (e.g., hot aisle/cold aisle, containment, grommets); and information technology efficiency (e.g., server virtualization, efficient servers, efficient data storage).
Efficient algorithm for optimizing adaptive quantum metrology processes.
Hentschel, Alexander; Sanders, Barry C
2011-12-01
Quantum-enhanced metrology infers an unknown quantity with accuracy beyond the standard quantum limit (SQL). Feedback-based metrological techniques are promising for beating the SQL but devising the feedback procedures is difficult and inefficient. Here we introduce an efficient self-learning swarm-intelligence algorithm for devising feedback-based quantum metrological procedures. Our algorithm can be trained with simulated or real-world trials and accommodates experimental imperfections, losses, and decoherence. PMID:22182087
Efficient Algorithm for Optimizing Adaptive Quantum Metrology Processes
NASA Astrophysics Data System (ADS)
Hentschel, Alexander; Sanders, Barry C.
2011-12-01
Quantum-enhanced metrology infers an unknown quantity with accuracy beyond the standard quantum limit (SQL). Feedback-based metrological techniques are promising for beating the SQL but devising the feedback procedures is difficult and inefficient. Here we introduce an efficient self-learning swarm-intelligence algorithm for devising feedback-based quantum metrological procedures. Our algorithm can be trained with simulated or real-world trials and accommodates experimental imperfections, losses, and decoherence.
GENERAL: Efficient Quantum Secure Direct Communication with Authentication
NASA Astrophysics Data System (ADS)
Liu, Wen-Jie; Chen, Han-Wu; Li, Zhi-Qiang; Liu, Zhi-Hao
2008-07-01
Two protocols of quantum direct communication with authentication [Phys. Rev. A 73 (2006) 042305] were recently indicated to be insecure against the authenticator Trent attacks [Phys. Rev. A 75 (2007) 026301]. We present two efficient protocols by using four Pauli operations, which are secure against inner Trent attacks as well as outer Eve attacks. Finally we generalize them to multiparty quantum direction communication.
Efficient Single Photon Detection by Quantum Dot Resonant Tunneling Diodes
J. C. Blakesley; P. See; A. J. Shields; B. E. Kardynal; P. Atkinson; I. Farrer; D. A. Ritchie
2005-01-01
We demonstrate that the resonant tunnel current through a double-barrier structure is sensitive to the capture of single photoexcited holes by an adjacent layer of quantum dots. This phenomenon could allow the detection of single photons with low dark count rates and high quantum efficiencies. The magnitude of the sensing current may be controlled via the thickness of the tunnel
Quantum Information Theory of Entanglement and Measurement
Nicolas J. Cerf; Chris Adami
1997-01-21
We present a quantum information theory that allows for a consistent description of entanglement. It parallels classical (Shannon) information theory but is based entirely on density matrices (rather than probability distributions) for the description of quantum ensembles. We find that quantum conditional entropies can be negative for entangled systems, which leads to a violation of well-known bounds in Shannon information theory. Such a unified information-theoretic description of classical correlation and quantum entanglement clarifies the link between them: the latter can be viewed as ``super-correlation'' which can induce classical correlation when considering a tripartite or larger system. Furthermore, negative entropy and the associated clarification of entanglement paves the way to a natural information-theoretic description of the measurement process. This model, while unitary and causal, implies the well-known probabilistic results of conventional quantum mechanics. It also results in a simple interpretation of the Kholevo theorem limiting the accessible information in a quantum measurement.
Improved quantum efficiency for electroluminescence in semiconducting polymers
Yong Cao; Ian D. Parker; Gang Yu; Chi Zhang; Alan J. Heeger
1999-01-01
Some conjugated polymers have luminescence properties that are potentially useful for applications such as light-emitting diodes, whose performance is ultimately limited by the maximum quantum efficiency theoretically attainable for electroluminescence, ,. If the lowest-energy excited states are strongly bound excitons (electron-hole pairs in singlet or triplet spin states), this theoretical upper limit is only 25% of the corresponding quantum efficiency
NASA Astrophysics Data System (ADS)
Cui, Ping
The thesis comprises two major themes of quantum statistical dynamics. One is the development of quantum dissipation theory (QDT). It covers the establishment of some basic relations of quantum statistical dynamics, the construction of several nonequivalent complete second-order formulations, and the development of exact QDT. Another is related to the applications of quantum statistical dynamics to a variety of research fields. In particular, unconventional but novel theories of the electron transfer in Debye solvents, quantum transport, and quantum measurement are developed on the basis of QDT formulations. The thesis is organized as follows. In Chapter 1, we present some background knowledge in relation to the aforementioned two themes of this thesis. The key quantity in QDT is the reduced density operator rho(t) ? trBrho T(t); i.e., the partial trace of the total system and bath composite rhoT(t) over the bath degrees of freedom. QDT governs the evolution of reduced density operator, where the effects of bath are treated in a quantum statistical manner. In principle, the reduced density operator contains all dynamics information of interest. However, the conventional quantum transport theory is formulated in terms of nonequilibrium Green's function. The newly emerging field of quantum measurement in relation to quantum information and quantum computing does exploit a sort of QDT formalism. Besides the background of the relevant theoretical development, some representative experiments on molecular nanojunctions are also briefly discussed. In chapter 2, we outline some basic (including new) relations that highlight several important issues on QDT. The content includes the background of nonequilibrium quantum statistical mechanics, the general description of the total composite Hamiltonian with stochastic system-bath interaction, a novel parameterization scheme for bath correlation functions, a newly developed exact theory of driven Brownian oscillator (DBO) systems, and its closely related solvation mode transformation of system-bath coupling Hamiltonian in general. The exact QDT of DBO systems is also used to clarify the validity of conventional QDT formulations that involve Markovian approximation. In Chapter 3, we develop three nonequivalent but all complete second-order QDT (CS-QDT) formulations. Two of them are of the conventional prescriptions in terms of time-local dissipation and memory kernel, respectively. The third one is called the correlated driving-dissipation equations of motion (CODDE). This novel CS-QDT combines the merits of the former two for its advantages in both the application and numerical implementation aspects. Also highlighted is the importance of correlated driving-dissipation effects on the dynamics of the reduced system. In Chapter 4, we construct an exact QDT formalism via the calculus on path integrals. The new theory aims at the efficient evaluation of non-Markovian dissipation beyond the weak system-bath interaction regime in the presence of time-dependent external field. By adopting exponential-like expansions for bath correlation function, hierarchical equations of motion formalism and continued fraction Liouville-space Green's function formalism are established. The latter will soon be used together with the Dyson equation technique for an efficient evaluation of non-perturbative reduced density matrix dynamics. The interplay between system-bath interaction strength, non-Markovian property, and the required level of hierarchy is also studied with the aid of simple spin-boson systems, together with the three proposed schemes to truncate the infinite hierarchy. In Chapter 5, we develop a nonperturbative theory of electron transfer (ET) in Debye solvents. The resulting exact and analytical rate expression is constructed on the basis of the aforementioned continued fraction Liouville-space Green's function formalism, together with the Dyson equation technique. Not only does it recover the celebrated Marcus' inversion and Kramers' turnover behaviors, the new theory also shows some disti
Quantum measurements of atoms using cavity QED
Dada, Adetunmise C.; Andersson, Erika [SUPA, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom); Jones, Martin L.; Kendon, Vivien M. [School of Physics and Astronomy, University of Leeds, Woodhouse Lane, Leeds LS2 9JT (United Kingdom); Everitt, Mark S. [School of Physics and Astronomy, University of Leeds, Woodhouse Lane, Leeds LS2 9JT (United Kingdom); National Institute of Informatics, 2-1-2 Hitotsubashi, Chiyoda ku, Tokyo 101-8430 (Japan)
2011-04-15
Generalized quantum measurements are an important extension of projective or von Neumann measurements in that they can be used to describe any measurement that can be implemented on a quantum system. We describe how to realize two nonstandard quantum measurements using cavity QED. The first measurement optimally and unambiguously distinguishes between two nonorthogonal quantum states. The second example is a measurement that demonstrates superadditive quantum coding gain. The experimental tools used are single-atom unitary operations effected by Ramsey pulses and two-atom Tavis-Cummings interactions. We show how the superadditive quantum coding gain is affected by errors in the field-ionization detection of atoms and that even with rather high levels of experimental imperfections, a reasonable amount of superadditivity can still be seen. To date, these types of measurements have been realized only on photons. It would be of great interest to have realizations using other physical systems. This is for fundamental reasons but also since quantum coding gain in general increases with code word length, and a realization using atoms could be more easily scaled than existing realizations using photons.
Non-Boolean probabilities and quantum measurement
Gerd Niestegge
2010-01-21
A non-Boolean extension of the classical probability model is proposed. The non-Boolean probabilities reproduce typical quantum phenomena. The proposed model is more general and more abstract, but easier to interpret, than the quantum mechanical Hilbert space formalism and exhibits a particular phenomenon (state-independent conditional probabilities) which may provide new opportunities for an understanding of the quantum measurement process. Examples of the proposed model are provided, using Jordan operator algebras.
Kim, T.; Liu, B.; Smith, R.; Athanasiou, M.; Gong, Y.; Wang, T., E-mail: t.wang@sheffield.ac.uk [Department of Electronic and Electrical Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom)
2014-04-21
A “coherent” nanocavity structure has been designed on two-dimensional well-ordered InGaN/GaN nanodisk arrays with an emission wavelength in the green spectral region, leading to a massive enhancement in resonance mode in the green spectra region. By means of a cost-effective nanosphere lithography technique, we have fabricated such a structure on an InGaN/GaN multiple quantum well epiwafer and have observed the “coherent” nanocavity effect, which leads to an enhanced spontaneous emission (SE) rate. The enhanced SE rate has been confirmed by time resolved photoluminescence measurements. Due to the coherent nanocavity effect, we have achieved a massive improvement in internal quantum efficiency with a factor of 88, compared with the as-grown sample, which could be significant to bridge the “green gap” in solid-state lighting.
WEAK MEASUREMENT IN QUANTUM MECHANICS ABRAHAM NEBEN
Rosner, Jonathan L.
WEAK MEASUREMENT IN QUANTUM MECHANICS ABRAHAM NEBEN PHYS 342 Final Project March 10, 2011 Contents of Postselection 4 4. Impossible Spin Measurements 5 5. Hardy's Paradox 5 6. Controversy over Weak Measurement 8 7 of a Measurement of a Component of the Spin of a Spin-1/2 Particle Can Turn Out to be 100." [1] The topic
A straightforward introduction to continuous quantum measurement
Kurt Jacobs; Daniel A. Steck
2006-01-01
We present a pedagogical treatment of the formalism of continuous quantum measurement. Our aim is to show the reader how the equations describing such measurements are derived and manipulated in a direct manner. We also give elementary background material for those new to measurement theory, and describe further various aspects of continuous measurements that should be helpful to those wanting
Chen, Shaoqiang; Zhu, Lin; Yoshita, Masahiro; Mochizuki, Toshimitsu; Kim, Changsu; Akiyama, Hidefumi; Imaizumi, Mitsuru; Kanemitsu, Yoshihiko
2015-01-01
World-wide studies on multi-junction (tandem) solar cells have led to record-breaking improvements in conversion efficiencies year after year. To obtain detailed and proper feedback for solar-cell design and fabrication, it is necessary to establish standard methods for diagnosing subcells in fabricated tandem devices. Here, we propose a potential standard method to quantify the detailed subcell properties of multi-junction solar cells based on absolute measurements of electroluminescence (EL) external quantum efficiency in addition to the conventional solar-cell external-quantum-efficiency measurements. We demonstrate that the absolute-EL-quantum-efficiency measurements provide I-V relations of individual subcells without the need for referencing measured I-V data, which is in stark contrast to previous works. Moreover, our measurements quantify the absolute rates of junction loss, non-radiative loss, radiative loss, and luminescence coupling in the subcells, which constitute the "balance sheets" of tandem solar cells. PMID:25592484
Chen, Shaoqiang; Zhu, Lin; Yoshita, Masahiro; Mochizuki, Toshimitsu; Kim, Changsu; Akiyama, Hidefumi; Imaizumi, Mitsuru; Kanemitsu, Yoshihiko
2015-01-01
World-wide studies on multi-junction (tandem) solar cells have led to record-breaking improvements in conversion efficiencies year after year. To obtain detailed and proper feedback for solar-cell design and fabrication, it is necessary to establish standard methods for diagnosing subcells in fabricated tandem devices. Here, we propose a potential standard method to quantify the detailed subcell properties of multi-junction solar cells based on absolute measurements of electroluminescence (EL) external quantum efficiency in addition to the conventional solar-cell external-quantum-efficiency measurements. We demonstrate that the absolute-EL-quantum-efficiency measurements provide I–V relations of individual subcells without the need for referencing measured I–V data, which is in stark contrast to previous works. Moreover, our measurements quantify the absolute rates of junction loss, non-radiative loss, radiative loss, and luminescence coupling in the subcells, which constitute the “balance sheets” of tandem solar cells. PMID:25592484
NASA Astrophysics Data System (ADS)
Chen, Shaoqiang; Zhu, Lin; Yoshita, Masahiro; Mochizuki, Toshimitsu; Kim, Changsu; Akiyama, Hidefumi; Imaizumi, Mitsuru; Kanemitsu, Yoshihiko
2015-01-01
World-wide studies on multi-junction (tandem) solar cells have led to record-breaking improvements in conversion efficiencies year after year. To obtain detailed and proper feedback for solar-cell design and fabrication, it is necessary to establish standard methods for diagnosing subcells in fabricated tandem devices. Here, we propose a potential standard method to quantify the detailed subcell properties of multi-junction solar cells based on absolute measurements of electroluminescence (EL) external quantum efficiency in addition to the conventional solar-cell external-quantum-efficiency measurements. We demonstrate that the absolute-EL-quantum-efficiency measurements provide I-V relations of individual subcells without the need for referencing measured I-V data, which is in stark contrast to previous works. Moreover, our measurements quantify the absolute rates of junction loss, non-radiative loss, radiative loss, and luminescence coupling in the subcells, which constitute the ``balance sheets'' of tandem solar cells.
G. M. D'Ariano; P. Perinotti; M. F. Sacchi
2005-07-12
Informationally complete measurements allow the estimation of expectation values of any operator on a quantum system, by changing only the data-processing of the measurement outcomes. In particular, an informationally complete measurement can be used to perform quantum tomography, namely to estimate the density matrix of the quantum state. The data-processing is generally nonunique, and can be optimized according to a given criterion. In this paper we provide the solution of the optimization problem which minimizes the variance in the estimation. We then consider informationally complete measurements performed over bipartite quantum systems focusing attention on universally covariant measurements, and compare their statistical efficiency when performed either locally or globally on the two systems. Among global measurements we consider the special case of Bell measurements, which allow to estimate the expectation of a restricted class of operators. We compare the variance in the three cases: local, Bell, and unrestricted global--and derive conditions for the operators to be estimated such that one type of measurement is more efficient than the other. In particular, we find that for factorized operators and Bell projectors the Bell measurement always performs better than the unrestricted global measurement, which in turn outperforms the local one. For estimation of the matrix elements of the density operator, the relative performances depend on the basis on which the state is represented, and on the matrix element being diagonal or off-diagonal, however, with the global unrestricted measurement generally performing better than the local one.
Quantum state estimation using weak measurements
Debmalya Das; Arvind
2015-05-22
We explore the possibility of using "weak measurements" without "weak value" for quantum state estimation. Since for weak measurements the disturbance caused during each measurement is small, we can rescue the state, unlike for the case of projective measurements. We use this property of weak measurements and design schemes for quantum state estimation for qubits and for Gaussian states. We show, via numerical simulations, that under certain circumstances, our method can outperform the estimation by projective measurements both for qubits and for Gaussian states. It turns out that ensemble size plays an important role and the scheme based on recycling works better for small ensembles.
M. Caironi; T. Agostinelli; D. Natali; M. Sampietro; R. Cugola; M. Catellani; S. Luzzati
2007-01-01
The paper studies the role of electrons and holes mobility in determining the external quantum efficiency (EQE) in photodetectors based on a 1:1 in weight blend of poly(3-hexylthiophene) (P3HT) and C61-butyric acid methyl ester (PCBM). In order to fairly correlate the optoelectronic properties (efficiency and transient photocurrent) measured on photodetectors with the transport properties measured on field effect transistors, the
Maxwell's demon, Szilard's engine and quantum measurements
Zurek, W.H.
1984-01-01
We propose and analyze a quantum version of Szilard's one-molecule engine. In particular, we recover, in the quantum context, Szilard's conclusion concerning the free energy cost of measurements: ..delta..F greater than or equal to k/sub B/T1n2 per bit of information.
Efficiency of open quantum walk implementation of dissipative quantum computing algorithms
I. Sinayskiy; F. Petruccione
2014-01-26
An open quantum walk formalism for dissipative quantum computing is presented. The approach is illustrated with the examples of the Toffoli gate and the Quantum Fourier Transform for 3 and 4 qubits. It is shown that the algorithms based on the open quantum walk formalism are more efficient than the canonical dissipative quantum computing approach. In particular, the open quantum walks can be designed to converge faster to the desired steady state and to increase the probability of detection of the outcome of the computation.
Continuous Measurement Quantum State Tomography of Atomic Ensembles
Carlos A. Riofrío
2011-11-23
Quantum state tomography is a fundamental tool in quantum information processing. It allows us to estimate the state of a quantum system by measuring different observables on many identically prepared copies of the system. This is, in general, a very time-consuming task that requires a large number of measurements. There are, however, systems in which the data acquisition can be done more efficiently. In fact, an ensemble of quantum systems can be prepared and manipulated by external fields while being continuously and collectively probed, producing enough information to estimate its state. This provides a basis for continuous measurement quantum tomography. In this protocol, an ensemble of identically prepared systems is collectively probed and controlled in a time-dependent manner to create an informationally complete continuous measurement record. The measurement history is then inverted to determine the state at the initial time. We use two different estimation methods: maximum likelihood and compressed sensing. The general formalism is applied to the case of reconstruction of the quantum state encoded in the magnetic sub-levels of a large-spin alkali atom, ${}^{133}$Cs. We apply this protocol to the case of reconstruction of states in the full 16-dimensional electronic-ground subspace ($F=3 \\oplus F=4$), controlled by microwaves and radio-frequency magnetic fields. We present an experimental demonstration of continuous measurement quantum tomography in an ensemble of cold cesium atoms with full control of its 16-dimensional Hilbert space. We show the exquisite level of control achieved in the lab and the excellent agreement between the theory discussed in this dissertation and the experimental results. This allows us to achieve fidelities >95% for low complexity quantum states, and >92% for arbitrary random states, which is a formidable accomplishment for a space of this size.
Quantum efficiency and temperature coefficients of GaInP\\/GaAs dual-junction solar cell
Lei Liu; NuoFu Chen; YiMing Bai; Ming Cui; Han Zhang; FuBao Gao; ZhiGang Yin; XingWang Zhang
2009-01-01
GaInP\\/GaAs dual-junction solar cell with a conversion efficiency of 25.2% has been fabricated using metalorganic chemical\\u000a vapor deposition (MOCVD) technique. Quantum efficiencies of the solar cell were measured within a temperature range from 25\\u000a to 160°C. The results indicate that the quantum efficiencies of the subcells increase slightly with the increasing temperature.\\u000a And red-shift phenomena of absorption limit for all
A space-efficient quantum computer simulator suitable for high-speed FPGA implementation
Michael P. Frank; Liviu Oniciuc; Uwe Meyer-Baese; Irinel Chiorescu
2009-10-08
Conventional vector-based simulators for quantum computers are quite limited in the size of the quantum circuits they can handle, due to the worst-case exponential growth of even sparse representations of the full quantum state vector as a function of the number of quantum operations applied. However, this exponential-space requirement can be avoided by using general space-time tradeoffs long known to complexity theorists, which can be appropriately optimized for this particular problem in a way that also illustrates some interesting reformulations of quantum mechanics. In this paper, we describe the design and empirical space-time complexity measurements of a working software prototype of a quantum computer simulator that avoids excessive space requirements. Due to its space-efficiency, this design is well-suited to embedding in single-chip environments, permitting especially fast execution that avoids access latencies to main memory. We plan to prototype our design on a standard FPGA development board.
Quantum computing measurement and intelligence
NASA Astrophysics Data System (ADS)
Ezziane, Zoheir
One of the grand challenges in the nanoscopic computing era is guarantees of robustness. Robust computing system design is confronted with quantum physical, probabilistic, and even biological phenomena, and guaranteeing high-reliability is much more difficult than ever before. Scaling devices down to the level of single electron operation will bring forth new challenges due to probabilistic effects and uncertainty in guaranteeing "zero-one" based computing. Minuscule devices imply billions of devices on a single chip, which may help mitigate the challenge of uncertainty by replication and redundancy. However, such device densities will create a design and validation nightmare with the sheer scale. The questions that confront computer engineers regarding the current status of nanocomputing material and the reliability of systems built from such minuscule devices are difficult to articulate and answer. This article illustrates and discusses two types of quantum algorithms as follows: (1) a simple quantum algorithm and (2) a quantum search algorithm. This article also presents a review of recent advances in quantum computing and intelligence and presents major achievements and obstacles for researchers in the near future.
On the theory of quantum measurement
NASA Technical Reports Server (NTRS)
Haus, Hermann A.; Kaertner, Franz X.
1994-01-01
Many so called paradoxes of quantum mechanics are clarified when the measurement equipment is treated as a quantized system. Every measurement involves nonlinear processes. Self consistent formulations of nonlinear quantum optics are relatively simple. Hence optical measurements, such as the quantum nondemolition (QND) measurement of photon number, are particularly well suited for such a treatment. It shows that the so called 'collapse of the wave function' is not needed for the interpretation of the measurement process. Coherence of the density matrix of the signal is progressively reduced with increasing accuracy of the photon number determination. If the QND measurement is incorporated into the double slit experiment, the contrast ratio of the fringes is found to decrease with increasing information on the photon number in one of the two paths.
Groverian entanglement measure of pure quantum states with arbitrary partitions
Shimoni, Yishai; Biham, Ofer [Racah Institute of Physics, The Hebrew University, Jerusalem 91904 (Israel)
2007-02-15
The Groverian entanglement measure of pure quantum states of n qubits is generalized to the case in which the qubits are divided into any p{<=}n parties. The entanglement between these parties is evaluated numerically using an efficient parametrization. To demonstrate this measure we apply it to symmetric states such as the Greenberg-Horne-Zeiliner state and the W state. Interestingly, this measure is equivalent to an entanglement measure introduced earlier [H. Barnum and N. Linden, J. Phys. A 34, 6787 (2001)], using different considerations.
Groverian entanglement measure of pure quantum states with arbitrary partitions
NASA Astrophysics Data System (ADS)
Shimoni, Yishai; Biham, Ofer
2007-02-01
The Groverian entanglement measure of pure quantum states of n qubits is generalized to the case in which the qubits are divided into any p?n parties. The entanglement between these parties is evaluated numerically using an efficient parametrization. To demonstrate this measure we apply it to symmetric states such as the Greenberg-Horne-Zeiliner state and the W state. Interestingly, this measure is equivalent to an entanglement measure introduced earlier [H. Barnum and N. Linden, J. Phys. A 34, 6787 (2001)], using different considerations.
Experimental measurement-device-independent verification of quantum steering
NASA Astrophysics Data System (ADS)
Kocsis, Sacha; Hall, Michael J. W.; Bennet, Adam J.; Saunders, Dylan J.; Pryde, Geoff J.
2015-01-01
Bell non-locality between distant quantum systems—that is, joint correlations which violate a Bell inequality—can be verified without trusting the measurement devices used, nor those performing the measurements. This leads to unconditionally secure protocols for quantum information tasks such as cryptographic key distribution. However, complete verification of Bell non-locality requires high detection efficiencies, and is not robust to typical transmission losses over long distances. In contrast, quantum or Einstein–Podolsky–Rosen steering, a weaker form of quantum correlation, can be verified for arbitrarily low detection efficiencies and high losses. The cost is that current steering-verification protocols require complete trust in one of the measurement devices and its operator, allowing only one-sided secure key distribution. Here we present measurement-device-independent steering protocols that remove this need for trust, even when Bell non-locality is not present. We experimentally demonstrate this principle for singlet states and states that do not violate a Bell inequality.
Measurement and Fundamental Processes in Quantum Mechanics
NASA Astrophysics Data System (ADS)
Jaeger, Gregg
2015-07-01
In the standard mathematical formulation of quantum mechanics, measurement is an additional, exceptional fundamental process rather than an often complex, but ordinary process which happens also to serve a particular epistemic function: during a measurement of one of its properties which is not already determined by a preceding measurement, a measured system, even if closed, is taken to change its state discontinuously rather than continuously as is usual. Many, including Bell, have been concerned about the fundamental role thus given to measurement in the foundation of the theory. Others, including the early Bohr and Schwinger, have suggested that quantum mechanics naturally incorporates the unavoidable uncontrollable disturbance of physical state that accompanies any local measurement without the need for an exceptional fundamental process or a special measurement theory. Disturbance is unanalyzable for Bohr, but for Schwinger it is due to physical interactions' being borne by fundamental particles having discrete properties and behavior which is beyond physical control. Here, Schwinger's approach is distinguished from more well known treatments of measurement, with the conclusion that, unlike most, it does not suffer under Bell's critique of quantum measurement. Finally, Schwinger's critique of measurement theory is explicated as a call for a deeper investigation of measurement processes that requires the use of a theory of quantum fields.
High-efficiency alignment-free quantum cryptography based on quantum interference
Qi Guo; Liu-Yong Cheng; Hong-Fu Wang; Shou Zhang
2014-11-04
We propose an alternative quantum cryptography protocol using the quantum interference effect. The efficiency of creating sifted key can reach 100\\% in principle, which is higher than previous protocols. Especially, compared with the typical quantum key distribution, the present scheme does not require the authorized parties to check their bases. Because the potential eavesdropper can only access part of the quantum system, the proposed scheme has natural practical security advantages. The scheme can be implemented with current technologies and opens promising possibilities for quantum cryptography.
Quantum efficiency of an InAs\\/GaSb type-II superlattice photodiode
Shin Mou; Jian Li; Shun Lien Chuang
2007-01-01
We present the experimentally measured and theoretically modeled quantum efficiency of an n-on-p InAs\\/GaSb superlattice photodiode with a cutoff wavelength of 7.5 microns. The model is based on an analytical photocurrent solution with all the parameters obtained by measurements. For instance, the optical absorption coefficient was obtained from transmission measurements and the transport parameters were obtained from electron beam induced
Efficient Quantum Circuits for Schur and Clebsch-Gordan Transforms
Dave Bacon; Isaac Chuang; Aram Harrow
2004-08-05
The Schur basis on n d-dimensional quantum systems is a generalization of the total angular momentum basis that is useful for exploiting symmetry under permutations or collective unitary rotations. We present efficient (size poly(n,d,log(1/\\epsilon)) for accuracy \\epsilon) quantum circuits for the Schur transform, which is the change of basis between the computational and the Schur bases. These circuits are based on efficient circuits for the Clebsch-Gordan transformation. We also present an efficient circuit for a limited version of the Schur transform in which one needs only to project onto different Schur subspaces. This second circuit is based on a generalization of phase estimation to any nonabelian finite group for which there exists a fast quantum Fourier transform.
Quantum efficiency enhancement in CsI/metal photocathodes
NASA Astrophysics Data System (ADS)
Kong, Lingmei; Joly, Alan G.; Droubay, Timothy C.; Hess, Wayne P.
2015-02-01
High quantum efficiency enhancement is found for hybrid metal-insulator photocathodes consisting of thin films of CsI deposited on Cu(1 0 0), Ag(1 0 0), Au(1 1 1) and Au films irradiated by 266 nm laser pulses. Low work functions (near or below 2 eV) are observed following ultraviolet laser activation. Work functions are reduced by roughly 3 eV from that of clean metal surfaces. We discuss various mechanisms of quantum efficiency enhancement for alkali halide/metal photocathode systems and conclude that the large change in work function, due to Cs accumulation of Cs metal at the metal-alkali halide interface, is the dominant mechanism for quantum efficiency enhancement.
Quantum Algorithm for Universal Implementation of the Projective Measurement of Energy
NASA Astrophysics Data System (ADS)
Nakayama, Shojun; Soeda, Akihito; Murao, Mio
2015-05-01
A projective measurement of energy (PME) on a quantum system is a quantum measurement determined by the Hamiltonian of the system. PME protocols exist when the Hamiltonian is given in advance. Unknown Hamiltonians can be identified by quantum tomography, but the time cost to achieve a given accuracy increases exponentially with the size of the quantum system. In this Letter, we improve the time cost by adapting quantum phase estimation, an algorithm designed for computational problems, to measurements on physical systems. We present a PME protocol without quantum tomography for Hamiltonians whose dimension and energy scale are given but which are otherwise unknown. Our protocol implements a PME to arbitrary accuracy without any dimension dependence on its time cost. We also show that another computational quantum algorithm may be used for efficient estimation of the energy scale. These algorithms show that computational quantum algorithms, with suitable modifications, have applications beyond their original context.
Quantum algorithm for universal implementation of the projective measurement of energy.
Nakayama, Shojun; Soeda, Akihito; Murao, Mio
2015-05-15
A projective measurement of energy (PME) on a quantum system is a quantum measurement determined by the Hamiltonian of the system. PME protocols exist when the Hamiltonian is given in advance. Unknown Hamiltonians can be identified by quantum tomography, but the time cost to achieve a given accuracy increases exponentially with the size of the quantum system. In this Letter, we improve the time cost by adapting quantum phase estimation, an algorithm designed for computational problems, to measurements on physical systems. We present a PME protocol without quantum tomography for Hamiltonians whose dimension and energy scale are given but which are otherwise unknown. Our protocol implements a PME to arbitrary accuracy without any dimension dependence on its time cost. We also show that another computational quantum algorithm may be used for efficient estimation of the energy scale. These algorithms show that computational quantum algorithms, with suitable modifications, have applications beyond their original context. PMID:26024155
Efficient Raman generation in a waveguide: A route to ultrafast quantum random number generation
NASA Astrophysics Data System (ADS)
England, D. G.; Bustard, P. J.; Moffatt, D. J.; Nunn, J.; Lausten, R.; Sussman, B. J.
2014-02-01
The inherent uncertainty in quantum mechanics offers a source of true randomness which can be used to produce unbreakable cryptographic keys. We discuss the development of a high-speed random number generator based on the quantum phase fluctuations in spontaneously initiated stimulated Raman scattering (SISRS). We utilize the tight confinement and long interaction length available in a Potassium Titanyl Phosphate waveguide to generate highly efficient SISRS using nanojoule pulse energies, reducing the high pump power requirements of the previous approaches. We measure the random phase of the Stokes output using a simple interferometric setup to yield quantum random numbers at 145 Mbps.
Efficient Raman generation in a waveguide: A route to ultrafast quantum random number generation
England, D. G.; Bustard, P. J.; Moffatt, D. J.; Nunn, J.; Lausten, R.; Sussman, B. J., E-mail: ben.sussman@nrc.ca [National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada)
2014-02-03
The inherent uncertainty in quantum mechanics offers a source of true randomness which can be used to produce unbreakable cryptographic keys. We discuss the development of a high-speed random number generator based on the quantum phase fluctuations in spontaneously initiated stimulated Raman scattering (SISRS). We utilize the tight confinement and long interaction length available in a Potassium Titanyl Phosphate waveguide to generate highly efficient SISRS using nanojoule pulse energies, reducing the high pump power requirements of the previous approaches. We measure the random phase of the Stokes output using a simple interferometric setup to yield quantum random numbers at 145 Mbps.
Fidelity Measures in Asymmetric Quantum Cloning
Alastair Kay
2014-07-18
Quantum Cloning is the quintessential no-go theorem of quantum mechanics -- possible in the classical world, but impossible to implement perfectly in the quantum world, and reflecting such fundamental properties of the quantum world that it is commonly used as a postulate in information theoretic explorations. Recent progress has enabled the derivation of optimal cloning results when an arbitrary single-qudit pure state is cloned to N imperfect copies, allowing arbitrary asymmetries in the cloning quality. However, this result was achieved using a specific measure of success, the single-copy fidelity. In this paper, we substantially extend the mathematical formalism in order to handle different quality measures by which collections of qubits are assessed.
Quantum efficiency of electron-beam pumped GaAs lasers
J. Lavine
1967-01-01
Measurements of differential external quantum efficiency as high as 66 percent have been observed at 77°K in an electron-beam pumped GaAs laser doped at2 times 10^{18}\\/cm3with Sn. Peak-power output of the order of 20 watts has been obtained at both 4.2° and 77°K.
Resource Efficient Gadgets for Compiling Adiabatic Quantum Optimization Problems
Ryan Babbush; Bryan O'Gorman; Alán Aspuru-Guzik
2013-07-30
We develop a resource efficient method by which the ground-state of an arbitrary k-local, optimization Hamiltonian can be encoded as the ground-state of a (k-1)-local optimization Hamiltonian. This result is important because adiabatic quantum algorithms are often most easily formulated using many-body interactions but experimentally available interactions are generally 2-body. In this context, the efficiency of a reduction gadget is measured by the number of ancilla qubits required as well as the amount of control precision needed to implement the resulting Hamiltonian. First, we optimize methods of applying these gadgets to obtain 2-local Hamiltonians using the least possible number of ancilla qubits. Next, we show a novel reduction gadget which minimizes control precision and a heuristic which uses this gadget to compile 3-local problems with a significant reduction in control precision. Finally, we present numerics which indicate a substantial decrease in the resources required to implement randomly generated, 3-body optimization Hamiltonians when compared to other methods in the literature.
Resource efficient gadgets for compiling adiabatic quantum optimization problems
NASA Astrophysics Data System (ADS)
Babbush, Ryan; O'Gorman, Bryan; Aspuru-Guzik, Alán
2013-11-01
We develop a resource efficient method by which the ground-state of an arbitrary k-local, optimization Hamiltonian can be encoded as the ground-state of a (k-1)-local optimization Hamiltonian. This result is important because adiabatic quantum algorithms are often most easily formulated using many-body interactions but experimentally available interactions are generally 2-body. In this context, the efficiency of a reduction gadget is measured by the number of ancilla qubits required as well as the amount of control precision needed to implement the resulting Hamiltonian. First, we optimize methods of applying these gadgets to obtain 2-local Hamiltonians using the least possible number of ancilla qubits. Next, we show a novel reduction gadget which minimizes control precision and a heuristic which uses this gadget to compile 3-local problems with a significant reduction in control precision. Finally, we present numerics which indicate a substantial decrease in the resources required to implement randomly generated, 3-body optimization Hamiltonians when compared to other methods in the literature.
Nonsymmetrized Correlations in Quantum Noninvasive Measurements
NASA Astrophysics Data System (ADS)
Bednorz, Adam; Bruder, Christoph; Reulet, Bertrand; Belzig, Wolfgang
2013-06-01
A long-standing problem in quantum mesoscopic physics is which operator order corresponds to noise expressions like ?I(-?)I(?)?, where I(?) is the measured current at frequency ?. Symmetrized order describes a classical measurement while nonsymmetrized order corresponds to a quantum detector, e.g., one sensitive to either emission or absorption of photons. We show that both order schemes can be embedded in quantum weak-measurement theory taking into account measurements with memory, characterized by a memory function which is independent of a particular experimental detection scheme. We discuss the resulting quasiprobabilities for different detector temperatures and how their negativity can be tested on the level of second-order correlation functions already. Experimentally, this negativity can be related to the squeezing of the many-body state of the transported electrons in an ac-driven tunnel junction.
Nonsymmetrized correlations in quantum noninvasive measurements.
Bednorz, Adam; Bruder, Christoph; Reulet, Bertrand; Belzig, Wolfgang
2013-06-21
A long-standing problem in quantum mesoscopic physics is which operator order corresponds to noise expressions like , where I(?) is the measured current at frequency ?. Symmetrized order describes a classical measurement while nonsymmetrized order corresponds to a quantum detector, e.g., one sensitive to either emission or absorption of photons. We show that both order schemes can be embedded in quantum weak-measurement theory taking into account measurements with memory, characterized by a memory function which is independent of a particular experimental detection scheme. We discuss the resulting quasiprobabilities for different detector temperatures and how their negativity can be tested on the level of second-order correlation functions already. Experimentally, this negativity can be related to the squeezing of the many-body state of the transported electrons in an ac-driven tunnel junction. PMID:23829718
An Evolutionary Formalism for Weak Quantum Measurements
Apoorva Patel; Parveen Kumar
2014-12-03
Unitary evolution and projective measurement are fundamental axioms of quantum mechanics. Even though projective measurement yields one of the eigenstates of the measured operator as the outcome, there is no theory that predicts which eigenstate will be observed in which experimental run. There exists only an ensemble description, which predicts probabilities of various outcomes over many experimental runs. We propose a dynamical evolution equation for the projective collapse of the quantum state in individual experimental runs, which is consistent with the well-established framework of quantum mechanics. In case of gradual weak measurements, its predictions for ensemble evolution are different from those of the Born rule. It is an open question whether or not suitably designed experiments can observe this alternate evolution.
Quantum efficiency and fission rate in tetracene
Wu, Tony Chang-Chi
2013-01-01
Using singlet fission in a photovoltaic cell, the theoretical energy conversion efficiency limit is larger than the Shockley-Queisser limit due to two excitons produced with one incident photon. In a singlet fission material, ...
Direct measurement of general quantum states using strong measurement
NASA Astrophysics Data System (ADS)
Zou, Ping; Zhang, Zhi-Ming; Song, Wei
2015-05-01
The direct state measurement (DSM) based on the weak measurement has the advantage of simplicity, versatility, and directness. However, the weak measurement will introduce an unavoidable error in the reconstructed quantum state. We modify the DSM by replacing the weak coupling between the system and the pointer by a strong one, and present two procedures for measuring quantum states, one of which can give the wave function or the density matrix directly. We can also measure the Dirac distribution of a discrete system directly. Furthermore, we propose quantum circuits for realizing these procedures, and the main body of the circuits consists of Toffoli gates. By numerical simulation, we find that our scheme can eliminate the biased error effectively.
External radiative quantum efficiency of 96% from a GaAs \\/ GaInP heterostructure
H. Gauck; T. H. Gfroerer; M. J. Renn; E. A. Cornell; K. A. Bertness
1997-01-01
GaAs\\/GaInP double heterostructures are index matched with ZnSe hemispheres to increase the coupling of photoluminescence out of the device. We measure external quantum efficiencies as large as 96% at room temperature using a bolometric calibration technique. When the carriers are optically injected near the bandgap energy, the luminescence is blueshifted by up to 1.4 kT. In this case, external efficiencies
External radiative quantum efficiency of 96% from a GaAs \\/ GaInP heterostructure
H. Gauck; T. H. Gfroerer; M. J. Renn; E. A. Cornell; K. A. Bertness
1997-01-01
. ?GaAs\\/GaInP double heterostructures are index matched with ZnSe hemispheres to increase the coupling of photoluminescence\\u000a out of the device. We measure external quantum efficiencies as large as 96% at room temperature using a bolometric calibration\\u000a technique. When the carriers are optically injected near the bandgap energy, the luminescence is blueshifted by up to 1.4?kT.\\u000a In this case, external efficiencies exceeding
Blind topological measurement-based quantum computation
Tomoyuki Morimae; Keisuke Fujii
2011-01-01
We propose a protocol of blind topological measurement-based quantum computation. It is fault-tolerant, and the threshold is $4.3\\\\times10^{-3}$ for erroneous preparation of initial states, erroneous CZ gates, and erroneous local measurements. Our protocol is also fault-tolerant against the detectable qubit loss.
Blind topological measurement-based quantum computation
Morimae, Tomoyuki
2011-01-01
We propose a protocol of blind topological measurement-based quantum computation. It is fault-tolerant, and the threshold is $4.3\\times10^{-3}$ for erroneous preparation of initial states, erroneous CZ gates, and erroneous local measurements. Our protocol is also fault-tolerant against the detectable qubit loss.
Direct measurement of the quantum wavefunction by strong measurements
Giuseppe Vallone; Daniele Dequal
2015-04-24
Weak measurements are supposed to be essential for the so called direct measurement of the quantum wavefunction [Nature (London) 474, 188 (2011)]. Here we show that direct measurement of the wavefunction can be obtained by using measurements of arbitrary strength. In particular, in the case of strong (i.e. projective) measurements, we compared the precision and the accuracy of the two methods, by showing that strong measurements outperform weak measurements in both. We also give the exact expression of the reconstructed wavefunction obtained by the weak measurement approach, allowing to define the range of applicability of such method.
A highly efficient hybrid GaAs solar cell based on colloidal-quantum-dot-sensitization.
Han, Hau-Vei; Lin, Chien-Chung; Tsai, Yu-Lin; Chen, Hsin-Chu; Chen, Kuo-Ju; Yeh, Yun-Ling; Lin, Wen-Yi; Kuo, Hao-Chung; Yu, Peichen
2014-01-01
This paper presents a hybrid design, featuring a traditional GaAs-based solar cell combined with various colloidal quantum dots. This hybrid design effectively boosts photon harvesting at long wavelengths while enhancing the collection of photogenerated carriers in the ultraviolet region. The merits of using highly efficient semiconductor solar cells and colloidal quantum dots were seamlessly combined to increase overall power conversion efficiency. Several photovoltaic parameters, including short-circuit current density, open circuit voltage, and external quantum efficiency, were measured and analyzed to investigate the performance of this hybrid device. Offering antireflective features at long wavelengths and luminescent downshifting for high-energy photons, the quantum dots effectively enhanced overall power conversion efficiency by as high as 24.65% compared with traditional GaAs-based devices. The evolution of weighted reflectance as a function of the dilution factor of QDs was investigated. Further analysis of the quantum efficiency response showed that the luminescent downshifting effect can be as much as 6.6% of the entire enhancement of photogenerated current. PMID:25034623
A Highly Efficient Hybrid GaAs Solar Cell Based on Colloidal-Quantum-Dot-Sensitization
Han, Hau-Vei; Lin, Chien-Chung; Tsai, Yu-Lin; Chen, Hsin-Chu; Chen, Kuo-Ju; Yeh, Yun-Ling; Lin, Wen-Yi; Kuo, Hao-Chung; Yu, Peichen
2014-01-01
This paper presents a hybrid design, featuring a traditional GaAs-based solar cell combined with various colloidal quantum dots. This hybrid design effectively boosts photon harvesting at long wavelengths while enhancing the collection of photogenerated carriers in the ultraviolet region. The merits of using highly efficient semiconductor solar cells and colloidal quantum dots were seamlessly combined to increase overall power conversion efficiency. Several photovoltaic parameters, including short-circuit current density, open circuit voltage, and external quantum efficiency, were measured and analyzed to investigate the performance of this hybrid device. Offering antireflective features at long wavelengths and luminescent downshifting for high-energy photons, the quantum dots effectively enhanced overall power conversion efficiency by as high as 24.65% compared with traditional GaAs-based devices. The evolution of weighted reflectance as a function of the dilution factor of QDs was investigated. Further analysis of the quantum efficiency response showed that the luminescent downshifting effect can be as much as 6.6% of the entire enhancement of photogenerated current. PMID:25034623
Quantum Limits of Measurements and Uncertainty Principle
Masanao Ozawa
2015-05-19
In this paper, we show how the Robertson uncertainty relation gives certain intrinsic quantum limits of measurements in the most general and rigorous mathematical treatment. A general lower bound for the product of the root-mean-square measurement errors arising in joint measurements of noncommuting observables is established. We give a rigorous condition for holding of the standard quantum limit (SQL) for repeated measurements, and prove that if a measuring instrument has no larger root-mean-square preparational error than the root-mean-square measurement errors then it obeys the SQL. As shown previously, we can even construct many linear models of position measurement which circumvent this condition for the SQL.
Spectral quantum efficiencies of semiconductor photodiodes in the far ultraviolet region
NASA Astrophysics Data System (ADS)
Saito, T.; Katori, K.; Nishi, M.; Onuki, H.
1989-07-01
The spectral quantum efficiencies and reflectances of p-i-n-type Si photodiodes and a Schottky-type GaAsP photodiode were measured in the wavelength region between 105 to 300 nm. These results are compared with an optical model using complex refractive indices. The spectral relative external quantum efficiencies are well interpreted within the model by assuming that the production energy of an electron-hole pair, ?, is wavelength independent. It is suggested that surface recombination of minority carriers occurs in some devices. The internal quantum efficiency for the GaAsP photodiode is shown to be constant in the photon energy range below about 5.4 eV. The recombination loss and the ? value are separately estimated.
Christopher E. Valdivia; Simon Chow; Simon Fafard; Olivier Thériault; Mark Yandt; Jeffrey F. Wheeldon; Anthony J. SpringThorpe; Brian Rioux; David McMeekin; Denis Masson; B. Riel; V. Aimez; R. Are?s; J. Cook; T. J. Hall; F. Shepherd; K. Hinzer
2010-01-01
Large commercial-grade 1 cm2 quantum dot enhanced triple-junction AlGaInP\\/InGaAs\\/Ge solar cells were characterized using high-concentration flash and continuous-illumination solar simulators. Cyrium Technologies Incorporated (Cyrium™) routinely achieves >40% efficiency under ~500 suns flash illumination at 25°C using its QDEC™ product line based on this design. For this research project, Cyrium used its Application-Specific Concentrator Cell (ASCC) program to design and manufacture
"High Quantum Efficiency of Band-Edge Emission from ZnO Nanowires"
GARGAS, DANIEL; GAO, HANWEI; WANG, HUNGTA; PEIDONG, YANG
2010-12-01
External quantum efficiency (EQE) of photoluminescence as high as 20 percent from isolated ZnO nanowires were measured at room temperature. The EQE was found to be highly dependent on photoexcitation density, which underscores the importance of uniform optical excitation during the EQE measurement. An integrating sphere coupled to a microscopic imaging system was used in this work, which enabled the EQE measurement on isolated ZnO nanowires. The EQE values obtained here are significantly higher than those reported for ZnO materials in forms of bulk, thin films or powders. Additional insight on the radiative extraction factor of one-dimensional nanostructures was gained by measuring the internal quantum efficiency of individual nanowires. Such quantitative EQE measurements provide a sensitive, noninvasive method to characterize the optical properties of low-dimensional nanostructures and allow tuning of synthesis parameters for optimization of nanoscale materials.
High quantum efficiency of band-edge emission from ZnO nanowires.
Gargas, Daniel J; Gao, Hanwei; Wang, Hungta; Yang, Peidong
2011-09-14
External quantum efficiency (EQE) of photoluminescence as high as 20% from isolated ZnO nanowires were measured at room temperature. The EQE was found to be highly dependent on photoexcitation density, which underscores the importance of uniform optical excitation during the EQE measurement. An integrating sphere coupled to a microscopic imaging system was used in this work, which enabled the EQE measurement on isolated ZnO nanowires. The EQE values obtained here are significantly higher than those reported for ZnO materials in forms of bulk, thin films or powders. Additional insight on the radiative extraction factor of one-dimensional nanostructures was gained by measuring the internal quantum efficiency of individual nanowires. Such quantitative EQE measurements provide a sensitive, noninvasive method to characterize the optical properties of low-dimensional nanostructures and allow tuning of synthesis parameters for optimization of nanoscale materials. PMID:21859081
NASA Astrophysics Data System (ADS)
Niu, X. Y.; Huang, X. L.; Shang, Y. F.; Wang, X. Y.
2015-04-01
Superposition principle plays a crucial role in quantum mechanics, thus its effects on thermodynamics is an interesting topic. Here, the effects of superpositions of quantum states on isoenergetic cycle are studied. We find superposition can improve the heat engine efficiency and release the positive work condition in general case. In the finite time process, we find the efficiency at maximum power output in superposition case is lower than the nonsuperposition case. This efficiency depends on one index of the energy spectrum of the working substance. This result does not mean the superposition discourages the heat engine performance. For fixed efficiency or fixed power, the superposition improves the power or efficiency respectively. These results show how quantum mechanical properties affect the thermodynamical cycle.
Wigner Measures in Noncommutative Quantum Mechanics
C. Bastos; N. C. Dias; J. N. Prata
2009-07-25
We study the properties of quasi-distributions or Wigner measures in the context of noncommutative quantum mechanics. In particular, we obtain necessary and sufficient conditions for a phase-space function to be a noncommutative Wigner measure, for a Gaussian to be a noncommutative Wigner measure, and derive certain properties of the marginal distributions which are not shared by ordinary Wigner measures. Moreover, we derive the Robertson-Schr\\"odinger uncertainty principle. Finally, we show explicitly how the set of noncommutative Wigner measures relates to the sets of Liouville and (commutative) Wigner measures.
Schottky-quantum dot photovoltaics for efficient infrared power conversion
Keith W. Johnston; Andras G. Pattantyus-Abraham; Jason P. Clifford; Stefan H. Myrskog; Dean D. MacNeil; Larissa Levina; Edward H. Sargent
2008-01-01
Planar Schottky photovoltaic devices were prepared from solution-processed PbS nanocrystal quantum dot films with aluminum and indium tin oxide contacts. These devices exhibited up to 4.2% infrared power conversion efficiency, which is a threefold improvement over previous results. Solar power conversion efficiency reached 1.8%. The simple, optimized architecture allows for direct implementation in multijunction photovoltaic device configurations.
Magneto-Optic Modulator with Unit Quantum Efficiency
NASA Astrophysics Data System (ADS)
Williamson, Lewis A.; Chen, Yu-Hui; Longdell, Jevon J.
2014-11-01
We propose a device for the reversible and quiet conversion of microwave photons to optical sideband photons that can reach 100% quantum efficiency. The device is based on an erbium-doped crystal placed in both an optical and microwave resonator. We show that efficient conversion can be achieved so long as the product of the optical and microwave cooperativity factors can be made large. We argue that achieving this regime is feasible with current technology and we discuss a possible implementation.
Vries, Andreas de [FH Suedwestfalen, University of Applied Sciences, Haldener Strasse 182, D-58095 Hagen (Germany)
2007-03-15
Quantum feedback control is a technology that can be used to drive a quantum system into a predetermined eigenstate. In this article, sufficient conditions for the experiment parameters of a quantum feedback control process of a homodyne measurement are given to guarantee feedback control of a spin-1/2 quantum system in case of imperfect detection efficiency. For the case of pure states and perfect detection efficiency, time scales of feedback control processes are calculated.
Quantum Measurement of Broadband Nonclassical Light Fields
P. Grünwald; D. Vasylyev; J. Häggblad; W. Vogel
2014-11-14
Based on the measurement of quantum correlation functions, the quantum statistical properties of spectral measurements are studied for broadband radiation fields. The spectral filtering of light before its detection is compared with the direct detection followed by the spectral analysis of the recorded photocurrents. As an example, the squeezing spectra of the atomic resonance fluorescence are studied for both types of filtering procedures. The conditions for which the detection of the nonclassical signatures of the radiation is possible are analyzed. For the considered example, photocurrent filtering appears to be the superior option to detect nonclassicality, due to the vacuum-noise effects in the optical filtering.
Quantum measurement of a mesoscopic spin ensemble
Giedke, G. [Institut fuer Quantenelektronik, ETH Zuerich, Wolfgang-Pauli-Strasse 16, 8093 Zurich (Switzerland); Max-Planck-Institut fuer Quantenoptik, H.-Kopfermann-Str., 85748 Garching (Germany); Taylor, J. M.; Lukin, M. D. [Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States); D'Alessandro, D. [Department of Mathematics, Iowa State University, Ames, Iowa 50011 (United States); Imamoglu, A. [Institut fuer Quantenelektronik, ETH Zuerich, Wolfgang-Pauli-Strasse 16, 8093 Zurich (Switzerland)
2006-09-15
We describe a method for precise estimation of the polarization of a mesoscopic spin ensemble by using its coupling to a single two-level system. Our approach requires a minimal number of measurements on the two-level system for a given measurement precision. We consider the application of this method to the case of nuclear-spin ensemble defined by a single electron-charged quantum dot: we show that decreasing the electron spin dephasing due to nuclei and increasing the fidelity of nuclear-spin-based quantum memory could be within the reach of present day experiments.
Absolute Quantum Efficiency of Photofluorescence of Anthracene Crystals
G T Wright
1955-01-01
The fluorescence characteristics of organic crystals differ appreciably from those of the emitting molecules due to self-absorption of the molecular fluorescence. These differences are investigated and properties of the fluorescence of the crystal are related to the corresponding properties of the molecular fluorescence; the equations developed are made the basis of an experimental determination of molecular quantum efficiencies of photofluorescence
Direct determination of quantum efficiency of semiconducting films
B. W. Faughnan; J. J. Hanak
1986-01-01
This patent describes a method which is independent of built-in photovoltage for determining the quantum efficiency of a single layer semiconductor sample of essentially a single conductive type. The first step in the determination consists of forming electrical connections (Schottky barrier formed in one case) by means of two electrodes with the opposing surfaces of the semiconductor sample. An external
An efficient quantum algorithm for the Moebius function
Peter J. Love
2014-12-11
We give an efficient quantum algorithm for the Moebius function $\\mu(n)$ from the natural numbers to $\\{-1,0,1\\}$. The cost of the algorithm is asymptotically quadratic in $\\log n$ and does not require the computation of the prime factorization of $n$ as an intermediate step.
Quantum memory for light: large efficiency at telecom wavelength
Julián Dajczgewand; Jean-Louis Le Gouët; Anne Louchet-Chauvet; Thierry Chanelière
2013-12-03
We implement the ROSE protocol in an erbium doped solid, compatible with the telecom range. The ROSE scheme is an adaptation of the standard 2-pulse photon echo to make it suitable for a quantum memory. We observe an efficiency of 40% in a forward direction by using specific orientations of the light polarizations, magnetic field and crystal axes.
Strategies to Boost Efficiencies of Quantum Pralay K. Santra
Shyamasundar, R.K.
, The most abundant source of renewable energy is the sun, which can be converted directly to useful forms abundant source of renewable energy is the sun, which can be converted directly to useful forms of energy Efficiencies of Quantum Stanford University The most abundant source of renewable energy is the sun, which can
High quantum efficiency GaP avalanche photodiodes.
McIntosh, Dion; Zhou, Qiugui; Chen, Yaojia; Campbell, Joe C
2011-09-26
Gallium Phosphide (GaP) reach-through avalanche photodiodes (APDs) are reported. The APDs exhibited dark current less than a pico-ampere at unity gain. A quantum efficiency of 70% was achieved with a recessed window structure; this is almost two times higher than previous work. PMID:21996902
Uniformity compensation for high-quantum-efficiency focal plane arrays
Stephen R. Horman; Matthew W. Zurasky; James J. Talamonti; Kenneth C. Hepfer
1997-01-01
NSWCDD has developed a new nonuniformity correction (NUC) technique that has been demonstrated to significantly reduce both fixed pattern and temporal noise in sensors using high quantum efficiency (QE) infrared (IR) staring focal plane arrays (FPA). Sensors using this technique have been shown to have good response in every pixel, i.e., there are no dead or anomalously noisy pixels anywhere
An efficient quantum algorithm for colored Jones polynomials
S. Garnerone; A. Marzuoli; M. Rasetti
2006-06-20
We construct a quantum algorithm to approximate efficiently the colored Jones polynomial of the plat presentation of any oriented link L at a fixed root of unity q. Our construction is based on SU(2) Chern-Simons topological quantum field theory (and associated Wess-Zumino-Witten conformal field theory) and exploits the q-deformed spin network as computational background. As proved in (S. Garnerone, A. Marzuoli, M. Rasetti, quant-ph/0601169), the colored Jones polynomial can be evaluated in a number of elementary steps, bounded from above by a linear function of the number of crossings of the link, and polynomially bounded with respect to the number of link strands. Here we show that the Kaul unitary representation of colored oriented braids used there can be efficiently approximated on a standard quantum circuit.
The Evolution of Quantum Measuring Devices
NASA Astrophysics Data System (ADS)
Roth, Yehuda
2014-03-01
A quantum measuring device is introduced through a projective operator of any complete set of states that span the Hilbert space. Consequently, even a "bizarre" basis such as a basis of states composed of superpositions between location states, is legitimate despite its incomprehensible interpretation of a particle located in some places simultaneously. The collapse scenario that lies in the essence of any quantum measuring device, suggests that measurement is actually an interpretation process that translate reality into the predefined concepts determined by the particular selection of the basis of states. The very fact that there are bases that contradict "common sense" suggests that our brain by serving as a measuring and interpreting "device", selects only unique measuring processes. We suggest a procedure of nonlinear recursive maps that dominant an evolution of states toward few selected bases of states.
Quantum measurement theory and the uncertainty principle
Masanao Ozawa
2015-07-08
Heisenberg's uncertainty principle states that canonically conjugate observables can only be simultaneously measured under the constraint that the product of their mean errors should be no less than a limit set by Planck's constant. Heisenberg claimed that this is a straightforward mathematical consequence of basic postulates for quantum mechanics. However, Heisenberg with the subsequent completion by Kennard has long been credited only with a well-known constraint for the product of the standard deviations. Here we examine Heisenberg's original derivation of the uncertainty principle and show that Heisenberg actually derived the above mentioned constraint for simultaneous measurements but using an obsolete postulate for quantum mechanics. This assumption, known as the repeatability hypothesis, or its approximate measurement version, formulated explicitly by von Neumann and Schr\\"{o}dinger, was broadly accepted until the 1970s, whereas it was abandoned in the 1980s, when completely general quantum measurement theory was established. We also survey recent investigations to establish the universally valid reformulation of Heisenberg's uncertainty principle under this general theory of quantum measurement.
Barkhouse, D Aaron R; Pattantyus-Abraham, Andras G; Levina, Larissa; Sargent, Edward H
2008-11-25
The use of thiol-terminated ligands has recently been reported to enhance 10-fold the power conversion efficiency (PCE) of colloidal quantum dot (CQD) photovoltaic (PV) devices. We find herein that, in a representative amine-capped PbS colloidal quantum dot materials system, improved mobility following thiol treatment accounts for only a 1.4-fold increase in PCE. We then proceed to investigate the origins of the remainder of the quadrupling in PCE following thiol treatment. We find through measurements of photoluminescence quantum efficiency that exposure to thiols dramatically enhances photoluminescence in colloidal quantum dot films. The same molecules increase open-circuit voltage (V(oc)) from 0.28 to 0.43 V. Combined, these findings suggest that mid-gap states, which serve as recombination centers (lowering external quantum efficiency (EQE)) and metal-semiconductor junction interface states (lowering V(oc)), are substantially passivated using thiols. Through exposure to thiols, we improve EQE from 5 to 22% and, combined with the improvement in V(oc), improve power conversion efficiency to 2.6% under 76 mW/cm(2) at 1 microm wavelength. These findings are consistent with recent reports in photoconductive PbS CQD photodetectors that thiol exposure substantially removes deep (0.3 eV) electron traps, leaving only shallow (0.1 eV) traps. PMID:19206403
Quantum noise, bits and jumps: uncertainties, decoherence, measurements and filtering
V. P. Belavkin
2001-01-01
A brief review of the history and drama of the development of quantum theory is given starting from Plank's quantum hypothesis exactly a 100 years ago all the way up to the modern developments in the theory of quantum measurement. It is shown that before the rise of quantum mechanics 75 years ago, the quantum theory had appeared first in
High Quantum Efficiency OLED Lighting Systems
Shiang, Joseph
2011-09-30
The overall goal of the program was to apply improvements in light outcoupling technology to a practical large area plastic luminaire, and thus enable the product vision of an extremely thin form factor high efficiency large area light source. The target substrate was plastic and the baseline device was operating at 35 LPW at the start of the program. The target LPW of the program was a >2x improvement in the LPW efficacy and the overall amount of light to be delivered was relatively high 900 lumens. Despite the extremely difficult challenges associated with scaling up a wet solution process on plastic substrates, the program was able to make substantial progress. A small molecule wet solution process was successfully implemented on plastic substrates with almost no loss in efficiency in transitioning from the laboratory scale glass to large area plastic substrates. By transitioning to a small molecule based process, the LPW entitlement increased from 35 LPW to 60 LPW. A further 10% improvement in outcoupling efficiency was demonstrated via the use of a highly reflecting cathode, which reduced absorptive loss in the OLED device. The calculated potential improvement in some cases is even larger, ~30%, and thus there is considerable room for optimism in improving the net light coupling efficacy, provided absorptive loss mechanisms are eliminated. Further improvements are possible if scattering schemes such as the silver nanowire based hard coat structure are fully developed. The wet coating processes were successfully scaled to large area plastic substrate and resulted in the construction of a 900 lumens luminaire device.
A Straightforward Introduction to Continuous Quantum Measurement
Kurt Jacobs; Daniel A. Steck
2006-11-06
We present a pedagogical treatment of the formalism of continuous quantum measurement. Our aim is to show the reader how the equations describing such measurements are derived and manipulated in a direct manner. We also give elementary background material for those new to measurement theory, and describe further various aspects of continuous measurements that should be helpful to those wanting to use such measurements in applications. Specifically, we use the simple and direct approach of generalized measurements to derive the stochastic master equation describing the continuous measurements of observables, give a tutorial on stochastic calculus, treat multiple observers and inefficient detection, examine a general form of the measurement master equation, and show how the master equation leads to information gain and disturbance. To conclude, we give a detailed treatment of imaging the resonance fluorescence from a single atom as a concrete example of how a continuous position measurement arises in a physical system.
A Straightforward Introduction to Continuous Quantum Measurement
Jacobs, K; Jacobs, Kurt; Steck, Daniel A.
2006-01-01
We present a pedagogical treatment of the formalism of continuous quantum measurement. Our aim is to show the reader how the equations describing such measurements are derived and manipulated in a direct manner. We also give elementary background material for those new to measurement theory, and describe further various aspects of continuous measurements that should be helpful to those wanting to use such measurements in applications. Specifically, we use the simple and direct approach of generalized measurements to derive the stochastic master equation describing the continuous measurements of observables, give a tutorial on stochastic calculus, treat multiple observers and inefficient detection, examine a general form of the measurement master equation, and show how the master equation leads to information gain and disturbance. To conclude, we give a detailed treatment of imaging the resonance fluorescence from a single atom as a concrete example of how a continuous position measurement arises in a physical...
High-efficiency quantum steganography based on the tensor product of Bell states
NASA Astrophysics Data System (ADS)
Xu, ShuJiang; Chen, XiuBo; Niu, XinXin; Yang, YiXian
2013-09-01
In this paper, we first propose a hidden rule among the secure message, the initial tensor product of two Bell states and the final tensor product when respectively applying local unitary transformations to the first particle of the two initial Bell states, and then present a high-efficiency quantum steganography protocol under the control of the hidden rule. In the proposed quantum steganography scheme, a hidden channel is established to transfer a secret message within any quantum secure direct communication (QSDC) scheme that is based on 2-level quantum states and unitary transformations. The secret message hiding/unhiding process is linked with the QSDC process only by unitary transformations. To accurately describe the capacity of a steganography scheme, a quantitative measure, named embedding efficiency, is introduced in this paper. The performance analysis shows that the proposed steganography scheme achieves a high efficiency as well as a good imperceptibility. Moreover, it is shown that this scheme can resist all serious attacks including the intercept-resend attack, measurement-resend attack, auxiliary particle attack and even the Denial of Service attack. To improve the efficiency of the proposed scheme, the hidden rule is extended based on the tensor product of multiple Bell states.
NASA Astrophysics Data System (ADS)
Yun, Joosun; Shim, Jong-In; Hirayama, Hideki
2015-02-01
The efficiency droop in 280-nm AlGaN multiple-quantum-well (MQW) ultraviolet (UV) light-emitting diodes (LEDs) is analyzed using the carrier rate equation. It is shown that the internal quantum efficiency (?IQE), injection efficiency (?inj), light-extraction efficiency (?LEE), Shockley–Read–Hall recombination coefficient (A), and Auger coefficient (C) can be determined by the carrier rate equation using the theoretical radiative recombination coefficient (B), experimentally measured wavelength spectrum, and external quantum efficiency (?EQE). The results show that the carrier spillover from the MQWs to the p-AlGaN layer is the main cause of the efficiency droop.
Measurements in the Levy quantum walk
Romanelli, A. [Instituto de Fisica, Facultad de Ingenieria, Universidad de la Republica, Casilla de correo 30, Codigo Postal 11000, Montevideo (Uruguay)
2007-11-15
We study the quantum walk subjected to measurements with a Levy waiting-time distribution. We find that the system has a sub-ballistic behavior instead of a diffusive one. We obtain an analytical expression for the exponent of the power law of the variance as a function of the characteristic parameter of the Levy distribution.
Non-disturbance criteria of quantum measurements
Wu Zhaoqi; Zhang Shifang; Wu Junde
2010-09-14
Using the general sequential product proposed by Shen and Wu in [J. Phys. A: Math. Theor. 42, 345203, 2009], we derive three criteria for describing non-disturbance between quantum measurements that may be unsharp with such new sequential products, which generalizes Gudder's results.
Thermal entanglement and efficiency of the quantum Otto cycle for the su(1,1) Tavis-Cummings system
L. Chotorlishvili; Z. Toklikishvili; J. Berakdar
2011-03-04
The influence of the dynamical Stark shift on the thermal entanglement and the efficiency of the quantum Otto cycle is studied for the su(1,1) Tavis-Cummings system. It is shown that the degree of the thermal entanglement becomes larger as the dynamical Stark shift increases. In contrast, the efficiency of the Otto cycle is degraded with an increase of the values of dynamical Stark shift. Expressions for the efficiency coefficient are derived. Using those expressions we identify the maximal efficiency of the quantum Otto cycle from the experimentally measured values of the dynamical Stark shift
NASA Astrophysics Data System (ADS)
ten Kate, O. M.; de Jong, M.; Hintzen, H. T.; van der Kolk, E.
2013-08-01
Solar cells of which the efficiency is not limited by the Shockley-Queisser limit can be obtained by integrating a luminescent spectral conversion layer into the cell structure. We have calculated the maximum efficiency of state-of-the-art c-Si, pc-Si, a-Si, CdTe, GaAs, CIS, CIGS, CGS, GaSb, and Ge solar cells with and without an integrated spectral shifting, quantum cutting, or quantum tripling layer using their measured internal quantum efficiency (IQE) curves. Our detailed balance limit calculations not only take into account light in-coupling efficiency of the direct AM1.5 spectral irradiance but also wavelength dependence of the refractive index and the IQEs of the cells and the angular dependent light in-coupling of the indirect spectral irradiance. An ideal quantum cutting layer enhances all cell efficiencies ranging from a modest 2.9% for c-Si to much larger values of 4.0%, 7.7%, and 11.2% for CIGS, Ge, and GaSb, respectively. A quantum tripling layer also enhances cell efficiencies, but to a lesser extent. These efficiency enhancements are largest for small band gap cells like GaSb (7.5%) and Ge (3.8%). Combining a quantum tripling and a quantum cutting layer would enhance efficiency of these cells by a factor of two. Efficiency enhancement by a simple spectral shifting layer is limited to less than 1% in case the IQE is high for blue and UV lights. However, for CdTe and GaSb solar cells, efficiency enhancements are as high as 4.6% and 3.5%, respectively. A shifting layer based on available red LED phosphors like Sr2Si5N8:Eu will raise CdTe efficiency by 3.0%.
An efficient quantum secure direct communication scheme with authentication
NASA Astrophysics Data System (ADS)
Yang, Yu-Guang; Wen, Qiao-Yan; Zhu, Fu-Chen
2007-07-01
In this paper an efficient quantum secure direct communication (QSDC) scheme with authentication is presented, which is based on quantum entanglement and polarized single photons. The present protocol uses Einstein-Podolsky-Rosen (EPR) pairs and polarized single photons in batches. A particle of the EPR pairs is retained in the sender's station, and the other is transmitted forth and back between the sender and the receiver, similar to the ``ping-pong'' QSDC protocol. According to the shared information beforehand, these two kinds of quantum states are mixed and then transmitted via a quantum channel. The EPR pairs are used to transmit secret messages and the polarized single photons used for authentication and eavesdropping check. Consequently, because of the dual contributions of the polarized single photons, no classical information is needed. The intrinsic efficiency and total efficiency are both 1 in this scheme as almost all of the instances are useful and each EPR pair can be used to carry two bits of information.
Measuring the efficiency of sound production.
Prestwich, Kenneth N
2007-01-01
Sound production efficiency is a complex phenotypic trait that incorporates biochemical and mechanical events beginning with substrate oxidation and ending with the radiation of sound. Its accurate measurement is significant in understanding the mechanisms and energetics underlying acoustic signaling and sexual selection. I show that in the short-tailed cricket Anurogryllus arboreus Walker, acoustic performance is apparently the same in acoustic free fields and in the reverberant conditions of a respirometry chamber. I present three methods for simultaneous and nearly simultaneous determination of calling metabolic rate and acoustic power output. The new methods yielded metabolic rates 3%-6% lower than matched controls using traditional flow-through respirometry (mean=8.1 mW); however, none of theses differences were statistically significant. I also evaluate four methods for determining the efficiency of sound production. The means of an individual's efficiencies calculated using these methods vary between 0.50% and 0.60%, with no statistically significant differences between the methods. I conclude with a critical evaluation of these techniques. PMID:17160888
Measurement-device-independent quantum key distribution over 200 km.
Tang, Yan-Lin; Yin, Hua-Lei; Chen, Si-Jing; Liu, Yang; Zhang, Wei-Jun; Jiang, Xiao; Zhang, Lu; Wang, Jian; You, Li-Xing; Guan, Jian-Yu; Yang, Dong-Xu; Wang, Zhen; Liang, Hao; Zhang, Zhen; Zhou, Nan; Ma, Xiongfeng; Chen, Teng-Yun; Zhang, Qiang; Pan, Jian-Wei
2014-11-01
Measurement-device-independent quantum key distribution (MDIQKD) protocol is immune to all attacks on detection and guarantees the information-theoretical security even with imperfect single-photon detectors. Recently, several proof-of-principle demonstrations of MDIQKD have been achieved. Those experiments, although novel, are implemented through limited distance with a key rate less than 0.1??bit/s. Here, by developing a 75 MHz clock rate fully automatic and highly stable system and superconducting nanowire single-photon detectors with detection efficiencies of more than 40%, we extend the secure transmission distance of MDIQKD to 200 km and achieve a secure key rate 3 orders of magnitude higher. These results pave the way towards a quantum network with measurement-device-independent security. PMID:25415890
Measurement-Device-Independent Quantum Key Distribution over 200 km
NASA Astrophysics Data System (ADS)
Tang, Yan-Lin; Yin, Hua-Lei; Chen, Si-Jing; Liu, Yang; Zhang, Wei-Jun; Jiang, Xiao; Zhang, Lu; Wang, Jian; You, Li-Xing; Guan, Jian-Yu; Yang, Dong-Xu; Wang, Zhen; Liang, Hao; Zhang, Zhen; Zhou, Nan; Ma, Xiongfeng; Chen, Teng-Yun; Zhang, Qiang; Pan, Jian-Wei
2014-11-01
Measurement-device-independent quantum key distribution (MDIQKD) protocol is immune to all attacks on detection and guarantees the information-theoretical security even with imperfect single-photon detectors. Recently, several proof-of-principle demonstrations of MDIQKD have been achieved. Those experiments, although novel, are implemented through limited distance with a key rate less than 0.1 bit /s . Here, by developing a 75 MHz clock rate fully automatic and highly stable system and superconducting nanowire single-photon detectors with detection efficiencies of more than 40%, we extend the secure transmission distance of MDIQKD to 200 km and achieve a secure key rate 3 orders of magnitude higher. These results pave the way towards a quantum network with measurement-device-independent security.
Measurement-device-independent quantum key distribution over 200 km
Yan-Lin Tang; Hua-Lei Yin; Si-Jing Chen; Yang Liu; Wei-Jun Zhang; Xiao Jiang; Lu Zhang; Jian Wang; Li-Xing You; Jian-Yu Guan; Dong-Xu Yang; Zhen Wang; Hao Liang; Zhen Zhang; Nan Zhou; Xiongfeng Ma; Teng-Yun Chen; Qiang Zhang; Jian-Wei Pan
2014-07-30
Measurement-device-independent quantum key distribution (MDIQKD) protocol is immune to all attacks on detection and guarantees the information-theoretical security even with imperfect single photon detectors. Recently, several proof-of-principle demonstrations of MDIQKD have been achieved. Those experiments, although novel, are implemented through limited distance with a key rate less than 0.1 bps. Here, by developing a 75 MHz clock rate fully-automatic and highly-stable system, and superconducting nanowire single photon detectors with detection efficiencies more than 40%, we extend the secure transmission distance of MDIQKD to 200 km and achieve a secure key rate of three orders of magnitude higher. These results pave the way towards a quantum network with measurement-device-independent security.
An efficient edge-functionalization method to tune the photoluminescence of graphene quantum dots
NASA Astrophysics Data System (ADS)
Qi, Bao-Ping; Hu, Hui; Bao, Lei; Zhang, Zhi-Ling; Tang, Bo; Peng, Ying; Wang, Bao-Shan; Pang, Dai-Wen
2015-03-01
An efficient edge-functionalization strategy with high specificity was employed to study the effects of conjugated structures on photoluminescence (PL) properties of graphene quantum dots (GQDs). Both the experimental results and density functional theory (DFT)-based calculations suggested the mechanism for conjugated structures in GQDs to tune the band gap of GQDs.An efficient edge-functionalization strategy with high specificity was employed to study the effects of conjugated structures on photoluminescence (PL) properties of graphene quantum dots (GQDs). Both the experimental results and density functional theory (DFT)-based calculations suggested the mechanism for conjugated structures in GQDs to tune the band gap of GQDs. Electronic supplementary information (ESI) available: Experimental details for the preparation of GQDs and m-GQDs, related characterization, computational details and quantum yield measurements. See DOI: 10.1039/c5nr00842e
Rao, Balaji R.; Srikanth, R.; Chandrashekar, C. M.; Banerjee, Subhashish [Poornaprajna Institute of Scientific Research, Sadashivnagar, Bengaluru 560 080 (India); Center for Quantum Sciences, The Institute of Mathematical Sciences, Chennai 600113 (India); Indian Institute of Technology Rajasthan, Jodhpur 342011 (India)
2011-06-15
Noisy quantum walks are studied from the perspective of comparing their quantumness as defined by two popular measures, measurement-induced disturbance (MID) and quantum discord (QD). While the former has an operational definition, unlike the latter, it also tends to overestimate nonclassicality because of a lack of optimization over local measurements. Applied to quantum walks, we find that MID, while acting as a loose upper bound on QD, still tends to reflect correctly trends in the behavior of the latter. However, there are regimes where its behavior is not indicative of nonclassicality: in particular, we find an instance where MID increases with the application of noise, where we expect a reduction of quantumness.
Quantum Bayesian methods and subsequent measurements
Neri, Filippo [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
2005-12-15
The use of Bayes theorem in quantum mechanics is discussed. It is shown that the quantum Bayes theorem follows from the ordinary quantum measurement theory, when applied to density operators that represent our a priori knowledge of a system. The examples studied involve measurements on multiple copies of the same (unknown) state. The theorem is used to determine the unknown state by successive measurements on several of the copies of the state. An idealized information-theoretic description of propagating CW laser beams is treated in detail. It is shown how photon detections on part of the beams can be used to determine the phase of the rest of the beams. Also discussed, are the limitations on the accuracy of the phase determination that follow from the fact that it is accomplished by the detection of a finite number of photons. Explicit expressions are derived for the conditional probabilities of detecting photons at different locations, given the numbers of photons detected in the past. The quantitative predictions could be used, in principle, to test proposed quantum states of propagating laser beams.
Optimal control of a quantum measurement
NASA Astrophysics Data System (ADS)
Egger, D. J.; Wilhelm, F. K.
2014-11-01
Pulses to steer the time evolution of quantum systems can be designed with optimal control theory. In most cases it is the coherent processes that can be controlled and one optimizes the time evolution toward a target unitary process, sometimes also in the presence of noncontrollable incoherent processes. Here we show how to extend the gradient ascent pulse engineering (GRAPE) algorithm in the case where the incoherent processes are controllable and the target time evolution is a nonunitary quantum channel. We perform a gradient search on a fidelity measure based on Choi matrices. We illustrate our algorithm by optimizing a phase qubit measurement pulse. We show how this technique can lead to a large measurement contrast close to 99 % . We also show, within the validity of our model, that this algorithm can produce short 1.4 -ns pulses with 98.2 % contrast.
Efficiency of quantum controlled non-Markovian thermalization
Victor Mukherjee; Vittorio Giovannetti; Rosario Fazio; Susana F. Huelga; Tommaso Calarco; Simone Montangero
2015-06-24
We study optimal control strategies to optimize the relaxation rate towards the fixed point of a quantum system in the presence of a non-Markovian dissipative bath. Contrary to naive expectations that suggest that memory effects might be exploited to improve optimal control effectiveness, non-Markovian effects influence the optimal strategy in a non trivial way: we present a necessary condition to be satisfied so that the effectiveness of optimal control is enhanced by non-Markovianity subject to suitable unitary controls. For illustration, we specialize our findings for the case of the dynamics of single qubit amplitude damping channels. The optimal control strategy presented here can be used to implement optimal cooling processes in quantum technologies and may have implications in quantum thermodynamics when assessing the efficiency of thermal micro-machines.
Efficiency of quantum controlled non-Markovian thermalization
NASA Astrophysics Data System (ADS)
Mukherjee, V.; Giovannetti, V.; Fazio, R.; Huelga, S. F.; Calarco, T.; Montangero, S.
2015-06-01
We study optimal control strategies to optimize the relaxation rate towards the fixed point of a quantum system in the presence of a non-Markovian (NM) dissipative bath. Contrary to naive expectations that suggest that memory effects might be exploited to improve optimal control effectiveness, NM effects influence the optimal strategy in a non trivial way: we present a necessary condition to be satisfied so that the effectiveness of optimal control is enhanced by NM subject to suitable unitary controls. For illustration, we specialize our findings for the case of the dynamics of single qubit amplitude damping channels. The optimal control strategy presented here can be used to implement optimal cooling processes in quantum technologies and may have implications in quantum thermodynamics when assessing the efficiency of thermal micro-machines.
Quantum Theory as Efficient Representation of Probabilistic Information
Johann Summhammer
2007-01-25
Quantum experiments yield random data. We show that the most efficient way to store this empirical information by a finite number of bits is by means of the vector of square roots of observed relative frequencies. This vector has the unique property that its dispersion becomes invariant of the underlying probabilities, and therefore invariant of the physical parameters. This also extends to the complex square roots, and it remains true under a unitary transformation. This reveals quantum theory as a theory for making predictions which are as accurate as the input information, without any statistical loss. Our analysis also suggests that from the point of view of information a slightly more accurate theory than quantum theory should be possible.
Sites, James R.
19th European Photovoltaic Solar Energy Conference Pre-Print 4AV.1.45 QUANTUM EFFICIENCY OF CdTe@lamar.colostate.edu ABSTRACT: When the quantum efficiency of a CdS/CdTe solar cell is measured under forward voltage contact, (4) photoconductive effects in the CdS and CdTe, and (5) any secondary barrier in the primary
Resonant infrared detector with substantially unit quantum efficiency
NASA Technical Reports Server (NTRS)
Farhoomand, Jam (inventor); Mcmurray, Robert E., Jr. (inventor)
1994-01-01
A resonant infrared detector includes an infrared-active layer which has first and second parallel faces and which absorbs radiation of a given wavelength. The detector also includes a first tuned reflective layer, disposed opposite the first face of the infrared-active layer, which reflects a specific portion of the radiation incident thereon and allows a specific portion of the incident radiation at the given wavelength to reach the infrared-active layer. A second reflective layer, disposed opposite the second face of the infrared-active layer, reflects back into the infrared-active layer substantially all of the radiation at the given wavelength which passes through the infrared-active layer. The reflective layers have the effect of increasing the quantum efficiency of the infrared detector relative to the quantum efficiency of the infrared-active layer alone.
Enhanced quantum efficiency from hybrid cesium halide/copper photocathodes
NASA Astrophysics Data System (ADS)
Kong, Lingmei; Joly, Alan G.; Droubay, Timothy C.; Gong, Yu; Hess, Wayne P.
2014-04-01
The quantum efficiency (QE) of Cu is found to increase dramatically when coated by a CsI film and then irradiated by a UV laser. Over three orders of magnitude quantum efficiency enhancement at 266 nm is observed in CsI/Cu(100), indicating potential application in future photocathode devices. Upon laser irradiation, a large work function reduction to a value less than 2 eV is also observed, significantly greater than for similarly treated CsBr/Cu(100). The initial QE enhancement, prior to laser irradiation, is attributed to interface interaction and the intrinsic properties of the Cs halide film. Further QE enhancement following activation is attributed to formation of inter-band states and Cs metal accumulation at the interface induced by laser irradiation.
Thermoelectric corrections to quantum voltage measurement
NASA Astrophysics Data System (ADS)
Stafford, Charles; Bergfield, Justin
2014-03-01
The voltage measured by a floating probe of a nonequilibrium quantum system is shown to exhibit nontrivial thermoelectric corrections at finite temperature. The voltage probe is modelled as a scanning potentiometer/thermometer that is allowed to equilibrate with a quantum system via local tunnel coupling. Once equilibrated, the net electrical and heat currents flowing into the probe are zero. This generalizes Buettiker's theory of voltage measurement at zero temperature to finite-temperature systems. In a quantum conductor with electrical bias, it is shown that the probe temperature generally differs from ambient temperature due to Peltier cooling/heating within the system, and that the temperature difference can be sizeable for modest bias voltages. Conversely, if the probe is held at ambient temperature, its voltage is shifted from the equilibrated value, leading to a significant error in voltage measurement. However, if there is a large thermal coupling of the probe to the ambient environment, thermal coupling between the probe and system becomes unimportant, and the voltage measurement becomes similar to the process at zero temperature, with negligible thermoelectric corrections. Work supported by U.S. Department of Energy under Award No. DE-SC0006699.
Kahl, Oliver; Ferrari, Simone; Kovalyuk, Vadim; Goltsman, Gregory N; Korneev, Alexander; Pernice, Wolfram H P
2015-01-01
Superconducting nanowire single-photon detectors (SNSPDs) provide high efficiency for detecting individual photons while keeping dark counts and timing jitter minimal. Besides superior detection performance over a broad optical bandwidth, compatibility with an integrated optical platform is a crucial requirement for applications in emerging quantum photonic technologies. Here we present SNSPDs embedded in nanophotonic integrated circuits which achieve internal quantum efficiencies close to unity at 1550?nm wavelength. This allows for the SNSPDs to be operated at bias currents far below the critical current where unwanted dark count events reach milli-Hz levels while on-chip detection efficiencies above 70% are maintained. The measured dark count rates correspond to noise-equivalent powers in the 10(-19)?W/Hz(-1/2) range and the timing jitter is as low as 35?ps. Our detectors are fully scalable and interface directly with waveguide-based optical platforms. PMID:26061283
Kahl, Oliver; Ferrari, Simone; Kovalyuk, Vadim; Goltsman, Gregory N.; Korneev, Alexander; Pernice, Wolfram H. P.
2015-01-01
Superconducting nanowire single-photon detectors (SNSPDs) provide high efficiency for detecting individual photons while keeping dark counts and timing jitter minimal. Besides superior detection performance over a broad optical bandwidth, compatibility with an integrated optical platform is a crucial requirement for applications in emerging quantum photonic technologies. Here we present SNSPDs embedded in nanophotonic integrated circuits which achieve internal quantum efficiencies close to unity at 1550?nm wavelength. This allows for the SNSPDs to be operated at bias currents far below the critical current where unwanted dark count events reach milli-Hz levels while on-chip detection efficiencies above 70% are maintained. The measured dark count rates correspond to noise-equivalent powers in the 10?19?W/Hz?1/2 range and the timing jitter is as low as 35?ps. Our detectors are fully scalable and interface directly with waveguide-based optical platforms. PMID:26061283
Thermoelectric efficiency of three-terminal quantum thermal machines
Francesco Mazza; Riccardo Bosisio; Giuliano Benenti; Vittorio Giovannetti; Rosario Fazio; Fabio Taddei
2014-08-28
The efficiency of a thermal engine working in linear response regime in a multi-terminals configuration is discussed. For the generic three-terminal case, we provide a general definition of local and non-local transport coefficients: electrical and thermal conductances, and thermoelectric powers. Within the Onsager formalism, we derive analytical expressions for the efficiency at maximum power, which can be written in terms of generalized figures of merit. Also, using two examples, we investigate numerically how a third terminal could improve the performance of a quantum system, and under which conditions non-local thermoelectric effects can be observed.
Towards an efficient atomic frequency comb quantum memory
NASA Astrophysics Data System (ADS)
Amari, A.; Walther, A.; Sabooni, M.; Huang, M.; Kröll, S.; Afzelius, M.; Usmani, I.; Lauritzen, B.; Sangouard, N.; de Riedmatten, H.
2010-09-01
We present an efficient photon-echo experiment based on atomic frequency combs [Phys. Rev. A 79, 052329 (2009)]. Echoes containing an energy of up to 35% of that of the input pulse are observed in a Pr3+-doped Y2SiO5 crystal. This material allows for the precise spectral holeburning needed to make a sharp and highly absorbing comb structure. We compare our results with a simple theoretical model with satisfactory agreement. Our results show that atomic frequency combs has the potential for high-efficiency storage of single photons as required in future long-distance communication based on quantum repeaters.
Measuring polynomial invariants of multiparty quantum states
Leifer, M.S.; Linden, N.; Winter, A. [Department of Mathematics, University of Bristol, University Walk, Bristol, BS8 1TW (United Kingdom); Department of Computer Science, University of Bristol, Merchant Venturers Building, Woodland Road, Bristol, BS8 1UB (United Kingdom)
2004-05-01
We present networks for directly estimating the polynomial invariants of multiparty quantum states under local transformations. The structure of these networks is closely related to the structure of the invariants themselves and this lends a physical interpretation to these otherwise abstract mathematical quantities. Specifically, our networks estimate the invariants under local unitary (LU) transformations and under stochastic local operations and classical communication (SLOCC). Our networks can estimate the LU invariants for multiparty states, where each party can have a Hilbert space of arbitrary dimension and the SLOCC invariants for multiqubit states. We analyze the statistical efficiency of our networks compared to methods based on estimating the state coefficients and calculating the invariants.
Efficient method for the calculation of dissipative quantum transport in quantum cascade lasers.
Greck, Peter; Birner, Stefan; Huber, Bernhard; Vogl, Peter
2015-03-01
We present a novel and very efficient method for calculating quantum transport in quantum cascade lasers (QCLs). It follows the nonequilibrium Green's function (NEGF) framework but sidesteps the calculation of lesser self-energies by replacing them by a quasi-equilibrium expression. This method generalizes the phenomenological Büttiker probe model by taking into account individual scattering mechanisms. It is orders of magnitude more efficient than a fully self-consistent NEGF calculation for realistic devices. We apply this method to a new THz QCL design which works up to 250 K - according to our calculations. PMID:25836876
Quantum Hall Devices as efficient and fast THz photodetectors
Nikolai G. Kalugin; Christian Stellmach; Yuri B. Vasilyev; Rene Bonk; Alexander Hirsch; Günter Hein; Georg Nachtwei
2006-01-01
Efficient THz photodetectors on the basis of quantum Hall (QH) system have been developed during the recent years. Engineering of the device shape and selection of the parameters of operation allow to implement QH detectors with response times ranging from 10 ns to milliseconds. The spectral resolution of QH detectors, ranging between 1-2 meV at energies of 8-12 meV of
High External Quantum Efficiency of Electroluminescence from Photoanodized Porous Silicon
Kohsuke Nishimura; Yasuyuki Nagao; Noriaki Ikeda
1998-01-01
Porous silicon (PS) light emitting diodes (LEDs) were fabricated from p+n Si wafers by photoanodization. The maximum external quantum efficiency (etaext) of electroluminescence (EL) from PS-LED up to 0.8%, which is the highest ever reported for PS-LEDs with solid state contact, was achieved under pulsed operation with 1% duty in ambient air. However, we found that PS-LED with a high
Thomas Chung; Stephen D. Bartlett; Andrew C. Doherty
2009-04-17
In measurement-based quantum computation (MBQC), local adaptive measurements are performed on the quantum state of a lattice of qubits. Quantum gates are associated with a particular measurement sequence, and one way of viewing MBQC is that such a measurement sequence prepares a resource state suitable for `gate teleportation'. We demonstrate how to quantify the performance of quantum gates in MBQC by using correlation functions on the pre-measurement resource state.
Quantum fluctuation theorems and power measurements
B. Prasanna Venkatesh; Gentaro Watanabe; Peter Talkner
2015-03-11
Work in the paradigm of quantum fluctuation theorems of Crooks and Jarzynski, is determined by projective measurements of energy at the beginning and end of the force protocol. In analogy to classical systems, we consider an alternate definition of work given by the integral of the supplied power determined by integrating up the results of repeated measurements of the instantaneous power during the force protocol. We observe that such a definition of work, in spite of taking account of the process dependence, has different possible values and statistics from the work determined by the conventional two energy measurement approach (TEMA). In the limit of many projective measurements of power, the system's dynamics is frozen in the power measurement basis due to the quantum Zeno effect leading to statistics only trivially dependent on the force protocol except for the case when the instantaneous power operator commutes with the total Hamiltonian at all times. We also consider properties of the joint statistics of power-based definition of work and TEMA work in protocols where both values are determined. This allows us to quantify their correlations. Relaxing the projective measurement condition, weak continuous measurements of power are considered within the stochastic master equation formalism. Even in this scenario the power-based work statistics is in general not able to reproduce qualitative features of the TEMA work statistics.
Detection of VUV light at high quantum efficiency with large area avalanche photodiodes (LAAPDs)
NASA Astrophysics Data System (ADS)
Chandrasekharan, R.; Messina, M.; Rubbia, A.
2006-11-01
Large Area Avalanche Photodiodes (LAAPDs) were used for a series of systematic measurements of the scintillation light in Ar, Kr, and Xe gas. Absolute quantum efficiencies are derived. Values for Xe and Kr are consistent with those given by the manufacturer. For the first time we show that argon scintillation (128 nm) can be detected at a quantum efficiency above 40%. Low-pressure argon gas is shown to emit significant amounts of non-UV radiation. The average energy expenditure for the creation of non-UV photons in argon gas at this pressure is measured to be below 378 eV. Further, the principle of light collection by means of flexible Al+MgF2 reflectors has been shown to work for argon scintillation light.
Optical and quantum efficiency analysis of (Ag,Cu)(In,Ga)Se2 absorber layers
Boyle, Jonathan; Hanket, Gregory; Shafarman, William
2009-06-09
(Ag,Cu)(In,Ga)Se2 thin films have been deposited by elemental co-evaporation over a wide range of compositions and their optical properties characterized by transmission and reflection measurements and by relative shift analysis of quantum efficiency device measurements. The optical bandgaps were determined by performing linear fits of (?h?)2 vs. h?, and the quantum efficiency bandgaps were determined by relative shift analysis of device curves with fixed Ga/(In+Ga) composition, but varying Ag/(Cu+Ag) composition. The determined experimental optical bandgap ranges of the Ga/(In+Ga) = 0.31, 0.52, and 0.82 groups, with Ag/(Cu+Ag) ranging from 0 to 1, were 1.19-1.45 eV, 1.32-1.56 eV, and 1.52-1.76 eV, respectively. The optical bowing parameter of the different Ga/(In+Ga) groups was also determined.
On geometro-stochastic theory of measurement and quantum geometry
Eduard Prugovecki
1990-01-01
The reasons for the fundamental incompatibility of quantum mechanics with classical relativistic geometries are reviewed, whereupon the basic principles of a theory of measurement leading to quantum geometries are stated and discussed. The ensuing conceptualization of quantum processes is formulated as an integral part of an all-pervasive concept of quantum reality in which systems as well as apparatuses are treated
Aleksey Mikryukov; Alexander Kovalev; Anatoly A. Liberman; Sergey Moskaluk
2011-01-01
This paper, for the first time, suggests a method of determining internal quantum efficiency of an opaque p+nn+ photodetector and some of its characteristics based on a comparison between experimental measurements of photodetector's voltage-current characteristics and characteristics calculated with PC1D. For our research we chose a silicon photodetector Hamamatsu 1337. It was necessary that reflection coefficient of the front surface
GaN-based Single Mirror Light Emitting Diodes with high external quantum efficiency
Christoph M. Zellweger; Julien Dorsaz; Jean-François Carlin; Hans-Jörg Bühlmann; Ross P. Stanley; Marc Ilegems
2003-01-01
We present a study on the improvement of the external Quantum Efficiency (QE) of Gallium-Nitride-based Light Emitting Diodes (LEDs) by the use of the Single Mirror (SMLED) design [N.E.J. Hunt et al., Electron. Lett. 28, 2169 (1992)]. Three different substrate emitting LEDs are compared by measurements and simulations. An increase in the external QE by more than a factor of
High quantum efficiency diode photodetector based on ultrathin InGaAs-on-Si films
Mikhail N. Naydenkov; Alexander V. Kvit; Mikhail V. Yakimov
2000-01-01
We report on a new type of a high quantum efficiency diode photodetector based on ultra-thin low temperature-grown InGaAs-on-Si heteroepitaxial layer. The device was characterized optically and electrically using low- temperature photoluminescence, capacitance-voltage, current- voltage, DLTS and spectral responsivity measurements. We study characteristics of the photodetectors with various In contents in InGaAs film. Photosensitivity spectral characteristics shift to the longer
JAKOB MAYA
1979-01-01
Interaction of ultraviolet radiation with diatomic and triatomic metal halide vapors is discussed. Patterns observed in ultraviolet absorption cross sections are noted. Measurements of quantum efficiency of fluorescence excited by photodissociation (QE = fluorescence photons out\\/ultraviolet photons in) are described. Results and their implications for 205 ± 15-nm deuterium, 213.9-nm-Zn resonance and deuterium VUV excitation are discussed. Applications of photodissociation
J. Maya
1979-01-01
Interaction of ultraviolet radiation with diatomic and triatomic metal halide vapors is discussed. Patterns observed in ultraviolet absorption cross sections are noted. Measurements of quantum efficiency of fluorescence excited by photodissociation (QE = fluorescence photons out\\/ultraviolet photons in) are described. Results and their implications for 205 plus or minus 15-nm deuterium, 213.9-nm-Zn resonance and deuterium VUV excitation are discussed. Applications
Continuous quantum measurement in spin environments
Dong Xie; An Min Wang
2014-08-31
We derive a formalism of stochastic master equations (SME) which describes the decoherence dynamics of a system in spin environments conditioned on the measurement record. Markovian and non-Markovian nature of environment can be revealed by a spectroscopy method based on weak quantum measurement (weak spectroscopy). On account of that correlated environments can lead to a nonlocal open system which exhibits strong non-Markovian effects although the local dynamics are Markovian, the spectroscopy method can be used to demonstrate that there is correlation between two environments.
Information Divergence and Distance Measures for Quantum States
NASA Astrophysics Data System (ADS)
Jiang, Nan; Zhang, Zhaozhi
2015-02-01
Both information divergence and distance are measures of closeness of two quantum states which are widely used in the theory of information processing and quantum cryptography. For example, the quantum relative entropy and trace distance are well known. Here we introduce a number of new quantum information divergence and distance measures into the literature and discuss their relations and properties. We also propose a method to analyze the properties and relations of various distance and pseudo-distance measures.
Lowney, D.P.; Heimann, P.A.; Padmore, H.A.; Gullikson, E.M.; MacPhee, A.G.; Falcone, R.W. [Experimental Systems Group, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States); Center for X-Ray Optics, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States); Department of Physics, University of California at Berkeley, Berkeley, California 94720 (United States)
2004-10-01
The performance of CsI photocathodes has been characterized for use with grazing incidence soft x rays. The total electron yield and pulsed quantum efficiency of a CsI photocathode has been measured in a reflection geometry as a function of photon energy (100 eV to 1 keV), angle of incidence, and the electric field between the anode and photocathode. The total electron yield and pulsed quantum efficiency increase as the x-ray penetration depth approaches the secondary electron escape depth. Unit quantum efficiency in a grazing incidence geometry is demonstrated. A weak electric-field dependence is observed for the total yield measurements; while no significant dependence is found for the pulsed quantum efficiency. The effect of the pulse height distribution on the detective quantum efficiency is discussed. Theoretical predictions agree accurately with experiment.
Efficient and Robust Quantum Key Distribution With Minimal State Tomography
Berthold-Georg Englert; Dagomir Kaszlikowski; Hui Khoon Ng; Wee Kang Chua; Jaroslav ?ehá?ek; Janet Anders
2008-05-19
We introduce the Singapore protocol, a qubit protocol for quantum key distribution that is fully tomographic, more efficient than other tomographic protocols, and very robust. Under ideal circumstances the efficiency is log_2(4/3)=0.415 key bits per qubit sent. This is 25% more than the efficiency of 1/3=0.333 for the standard six-state protocol, which sets the benchmark. We describe a simple two-way communication scheme that extracts 0.4 key bits per qubit and thus gets close to the information-theoretical limit. The noise thresholds that we report for a hierarchy of eavesdropping attacks demonstrate the robustness of the protocol: A secure key can be extracted if there is less than 38.9% noise.
Quantum coherence in photosynthesis for efficient solar-energy conversion
NASA Astrophysics Data System (ADS)
Romero, Elisabet; Augulis, Ramunas; Novoderezhkin, Vladimir I.; Ferretti, Marco; Thieme, Jos; Zigmantas, Donatas; van Grondelle, Rienk
2014-09-01
The crucial step in the conversion of solar to chemical energy in photosynthesis takes place in the reaction centre, where the absorbed excitation energy is converted into a stable charge-separated state by ultrafast electron transfer events. However, the fundamental mechanism responsible for the near-unity quantum efficiency of this process is unknown. Here we elucidate the role of coherence in determining the efficiency of charge separation in the plant photosystem II reaction centre by comprehensively combining experiment (two-dimensional electronic spectroscopy) and theory (Redfield theory). We reveal the presence of electronic coherence between excitons as well as between exciton and charge-transfer states that we argue to be maintained by vibrational modes. Furthermore, we present evidence for the strong correlation between the degree of electronic coherence and efficient and ultrafast charge separation. We propose that this coherent mechanism will inspire the development of new energy technologies.
Measuring Productive Efficiency: An Application to Illinois Strip Mines
P. Byrnes; R. Färe; S. Grosskopf
1984-01-01
The purpose of this paper is to apply a generalized version of the Farrell measure of technical efficiency to a sample of Illinois strip mines. We disaggregate the original Farrell measure (which was designed to measure lost output or wasted inputs due to underutilization of inputs) into three mutually exclusive and exhaustive components: (1) a measure of purely technical efficiency,
Optimum and efficient sampling for variational quantum Monte Carlo.
Trail, J R; Maezono, Ryo
2010-11-01
Quantum mechanics for many-body systems may be reduced to the evaluation of integrals in 3N dimensions using Monte Carlo, providing the Quantum Monte Carlo ab initio methods. Here we limit ourselves to expectation values for trial wave functions, that is to variational quantum Monte Carlo. Almost all previous implementations employ samples distributed as the physical probability density of the trial wave function, and assume the central limit theorem to be valid. In this paper we provide an analysis of random error in estimation and optimization that leads naturally to new sampling strategies with improved computational and statistical properties. A rigorous lower limit to the random error is derived, and an efficient sampling strategy presented that significantly increases computational efficiency. In addition the infinite variance heavy tailed random errors of optimum parameters in conventional methods are replaced with a Normal random error, strengthening the theoretical basis of optimization. The method is applied to a number of first row systems and compared with previously published results. PMID:21054019
Measurement-Based Quantum Computation and Undecidable Logic
Maarten van den Nest; Hans J. Briegel
2008-01-01
We establish a connection between measurement-based quantum computation and the field of mathematical logic. We show that the computational power of an important class of quantum states called graph states, representing resources for measurement-based quantum computation, is reflected in the expressive power of (classical) formal logic languages defined on the underlying mathematical graphs. In particular, we show that for all
Measurement-Based and Universal Blind Quantum Computation
NASA Astrophysics Data System (ADS)
Broadbent, Anne; Fitzsimons, Joseph; Kashefi, Elham
Measurement-based quantum computation (MBQC) is a novel approach to quantum computation where the notion of measurement is the main driving force of computation. This is in contrast with the more traditional circuit model which is based on unitary operation. We review here the mathematical model underlying MBQC and the first quantum cryptographic protocol designed using the unique features of MBQC.
Two-photon interferometry illuminates quantum measurements
Art Hobson
2013-07-12
The quantum measurement problem still finds no consensus. Nonlocal interferometry provides an unprecedented experimental probe by entangling two photons in the "measurement state" (MS). The experiments show that each photon "measures" the other; the resulting entanglement decoheres both photons; decoherence collapses both photons to unpredictable but definite outcomes; and the two-photon MS continues evolving coherently. Thus, contrary to common opinion, when a two-part system is in the MS, the outcomes actually observed at both subsystems are definite. Although standard quantum physics postulates definite outcomes, two-photon interferometry verifies them to be not only consistent with, but actually a prediction of, the other principles. Nonlocality is the key to understanding this. As a consequence of nonlocality, the states we actually observe are the local states. These actually-observed local states collapse, while the global MS, which can be "observed" only after the fact by collecting coincidence data from both subsystems, continues its unitary evolution. This conclusion implies a refined understanding of the eigenstate principle: Following a measurement, the actually-observed local state instantly jumps into the observed eigenstate. Various experts' objections are rebutted.
Efficient quantum trajectory representation of wavefunctions evolving in imaginary time
Garashchuk, Sophya; Mazzuca, James; Vazhappilly, Tijo [Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208 (United States)
2011-07-21
The Boltzmann evolution of a wavefunction can be recast as imaginary-time dynamics of the quantum trajectory ensemble. The quantum effects arise from the momentum-dependent quantum potential - computed approximately to be practical in high-dimensional systems - influencing the trajectories in addition to the external classical potential [S. Garashchuk, J. Chem. Phys. 132, 014112 (2010)]. For a nodeless wavefunction represented as {psi}(x, t) = exp ( -S(x, t)/({Dirac_h}/2{pi})) with the trajectory momenta defined by {nabla}S(x, t), analysis of the Lagrangian and Eulerian evolution shows that for bound potentials the former is more accurate while the latter is more practical because the Lagrangian quantum trajectories diverge with time. Introduction of stationary and time-dependent components into the wavefunction representation generates new Lagrangian-type dynamics where the trajectory spreading is controlled improving efficiency of the trajectory description. As an illustration, different types of dynamics are used to compute zero-point energy of a strongly anharmonic well and low-lying eigenstates of a high-dimensional coupled harmonic system.
Carruthers, G R
1987-07-15
We have measured and compared the quantum efficiencies of microchannel plate (MCP) detectors in the far- UV (below 2000-A) wavelength range using CsI photocathodes (a) deposited on the front surfaces of microchannel plates and (b) deposited on solid substrates as opaque photocathodes with the resulting photoelectrons input to microchannel plates. The efficiencies were measured in both pulse-counting and photodiode modes of operation. Typical efficiencies are ~15% at 1216 A for a CsI-coated MCP compared with 65% for an opaque CsI photocathode MCP detector. Special processing has yielded an efficiency as high as 20% for a CsI-coated MCP. This may possibly be further improved by optimization of the tilt angle of the MCP channels relative to the front face of the MCP and incident radiation. However, at present there still remains a factor of at least 3 quantum efficiency advantage in the separate opaque CsI photocathode configuration. PMID:20489984
Quantum Dot Solar Cells: High Efficiency through Multiple Exciton Generation
Hanna, M. C.; Ellingson, R. J.; Beard, M.; Yu, P.; Micic, O. I.; Nozik, A. J.; c.
2005-01-01
Impact ionization is a process in which absorbed photons in semiconductors that are at least twice the bandgap can produce multiple electron-hole pairs. For single-bandgap photovoltaic devices, this effect produces greatly enhanced theoretical thermodynamic conversion efficiencies that range from 45-85%, depending upon solar concentration, the cell temperature, and the number of electron-hole pairs produced per photon. For quantum dots (QDs), electron-hole pairs exist as excitons. We have observed astoundingly efficient multiple exciton generation (MEG) in QDs of PbSe (bulk Eg = 0.28 eV), ranging in diameter from 3.9 to 5.7nm (Eg = 0.73, 0.82, and 0.91 eV, respectively). The effective masses of electron and holes are about equal in PbSe, and the onset for efficient MEG occurs at about three times the QD HOMO-LUMO transition (its ''bandgap''). The quantum yield rises quickly after the onset and reaches 300% at 4 x Eg (3.64 eV) for the smallest QD; this means that every QD in the sample produces three electron-hole pairs/photon.
Measurement-only topological quantum computation via anyonic interferometry
Bonderson, Parsa [Microsoft Research, Station Q, Elings Hall, University of California, Santa Barbara, CA 93106 (United States)], E-mail: parsab@microsoft.com; Freedman, Michael [Microsoft Research, Station Q, Elings Hall, University of California, Santa Barbara, CA 93106 (United States)], E-mail: michaelf@microsoft.com; Nayak, Chetan [Microsoft Research, Station Q, Elings Hall, University of California, Santa Barbara, CA 93106 (United States); Department of Physics, University of California, Santa Barbara, CA 93106 (United States)], E-mail: nayak@kitp.ucsb.edu
2009-04-15
We describe measurement-only topological quantum computation using both projective and interferometrical measurement of topological charge. We demonstrate how anyonic teleportation can be achieved using 'forced measurement' protocols for both types of measurement. Using this, it is shown how topological charge measurements can be used to generate the braiding transformations used in topological quantum computation, and hence that the physical transportation of computational anyons is unnecessary. We give a detailed discussion of the anyonics for implementation of topological quantum computation (particularly, using the measurement-only approach) in fractional quantum Hall systems.
Exactly decohering quantum measurement without environment
Eric A. Galapon
2015-05-26
Current quantum orthodoxy claims that the statistical collapse of the wave-function arises from the interaction of the measuring instrument with its environment through the phenomenon known as environment induced decoherence. Here it is shown that there exists a measurement scheme that is exactly decohering without the aid of an environment. The scheme relies on the assumption that the meter is decomposable into probe and pointer, with the probe taken to be inaccessible for observation. Under the assumption that the probe and the pointer initial states are momentum limited, it is shown that coherences die out within a finite interval of time and the pointer states are exactly orthogonal. These lead to the fundamental realization that dispersion of correlation does not require an external infinite number of degrees of freedom. An internal one degree of freedom is already sufficient to delocalize the correlations and leave its subparts in a classical mixed state, so that decoherence may occur even for isolated measuring instruments.
The Unreasonable Success of Quantum Probability II: Quantum Measurements as Universal Measurements
Diederik Aerts; Massimiliano Sassoli de Bianchi
2014-09-10
In the first part of this two-part article, we have introduced and analyzed a multidimensional model, called the 'general tension-reduction' (GTR) model, able to describe general quantum-like measurements with an arbitrary number of outcomes, and we have used it as a general theoretical framework to study the most general possible condition of lack of knowledge in a measurement, so defining what we have called a 'universal measurement'. In this second part, we present the formal proof that universal measurements, which are averages over all possible forms of fluctuations, produce the same probabilities as measurements characterized by 'uniform' fluctuations on the measurement situation. Since quantum probabilities can be shown to arise from the presence of such uniform fluctuations, we have proven that they can be interpreted as the probabilities of a first-order non-classical theory, describing situations in which the experimenter lacks complete knowledge about the nature of the interaction between the measuring apparatus and the entity under investigation. This same explanation can be applied -- mutatis mutandis -- to the case of cognitive measurements, made by human subjects on conceptual entities, or in decision processes, although it is not necessarily the case that the structure of the set of states would be in this case strictly Hilbertian. We also show that universal measurements correspond to maximally 'robust' descriptions of indeterministic reproducible experiments, and since quantum measurements can also be shown to be maximally robust, this adds plausibility to their interpretation as universal measurements, and provides a further element of explanation for the great success of the quantum statistics in the description of a large class of phenomena.
Efficient solution-processed small-molecule solar cells by insertion of graphene quantum dots.
Wang, Dong Hwan; Kim, Jung Kyu; Jin Kim, Sang; Hee Hong, Byung; Park, Jong Hyeok
2014-12-21
In this work, we have demonstrated the results of several positive effects that arise from the addition of graphene quantum dots (GQDs) to solution-processed small molecule bulk-heterojunction (SM-BHJ) solar cells fabricated from a p-DTS(FBTTh(2))(2)/[6,6]-phenyl C(71) butyric acid methyl-ester (PC(71)BM). The device with an optimized ratio of GQDs exhibits increased current density and fill factor owing to 10% improved external quantum efficiency (EQE) and induction of a favorable SM-BHJ morphology. Additionally, the multiple scattering of the GQDs in the SM-BHJ leads to longer optical pathlengths according to the analysis of diffuse reflectance spectra and UV/Vis absorption spectra. The GQD inserted SM-BHJ film at the optimized concentration exhibits decreased charge transport resistance significantly by impedance measurements with effective charge extraction in the device which contributes to 15% enhancement of power conversion efficiency (PCE). PMID:25373477
The effect of surface cleaning on quantum efficiency in AlGaN photocathode
NASA Astrophysics Data System (ADS)
Hao, Guanghui; Zhang, Yijun; Jin, Muchun; Feng, Cheng; Chen, Xinlong; Chang, Benkang
2015-01-01
To improve the quantum efficiency of AlGaN photocathode, various surfaces cleaning techniques for the removal of alumina and carbon from AlGaN photocathode surface were investigated. The atomic compositions of AlGaN photocathode structure and surface were measured by the X-ray photoelectron spectroscopy and Ar+ ion sputtering. It is found that the boiling KOH solution and the mixture of sulfuric acid and hydrogen peroxide, coupled with the thermal cleaning at 850 °C can effectively remove the alumina and carbon from the AlGaN photocathode surface. The quantum efficiency of AlGaN photocathode is improved to 35.1% at 240 nm, an increase of 50% over the AlGaN photocathode chemically cleaned by only the mixed solution of sulfuric acid and hydrogen peroxide and thermally cleaned at 710 °C.
Efficient solution-processed small-molecule solar cells by insertion of graphene quantum dots
NASA Astrophysics Data System (ADS)
Wang, Dong Hwan; Kim, Jung Kyu; Jin Kim, Sang; Hee Hong, Byung; Park, Jong Hyeok
2014-11-01
In this work, we have demonstrated the results of several positive effects that arise from the addition of graphene quantum dots (GQDs) to solution-processed small molecule bulk-heterojunction (SM-BHJ) solar cells fabricated from a p-DTS(FBTTh2)2/[6,6]-phenyl C71 butyric acid methyl-ester (PC71BM). The device with an optimized ratio of GQDs exhibits increased current density and fill factor owing to 10% improved external quantum efficiency (EQE) and induction of a favorable SM-BHJ morphology. Additionally, the multiple scattering of the GQDs in the SM-BHJ leads to longer optical pathlengths according to the analysis of diffuse reflectance spectra and UV/Vis absorption spectra. The GQD inserted SM-BHJ film at the optimized concentration exhibits decreased charge transport resistance significantly by impedance measurements with effective charge extraction in the device which contributes to 15% enhancement of power conversion efficiency (PCE).In this work, we have demonstrated the results of several positive effects that arise from the addition of graphene quantum dots (GQDs) to solution-processed small molecule bulk-heterojunction (SM-BHJ) solar cells fabricated from a p-DTS(FBTTh2)2/[6,6]-phenyl C71 butyric acid methyl-ester (PC71BM). The device with an optimized ratio of GQDs exhibits increased current density and fill factor owing to 10% improved external quantum efficiency (EQE) and induction of a favorable SM-BHJ morphology. Additionally, the multiple scattering of the GQDs in the SM-BHJ leads to longer optical pathlengths according to the analysis of diffuse reflectance spectra and UV/Vis absorption spectra. The GQD inserted SM-BHJ film at the optimized concentration exhibits decreased charge transport resistance significantly by impedance measurements with effective charge extraction in the device which contributes to 15% enhancement of power conversion efficiency (PCE). Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04944f
Measuring efficiency in the hotel sector
Carlos Pestana Barros
2005-01-01
This study discusses, by means of data envelopment analysis, the efficiency of individual hotels belonging to the Portuguese state-owned chain, Pousadas de Portugal, which is managed by the enterprise, ENATUR. The use of this technique for the analysis of intrachain comparative hotel efficiency can be of value in examining the competitiveness of the chain as a whole. By identifying the
Relativistic Quantum Metrology: Exploiting relativity to improve quantum measurement technologies
Ahmadi, Mehdi; Bruschi, David Edward; Sabín, Carlos; Adesso, Gerardo; Fuentes, Ivette
2014-01-01
We present a framework for relativistic quantum metrology that is useful for both Earth-based and space-based technologies. Quantum metrology has been so far successfully applied to design precision instruments such as clocks and sensors which outperform classical devices by exploiting quantum properties. There are advanced plans to implement these and other quantum technologies in space, for instance Space-QUEST and Space Optical Clock projects intend to implement quantum communications and quantum clocks at regimes where relativity starts to kick in. However, typical setups do not take into account the effects of relativity on quantum properties. To include and exploit these effects, we introduce techniques for the application of metrology to quantum field theory. Quantum field theory properly incorporates quantum theory and relativity, in particular, at regimes where space-based experiments take place. This framework allows for high precision estimation of parameters that appear in quantum field theory including proper times and accelerations. Indeed, the techniques can be applied to develop a novel generation of relativistic quantum technologies for gravimeters, clocks and sensors. As an example, we present a high precision device which in principle improves the state-of-the-art in quantum accelerometers by exploiting relativistic effects. PMID:24851858
Relativistic Quantum Metrology: Exploiting relativity to improve quantum measurement technologies
NASA Astrophysics Data System (ADS)
Ahmadi, Mehdi; Bruschi, David Edward; Sabín, Carlos; Adesso, Gerardo; Fuentes, Ivette
2014-05-01
We present a framework for relativistic quantum metrology that is useful for both Earth-based and space-based technologies. Quantum metrology has been so far successfully applied to design precision instruments such as clocks and sensors which outperform classical devices by exploiting quantum properties. There are advanced plans to implement these and other quantum technologies in space, for instance Space-QUEST and Space Optical Clock projects intend to implement quantum communications and quantum clocks at regimes where relativity starts to kick in. However, typical setups do not take into account the effects of relativity on quantum properties. To include and exploit these effects, we introduce techniques for the application of metrology to quantum field theory. Quantum field theory properly incorporates quantum theory and relativity, in particular, at regimes where space-based experiments take place. This framework allows for high precision estimation of parameters that appear in quantum field theory including proper times and accelerations. Indeed, the techniques can be applied to develop a novel generation of relativistic quantum technologies for gravimeters, clocks and sensors. As an example, we present a high precision device which in principle improves the state-of-the-art in quantum accelerometers by exploiting relativistic effects.
Relativistic quantum metrology: exploiting relativity to improve quantum measurement technologies.
Ahmadi, Mehdi; Bruschi, David Edward; Sabín, Carlos; Adesso, Gerardo; Fuentes, Ivette
2014-01-01
We present a framework for relativistic quantum metrology that is useful for both Earth-based and space-based technologies. Quantum metrology has been so far successfully applied to design precision instruments such as clocks and sensors which outperform classical devices by exploiting quantum properties. There are advanced plans to implement these and other quantum technologies in space, for instance Space-QUEST and Space Optical Clock projects intend to implement quantum communications and quantum clocks at regimes where relativity starts to kick in. However, typical setups do not take into account the effects of relativity on quantum properties. To include and exploit these effects, we introduce techniques for the application of metrology to quantum field theory. Quantum field theory properly incorporates quantum theory and relativity, in particular, at regimes where space-based experiments take place. This framework allows for high precision estimation of parameters that appear in quantum field theory including proper times and accelerations. Indeed, the techniques can be applied to develop a novel generation of relativistic quantum technologies for gravimeters, clocks and sensors. As an example, we present a high precision device which in principle improves the state-of-the-art in quantum accelerometers by exploiting relativistic effects. PMID:24851858
Efficient quantum memory using a weakly absorbing sample
Mahmood Sabooni; Qian Li; Stefan Kröll; Lars Rippe
2013-01-03
A light-storage experiment with a total (storage and retrieval) efficiency $\\eta=58 \\pm 5%$ is carried out by enclosing a sample, with a single pass absorption of 10%, in an impedance-matched cavity. The experiment is carried out using the Atomic Frequency Comb (AFC) technique in a praseodymium-doped crystal ($0.05%Pr^{3+}:Y_2SiO_5$) and the cavity is created by reflection coating the crystal surfaces. The AFC technique has previously by far demonstrated the highest multi-mode capacity of all quantum memory concepts tested experimentally. We claim that the present work shows that it is realistic to create efficient, on-demand, long storage time AFC memories.
Dynamical decoupling efficiency versus quantum non-Markovianity
Carole Addis; Francesco Ciccarello; Michele Cascio; G. Massimo Palma; Sabrina Maniscalco
2015-02-09
We investigate the relationship between non-Markovianity and the effectiveness of a dynamical decoupling protocol for qubits undergoing pure dephasing. We consider an exact model in which dephasing arises due to a bosonic environment with a spectral density of the Ohmic class. This is parametrised by an Ohmicity parameter by changing which we can model both Markovian and non-Markovian environments. Interestingly, we find that engineering a non-Markovian environment is detrimental to the efficiency of the dynamical decoupling scheme, leading to a worse coherence preservation. We show that each dynamical decoupling pulse reverses the flow of quantum information and, on this basis, we investigate the connection between dynamical decoupling efficiency and the reservoir spectral density. Finally, in the spirit of reservoir engineering, we investigate the optimum system-reservoir parameters for achieving maximum stationary coherences.
Quantum Efficiency and Topography of Heated and Plasma-Cleaned Copper Photocathode Surfaces
Palmer, Dennis T.; /Titan PSD; Kirby, R.E.; King, F.K.; /SLAC
2005-08-04
We present measurements of photoemission quantum efficiency (QE) for copper photocathodes heated and cleaned by low energy argon and hydrogen ion plasma. The QE and surface roughness parameters were measured before and after processing and surface chemical composition was tracked in-situ with x-ray photoelectron spectroscopy (XPS). Thermal annealing at 230 C was sufficient to improve the QE by 3-4 orders of magnitude, depending on the initial QE. Exposure to residual gas slowly reduced the QE but it was easily restored by argon ion cleaning for a few minutes. XPS showed that the annealing or ion bombardment removed surface water and hydrocarbons.
Current injection efficiency induced efficiency-droop in InGaN quantum well light-emitting diodes
Gilchrist, James F.
gradually with further increase in current due to the large carrier thermionic emis- sion. Structures of injected current that recombine in the QW active region, and the radiative efficiency (gRadiative) isCurrent injection efficiency induced efficiency-droop in InGaN quantum well light-emitting diodes
Heath, D F; McElaney, J H
1968-10-01
The quantum efficiences of spectrally selective photocathodes for the middle and vacuum uv (semitransparent depositions of CsI, CuI, and CsTe on Al(2)O(3) windows, a solid tungsten photocathode behind a MgF(2) window) were measured before their use as detectors in a rocket experiment, one year later, and after irradiation by high energy electrons. Only the CsI photodiode showed any change in quantum efficiency, a notable increase after irradiation. Two additional CsI diodes were then irradiated, one with high energy electrons, the other with gamma rays. However, these diodes showed no change in quantum efficiency. The quantum efficiencies of all the photodiodes appear stable with time. The CuI and CsTe diodes also remain stable under irradiation, while the CsI diode may exhibit an increase in quantum efficiency after irradiation. PMID:20068933
Exactly decohering quantum measurement without environment
Galapon, Eric A
2015-01-01
Current quantum orthodoxy claims that the statistical collapse of the wave-function arises from the interaction of the measuring instrument with its environment through the phenomenon known as environment induced decoherence. Here it is shown that there exists a measurement scheme that is exactly decohering without the aid of an environment. The scheme relies on the assumption that the meter is decomposable into probe and pointer, with the probe taken to be inaccessible for observation. Under the assumption that the probe and the pointer initial states are momentum limited, it is shown that coherences die out within a finite interval of time and the pointer states are exactly orthogonal. These lead to the fundamental realization that dispersion of correlation does not require an external infinite number of degrees of freedom. An internal one degree of freedom is already sufficient to delocalize the correlations and leave its subparts in a classical mixed state, so that decoherence may occur even for isolated ...
J. R. Lang; C. J. Neufeld; C. A. Hurni; S. C. Cruz; E. Matioli; U. K. Mishra; J. S. Speck
2011-01-01
High external quantum efficiency (EQE) p-i-n heterojunction solar cells grown by NH3-based molecular beam epitaxy are presented. EQE values including optical losses are greater than 50% with fill-factors over 72% when illuminated with a 1 sun AM0 spectrum. Optical absorption measurements in conjunction with EQE measurements indicate an internal quantum efficiency greater than 90% for the InGaN absorbing layer. By
Broadband quantum efficiency enhancement in high index nanowire resonators.
Yang, Yiming; Peng, Xingyue; Hyatt, Steven; Yu, Dong
2015-05-13
Light trapping in subwavelength semiconductor nanowires (NWs) offers a promising approach to simultaneously reducing material consumption and enhancing photovoltaic performance. Nevertheless, the absorption efficiency of a NW, defined by the ratio of optical absorption cross section to the NW diameter, lingers around 1 in existing NW photonic devices, and the absorption enhancement suffers from a narrow spectral width. Here, we show that the absorption efficiency can be significantly improved in NWs with higher refractive indices, by an experimental observation of up to 350% apparent external quantum efficiency in lead sulfide NW resonators, a 3-fold increase compared to Si NWs. Furthermore, broadband absorption enhancement is achieved in single tapered NWs, where light of various wavelengths is absorbed at segments with different diameters. Overall, the single NW Schottky junction solar cells benefit from optical resonance, near bandgap open circuit voltage, and long minority carrier diffusion length, demonstrating power conversion efficiency comparable to Si and III-V single NW coaxial p-n junction cells but with much simpler fabrication processes. PMID:25919358
Solution processable MOF yellow phosphor with exceptionally high quantum efficiency.
Gong, Qihan; Hu, Zhichao; Deibert, Benjamin J; Emge, Thomas J; Teat, Simon J; Banerjee, Debasis; Mussman, Brianna; Rudd, Nathan D; Li, Jing
2014-12-01
An important aspect in the research and development of white light-emitting diodes (WLEDs) is the discovery of highly efficient phosphors free of rare-earth (RE) elements. Herein we report the design and synthesis of a new type of RE-free, blue-excitable yellow phosphor, obtained by combining a strongly emissive molecular fluorophore with a bandgap modulating co-ligand, in a three-dimensional metal organic framework. [Zn6(btc)4(tppe)2(DMA)2] (btc = benzene-1,3,5-tricarboxylate, tppe = 1,1,2,2-tetrakis(4-(pyridin-4-yl)phenyl)ethene, DMA = dimethylacetamide) crystallizes in a new structure type and emits bright yellow light when excited by a blue light source. It possesses the highest internal quantum yield among all RE-free, blue-excitable yellow phosphors reported to date, with a value as high as 90.7% (?ex = 400 nm). In addition to its high internal quantum yield, the new yellow phosphor also demonstrates high external quantum yield, luminescent and moisture stability, solution processability, and color tunability, making it a promising material for use in phosphor conversion WLEDs. PMID:25387030
Quantum Coherence in (Brain) Microtubules and Efficient Energy and Information Transport
NASA Astrophysics Data System (ADS)
Mavromatos, Nick E.
2011-12-01
Prompted by recent experimental results in marine algae, indicating quantum entanglement at ambient temperature, with correlations between essential biological units separated by distances as long as 20 Angstroms and decoherence times, due to environmental influences, of order 400 fs, I review here a related topic proposed several years ago in connection with the possible rôle of quantum mechanics and/or field theory on dissipation-free energy transfer in (brain) microtubules (MT). The basic assumption was to view the cell MT as quantum electrodynamical cavities, providing sufficient isolation in vivo to enable the formation of electric-dipole quantum coherent solitonic states across the tubulin dimer walls. Crucial to this, were argued to be the electromagnetic interactions of the dipole moments of the tubulin dimers with the dipole quanta in the ordered water interiors of the MT, that play the rôle of quantum coherent cavity modes. Quantum entanglement between tubulin dimers was argued to be possible, provided there exists sufficient isolation from other environmental cell effects. Thus, decoherence times as long as 10-7 -10-6 s could characterise the MT systems. The model was based on certain ferroelectric aspects of MT. In the talk I revisit these decoherence time scales in light of the algae measurements and argue that, even if the environmental decoherence implies short time scales of order of a few hundreds of fs, this is a sufficient time for some kind of quantum computation to take place in (brain) MT, so that within these time scales the cell "quantum calculates" the optimal "path" along which energy and signal (information) are transported most efficiently along the MT.
Radix-independent, efficient arrays for multi-level n-qudit quantum and reversible computation
NASA Astrophysics Data System (ADS)
Mohammadi, Majid
2015-05-01
Multiple-valued quantum logic allows the designers to reduce the number of cells while obtaining more functionality in the quantum circuits. Large r-valued reversible or quantum gates (r stands for radix and is more than 2) cannot be directly realized in the current quantum technology. Therefore, we are interested in designing the large reversible and quantum controlled gates using the arrays of one-quantum digit (qudit) or two-qudit gates. In our previous work, we proposed quantum arrays to implement the r-valued quantum circuits. In this paper, we propose novel efficient structures and arrays, for r-valued quantum logic gates. The quantum costs of the developed quantum arrays are independent of the radix of calculations in the quantum circuit.
G. M. DAriano; P. Perinotti; M. F. Sacchi
2005-01-01
Informationally complete measurements allow the estimation of expectation values of any operator on a quantum system, by changing only the data processing of the measurement outcomes. In particular, an informationally complete measurement can be used to perform quantum tomography, namely to estimate the density matrix of the quantum state. The data processing is generally nonunique, and can be optimized according
Efficient circuit implementation of quantum walks on non-degree-regular graphs
NASA Astrophysics Data System (ADS)
Loke, T.; Wang, J. B.
2012-10-01
This paper presents a set of highly efficient quantum circuits for discrete-time quantum walks on non-degree-regular graphs. In particular, we describe a general procedure for constructing highly efficient quantum circuits for quantum walks on star graphs of any degree and Cayley trees with an arbitrary number of layers, which are nonsparse in general. We also show how to modify these circuits to implement a full quantum-walk search algorithm on these graphs, without reference to a “black-box” oracle. This provides a practically implementable method to explore quantum-walk-based algorithms with the aim of eventual real-world applications.
Blind topological measurement-based quantum computation
Tomoyuki Morimae; Keisuke Fujii
2012-09-06
Blind quantum computation is a novel secure quantum-computing protocol that enables Alice, who does not have sufficient quantum technology at her disposal, to delegate her quantum computation to Bob, who has a fully fledged quantum computer, in such a way that Bob cannot learn anything about Alice's input, output and algorithm. A recent proof-of-principle experiment demonstrating blind quantum computation in an optical system has raised new challenges regarding the scalability of blind quantum computation in realistic noisy conditions. Here we show that fault-tolerant blind quantum computation is possible in a topologically protected manner using the Raussendorf-Harrington-Goyal scheme. The error threshold of our scheme is 0.0043, which is comparable to that (0.0075) of non-blind topological quantum computation. As the error per gate of the order 0.001 was already achieved in some experimental systems, our result implies that secure cloud quantum computation is within reach.
Towards Minimal Resources of Measurement-based Quantum Computation
Simon Perdrix
2007-04-02
We improve the upper bound on the minimal resources required for measurement-based quantum computation. Minimizing the resources required for this model is a key issue for experimental realization of a quantum computer based on projective measurements. This new upper bound allows also to reply in the negative to the open question about the existence of a trade-off between observable and ancillary qubits in measurement-based quantum computation.
Effective fault-tolerant quantum computation with slow measurements
David P. DiVincenzo; Panos Aliferis
2006-08-03
How important is fast measurement for fault-tolerant quantum computation? Using a combination of existing and new ideas, we argue that measurement times as long as even 1,000 gate times or more have a very minimal effect on the quantum accuracy threshold. This shows that slow measurement, which appears to be unavoidable in many implementations of quantum computing, poses no essential obstacle to scalability.
KLM quantum computation as a measurement based computation
Sandu Popescu
2006-10-04
We show that the Knill Laflamme Milburn method of quantum computation with linear optics gates can be interpreted as a one-way, measurement based quantum computation of the type introduced by Briegel and Rausendorf. We also show that the permanent state of n n-dimensional systems is a universal state for quantum computation.
Entanglement as measure of electronelectron correlation in quantum chemistry calculations
Kais, Sabre
Entanglement as measure of electronelectron correlation in quantum chemistry calculations Zhen, United States Received 19 March 2005; in final form 12 July 2005 Abstract In quantum chemistry point and the major approach for quanti- tative electronic structure calculations. In quantum chemistry
Efficient Optimization of Performance Measures by Classifier Adaptation
Tsang Wai Hung "Ivor"
Efficient Optimization of Performance Measures by Classifier Adaptation Nan Li, Ivor W. Tsang needed to learn classifiers that optimize domain specific performance measures. Previously, the research has focused on learning the needed classifier in isolation, yet learning nonlinear classifier
Hybrid architecture for encoded measurement-based quantum computation
Zwerger, M.; Briegel, H. J.; Dür, W.
2014-01-01
We present a hybrid scheme for quantum computation that combines the modular structure of elementary building blocks used in the circuit model with the advantages of a measurement-based approach to quantum computation. We show how to construct optimal resource states of minimal size to implement elementary building blocks for encoded quantum computation in a measurement-based way, including states for error correction and encoded gates. The performance of the scheme is determined by the quality of the resource states, where within the considered error model a threshold of the order of 10% local noise per particle for fault-tolerant quantum computation and quantum communication. PMID:24946906
Mutlugun, Evren; Samarskaya, Olga; Ozel, Tuncay; Cicek, Neslihan; Gaponik, Nikolai; Eychmüller, Alexander; Demir, Hilmi Volkan
2010-05-10
We present light harvesting of aqueous colloidal quantum dots to nonradiatively transfer their excitonic excitation energy efficiently to dye molecules in water, without requiring ligand exchange. These as-synthesized CdTe quantum dots that are used as donors to serve as light-harvesting antennas are carefully optimized to match the electronic structure of Rhodamine B molecules used as acceptors for light harvesting in aqueous medium. By varying the acceptor to donor concentration ratio, we measure the light harvesting factor, along with substantial lifetime modifications of these water-soluble quantum dots, from 25.3 ns to 7.2 ns as a result of their energy transfer with efficiency levels up to 86%. Such nonradiative energy transfer mediated light harvesting in aqueous medium holds great promise for future quantum dot multiplexed dye biodetection systems. PMID:20588924
The amplification of weak measurements under quantum noise
Xuanmin Zhu; Yu-Xiang Zhang
2015-05-08
The influence of outside quantum noises on the amplification of weak measurements is investigated. Three typical quantum noises are discussed. The maximum values of the pointer's shifts decrease sharply with the strength of the depolarizing channel and phase damping. In order to obtain significant amplified signals, the preselection quantum systems must be kept away from the two quantum noises. Interestingly, the amplification effect is immune to the amplitude damping noise.
Nanocrystal energetics via quantum similarity measures
NASA Astrophysics Data System (ADS)
Törehan Balta, M. ?.; K?l?ç, Çetin
2014-03-01
We first develop a descriptor-based representation of atomic environments by devising two local similarity indices defined from an atom-partitioned quantum-chemical descriptor. Then, we employ this representation to explore the size-, shape- and composition-dependent nanocrystal energetics. For this purpose, we utilize an energy difference ? that is related to the atomic chemical potential, which enables one to characterize energetic heterogeneities. Employing first-principles calculations based on the density functional theory for a set of database systems, namely unary atomic clusters in the shape of regular polyhedra and the bulk solids of C, Si, Pd and Pt, we explore the correlations between the energy difference ? and similarity indices. We find that there exists an interconnection between nanocrystal energetics and quantum similarity measures. Accordingly, we develop a means for computing total energy differences from the similarity indices via interpolation, and utilize a test set comprising a variety of unary nanocrystals and binary nanoalloys/nanocompounds for validation. Our findings indicate that the similarity-based energies could be utilized in computer-aided design of nanoparticles.
Quantum efficiency test set up performances for NIR detector characterization at ESTEC
NASA Astrophysics Data System (ADS)
Crouzet, P.-E.; Duvet, L.; De Wit, F.; Beaufort, T.; Blommaert, S.; Butler, B.; Van Duinkerken, G.; ter Haar, J.; Heijnen, J.; van der Luijt, K.; Smit, H.; Viale, T.
2014-07-01
The Payload Technology Validation Section (Future mission preparation Office) at ESTEC is in charge of specific mission oriented validation activities, for science and robotic exploration missions, aiming at reducing development risks in the implementation phase. These activities take place during the early mission phases or during the implementation itself. In this framework, a test set up to characterize the quantum efficiency of near infrared detectors has been developed. The first detector to be tested will an HAWAII-2RG detector with a 2.5?m cut off, it will be used as commissioning device in preparation to the tests of prototypes European detectors developed under ESA funding. The capability to compare on the same setup detectors from different manufacturers will be a unique asset for the future mission preparation office. This publication presents the performances of the quantum efficiency test bench to prepare measurements on the HAWAII-2RG detector. A SOFRADIR Saturn detector has been used as a preliminary test vehicle for the bench. A test set up with a lamp, chopper, monochromator, pinhole and off axis mirrors allows to create a spot of 1mm diameter between 700nm and 2.5?m.The shape of the beam has been measured to match the rms voltage read by the Merlin Lock -in amplifier and the amplitude of the incoming signal. The reference detectors have been inter-calibrated with an uncertainty up to 3 %. For the measurement with HAWAII-2RG detector, the existing cryostat [1] has been modified to adapt cold black baffling, a cold filter wheel and a sapphire window. An statistic uncertainty of +/-2.6% on the quantum efficiency on the detector under test measurement is expected.
Efficient light emitting devices utilizing CdSe(ZnS) quantum dots in organic host matrices
Coe-Sullivan, Seth (Seth Alexander)
2002-01-01
We demonstrate efficient electroluminescence from thin film structures containing core-shell CdSe(ZnS) quantum dots dispersed in molecular organic host materials. In the most efficient devices, excitons are created on the ...
Measurement and control in quantum information science
NASA Astrophysics Data System (ADS)
Mabuchi, Hideo
2005-03-01
Quantum information science has a broad interface with control theory. In the region of overlap between these two thriving fields, one finds compelling problems ranging from robust and time-optimal control of quantum dynamics to the analysis and design of concatenated coding schemes. In this talk I will begin with a brief overview of recent work on applications of control theory in quantum information science, and then provide a more detailed review of my own group's research on quantum feedback control, quantum state preparation and quantum metrology.
High quantum-efficiency photon-number-resolving detector for photonic on-chip information processing
Calkins, Brice; Lita, Adriana E; Metcalf, Benjamin J; Kolthammer, W Steven; Linares, Antia Lamas; Spring, Justin B; Humphreys, Peter C; Mirin, Richard P; Gates, James C; Smith, Peter G R; Walmsley, Ian A; Gerrits, Thomas; Nam, Sae Woo
2013-01-01
The integrated optical circuit is a promising architecture for the realization of complex quantum optical states and information networks. One element that is required for many of these applications is a high-efficiency photon detector capable of photon-number discrimination. We present an integrated photonic system in the telecom band at 1550 nm based on UV-written silica-on-silicon waveguides and modified transition-edge sensors capable of number resolution and over 40% efficiency. Exploiting the mode transmission failure of these devices, we multiplex three detectors in series to demonstrate a combined 79% +/- 2% detection efficiency with a single pass, and 88% +/- 3% at the operating wavelength of an on-chip terminal reflection grating. Furthermore, our optical measurements clearly demonstrate no significant unexplained loss in this system due to scattering or reflections. This waveguide and detector design therefore allows the placement of number-resolving single-photon detectors of predictable efficienc...
Quantum efficiency of back-illuminated CCD detectors in the VUV region (30 200 nm)
NASA Astrophysics Data System (ADS)
Garnir, H. P.; Lefèbvre, P.-H.
2005-07-01
Charge-coupled devices (CCD's) are the detectors of choice for spectroscopy of highly charged ions due to their good linearity, spatial resolution, and high quantum efficiency (QE) over a wide wavelength range going from the ?-rays to the far infrared. However, the efficiency in the UV region of back-illuminated CCDs is not well known because of the lack of commercially available calibrated light sources in that wavelength range. By using the beam-foil light source, which produces well controlled line rich spectrum all over the XUV and VUV spectra, we have been able to measure the QE of our CCD over a large wavelength range. Our results are in accordance with the data gathered from the literature and allow us to propose a "universal" curve for the QE efficiency of CCDs in the 30-200 nm region.
Measuring efficiency in wholesale electricity markets
Bowden, Nicholas S.
2009-06-15
The mechanisms of the bid-based economic dispatch and market power mitigation algorithms which result in the market clearing price epitomize the complexity of the new regulatory regime. The augmented Lerner Index presented here offers a method to objectively assess the efficiency of the new structure. (author)
Measuring Charter School Efficiency: An Early Appraisal
ERIC Educational Resources Information Center
Carpenter, Dick M., II; Noller, Scott L.
2010-01-01
In an era of increased accountability and challenging times for public finance, charter schools built on decentralization, grassroots accountability, and market forces may provide, in the spirit of "educational laboratories," lessons for increasing student achievement more efficiently through diverse and innovative management, organization,…
Measuring Corporate Social Performance: An Efficiency Perspective
Delmas, Magali
: Corporate Social Performance; KLD; Efficiency; Data Envelopment Analysis. #12;1 1 INTRODUCTION Stakeholders evaluation of current aggregation approaches and proposes a new methodology based on Data Envelopment Analysis (DEA) to compute a CSP index. DEA is independent of subjective weight specifications and provides
Measuring ecological efficiency with data envelopment analysis (DEA)
H. Dyckhoff; K. Allen
2001-01-01
The measurement of ecological efficiency provides some important information for the companies’ environmental management. Ecological efficiency is usually measured by comparing environmental performance indicators. Data envelopment analysis (DEA) shows a high potential to support such comparisons, as no explicit weights are needed to aggregate the indicators. In general, DEA assumes that inputs and outputs are ‘goods’, but from an ecological
Experimental feedback control of quantum systems using weak measurements.
Gillett, G G; Dalton, R B; Lanyon, B P; Almeida, M P; Barbieri, M; Pryde, G J; O'Brien, J L; Resch, K J; Bartlett, S D; White, A G
2010-02-26
A goal of the emerging field of quantum control is to develop methods for quantum technologies to function robustly in the presence of noise. Central issues are the fundamental limitations on the available information about quantum systems and the disturbance they suffer in the process of measurement. In the context of a simple quantum control scenario-the stabilization of nonorthogonal states of a qubit against dephasing-we experimentally explore the use of weak measurements in feedback control. We find that, despite the intrinsic difficultly of implementing them, weak measurements allow us to control the qubit better in practice than is even theoretically possible without them. Our work shows that these more general quantum measurements can play an important role for feedback control of quantum systems. PMID:20366921
Measure synchronization in quantum many-body systems
NASA Astrophysics Data System (ADS)
Qiu, Haibo; Juliá-Díaz, Bruno; Garcia-March, Miguel Angel; Polls, Artur
2014-09-01
The concept of measure synchronization between two coupled quantum many-body systems is presented. In general terms we consider two quantum many-body systems whose dynamics gets coupled through the contact particle-particle interaction. This coupling is shown to produce measure synchronization, a generalization of synchrony to a large class of systems which takes place in absence of dissipation. We find that in quantum measure synchronization, the many-body quantum properties for the two subsystems, e.g., condensed fractions and particle fluctuations, behave in a coordinated way. To illustrate the concept we consider a simple case of two species of bosons occupying two distinct quantum states. Measure synchronization can be readily explored with state-of-the-art techniques in ultracold atomic gases and, if properly controlled, be employed to build targeted quantum correlations in a sympathetic way.
Unifying Quantum Computation with Projective Measurements only and One-Way Quantum Computation
Philippe Jorrand; Simon Perdrix
2004-04-21
Quantum measurement is universal for quantum computation. Two models for performing measurement-based quantum computation exist: the one-way quantum computer was introduced by Briegel and Raussendorf, and quantum computation via projective measurements only by Nielsen. The more recent development of this second model is based on state transfers instead of teleportation. From this development, a finite but approximate quantum universal family of observables is exhibited, which includes only one two-qubit observable, while others are one-qubit observables. In this article, an infinite but exact quantum universal family of observables is proposed, including also only one two-qubit observable. The rest of the paper is dedicated to compare these two models of measurement-based quantum computation, i.e. one-way quantum computation and quantum computation via projective measurements only. From this comparison, which was initiated by Cirac and Verstraete, closer and more natural connections appear between these two models. These close connections lead to a unified view of measurement-based quantum computation.
High quantum efficiency for Pt2Si Schottky-barrier diodes in the vacuum ultraviolet
NASA Astrophysics Data System (ADS)
Hajsaid, M.; Charlson, E. J.; Charlson, E. M.; Zhao, G.; Meese, J. M.; Stacy, T.; Popovici, G.; Prelas, M. A.
1994-06-01
In the current study an effort was made to extend the front-illumination mode experiments into the 100-200 nm vacuum ultraviolet range. It was found that devices that were configured to form the Pt2Si phase, always displayed higher efficiencies in the VUV. Fabrication of the Pt2Si morphology was mainly determined by the annealing temperature. Thus, the formation and measurement of this variety of the device were stressed. The quantum efficiency measurements of the two sets of Pt2Si photodiodes were obtained by using the difference in short-circuit photocurrent of the device currents with and without illumination. Two major factors influenced the detector response, namely, substrate resistivity and thickness of the silicide film. The results showed that there was a maximum thickness of the silicide film for maximal photoresponse in the VUV wavelength range.
In situ measurement of the dynamic structure factor in ultracold quantum gases
Weimer, Hendrik
2011-01-01
We propose an experimental setup to efficiently measure the dynamic structure factor of ultracold quantum gases. Our method uses the interaction of the trapped atomic system with two different cavity modes, which are driven by external laser fields. By measuring the output fields of the cavity the dynamic structure factor of the atomic system can be determined. Contrary to previous approaches the atomic system is not destroyed during the measurement process.
In situ measurement of the dynamic structure factor in ultracold quantum gases
Hendrik Weimer; Hans Peter Büchler
2012-04-09
We propose an experimental setup to efficiently measure the dynamic structure factor of ultracold quantum gases. Our method uses the interaction of the trapped atomic system with two different cavity modes, which are driven by external laser fields. By measuring the output fields of the cavity the dynamic structure factor of the atomic system can be determined. Contrary to previous approaches the atomic system is not destroyed during the measurement process.
Calkins, Brice; Mennea, Paolo L; Lita, Adriana E; Metcalf, Benjamin J; Kolthammer, W Steven; Lamas-Linares, Antia; Spring, Justin B; Humphreys, Peter C; Mirin, Richard P; Gates, James C; Smith, Peter G R; Walmsley, Ian A; Gerrits, Thomas; Nam, Sae Woo
2013-09-23
The integrated optical circuit is a promising architecture for the realization of complex quantum optical states and information networks. One element that is required for many of these applications is a high-efficiency photon detector capable of photon-number discrimination. We present an integrated photonic system in the telecom band at 1550 nm based on UV-written silica-on-silicon waveguides and modified transition-edge sensors capable of number resolution and over 40 % efficiency. Exploiting the mode transmission failure of these devices, we multiplex three detectors in series to demonstrate a combined 79 % ± 2 % detection efficiency with a single pass, and 88 % ± 3 % at the operating wavelength of an on-chip terminal reflection grating. Furthermore, our optical measurements clearly demonstrate no significant unexplained loss in this system due to scattering or reflections. This waveguide and detector design therefore allows the placement of number-resolving single-photon detectors of predictable efficiency at arbitrary locations within a photonic circuit - a capability that offers great potential for many quantum optical applications. PMID:24104153
Quantum measurement with entangled-photon states
Alexander Sergienko
Two photons in a pair generated in the nonlinear process of spontaneous parametric down conversion (SPDC) are, in general, strongly entangled. Accordingly, they contain extremely strong energy, time, polarization, and momentum quantum correlations. This entanglement involving more than one pair of quantum variable has served as a powerful tool in fundamental studies of quantum theory. It is now playing a
Quantum information theory of entanglement and measurement
Nicolas J. Cerf; Chris Adami
1998-01-01
We present a quantum information theory that allows for a consistent description of entanglement. It parallels classical (Shannon) information theory but is based entirely on density matrices rather than probability distributions for the description of quantum ensembles. We find that quantum (von Neumann) conditional entropies can be negative for entangled systems, which leads to a violation of entropic Bell inequalities.
Measurements of cold spray deposition efficiency
S. V. Klinkov; V. F. Kosarev
2006-01-01
An analytical model of the kinetics of coating formation during cold spray is presented. The model is used to correct experimental\\u000a data on deposition efficiency. The experimentally observed values are shown to be affected by experimental conditions, such\\u000a as the velocity of substrate motion, the number of passes, the mass of a single portion of powder, and the exposure time
Effect of Quantum Point Contact Measurement on Electron Spin State in Quantum Dot
Fei-Yun Zhu; Zhi-Cheng Zhu; Tao Tu; Hua Tu; Guang-Can Guo; Guo-Ping Guo
2009-01-09
We study the time evolution of two electron spin states in a double quantum-dot system, which includes a nearby quantum point contact (QPC) as a measurement device. We obtain that the QPC measurement induced decoherence is in time scales of microsecond. We also find that the enhanced QPC measurement will trap the system in its initial spin states, which is consistent with quantum Zeno effect.
Security bounds for efficient decoy-state quantum key distribution
Marco Lucamarini; James F. Dynes; Bernd Fröhlich; Zhiliang Yuan; Andrew J. Shields
2015-03-25
Information-theoretical security of quantum key distribution (QKD) has been convincingly proven in recent years and remarkable experiments have shown the potential of QKD for real world applications. Due to its unique capability of combining high key rate and security in a realistic finite-size scenario, the efficient version of the BB84 QKD protocol endowed with decoy states has been subject of intensive research. Its recent experimental implementation finally demonstrated a secure key rate beyond 1 Mbps over a 50 km optical fiber. However the achieved rate holds under the restrictive assumption that the eavesdropper performs collective attacks. Here, we review the protocol and generalize its security. We exploit a map by Ahrens to rigorously upper bound the Hypergeometric distribution resulting from a general eavesdropping. Despite the extended applicability of the new protocol, its key rate is only marginally smaller than its predecessor in all cases of practical interest.
Uniformity compensation for high-quantum-efficiency focal plane arrays
NASA Astrophysics Data System (ADS)
Horman, Stephen R.; Zurasky, Matthew W.; Talamonti, James J.; Hepfer, Kenneth C.
1997-08-01
NSWCDD has developed a new nonuniformity correction (NUC) technique that has been demonstrated to significantly reduce both fixed pattern and temporal noise in sensors using high quantum efficiency (QE) infrared (IR) staring focal plane arrays (FPA). Sensors using this technique have been shown to have good response in every pixel, i.e., there are no dead or anomalously noisy pixels anywhere in the field of view (FOV). This technique will also enable development of sensors with very small apertures as well as those which can dynamically trade off sensitivity, resolution and frame rate. In addition, effective yield of detector production will be enhanced, since these benefits can be obtained using arrays that would be rejected for most applications, were conventional NUC used. This technique has been demonstrated to work as specified through analysis of real time data. A high performance, concept demonstration sensor, is in the final stages of acceptance testing, with delivery planned for April 1997.
Measurement-Based Quantum Computation and Undecidable Logic
Maarten Van den NestHans; Hans J. Briegel
2008-01-01
We establish a connection between measurement-based quantum computation and the field of mathematical logic. We show that\\u000a the computational power of an important class of quantum states called graph states, representing resources for measurement-based quantum computation, is reflected in the expressive power of (classical) formal\\u000a logic languages defined on the underlying mathematical graphs. In particular, we show that for all
Measurement-Based and Universal Blind Quantum Computation
Anne Broadbent; Joseph Fitzsimons; Elham Kashefi
2010-01-01
\\u000a Measurement-based quantum computation (MBQC) is a novel approach to quantum computation where the notion of measurement is\\u000a the main driving force of computation. This is in contrast with the more traditional circuit model which is based on unitary\\u000a operation. We review here the mathematical model underlying MBQC and the first quantum cryptographic protocol designed using\\u000a the unique features of MBQC.
High-conjugation-efficiency aqueous CdSe quantum dots.
Au, Giang H T; Shih, Wan Y; Shih, Wei-Heng
2013-11-12
Quantum dots (QDs) are photoluminescent nanoparticles that can be directly or indirectly coupled with a receptor such as an antibody to specifically image a target biomolecule such as an antigen. Recent studies have shown that QDs can be directly made at room temperature and in an aqueous environment (AQDs) with 3-mercaptopropionic acid (MPA) as the capping ligand without solvent and ligand exchange typically required by QDs made by the organic solvent routes (OQDs). In this study, we have synthesized CdSe AQDs and compared their conjugation efficiency and imaging efficacy with commercial carboxylated OQDs in HT29 colon cancer cells using a primary antibody-biotinylated secondary antibody-streptavidin (SA) sandwich. We showed that the best imaging condition for AQDs occurred when one AQD was bound with 3 ± 0.3 SA with a nominal SA/AQD ratio of 4 corresponding to an SA conjugation efficiency of 75 ± 7.5%. In comparison, for commercial CdSe-ZnS OQDs to achieve 2.7 ± 0.4 bound SAs per OQD for comparable imaging efficacy a nominal SA/OQD ratio of 80 was needed corresponding to an SA conjugation efficiency of 3.4 ± 0.5% for CdSe-ZnS OQDs. The more than 10 times better SA conjugation efficiency of the CdSe AQDs as compared to that of the CdSe-ZnS OQDs was attributed to more capping molecules on the AQD surface as a result of the direct aqueous synthesis. More capping molecules on the AQD surface also allowed the SA-AQD conjugate to be stable in cell culture medium for more than three days without losing their staining capability in a flowing cell culture medium. In contrast, SA-OQD conjugates aggregated in cell culture medium and in phosphate buffer saline solution over time. PMID:24151632
Efficient Chlorophyll Fluorescence Measurements of Sugarcane
Technology Transfer Automated Retrieval System (TEKTRAN)
As with many crops, chlorophyll fluorescence emission is a promising tool for measuring responses of sugarcane (Saccharum spp.) to biotic and abiotic stresses. Chlorophyll fluorescence can be easily measured using portable fluorometers. However, several factors should be considered in order to op...
Tulsi Dass
2006-12-29
Supmech, an algebraic scheme of mechanics integrating noncommutative symplectic geometry and noncommutative probability, subsumes quantum and classical mechanics and permits consistent treatment of interaction of quantum and classical systems. Quantum measurements are treated in this framework; the von Neumann reduction rule (generally postulated) is derived and interpreted in physical terms.
Time-efficient implementation of quantum search with qudits
NASA Astrophysics Data System (ADS)
Ivanov, S. S.; Tonchev, H. S.; Vitanov, N. V.
2012-06-01
We propose a simpler and more efficient scheme for the implementation of the multivalued Grover's quantum search. The multivalued search generalizes the original Grover's search by replacing qubits with qudits—quantum systems of d discrete states. The qudit database is exponentially larger than the qubit database and thus it requires fewer particles to control. The Hadamard gate, which is the key elementary gate in the qubit implementation of Grover's search, is replaced by a d-dimensional (complex-valued) unitary matrix F, the only condition for which is to have a column of equal moduli elements irrespective of their phases; it can be realized through any physical interaction, which achieves an equal-weight superposition state. An example of such a transformation is the d-dimensional discrete Fourier transform, used in earlier proposals; however, its construction is much more costly than that of the far simpler matrix F. We present examples of how such a transform F can be constructed in realistic qudit systems in a single interaction step.
Collier, J; Aldoohan, S; Gill, K
2014-06-01
Purpose: Reducing patient dose while maintaining (or even improving) image quality is one of the foremost goals in CT imaging. To this end, we consider the feasibility of optimizing CT scan protocols in conjunction with the application of different beam-hardening filtrations and assess this augmentation through noise-power spectrum (NPS) and detector quantum efficiency (DQE) analysis. Methods: American College of Radiology (ACR) and Catphan phantoms (The Phantom Laboratory) were scanned with a 64 slice CT scanner when additional filtration of thickness and composition (e.g., copper, nickel, tantalum, titanium, and tungsten) had been applied. A MATLAB-based code was employed to calculate the image of noise NPS. The Catphan Image Owl software suite was then used to compute the modulated transfer function (MTF) responses of the scanner. The DQE for each additional filter, including the inherent filtration, was then computed from these values. Finally, CT dose index (CTDIvol) values were obtained for each applied filtration through the use of a 100 mm pencil ionization chamber and CT dose phantom. Results: NPS, MTF, and DQE values were computed for each applied filtration and compared to the reference case of inherent beam-hardening filtration only. Results showed that the NPS values were reduced between 5 and 12% compared to inherent filtration case. Additionally, CTDIvol values were reduced between 15 and 27% depending on the composition of filtration applied. However, no noticeable changes in image contrast-to-noise ratios were noted. Conclusion: The reduction in the quanta noise section of the NPS profile found in this phantom-based study is encouraging. The reduction in both noise and dose through the application of beam-hardening filters is reflected in our phantom image quality. However, further investigation is needed to ascertain the applicability of this approach to reducing patient dose while maintaining diagnostically acceptable image qualities in a clinical setting.
OSP Quantum Mechanics: Single Measurments of Spin States Worksheet
NSDL National Science Digital Library
Belloni, Mario
This set of tutorial worksheets, based on the OSP Quantum Mechanics Simulations, help students explore the measurement of quantum spins. The tutorial starts with an introduction of the physics of spins, and then presents the results of a single measurement on pure, mixed, and superposition states.
Toward quantum-limited position measurements using optically levitated microspheres
Kenneth G. Libbrecht; Eric D. Black
2004-01-01
We propose the use of optically levitated microspheres as test masses in experiments aimed at reaching and potentially exceeding the standard quantum limit for position measurements. Optically levitated microspheres have low mass and are essentially free of suspension thermal noise, making them well suited for experimentally testing our understanding of quantum-limited measurements.
Engineering quantum states, nonlinear measurements and anomalous diffusion by imaging
Kurt Jacobs; Daniel A. Steck
2011-01-01
We show that well-separated quantum superposition states, measurements of strongly nonlinear observables and quantum dynamics driven by anomalous diffusion can all be achieved for single atoms or molecules by imaging spontaneous photons that they emit via resonance florescence. To generate anomalous diffusion we introduce continuous measurements driven by Lévy processes and prove a number of results regarding their properties. In
Uwe Rau
2007-01-01
A rigorous proof for a reciprocity theorem that relates the spectral and angular dependences of the electroluminescence of solar cells and light emitting diodes to the spectral and angular quantum efficiency of photocarrier collection is given. An additional relation is derived that connects the open circuit voltage of a solar cell and its electroluminescence quantum efficiency.
Ilan Bloom; Yael Nemirovsky
1991-01-01
The quantum efficiency and crosstalk of backside-illuminated indium antimonide photodiodes in hybrid focal plane arrays are calculated. An improved structure with crosswise ohmic contacts at the backside of the thinned InSb substrate is described. The simulations predict a significant reduction in the crosstalk while retaining high quantum efficiency
Current injection efficiency of InGaAsN quantum-well lasers Nelson Tansua
Gilchrist, James F.
Current injection efficiency of InGaAsN quantum-well lasers Nelson Tansua Department of Electrical-threshold current injection efficiency of quantum well QW lasers is clarified. The analysis presented here lasers. The role of heavy-hole leakage in the InGaAsN QW lasers is shown to be significant in determining
High-quantum-efficiency C-QWIP FPA-based IR cameras
John Devitt; David P. Forrai; Darrel Endres; Richard Rawe; Bob Fischer; K. K. Choi; V. Swaminathan
2006-01-01
Current generation QWIP detectors, although very cost effective, have relatively narrow spectral range and low quantum efficiencies. Tactical operation is generally limited to a single spectral band. These limitations arise from the design approach and restrict applications to those that can tolerate these performance limitations. Using recent device design improvements, a novel material, and special processing approaches, High Quantum Efficiency
High accuracy radiation efficiency measurement techniques
NASA Technical Reports Server (NTRS)
Kozakoff, D. J.; Schuchardt, J. M.
1981-01-01
The relatively large antenna subarrays (tens of meters) to be used in the Solar Power Satellite, and the desire to accurately quantify antenna performance, dictate the requirement for specialized measurement techniques. The error contributors associated with both far-field and near-field antenna measurement concepts were quantified. As a result, instrumentation configurations with measurement accuracy potential were identified. In every case, advances in the state of the art of associated electronics were found to be required. Relative cost trade-offs between a candidate far-field elevated antenna range and near-field facility were also performed.
Microwave Directional Coupler for Quantum Measurement
NASA Astrophysics Data System (ADS)
Xu, Victoria; Macklin, Chris; Eddins, Andrew; Siddiqi, Irfan
2014-03-01
We present the design of a 20dB single-section directional coupler using two edge-coupled, conductor-backed coplanar waveguides (CPW). We begin with an electromagnetic analysis of the physical mechanisms that allow two waveguides to form a directional coupler. Based on the coplanar waveguide geometry used for the coupler, we experienced inherently limited directivity in the performance, and we discuss the mechanisms by which we optimize for directivity despite geometric limitations. After laying out the theory behind CPW directional couplers, an electromagnetic analysis of our simulated design is presented. Two iterations of designs were fabricated. The final directional coupler yields simulated and measured performance even beyond the level of our design goals. At the center frequency of 6 GHz, our coupler showed comparable performance to commercial directional couplers. The 20-dB directional coupler serves as a solid-state equivalent of a 99/1 beam splitter for microwave photons, and will further enable on-chip experiments in quantum measurement. This work was funded by National Science Foundation Award ECCS-0939514.
Effect of Preparation Method on Luminescence Properties and Quantum Efficiency of CdTe QDs
NASA Astrophysics Data System (ADS)
Saad, A. M.; Baker, M. M.; Kana, M. A.; Azzouz, I. M.
2013-03-01
The effect of preparation procedure on the optical properties of CdTe semiconductor nanoparticles (NPs) has been investigated. CdTe NPs have been prepared via two different methods, organometallic pyrolysis method and microwave assisted aqueous based method. The nanostructure for the prepared NPs via both methods was confirmed by transmission electron microscopy, absorption and photoluminescence spectroscopy. Comparison between the quantum yield emissions of the as-prepared NPs of both methods is presented. The results shows that CdTe NPs which prepared via microwave assisted aqueous method yielded a much higher quantum efficiency (>41%). Amplified stimulated emission is investigated at room temperature (300K) and at low temperature (10K). Lifetime is also measured.
Efficient multimode quantum memory based on photon echo in an optimal QED cavity
Moiseev, Sergey A. [Kazan Physical-Technical Institute of the Russian Academy of Sciences, 10/7 Sibirsky Trakt, Kazan RU-420029 (Russian Federation); Institute for Informatics of Tatarstan Academy of Sciences, 20 Mushtary, Kazan RU-420012 (Russian Federation); Physical Department of Kazan State University, Kremlevskaya 18, Kazan RU-420008 (Russian Federation); Andrianov, Sergey N. [Institute for Informatics of Tatarstan Academy of Sciences, 20 Mushtary, Kazan RU-420012 (Russian Federation); Physical Department of Kazan State University, Kremlevskaya 18, Kazan RU-420008 (Russian Federation); Gubaidullin, Firdus F. [Kazan Physical-Technical Institute of the Russian Academy of Sciences, 10/7 Sibirsky Trakt, Kazan RU-420029 (Russian Federation); Institute for Informatics of Tatarstan Academy of Sciences, 20 Mushtary, Kazan RU-420012 (Russian Federation)
2010-08-15
Effective multimode photon echo quantum memory on multiatomic ensemble in the QED cavity is proposed. We obtain the analytical solution for the quantum memory efficiency that can be equal to unity when optimal conditions for the cavity and atomic parameters are held. Detailed analysis of the optimal conditions is performed. Numerical estimation for realistic atomic and cavity parameters demonstrates the high efficiency of the quantum memory for an optically thin resonant atomic system that opens a door for real applications.
Blind topological measurement-based quantum computation
NASA Astrophysics Data System (ADS)
Morimae, Tomoyuki; Fujii, Keisuke
2012-09-01
Blind quantum computation is a novel secure quantum-computing protocol that enables Alice, who does not have sufficient quantum technology at her disposal, to delegate her quantum computation to Bob, who has a fully fledged quantum computer, in such a way that Bob cannot learn anything about Alice's input, output and algorithm. A recent proof-of-principle experiment demonstrating blind quantum computation in an optical system has raised new challenges regarding the scalability of blind quantum computation in realistic noisy conditions. Here we show that fault-tolerant blind quantum computation is possible in a topologically protected manner using the Raussendorf-Harrington-Goyal scheme. The error threshold of our scheme is 4.3×10-3, which is comparable to that (7.5×10-3) of non-blind topological quantum computation. As the error per gate of the order 10-3 was already achieved in some experimental systems, our result implies that secure cloud quantum computation is within reach.
Quantum optical arbitrary waveform manipulation and measurement in real time.
Kowligy, Abijith S; Manurkar, Paritosh; Corzo, Neil V; Velev, Vesselin G; Silver, Michael; Scott, Ryan P; Yoo, S J B; Kumar, Prem; Kanter, Gregory S; Huang, Yu-Ping
2014-11-17
We describe a technique for dynamic quantum optical arbitrary-waveform generation and manipulation, which is capable of mode selectively operating on quantum signals without inducing significant loss or decoherence. It is built upon combining the developed tools of quantum frequency conversion and optical arbitrary waveform generation. Considering realistic parameters, we propose and analyze applications such as programmable reshaping of picosecond-scale temporal modes, selective frequency conversion of any one or superposition of those modes, and mode-resolved photon counting. We also report on experimental progress to distinguish two overlapping, orthogonal temporal modes, demonstrating over 8 dB extinction between picosecond-scale time-frequency modes, which agrees well with our theory. Our theoretical and experimental progress, as a whole, points to an enabling optical technique for various applications such as ultradense quantum coding, unity-efficiency cavity-atom quantum memories, and high-speed quantum computing. PMID:25402035
Measuring hospital efficiency with frontier cost functions.
Zuckerman, S; Hadley, J; Iezzoni, L
1994-10-01
This paper uses a stochastic frontier multiproduct cost function to derive hospital-specific measures of inefficiency. The cost function includes direct measures of illness severity, output quality, and patient outcomes to reduce the likelihood that the inefficiency estimates are capturing unmeasured differences in hospital outputs. Models are estimated using data from the AHA Annual Survey, Medicare Hospital Cost Reports, and MEDPAR. We explicitly test the assumption of output endogeneity and reject it in this application. We conclude that inefficiency accounts for 13.6 percent of total hospital costs. This estimate is robust with respect to model specification and approaches to pooling data across distinct groups of hospitals. PMID:10138854
Reiner H. Windisch; Alexander Knobloch; Jan Potemans; Barundeb Dutta; G. H. Dohler; G. Borghs; P. L. Heremans
1999-01-01
We report on nonresonant cavity light-emitting diodes (NRC-LED) with large quantum efficiencies and high speed. A maximum quantum efficiency of 31% is measured for a device with an active layer thickness of 120 nm, and 18.7% for a device having an active layer of 30 nm. Further, we report on optical rise and fall times of NRC-LEDs. Even when switched
I. Schnitzer; E. Yablonovitch; C. Caneau; A. Ersen; T. J. Gmitter
1992-01-01
Thin film (5000~),ALGaAs\\/GaAs\\/AlGaAs double heterostructures, are floated off thcir substrates by the epitaxial liftoff technique and mounted on various high reflectivity surfaces. From the absolute photoluminescence intensity, we measure internal and external quantum efficiencies of 99.7% and 72%, respectively. This novel configuration, as wcll as its world rccord spontaneous emission quantum efficiency, is expected to play a significant role in
I. Schnitzer; E. Yablonovitch; C. Caneau; T. J. Gmitter
1993-01-01
Optically thin AlGaAs\\/GaAs\\/AlGaAs double heterostructures, (5000 A?), are floated off their substrates by the epitaxial liftoff technique and mounted on various high reflectivity surfaces. From the absolute photoluminescence intensity, we measure internal and external quantum efficiencies of 99.7% and 72%, respectively. High spontaneous emission quantum efficiency, is important for photon number squeezed light, diode lasers, single-mode light-emitting-diodes, optical interconnects, and
J. D. Morse; R. P. Jr. Mariella
1991-01-01
Metal-Semiconductor-Metal (MSM) photodiodes fabricated from low temperature all grown GaAs by molecular beam epitaxy have been characterized for wavelengths extending out to 1.5[mu]m. External quantum efficiencies on the order of 0.5 % have been measured for subbandgap wavelengths, which translates to internal quantum efficiencies of 2--4 % for the interdigitated electrode structure with 1[mu]m finger spacing and width. Although the
Quantum and conversion efficiency calculation of AlGaAs/GaAs multiple quantum well solar cells
NASA Astrophysics Data System (ADS)
Rimada, J. C.; Hernandez, L.; Connolly, J. P.; Barnham, K. W. J.
2005-07-01
The quantum well solar cell (QWSC) is a novel device that has been proposed by Barnham and co-workers at Imperial College London. In this work, the quantum efficiency for AlGaAs/GaAs QWSC has been calculated and compared with available data from the group at Imperial College London. Quantum efficiency calculations will be presented and compared with experimental data for several AlGaAs/GaAs QWSC, obtaining good agreement. The photocurrent then is calculated from the quantum efficiency calculations and included in the J(V) relation to optimize the efficiency of AlGaAs/GaAs QWSC. It also shows that for a range of quantum well widths and barrier bandgaps the conversion efficiencies of the quantum well solar cell are higher than the corresponding homogeneous p-i-n solar cell. Our results give a broad representation of quantum well solar cell operation, and provide a profitable guide for designing and interpreting the performance characteristics of AlGaAs/GaAs QWSCs.
Testing sequential quantum measurements: how can maximal knowledge be extracted?
Nagali, Eleonora; Felicetti, Simone; de Assis, Pierre-Louis; D'Ambrosio, Vincenzo; Filip, Radim; Sciarrino, Fabio
2012-01-01
The extraction of information from a quantum system unavoidably implies a modification of the measured system itself. In this framework partial measurements can be carried out in order to extract only a portion of the information encoded in a quantum system, at the cost of inducing a limited amount of disturbance. Here we analyze experimentally the dynamics of sequential partial measurements carried out on a quantum system, focusing on the trade-off between the maximal information extractable and the disturbance. In particular we implement two sequential measurements observing that, by exploiting an adaptive strategy, is possible to find an optimal trade-off between the two quantities. PMID:22720131
Photo-activated biological processes as quantum measurements
Atac Imamoglu; K. Birgitta Whaley
2014-08-21
We outline a framework for describing photo-activated biological reactions as generalized quantum measurements of external fields, for which the biological system takes on the role of a quantum meter. By using general arguments regarding the Hamiltonian that describes the measurement interaction, we identify the cases where it is essential for a complex chemical or biological system to exhibit non-equilibrium quantum coherent dynamics in order to achieve the requisite functionality. We illustrate the analysis by considering measurement of the solar radiation field in photosynthesis and measurement of the earth's magnetic field in avian magnetoreception.
Quantum nondemolition measurement of a single electron spin in a quantum dot
Mitsuro Sugita; Susumu Machida; Yoshihisa Yamamoto
2003-01-15
We propose a scheme for the quantum nondemolition (QND) measurement of a single electron spin in a single quantum dot (QD). Analytical expressions are obtained for the optical Faraday effect between a quantum dot exciton and microcavity field. The feasibility of the QND measurement of a single electron spin is discussed for a GaAs/AlAs microcavity with an InAs QD.
The Efficiency of Private Universities As Measured By Graduation Rates
EDWARD. C. KOKKELENBERG; Eshna Sinha; John D. Porter; Gary L. Blose
2008-01-01
It is well known that human capital is enhanced by graduation from a college or university. How efficient are such institutions in conveying this mark of human capital? Efficiency and productivity in private higher education is measured by using undergraduate graduation rates as the output, and demographic variables, the quality of the students, and the annual expenditures (adjusted for academic
A rectangular cavity for cell phone antenna efficiency measurement
A. P. Raiva; J. Fabrega-Sanchez
2005-01-01
Electromagnetic cavities can be used to measure antenna efficiency. Enclosing an antenna within a conducting rectangular or spherical cavity can eliminate the radiation resistance from the impedance without changing the loss resistance of the antenna. The cavity size should avoid both the disturbance of the field near the antenna and the cavity's resonance. The efficiency of the antenna is calculated
Verification for measurement-only blind quantum computing
NASA Astrophysics Data System (ADS)
Morimae, Tomoyuki
2014-06-01
Blind quantum computing is a new secure quantum computing protocol where a client who does not have any sophisticated quantum technology can delegate her quantum computing to a server without leaking any privacy. It is known that a client who has only a measurement device can perform blind quantum computing [T. Morimae and K. Fujii, Phys. Rev. A 87, 050301(R) (2013), 10.1103/PhysRevA.87.050301]. It has been an open problem whether the protocol can enjoy the verification, i.e., the ability of the client to check the correctness of the computing. In this paper, we propose a protocol of verification for the measurement-only blind quantum computing.
Second law of thermodynamics and quantum feedback control: Maxwell's demon with weak measurements
Jacobs, Kurt [Department of Physics, University of Massachusetts at Boston, Boston, Massachusetts 02125 (United States)
2009-07-15
Recently Sagawa and Ueda [Phys. Rev. Lett. 100, 080403 (2008)] derived a bound on the work that can be extracted from a quantum system with the use of feedback control. For many quantum measurements their bound was not tight. We show that a tight version of this bound follows straightforwardly from recent work on Maxwell's demon by Alicki et al. [Open Syst. Inf. Dyn. 11, 205 (2004)], for both discrete and continuous feedback control. Our analysis also shows that bare, efficient measurements always do non-negative work on a system in equilibrium, but do not add heat.
Measuring energy efficiency in the United States` economy: A beginning
NONE
1995-10-01
Energy efficiency is a vital component of the Nation`s energy strategy. One of the Department of Energy`s missions are to promote energy efficiency to help the Nation manage its energy resources. The ability to define and measure energy efficiency is essential to this objective. In the absence of consistent defensible measures, energy efficiency is a vague, subjective concept that engenders directionless speculation and confusion rather than insightful analysis. The task of defining and measuring energy efficiency and creating statistical measures as descriptors is a daunting one. This publication is not a final product, but is EIA`s first attempt to define and measure energy efficiency in a systematic and robust manner for each of the sectors and the United States economy as a whole. In this process, EIA has relied on discussions, customer reviews, in-house reviews, and seminars that have focused on energy efficiency in each of the sectors. EIA solicits the continued participation of its customers in further refining this work.
Efficient synthesis of probabilistic quantum circuits with fallback
NASA Astrophysics Data System (ADS)
Bocharov, Alex; Roetteler, Martin; Svore, Krysta M.
2015-05-01
Repeat-until-success (RUS) circuits can approximate a given single-qubit unitary with an expected number of T gates of about 1/3 of what is required by optimal, deterministic, ancilla-free decompositions over the Clifford + T gate set. In this work, we introduce a more general and conceptually simpler circuit decomposition method that allows for synthesis into protocols that probabilistically implement quantum circuits over several universal gate sets including, but not restricted to, the Clifford + T gate set. The protocol, which we call probabilistic quantum circuits with fallback (PQF), implements a walk on a discrete Markov chain in which the target unitary is an absorbing state and in which transitions are induced by multiqubit unitaries followed by measurements. In contrast to RUS protocols, the presented PQF protocols are guaranteed to terminate after a finite number of steps. Specifically, we apply our method to the Clifford + T , Clifford + V , and Clifford + ? /12 gate sets to achieve decompositions with expected gate counts of logb(1 /? ) +O {ln[ln(1 /? ) ] } , where b is a quantity related to the expansion property of the underlying universal gate set.
NASA Astrophysics Data System (ADS)
Rowe, M. A.; Gansen, E. J.; Greene, M.; Hadfield, R. H.; Harvey, T. E.; Su, M. Y.; Nam, S. W.; Mirin, R. P.; Rosenberg, D.
2006-12-01
We investigate the operation of a quantum dot, optically gated, field-effect transistor as a photon detector. The detector exhibits time-gated, single-shot, single-photon sensitivity, a linear response, and an internal quantum efficiency of up to (68±18)% at 4K. Given the noise of the detector system, they find that a particular discriminator level can be chosen so the device operates with an internal quantum efficiency of (53±11)% and dark counts of 0.003 counts per shot.
Integral quantum fluctuation theorems under measurement and feedback control.
Funo, Ken; Watanabe, Yu; Ueda, Masahito
2013-11-01
We derive integral quantum fluctuation theorems and quantum Jarzynski equalities for a feedback-controlled system and a memory which registers outcomes of the measurement. The obtained equalities involve the information content, which reflects the information exchange between the system and the memory, and take into account the back action of a general measurement contrary to the classical case. The generalized second law of thermodynamics under measurement and feedback control is reproduced from these equalities. PMID:24329228
Measured quantum probability distribution functions for Brownian motion
Ford, G. W.; O'Connell, R. F. [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040 (United States); Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803-4001 (United States)
2007-10-15
The quantum analog of the joint probability distributions describing a classical stochastic process is introduced. A prescription is given for constructing the quantum distribution associated with a sequence of measurements. For the case of quantum Brownian motion this prescription is illustrated with a number of explicit examples. In particular, it is shown how the prescription can be extended in the form of a general formula for the Wigner function of a Brownian particle entangled with a heat bath.
Measured quantum probability distribution functions for Brownian motion
G. W. Ford; R. F. O'Connell
2007-10-17
The quantum analog of the joint probability distributions describing a classical stochastic process is introduced. A prescription is given for constructing the quantum distribution associated with a sequence of measurements. For the case of quantum Brownian motion this prescription is illustrated with a number of explicit examples. In particular it is shown how the prescription can be extended in the form of a general formula for the Wigner function of a Brownian particle entangled with a heat bath.
A graphical approach to measurement-based quantum computing
Ross Duncan
2012-03-28
Quantum computations are easily represented in the graphical notation known as the ZX-calculus, a.k.a. the red-green calculus. We demonstrate its use in reasoning about measurement-based quantum computing, where the graphical syntax directly captures the structure of the entangled states used to represent computations, and show that the notion of information flow within the entangled states gives rise to rewriting strategies for proving the correctness of quantum programs.
Toward Quantum-Limited Position Measurements Using Optically Levitated Microspheres
Kenneth G. Libbrecht; Eric D Black
2003-11-20
We describe the use of optically levitated microspheres as test masses in experiments aimed at reaching and potentially exceeding the standard quantum limit for position measurements. Optically levitated microspheres have low mass and are essentially free of suspension thermal noise, making them well suited for reaching the quantum regime. Table-top experiments using microspheres can bridge the gap between quantum-limited position measurements of single atoms and measurements with multi-kg test masses like those being used in interferometric gravitational wave detectors.
On determining which quantum measurement performs better for state estimation
Jaroslav Rehacek; Yong Siah Teo; Zdenek Hradil
2014-10-15
We introduce an operational and statistically meaningful measure, the quantum tomographic transfer function, that possesses important physical invariance properties for judging whether a given informationally complete quantum measurement performs better tomographically in quantum-state estimation relative to other informationally complete measurements. This function is independent of the unknown true state of the quantum source, and is directly related to the average optimal tomographic accuracy of an unbiased state estimator for the measurement in the limit of many sampling events. For the experimentally-appealing minimally complete measurements, the transfer function is an extremely simple formula. We also give an explicit expression for this transfer function in terms of an ordered expansion that is readily computable and illustrate its usage with numerical simulations, and its consistency with some known results.
Bulk heterojunction solar cells with internal quantum efficiency approaching 100%
Sung Heum Park; Anshuman Roy; Serge Beaupré; Shinuk Cho; Nelson Coates; Ji Sun Moon; Daniel Moses; Mario Leclerc; Kwanghee Lee; Alan J. Heeger
2009-01-01
We report the fabrication and measurement of solar cells with 6% power conversion efficiency using the alternating co-polymer, poly[N-9''-hepta-decanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole) (PCDTBT) in bulk heterojunction composites with the fullerene derivative [6,6]-phenyl C70-butyric acid methyl ester (PC70BM). The PCDTBT\\/PC70BM solar cells exhibit the best performance of any bulk heterojunction system studied to date, with JSC = 10.6 mA cm-2, VOC = 0.88 V,
Quantum mechanicallycomplete measurements in electron impact excitation of helium
Quantum mechanicallycomplete measurements in electron impact excitation of helium Andrew G. Mikosza, Nedlands, Perth. 6907, Australia. Abstract. A complete quantum description of the 3! D state of helium, with the Convergent Close Coupling (CCC) calculations. Previous data for helium at 40eV incident electrons
Topos logic in measurement-based quantum computation
Leon Loveridge; Raouf Dridi; Robert Raussendorf
2015-03-12
We report first steps towards elucidating the relationship between contextuality, measurement-based quantum computation (MBQC) and the non-classical logic of a topos associated with the computation. We show that, in a class of MBQC, classical universality requires non-classical logic, which is 'consumed' during the course of the computation, thereby pinpointing another potential quantum computational resource.
Blind quantum computation for Alice who does only measurements
Morimae, Tomoyuki
2012-01-01
Blind quantum computation is a secure quantum computing protocol which enables Alice who does not have sufficient quantum technology to ask Bob to perform quantum computation on Bob's fully-fledged quantum computer in such a way that Bob cannot learn anything about Alice's input, output, and algorithm. In previous proposals, Alice needs to have a device which generates quantum states, such as single-photon states. Here we show that Alice who does only measurements, such as the polarization measurements with a threshold detector, can perform the blind quantum computation. In several experimental setups, such as optical systems, the measurement of a state is much easier than the generation of a single-qubit state. Therefore our protocols can ease Alice's burden. Furthermore, the security of our protocols is device independent in the sense that Alice does not need to trust her measurement device. Finally, the security of our protocols is based on the no-signaling principle, which is more fundamental than quantum...
Improving Students' Understanding of Quantum Measurement. I. Investigation of Difficulties
ERIC Educational Resources Information Center
Zhu, Guangtian; Singh, Chandralekha
2012-01-01
We describe the difficulties that advanced undergraduate and graduate students have with quantum measurement within the standard interpretation of quantum mechanics. We explore the possible origins of these difficulties by analyzing student responses to questions from both surveys and interviews. Results from this research are applied to develop…
Lasing-induced reduction in core heating in high wall plug efficiency quantum cascade lasers
Anthony J. Hoffman; Phillip X. Braun; Matthew D. Escarra; Scott S. Howard; Kale J. Franz; Xiaojun Wang; Jenyu Fan; Claire Gmachl
2009-01-01
Quantum cascade (QC) laser core heating is a primary impediment to high device wall plug efficiency (WPE). Here, we demonstrate that efficient photon generation produces a quantifiable reduction in heating of the QC laser core temperature. By superimposing low duty cycle current pulses on a core-heating dc baseline, we observe the instantaneous threshold current and current efficiency evolution as the
NASA Astrophysics Data System (ADS)
Davanço, M.; Rakher, M. T.; Wegscheider, W.; Schuh, D.; Badolato, A.; Srinivasan, K.
2011-09-01
We demonstrate a spectrally broadband and efficient technique for collecting emission from a single InAs quantum dot directly into a standard single mode optical fiber. In this approach, an optical fiber taper waveguide is placed in contact with a suspended GaAs nanophotonic waveguide with embedded quantum dots, forming a broadband directional coupler with standard optical fiber input and output. Efficient photoluminescence collection over a wavelength range of tens of nanometers is demonstrated, and a maximum collection efficiency of 6% (corresponding single photon rate of 3.0 MHz) into a single mode optical fiber is estimated for a single quantum dot exciton.
Long-Distance Measurement-Device-Independent Multiparty Quantum Communication
NASA Astrophysics Data System (ADS)
Fu, Yao; Yin, Hua-Lei; Chen, Teng-Yun; Chen, Zeng-Bing
2015-03-01
The Greenberger-Horne-Zeilinger (GHZ) entanglement, originally introduced to uncover the extreme violation of local realism against quantum mechanics, is an important resource for multiparty quantum communication tasks. But the low intensity and fragility of the GHZ entanglement source in current conditions have made the practical applications of these multiparty tasks an experimental challenge. Here we propose a feasible scheme for practically distributing the postselected GHZ entanglement over a distance of more than 100 km for experimentally accessible parameter regimes. Combining the decoy-state and measurement-device-independent protocols for quantum key distribution, we anticipate that our proposal suggests an important avenue for practical multiparty quantum communication.
Compressing measurements in quantum dynamic parameter estimation
Magesan, Easwar
We present methods that can provide an exponential savings in the resources required to perform dynamic parameter estimation using quantum systems. The key idea is to merge classical compressive sensing techniques with ...
Jian Fu; Shuo Sun
2010-03-30
We demonstrate that a tensor product structure could be obtained by introducing pseudorandom phase sequences into classical fields with two orthogonal modes. Using classical fields modulated with pseudorandom phase sequences, we discuss efficient simulation of several typical quantum states, including product state, Bell states, GHZ state, and W state. By performing quadrature demodulation scheme, we could obtain the mode status matrix of the simulating classical fields, based on which we propose a sequence permutation mechanism to reconstruct the simulated quantum states. The research on classical simulation of quantum states is important, for it not only enables potential practical applications in quantum computation, but also provides useful insights into fundamental concepts of quantum mechanics.
Efficient quantum simulation of fermionic and bosonic models in trapped ions
L. Lamata; A. Mezzacapo; J. Casanova; E. Solano
2014-06-18
We analyze the efficiency of quantum simulations of fermionic and bosonic models in trapped ions. In particular, we study the optimal time of entangling gates and the required number of total elementary gates. Furthermore, we exemplify these estimations in the light of quantum simulations of quantum field theories, condensed-matter physics, and quantum chemistry. Finally, we show that trapped-ion technologies are a suitable platform for implementing quantum simulations involving interacting fermionic and bosonic modes, paving the way for overcoming classical computers in the near future.
Implementation and Measurement Efficiency of Multidimensional Computerized Adaptive Testing
ERIC Educational Resources Information Center
Wang, Wen-Chung; Chen, Po-Hsi
2004-01-01
Multidimensional adaptive testing (MAT) procedures are proposed for the measurement of several latent traits by a single examination. Bayesian latent trait estimation and adaptive item selection are derived. Simulations were conducted to compare the measurement efficiency of MAT with those of unidimensional adaptive testing and random…
Quantum States as Probabilities from Symmetric Informationally Complete Measurements
NASA Astrophysics Data System (ADS)
Ericsson, Åsa
2011-03-01
If you pick d2 symmetrically spread vectors in a d -dimensional Hilbert space, you get a symmetric informationally complete set of quantum states (or SIC for short). SICs have applications within quantum information science, such as to quantum state tomography and quantum cryptography, and are also of interest for foundational studies of quantum mechanics. In this talk I will review the representation of quantum states as probability distributions over the outcomes of a SIC measurement. Not all probability distributions correspond to quantum states, thus quantum state space is a restricted subset of all potentially available probabilities. We will explore how this restriction can be characterized. A recent publication (Fuchs and Schack, arXiv:0906.2187) advocates the SIC-representation and suggests that the Born rule rewritten in this language can be taken as a postulate for quantum mechanics. This motivates the introduction of so-called maximally consistent sets (Appleby, Ericsson, and Fuchs, arXiv:0910.2750); one such set is quantum state space. This work was supported in part by the U.S. Office of Naval Research (Grant No. N00014-09-1-0247).
Noninvasive electron microscopy with interaction-free quantum measurements
Putnam, William P.
We propose the use of interaction-free quantum measurements with electrons to eliminate sample damage in electron microscopy. This might allow noninvasive molecular-resolution imaging. We show the possibility of such ...
Quantum capacitance measurements of single-layer molybdenum disulfide
Kononov, Alina
2014-01-01
Through this thesis, heterostructures composed of a thin layer of hexagonal boron nitride atop a monolayer of molybdenum disulfide were fabricated with the goal of measuring quantum capacitance and probing the transition ...
Demonstration of Quantum Nonlocality in the Presence of Measurement Dependence
NASA Astrophysics Data System (ADS)
Aktas, Djeylan; Tanzilli, Sébastien; Martin, Anthony; Pütz, Gilles; Thew, Rob; Gisin, Nicolas
2015-06-01
Quantum nonlocality stands as a resource for device independent quantum information processing (DIQIP), such as, for instance, device independent quantum key distribution. We investigate, experimentally, the assumption of limited measurement dependence, i.e., that the measurement settings used in Bell inequality tests or DIQIP are partially influenced by the source of entangled particle and/or by an adversary. Using a recently derived Bell-like inequality [G. Pütz, Phys. Rev. Lett. 113, 190402 (2014)] and a 99% fidelity source of partially entangled polarization photonic qubits, we obtain a clear violation of the inequality, excluding a much larger range of measurement dependent local models than would be possible with an adapted Clauser-Horne-Shimony-Holt (CHSH) inequality. It is therefore shown that the measurement independence assumption can be widely relaxed while still demonstrating quantum nonlocality.
Cemine, Vernon Julius; Blanca, Carlo Mar; Saloma, Caesar
2006-09-20
We map the external quantum efficiency (QE) distribution of a silicon photodiode (PD) sample via a thermographic imaging technique based on optical-feedback laser confocal microscopy. An image pair consisting of the confocal reflectance image and the 2D photocurrent map is simultaneously acquired to delineate the following regions of interest on the sample: the substrate, the n-type region, the pn overlay, and the bonding pad. The 2D QE distribution is derived from the photocurrent map to quantify the optical performance of these sites. The thermal integrity of the sample is then evaluated by deriving the rate of change of QE with temperature T at each point on the silicon PD. These gradient maps function not only as stringent measures of local thermal QE activity but they also expose probable defect locations on the sample at high spatial resolution - a capability that is not feasible with existing bulk measurement techniques.
Dirichlet series as interfering probability amplitudes for quantum measurements
NASA Astrophysics Data System (ADS)
Feiler, C.; Schleich, W. P.
2015-06-01
We show that all Dirichlet series, linear combinations of them and their analytical continuations represent probability amplitudes for measurements on time-dependent quantum systems. In particular, we connect an arbitrary Dirichlet series to the time evolution of an appropriately prepared quantum state in a non-linear oscillator with logarithmic energy spectrum. However, the realization of a superposition of two Dirichlet sums and its analytical continuation requires two quantum systems which are entangled, and a joint measurement. We illustrate our approach of implementing arbitrary Dirichlet series in quantum systems using the example of the Riemann zeta function and relate its non-trivial zeros to the interference of two quantum states reminiscent of a Schrödinger cat.
Engineering Quantum States, Nonlinear Measurements, and Anomalous Diffusion by Imaging
Kurt Jacobs; Daniel A. Steck
2010-01-01
We show that well-separated quantum superposition states, measurements of\\u000astrongly nonlinear observables, and quantum dynamics driven by anomalous\\u000adiffusion can all be achieved for single atoms or molecules by imaging\\u000aspontaneous photons that they emit via resonance florescence. To generate\\u000aanomalous diffusion we introduce continuous measurements driven by L\\\\'evy\\u000aprocesses, and prove a number of results regarding their properties. In
Fast automotive diesel exhaust measurement using quantum cascade lasers
NASA Astrophysics Data System (ADS)
Herbst, J.; Brunner, R.; Lambrecht, A.
2013-12-01
Step by step, US and European legislations enforce the further reduction of atmospheric pollution caused by automotive exhaust emissions. This is pushing automotive development worldwide. Fuel efficient diesel engines with SCRtechnology can impede NO2-emission by reduction with NH3 down to the ppm range. To meet the very low emission limits of the Euro6 resp. US NLEV (National Low Emission Vehicle) regulations, automotive manufacturers have to optimize continuously all phases of engine operation and corresponding catalytic converters. Especially nonstationary operation holds a high potential for optimizing gasoline consumption and further reducing of pollutant emissions. Test equipment has to cope with demanding sensitivity and speed requirements. In the past Fraunhofer IPM has developed a fast emission analyzer called DEGAS (Dynamic Exhaust Gas Analyzer System), based on cryogenically cooled lead salt lasers. These systems have been used at Volkswagen AG`s test benches for a decade. Recently, IPM has developed DEGAS-Next which is based on cw quantum cascade lasers and thermoelectrically cooled detectors. The system is capable to measure three gas components (i.e. NO, NO2, NH3) in two channels with a time resolution of 20 ms and 1 ppm detection limits. We shall present test data and a comparison with fast FTIR measurements.
Stability of continuous-time quantum filters with measurement imperfections
NASA Astrophysics Data System (ADS)
Amini, H.; Pellegrini, C.; Rouchon, P.
2014-07-01
The fidelity between the state of a continuously observed quantum system and the state of its associated quantum filter, is shown to be always a submartingale. The observed system is assumed to be governed by a continuous-time Stochastic Master Equation (SME), driven simultaneously by Wiener and Poisson processes and that takes into account incompleteness and errors in measurements. This stability result is the continuous-time counterpart of a similar stability result already established for discrete-time quantum systems and where the measurement imperfections are modelled by a left stochastic matrix.
Characterization of LBNL SNAP CCD's: Quantum efficiency, reflectivity, and point-spread function
NASA Astrophysics Data System (ADS)
Groom, Donald E.; Bebek, C. J.; Fabricius, M.; Fairfield, J. A.; Karcher, A.; Kolbe, W. F.; Roe, N. A.; Steckert, J.
2006-12-01
A Quantum Efficiency Machine has been developed at Lawrence Berkeley Lab to measure the quantum efficiency (QE) of the novel thick CCD's planned for use in the Supernova/Acceleration Probe (SNAP) mission. It is conventional, but with significant innovations. The most important of these is that the reference photodiode (PD) is coplanar with the cold CCD inside the dewar. The PD is on a separate heat sink regulated to the PD calibration temperature. The effects of geometry and reflections from the dewar window are eliminated, and since the PD and the CCD are observed simultaneously, light intensity regulation is not an issue. A ``dark box'' provides space between the exit port of the integrating sphere and the CCD dewar, ensuring nearly uniform illumination. It also provides a home for a reflectometer and spot projector, both of which are fed by the alternate beam of the monochromator. The measurement of reflectivity (R) is essential for corroborating the QE measurements, since QE < 1-R everywhere, and QE = 1-R over much of the spectral region. In our reflectometer the light monitor and the CCD carriage are both moved so that no extra mirrors are introduced. The intrinsic point-spread function (PSF) of a CCD is limited by transverse diffusion of the charge carriers as they drift to the potential wells, driven by the electric field produced by the substrate bias potential---hence a bias voltage that is normally several times that needed for total depletion. A precision spot projector is installed in the dark box for the measurements. A PSF rms width of 3.7 pm 0.2 um is obtained for the 200 um thick SNAP CCD's biased at 115 V, thus meeting the SNAP design goals. The result agrees with simple theory once the electric field dependence of carrier mobility is taken into account.
Blind quantum computation protocol in which Alice only makes measurements
NASA Astrophysics Data System (ADS)
Morimae, Tomoyuki; Fujii, Keisuke
2013-05-01
Blind quantum computation is a new secure quantum computing protocol which enables Alice (who does not have sufficient quantum technology) to delegate her quantum computation to Bob (who has a full-fledged quantum computer) in such a way that Bob cannot learn anything about Alice's input, output, and algorithm. In previous protocols, Alice needs to have a device which generates quantum states, such as single-photon states. Here we propose another type of blind computing protocol where Alice does only measurements, such as the polarization measurements with a threshold detector. In several experimental setups, such as optical systems, the measurement of a state is much easier than the generation of a single-qubit state. Therefore our protocols ease Alice's burden. Furthermore, the security of our protocol is based on the no-signaling principle, which is more fundamental than quantum physics. Finally, our protocols are device independent in the sense that Alice does not need to trust her measurement device in order to guarantee the security.
Schwörer, Magnus; Lorenzen, Konstantin; Mathias, Gerald; Tavan, Paul
2015-03-14
Recently, a novel approach to hybrid quantum mechanics/molecular mechanics (QM/MM) molecular dynamics (MD) simulations has been suggested [Schwörer et al., J. Chem. Phys. 138, 244103 (2013)]. Here, the forces acting on the atoms are calculated by grid-based density functional theory (DFT) for a solute molecule and by a polarizable molecular mechanics (PMM) force field for a large solvent environment composed of several 10(3)-10(5) molecules as negative gradients of a DFT/PMM hybrid Hamiltonian. The electrostatic interactions are efficiently described by a hierarchical fast multipole method (FMM). Adopting recent progress of this FMM technique [Lorenzen et al., J. Chem. Theory Comput. 10, 3244 (2014)], which particularly entails a strictly linear scaling of the computational effort with the system size, and adapting this revised FMM approach to the computation of the interactions between the DFT and PMM fragments of a simulation system, here, we show how one can further enhance the efficiency and accuracy of such DFT/PMM-MD simulations. The resulting gain of total performance, as measured for alanine dipeptide (DFT) embedded in water (PMM) by the product of the gains in efficiency and accuracy, amounts to about one order of magnitude. We also demonstrate that the jointly parallelized implementation of the DFT and PMM-MD parts of the computation enables the efficient use of high-performance computing systems. The associated software is available online. PMID:25770527
Characterization of measurements in quantum communication. Ph.D. Thesis
NASA Technical Reports Server (NTRS)
Chan, V. W. S.
1975-01-01
A characterization of quantum measurements by operator valued measures is presented. The generalized measurements include simultaneous approximate measurement of noncommuting observables. This characterization is suitable for solving problems in quantum communication. Two realizations of such measurements are discussed. The first is by adjoining an apparatus to the system under observation and performing a measurement corresponding to a self-adjoint operator in the tensor-product Hilbert space of the system and apparatus spaces. The second realization is by performing, on the system alone, sequential measurements that correspond to self-adjoint operators, basing the choice of each measurement on the outcomes of previous measurements. Simultaneous generalized measurements are found to be equivalent to a single finer grain generalized measurement, and hence it is sufficient to consider the set of single measurements. An alternative characterization of generalized measurement is proposed. It is shown to be equivalent to the characterization by operator-values measures, but it is potentially more suitable for the treatment of estimation problems. Finally, a study of the interaction between the information-carrying system and a measurement apparatus provides clues for the physical realizations of abstractly characterized quantum measurements.
Min, Hyegeun; Jo, Seong-Min; Kim, Hak-Sung
2015-06-01
Circulating tumor cells (CTCs) are valuable biomarkers for monitoring the status of cancer patients and drug efficacy. However, the number of CTCs in the blood is extremely low, and the isolation and detection of CTCs with high efficiency and sensitivity remain a challenge. Here, we present an approach to the efficient capturing and simple quantification of CTCs using quantum dots and magnetic beads. Anti-EpCAM antibody-conjugated quantum dots are used for the targeting and quantification of CTCs, and quantum-dot-attached CTCs are isolated using anti-IgG-modified magnetic beads. Our approach is shown to result in a capture efficiency of about 70%-80%, enabling the simple quantification of captured CTCs based on the fluorescence intensity of the quantum dots. The present method can be used effectively in the capturing and simple quantification of CTCs with high efficiency for cancer diagnosis and monitoring. PMID:25630488
Reusswig, Philip David
We demonstrate bilayer organic photovoltaic cells that incorporate a singlet exciton fission sensitizer layer to increase the external quantum efficiency (EQE). This solar cell architecture is realized by pairing the singlet ...
Reverse current and external quantum efficiency of zinc diffused 1.3-µm GaAlAsSb photodiodes
M. Mebarki; T. Belatoui; A. Joullie; B. Orsal; R. Alabedra
1990-01-01
Zinc-diffused p+n photodiodes were prepared from 1.3-?m GaAlAsSb solid solution grown on GaSb (111) substrate by liquid-phase epitaxy. The reverse dark current was measured in the 77–300 K temperature domain. It has been found dominated by a defect tunneling component in a wide voltage range. The study of spectral photoresponse shows external quantum efficiency (without AR coating) as high as
Tagging Efficiency for Nuclear Physics Measurements at MAX-lab
NASA Astrophysics Data System (ADS)
Miller, Nevin; Elofson, David; Lewis, Codie; O'Brien, Erin; Buggelli, Kelsey; O'Connor, Kyle; O'Rielly, Grant; Maxtagg Team
2014-09-01
A careful study of the tagging efficiency during measurements of near threshold pion photoproduction and high energy Compton scattering has been performed. These experiments are being done at the MAX-lab tagged photon Facility during the June 2014 run period. The determination of the final results from these experiments depends on knowledge of the incident photon flux. The tagging efficiency is a critical part of the photon flux calculation. In addition to daily measurements of the tagging efficiency, a beam monitor was used during the production data runs to monitor the relative tagging efficiency. Two trigger types were used in the daily measurements; one was a logical OR from the tagger array and the other was from the Pb-glass photon detector. Investigations were made to explore the effect of the different trigger conditions and the differences between single and multi hit TDCs on the tagging efficiency. In addition the time evolution and overall uncertainty in the tagging efficiency for each tagger channel was determined. The results will be discussed.
Review paper: Toward highly efficient quantum-dot-and dye-sensitized solar cells
Park, Byungwoo
Review paper: Toward highly efficient quantum-dot- and dye-sensitized solar cells Hongsik Choi Interface control Light harvesting Tandem solar cell a b s t r a c t Dye- and quantum-dot-sensitized solar technologies of silicon-based solar cells should be resolved [7]. Dye-sensitized solar cells (DSSCs) have been
Efficient Quantum Monte Carlo Energies for Molecular Dynamics Simulations Jeffrey C. Grossman
Mitas, Lubos
Efficient Quantum Monte Carlo Energies for Molecular Dynamics Simulations Jeffrey C. Grossman methods has prevented their application to molecular dynamics simulations in which a typical trajectory the many-body quantum Monte Carlo (QMC) approach ``on-the-fly'' throughout a molecular dynamics (MD
Enhancement of Radiative Efficiency with Staggered InGaN Quantum Well Light Emitting Diodes
Tansu, Nelson; Dierolf, Volkmar; Huang, Gensheng; Penn, Samson; Zhao, Hongping; Liu, Guangyu; Li, Xiaohang; Poplawsky, Jonathan
2011-07-14
The technology on the large overlap InGaN QWs developed in this program is currently implemented in commercial technology in enhancing the internal quantum efficiency in major LED industry in US and Asia. The scientific finding from this work supported by the DOE enabled the implementation of this step-like staggered quantum well in the commercial LEDs.
Five measurement bases determine pure quantum states on any dimension
D. Goyeneche; G. Cañas; S. Etcheverry; E. S. Gómez; G. B. Xavier; G. Lima; A. Delgado
2015-05-13
A long standing problem in quantum mechanics is the minimum number of observables required for the characterisation of unknown pure quantum states. The solution to this problem is specially important for the developing field of high-dimensional quantum information processing. In this work we demonstrate that any pure d-dimensional state is unambiguously reconstructed by measuring 5 observables, that is, via projective measurements onto the states of 5 orthonormal bases. Thus, in our method the total number of different measurement outcomes (5d) scales linearly with d. The state reconstruction is robust against experimental errors and requires simple post-processing, regardless of d. We experimentally demonstrate the feasibility of our scheme through the reconstruction of 8-dimensional quantum states, encoded in the momentum of single photons.
Makoto Naruse; Erich Runge; Kiyoshi Kobayashi; Motoichi Ohtsu
2010-01-01
We investigated the efficient optical excitation transfer in layered quantum dot structures by introducing a network of optical near-field interactions. With a density-matrix-based formalization of interdot near-field interactions, our theoretical approach allows systematic analysis of layered CdTe quantum dot systems, revealing dominant factors contributing to the efficient optical excitation transfer and demonstrating good agreement with previous experimental observations. We also
Stable, high quantum efficiency silicon photodiodes for vacuum-UV applications
NASA Astrophysics Data System (ADS)
Korde, Raj; Canfield, L. Randall; Wallis, Brad
1988-01-01
Silicon photodiodes have been developed by defect-free phosphorus diffusion having practically no carrier recombination at the SiSiO2 interface or in the front diffused region. The quantum efficiency of these photodiodes was found to be around 120 percent at 100 nm. Unlike the previously tested silicon photodiodes, the developed photodiodes exhibit extremely stable quantum efficiency over extended periods of time. The possibility of using these photodiodes as vacuum ultraviolet detector standards is being currently investigated.
NASA Astrophysics Data System (ADS)
Alencar, Lorena D. S.; Pilla, Viviane; Andrade, Acácio A.; Donatti, Dario A.; Vollet, Dimas R.; De Vicente, Fábio S.
2014-04-01
The thermo-optical properties of CdSe/ZnS core-shell quantum dots (QDs) embedded in organic/silica hybrid colloids (organic/silica sols) were measured using the thermal lens (TL) technique. GPTS/TEOS-derived organic/silica hybrid colloids were prepared by a sol-gel method from the hydrolysis reaction of 3-glycidoxypropyltrimethoxysilane (GPTS) and tetraethylorthosilicate (TEOS) alkoxides. TL transient measurements were performed to study the effect of the CdSe/ZnS QDs (with three different sizes ? 2.4, 2.9 and 4.4 nm) embedded in GPTS/TEOS-derived organic/silica sols. The thermal diffusivity, the fraction thermal load and the radiative quantum efficiency (?) were determined. Fluorescence measurements corroborate the TL results and high ? values were obtained.
Informationally complete joint measurements on finite quantum systems
Claudio Carmeli; Teiko Heinosaari; Alessandro Toigo
2011-11-15
We show that there are informationally complete joint measurements of two conjugated observables on a finite quantum system, meaning that they enable to identify all quantum states from their measurement outcome statistics. We further demonstrate that it is possible to implement a joint observable as a sequential measurement. If we require minimal noise in the joint measurement, then the joint observable is unique. If the dimension d is odd, then this observable is informationally complete. But if d is even, then the joint observable is not informationally complete and one has to allow more noise in order to obtain informational completeness.
Low cost cylindrical converter for measuring lead efficiency
NASA Technical Reports Server (NTRS)
Hatch, G. L.; Nakata, L.; Britt, E. J.
1979-01-01
A low cost cylindrical thermionic converter has been designed, fabricated, and tested for use in a NASA-JPL program to directly measure converter lead efficiencies using various electrode materials and surfaces. Efficiency measurements are made using input emitter heater power, output power at the leads, and calculated values of the parasitic losses that would not be present in the application configuration. This information can be used to predict the performance characteristics of the advanced converters currently under development. A series of five converters has been tested. Both structured and smooth molybdenum collectors have been used. Emitters included smooth molybdenum, smooth rhenium, and microstructured rhenium. Cesium pressure families of current-voltage curves are presented for emitter temperatures of 1600, 1700, and 1800 K, along with measured efficiencies as a function of converter current densities for each temperature.
Quantum control and measurement of spins in laser cooled gases
NASA Astrophysics Data System (ADS)
Deutsch, Ivan
2012-10-01
Quantum information processing (QIP) requires three important ingredients: (i) preparing a desired initial quantum state, usually highly pure; (ii) controlling the dynamical evolution, usually via a desired unitary transformation; (iii) measuring the desired information encoded in the final quantum state. Many physical platforms are being developed for QIP, including trapped ions, semiconductor quantum dots, and atoms in optical lattices. In these cases, it is the spins of the system that encode the quantum information. Spins are natural carriers of quantum information given their long coherence times and our ability to control them with a variety of external electromagnetic fields. In addition, spins in laser-cooled atomic gases are an excellent testbed for exploring QIP protocols because of our ability to initially prepare highly pure states and employ the well-developed tools of quantum optics and coherent spectroscopy. In this talk I will give an overview of recent theory and experiment in the control and measurement of spins in laser-cooled atomic gases. We consider the hyperfine magnetic sublevels in the ground electronic states of ^133Cs, a 16-dimensional Hilbert space. We can explore all three ingredients described above: preparation of an arbitrary superposition state, evolution through an arbitrary unitary matrix, and readout through quantum state reconstruction of the full density matrix. We employ the tools of optimal quantum control and quantum estimation theory. The implementation involves atoms controlled by radio-frequency, microwave, a optical fields, and measured via polarization spectroscopy. The experiment is performed in the group of Prof. Poul S. Jessen, University of Arizona. This work was supported by the National Science Foundation.
On the efficiency factor for Jicamarca incoherent scatter measurements
NASA Astrophysics Data System (ADS)
Rodrigues, F. S.; Nicolls, M. J.; Hysell, D. L.; Chau, J. L.
2007-05-01
Sulzer and Gonzalez (1999) found that electron coulomb collisions have an important effect on the incoherent scattering of radio waves by a plasma at small aspect angles. The primary effect of electron coulomb collisions on incoherent scattering at small aspect angles is the narrowing of the spectrum. Another interesting effect of the collisions is the control of the efficiency factor (Milla and Kudeki, 2006), which is defined as a proportionality factor between the plasma electron density and the normalized total scattering cross section. For unmagnetized plasmas or the case of large aspect angles, the efficiency factor is approximately 1/(1+Te/Ti). Milla and Kudeki (2006), however, pointed out that the efficiency factor is far more complicated for small aspect angles. An analytical expression of the efficiency factor for small aspect angles does not exist yet. In this work, proper efficiency factor for Jicamarca measurements were obtained using numerical integration of the incoherent scatter spectrum including magnetic field and coulomb effects. The results were used to correct backscattered power profiles measured at Jicamarca. Corrected power profiles were compared with electron density profiles measured simultaneously using Faraday rotation. A good agreement between corrected power profiles and electron density profiles has been found. This result not only improves electron density measurements at Jicamarca, but also validates the formulation of Woodman (2006) and Kudeki and Milla (2006) based on the coulomb effects discovered by Sulzer and Gonzalez (1999).
Quantum Measurement Theory in Gravitational-Wave Detectors
NASA Astrophysics Data System (ADS)
Danilishin, Stefan L.; Khalili, Farid Ya.
2012-04-01
The fast progress in improving the sensitivity of the gravitational-wave detectors, we all have witnessed in the recent years, has propelled the scientific community to the point at which quantum behavior of such immense measurement devices as kilometer-long interferometers starts to matter. The time when their sensitivity will be mainly limited by the quantum noise of light is around the corner, and finding ways to reduce it will become a necessity. Therefore, the primary goal we pursued in this review was to familiarize a broad spectrum of readers with the theory of quantum measurements in the very form it finds application in the area of gravitational-wave detection. We focus on how quantum noise arises in gravitational-wave interferometers and what limitations it imposes on the achievable sensitivity. We start from the very basic concepts and gradually advance to the general linear quantum measurement theory and its application to the calculation of quantum noise in the contemporary and planned interferometric detectors of gravitational radiation of the first and second generation. Special attention is paid to the concept of the Standard Quantum Limit and the methods of its surmounting.
Quantum Measurement Theory in Gravitational-Wave Detectors
Stefan L. Danilishin; Farid Ya. Khalili
2012-05-09
The fast progress in improving the sensitivity of the gravitational-wave (GW) detectors, we all have witnessed in the recent years, has propelled the scientific community to the point, when quantum behaviour of such immense measurement devices as kilometer-long interferometers starts to matter. The time, when their sensitivity will be mainly limited by the quantum noise of light is round the corner, and finding the ways to reduce it will become a necessity. Therefore, the primary goal we pursued in this review was to familiarize a broad spectrum of readers with the theory of quantum measurements in the very form it finds application in the area of gravitational-wave detection. We focus on how quantum noise arises in gravitational-wave interferometers and what limitations it imposes on the achievable sensitivity. We start from the very basic concepts and gradually advance to the general linear quantum measurement theory and its application to the calculation of quantum noise in the contemporary and planned interferometric detectors of gravitational radiation of the first and second generation. Special attention is paid to the concept of Standard Quantum Limit and the methods of its surmounting.
Measures of quantum correlations in infinite-dimensional systems
M. E. Shirokov
2015-06-21
Several important measures of quantum correlations of a state of a finite-dimensional composite system are defined as linear combinations of marginal entropies of this state. This paper is devoted to the infinite-dimensional generalizations of such quantities and to the analysis of their properties. We introduce the notion of faithful extension of a linear combination of marginal entropies and consider several concrete examples starting with the quantum mutual information and the quantum conditional entropy. Then we show that the conditional mutual information can be uniquely defined as a lower semicontinuous function on the set of all states of a tripartite infinite-dimensional system possessing all the basic properties valid in finite dimensions. Infinite-dimensional generalizations of some other measures of quantum correlations in multipartite quantum systems are also considered. It is shown that almost all of these generalized measures are globally lower semicontinuous and possess local continuity properties which essentially simplify their use in analysis of quantum systems. In the second part of the paper we consider applications of the general results of its first part, in particular, to the theory of infinite-dimensional quantum channels and their capacities. We also show the existence of the Fawzi-Renner recovery channel reproducing marginal states for all tripartite states (including states with infinite marginal entropies) starting with the corresponding finite-dimensional result.
A spatio-temporal detective quantum efficiency and its application to fluoroscopic systems
Friedman, S. N.; Cunningham, I. A. [Sackler School of Medicine, Faculty of Medicine, Tel Aviv University, Ramat Aviv 69978 (Israel); Imaging Research Laboratories, Robarts Research Institute and Lawson Health Research Institute, 100 Perth Drive, London, Ontario N6A 5K8 (Canada) and Department of Medical Biophysics, University of Western Ontario, 1151 Richmond Street, London, Ontario N6A 5B8 (Canada)
2010-11-15
Purpose: Fluoroscopic x-ray imaging systems are used extensively in spatio-temporal detection tasks and require a spatio-temporal description of system performance. No accepted metric exists that describes spatio-temporal fluoroscopic performance. The detective quantum efficiency (DQE) is a metric widely used in radiography to quantify system performance and as a surrogate measure of patient ''dose efficiency.'' It has been applied previously to fluoroscopic systems with the introduction of a temporal correction factor. However, the use of a temporally-corrected DQE does not provide system temporal information and it is only valid under specific conditions, many of which are not likely to be satisfied by suboptimal systems. The authors propose a spatio-temporal DQE that describes performance in both space and time and is applicable to all spatio-temporal quantum-based imaging systems. Methods: The authors define a spatio-temporal DQE (two spatial-frequency axes and one temporal-frequency axis) in terms of a small-signal spatio-temporal modulation transfer function (MTF) and spatio-temporal noise power spectrum (NPS). Measurements were made on an x-ray image intensifier-based bench-top system using continuous fluoroscopy with an RQA-5 beam at 3.9 {mu}R/frame and hardened 50 kVp beam (0.8 mm Cu filtration added) at 1.9 {mu}R/frame. Results: A zero-frequency DQE value of 0.64 was measured under both conditions. Nonideal performance was noted at both larger spatial and temporal frequencies; DQE values decreased by {approx}50% at the cutoff temporal frequency of 15 Hz. Conclusions: The spatio-temporal DQE enables measurements of decreased temporal system performance at larger temporal frequencies analogous to previous measurements of decreased (spatial) performance. This marks the first time that system performance and dose efficiency in both space and time have been measured on a fluoroscopic system using DQE and is the first step toward the generalized use of DQE on clinical fluoroscopic systems.
NASA Astrophysics Data System (ADS)
Figueiredo, M. S.; Santos, F. A.; Yukimitu, K.; Moraes, J. C. S.; Silva, J. R.; Baesso, M. L.; Nunes, L. A. O.; Andrade, L. H. C.; Lima, S. M.
2013-10-01
Erbium doped tellurite glasses (TeO2 + Li2O + TiO2) were prepared by conventional melt-quenching method to study the influence of the Er3+ concentration on the luminescence quantum efficiency (?) at 1.5 ?m. Absorption and luminescence data were used to characterize the samples, and the ? parameter was measured using the well-known thermal lens spectroscopy. For low Er3+ concentration, the measured values are around 76%, and the concentration behavior of ? shows Er-Er and Er-OH- interactions, which agreed with the measured lifetime values.
Efficient free energy calculations of quantum systems through computer simulations
Alex Antonelli; Rafael Ramirez; Carlos Herrero; Eduardo Hernandez
2009-01-01
In general, the classical limit is assumed in computer simulation calculations of free energy. This approximation, however, is not justifiable for a class of systems in which quantum contributions for the free energy cannot be neglected. The inclusion of quantum effects is important for the determination of reliable phase diagrams of these systems. In this work, we present a new
The modern tools of quantum mechanics (A tutorial on quantum states, measurements, and operations)
Matteo G. A. Paris
2012-10-13
This tutorial is devoted to review the modern tools of quantum mechanics, which are suitable to describe states, measurements, and operations of realistic, not isolated, systems in interaction with their environment, and with any kind of measuring and processing devices. We underline the central role of the Born rule and and illustrate how the notion of density operator naturally emerges, together the concept of purification of a mixed state. In reexamining the postulates of standard quantum measurement theory, we investigate how they may formally generalized, going beyond the description in terms of selfadjoint operators and projective measurements, and how this leads to the introduction of generalized measurements, probability operator-valued measures (POVM) and detection operators. We then state and prove the Naimark theorem, which elucidates the connections between generalized and standard measurements and illustrates how a generalized measurement may be physically implemented. The "impossibility" of a joint measurement of two non commuting observables is revisited and its canonical implementations as a generalized measurement is described in some details. Finally, we address the basic properties, usually captured by the request of unitarity, that a map transforming quantum states into quantum states should satisfy to be physically admissible, and introduce the notion of complete positivity (CP). We then state and prove the Stinespring/Kraus-Choi-Sudarshan dilation theorem and elucidate the connections between the CP-maps description of quantum operations, together with their operator-sum representation, and the customary unitary description of quantum evolution. We also address transposition as an example of positive map which is not completely positive, and provide some examples of generalized measurements and quantum operations.
Repeatable measurements in quantum theory: Their role and feasibility
Busch, P. [Harvard Univ., Cambridge, MA (United States); Grabowski, M. [Nicolaus Copernicus Univ., Torun (Poland); Lahti, P.J. [Univ. of Turku (Finland)
1995-09-01
Recent advantages in experimental quantum physics call for a careful reconsideration of the measurements process in quantum mechanics. In this paper we describe the structure of the ideal measurements and their status among the repeatable measurements. Then we provide an exhaustive account of the interrelations between repeatability and the apparently weaker notions of value reproducible or first-kind measurements. We demonstrate the close link between repeatable measurements and discrete observables and show how the ensuing measurement limitations for continuous observables can be lifted in a way that is in full accordance with actual experimental practice. We present examples of almost repeatable measurements of continuous observables and some realistic models of weakly disturbing measurements.
Realization of Measurement and the Standard Quantum Limit
Masanao Ozawa
2015-05-05
This paper, following [M. Ozawa, Phys. Rev. Lett. 60, 385 (1988)], reports a refutation of the claim that for monitoring the position of a free mass such as gravitational-wave interferometers the sensitivity is limited by the so called standard quantum limit (SQL) due to the uncertainty principle. The latest proof of the SQL is analyzed to revleal an unsupported assumption on quantum measurements. Quantum measurement theory is introduced to give a general criterion for physically realizable measurements in quantum mechanics. A theory of approximate position measurements is developed to obtain a rigorous condition for the SQL and also to show that a precise position measurement can leave the object in an arbitrary family of states independent of the input state. This concludes that Yuen's proposal of breaking the SQL by a contractive state measurement, a measurement of the position leaving the free mass in a state with the position uncertainty decreasing in time, is physically realizable in principle. To enforce this conclusion, a model for error-free position measurement that leaves the object in a contractive state is constructed with a solvable Hamiltonian for measuring interaction. Finally, this model is shown to break the SQL with arbitrary accuracy.
Efficiency at Maximum Power Output of a Quantum-Mechanical Brayton Cycle
NASA Astrophysics Data System (ADS)
Yuan, Yuan; He, Ji-Zhou; Gao, Yong; Wang, Jian-Hui
2014-03-01
The performance in finite time of a quantum-mechanical Brayton engine cycle is discussed, without introduction of temperature. The engine model consists of two quantum isoenergetic and two quantum isobaric processes, and works with a single particle in a harmonic trap. Directly employing the finite-time thermodynamics, the efficiency at maximum power output is determined. Extending the harmonic trap to a power-law trap, we find that the efficiency at maximum power is independent of any parameter involved in the model, but depends on the confinement of the trapping potential.
Absolute quantum yield measurements of colloidal NaYF4: Er3+, Yb3+ upconverting nanoparticles
John-Christopher Boyer
2010-01-01
In this communication we describe a technique for measuring the absolute quantum yields (QYs) of upconverting nanomaterials based on the use of a commercially available fluorimeter and an integrating sphere. Using this setup, we have successfully acquired luminescence efficiency data (pump laser, absorbed pump, and visible emitted intensities) for lanthanide-doped upconverting nanoparticles. QYs in the range of 0.005% to 0.3%
Highly linear and efficient phase modulators based on GaInAsP-InP three-step quantum wells
Mohseni, Hooman
Highly linear and efficient phase modulators based on GaInAsP-InP three-step quantum wells H Highly linear and efficient phase modulators based on three-step quantum wells are reported. The spatial separation of electron and hole wave functions in the three-step quantum well leads to enhancement
Measurement-based quantum computation and undecidable logic
M. Van den Nest; H. J. Briegel
2008-03-27
We establish a connection between measurement-based quantum computation and the field of mathematical logic. We show that the computational power of an important class of quantum states called graph states, representing resources for measurement-based quantum computation, is reflected in the expressive power of (classical) formal logic languages defined on the underlying mathematical graphs. In particular, we show that for all graph state resources which can yield a computational speed-up with respect to classical computation, the underlying graphs--describing the quantum correlations of the states--are associated with undecidable logic theories. Here undecidability is to be interpreted in a sense similar to Goedel's incompleteness results, meaning that there exist propositions, expressible in the above classical formal logic, which cannot be proven or disproven.
NASA Technical Reports Server (NTRS)
Carruthers, George R.
1987-01-01
Measurements and comparisons have been made of the quantum efficiencies of microchannel plate (MCP) detectors in the far-UV (below 2000-A) wavelength range using CsI photocathodes (a) deposited on the front surfaces of microchannel plates and (b) deposited on solid substrates as opaque photocathodes with the resulting photoelectrons input to microchannel plates. The efficiences were measured in both pulse-counting and photodiode modes of operation. Typical efficiencies are about 15 percent at 1216 A for a CsI-coated MCP compared with 65 percent for an opaque CsI photocathode MCP detector. Special processing has yielded an efficiency as high as 20 percent for a CsI-coated MCP. This may possibly be further improved by optimization of the tilt angle of the MCP channels relative to the front face of the MCP and incident radiation. However, at present there still remains a factor of at least 3 quantum efficiency advantage in the separate opaque CsI photocathode configuration.
NASA Astrophysics Data System (ADS)
Carruthers, George R.
1987-07-01
Measurements and comparisons have been made of the quantum efficiencies of microchannel plate (MCP) detectors in the far-UV (below 2000-A) wavelength range using CsI photocathodes (a) deposited on the front surfaces of microchannel plates and (b) deposited on solid substrates as opaque photocathodes with the resulting photoelectrons input to microchannel plates. The efficiences were measured in both pulse-counting and photodiode modes of operation. Typical efficiencies are about 15 percent at 1216 A for a CsI-coated MCP compared with 65 percent for an opaque CsI photocathode MCP detector. Special processing has yielded an efficiency as high as 20 percent for a CsI-coated MCP. This may possibly be further improved by optimization of the tilt angle of the MCP channels relative to the front face of the MCP and incident radiation. However, at present there still remains a factor of at least 3 quantum efficiency advantage in the separate opaque CsI photocathode configuration.
A setup for the precision measurement of multianode photomultiplier efficiency
Carl Blaksley; Philippe Gorodetzky
2014-06-23
In many applications, such as the detection of ultra-high energy cosmic rays using the air fluorescence method, the number of photons incident on the detector must be known. This requires a precise knowledge of the absolute efficiency of the photodetectors used. We present an experimental setup for measuring the single photoelectron gain and efficiency of multi-anode photomultipliers with a total uncertainty on the order of a few percent. This precision is obtained by using a comparison to a NIST calibrated photodiode, and the presented method can be applied to both vacuum photomultiplier tubes and other photodetectors. This work is motivated by the need to calibrate the focal surface of the EUSO-Balloon instrument, which is a technical pathfinder for the future JEM-EUSO mission. A complete discussion of photomultiplier calibration is presented and the efficiency measurement technique is discussed in detail. Example results are given to illustrate the key points of the method.
Test and measurement on quantum key distribution systems
NASA Astrophysics Data System (ADS)
Tomita, Akihisa
2009-01-01
As in conventional communication systems, test and measurement play important roles in quantum key distribution (QKD) systems. Besides the observation that QKD protocols estimate the bound of information leakage from the measurement results on the transmission channel, test of quantum apparatus is necessary to ensure that the assumptions behind the security proof are satisfied in practice. Moreover, precise characterization of the device imperfection improves the final key rate, because one can specify the effect of the errors originated from the devices and sbtract it. However, careful consideration is required to guarantee that the test and measurement procedure will not open a loop-hole to the eavesdroppers.
Engineering Quantum States, Nonlinear Measurements, and Anomalous Diffusion by Imaging
Kurt Jacobs; Daniel Steck
2010-08-24
We show that well-separated quantum superposition states, measurements of strongly nonlinear observables, and quantum dynamics driven by anomalous diffusion can all be achieved for single atoms or molecules by imaging spontaneous photons that they emit via resonance florescence. To generate anomalous diffusion we introduce continuous measurements driven by L\\'evy processes, and prove a number of results regarding their properties. In particular we present strong evidence that the only stable L\\'evy density that can realize a strictly continuous measurement is the Gaussian.
Engineering Quantum States, Nonlinear Measurements, and Anomalous Diffusion by Imaging
Jacobs, Kurt
2010-01-01
We show that well-separated quantum superposition states, measurements of strongly nonlinear observables, and quantum dynamics driven by anomalous diffusion can all be achieved for single atoms or molecules by imaging spontaneous photons that they emit via resonance florescence. To generate anomalous diffusion we introduce continuous measurements driven by L\\'evy processes, and prove a number of results regarding their properties. In particular we present strong evidence that the only stable L\\'evy density that can realize a strictly continuous measurement is the Gaussian.
NASA Technical Reports Server (NTRS)
Braginsky, V. B.; Vorontsov, Y. I.; Thorne, K. S.
1979-01-01
Future gravitational wave antennas will be approximately 100 kilogram cylinders, whose end-to-end vibrations must be measured so accurately (10 to the -19th power centimeters) that they behave quantum mechanically. Moreover, the vibration amplitude must be measured over and over again without perturbing it (quantum nondemolition measurement). This contrasts with quantum chemistry, quantum optics, or atomic, nuclear, and elementary particle physics where measurements are usually made on an ensemble of identical objects, and care is not given to whether any single object is perturbed or destroyed by the measurement. Electronic techniques required for quantum nondemolition measurements are described as well as the theory underlying them.
NASA Astrophysics Data System (ADS)
Cao, Zheng-Wen; Feng, Xiao-Yi; Peng, Jin-Ye; Zeng, Gui-Hua; Qi, Xiao-Fei
2015-06-01
By analyzing the basic properties of a class of three-particle W states, we show how to establish a non-symmetric channel to realize a quantum dense code scheme, each quantum pair can carry log2 18 bits of classical message by employing different kinds of unitary transformation in three-dimensional Hilbert space, which can improve the transmission efficiency of classical message. Based on this quantum dense code, we propose a novel quantum secure direct communication scheme. The security of the scheme is also discussed in detail, and the error rate for eavesdropper is 50 %.
Quantum and concept combination, entangled measurements, and prototype theory.
Aerts, Diederik
2014-01-01
We analyze the meaning of the violation of the marginal probability law for situations of correlation measurements where entanglement is identified. We show that for quantum theory applied to the cognitive realm such a violation does not lead to the type of problems commonly believed to occur in situations of quantum theory applied to the physical realm. We briefly situate our quantum approach for modeling concepts and their combinations with respect to the notions of "extension" and "intension" in theories of meaning, and in existing concept theories. PMID:24482332
CP Measurement in Quantum Teleportation of Neutral Mesons
Yu Shi; Yue-Liang Wu
2008-07-08
Quantum teleportation using neutral pseudoscalar mesons shows novel connections between particle physics and quantum information. The projection basis, which is crucial in the teleportation process, is determined by the conservation laws of particle physics, and is different from the Bell basis, as in the usual case. Here we show that one can verify the teleportation process by CP measurement. This method significantly simplifies the high energy quantum teleportation protocol. Especially, it is rigorous, and is independent of whether CP is violated in weak decays. This method can also be applied to general verification of Einstein-Podolsky-Rosen correlations in particle physics.
Robust Shot Noise Measurement for Continuous Variable Quantum Key Distribution
Sébastien Kunz-Jacques; Paul Jouguet
2015-01-17
We study a practical method to measure the shot noise in real time in Continuous Variable Quantum Key Distribution (CVQKD) systems. The amount of secret key that can be extracted from the raw statistics depends strongly on this quantity since it affects in particular the computation of the excess noise (i.e. noise in excess of the shot noise) added by an eavesdropper on the quantum channel. Some powerful quantum hacking attacks relying on faking the estimated value of the shot noise to hide an intercept and resend strategy were proposed. Here, we provide experimental evidence that our method can defeat the saturation attack and the wavelength attack.
Fault-Tolerant Error Correction with Efficient Quantum Codes
DiVincenzo, D.P.; Shor, P.W. [IBM T. J. Watson Research Center, Yorktown Heights, New York 10598 (United States)] [IBM T. J. Watson Research Center, Yorktown Heights, New York 10598 (United States); [AT& T Research, Murray Hill, New Jersey 07974 (United States)
1996-10-01
We exhibit a simple, systematic procedure for detecting and correcting errors using any of the recently reported quantum error-correcting codes. The procedure is shown explicitly for a code in which one qubit is mapped into five. The quantum networks obtained are fault tolerant, that is, they can function successfully even if errors occur during the error correction. Our construction is derived using a recently introduced group-theoretic framework for unifying all known quantum codes. {copyright} {ital 1996 The American Physical Society.}
Using reflectance measurements to determine light use efficiency in corn
Technology Transfer Automated Retrieval System (TEKTRAN)
This study examines the ability of narrow band vegetation indexes to detect spectral changes associated with stress and relate them to light use efficiency (LUE) over the course of a day as well as through the growing season. In a corn field in Beltsville, MD, carbon flux measurements were made at a...
MEASURING THE USABILITY OF PAPER BALLOTS: EFFICIENCY, EFFECTIVENESS, AND SATISFACTION
Byrne, Mike
MEASURING THE USABILITY OF PAPER BALLOTS: EFFICIENCY, EFFECTIVENESS, AND SATISFACTION Sarah P on existing voting systems. Three traditional paper ballots were empirically evaluated to collect baseline data that can later be compared to newer, electronic voting systems. Usability was evaluated using