Boer, V O; van Lier, A L H M W; Hoogduin, J M; Wijnen, J P; Luijten, P R; Klomp, D W J
2011-11-01
In vivo MRS of the human brain at ultrahigh field allows for the identification of a large number of metabolites at higher spatial resolutions than currently possible in clinical practice. However, the in vivo localization of single-voxel spectroscopy has been shown to be challenging at ultrahigh field because of the low bandwidth of refocusing radiofrequency (RF) pulses. Thus far, the proposed methods for localized MRS at 7 T suffer from long TE, inherent signal loss and/or a large chemical shift displacement artifact that causes a spatial displacement between resonances, and results in a decreased efficiency in editing sequences. In this work, we show that, by driving a standard volume coil with two RF amplifiers, focusing the B 1+ field in a certain location and using high-bandwidth adiabatic refocusing pulses, a semi-LASER (semi-localized by adiabatic selective refocusing) localization is feasible at short TE in the human brain with full signal acquisition and a low chemical shift displacement artifact at 7 T. PMID:21294206
Optimized selective lactate excitation with a refocused multiple-quantum filter
NASA Astrophysics Data System (ADS)
Holbach, Mirjam; Lambert, Jörg; Johst, Sören; Ladd, Mark E.; Suter, Dieter
2015-06-01
Selective detection of lactate signals in in vivo MR spectroscopy with spectral editing techniques is necessary in situations where strong lipid or signals from other molecules overlap the desired lactate resonance in the spectrum. Several pulse sequences have been proposed for this task. The double-quantum filter SSel-MQC provides very good lipid and water signal suppression in a single scan. As a major drawback, it suffers from significant signal loss due to incomplete refocussing in situations where long evolution periods are required. Here we present a refocused version of the SSel-MQC technique that uses only one additional refocussing pulse and regains the full refocused lactate signal at the end of the sequence.
Self-refocused slice selection by magic echo DANTE with 270° flipping Gaussian RF modulation
NASA Astrophysics Data System (ADS)
Masumoto, Hidefumi; Hashimoto, Takeyuki; Matsui, Shigeru
2010-04-01
The method of slice selection proposed for solid-state MRI by combining DANTE selective excitation with magic echo (ME) line narrowing requires a rephasing period ca. 0.6 times the DANTE excitation period. The added rephasing period results in a significant loss of sensitivity due to transverse relaxation. To solve the sensitivity problem, we make use of the self-refocusing effect of the 270° Gaussian-shaped soft pulse by introducing a 270° flipping Gaussian modulation to the ME DANTE method. This eliminates the rephasing period. The utility of the improved method is demonstrated by experiments performed on test samples of adamantane and polycarbonate.
[Bond selective chemistry beyond the adiabatic approximation
Butler, L.J.
1993-02-28
The adiabatic Born-Oppenheimer potential energy surface approximation is not valid for reaction of a wide variety of energetic materials and organic fuels; coupling between electronic states of reacting species plays a key role in determining the selectivity of the chemical reactions induced. This research program initially studies this coupling in (1) selective C-Br bond fission in 1,3- bromoiodopropane, (2) C-S:S-H bond fission branching in CH[sub 3]SH, and (3) competition between bond fission channels and H[sub 2] elimination in CH[sub 3]NH[sub 2].
Bond selective chemistry beyond the adiabatic approximation
Butler, L.J.
1993-12-01
One of the most important challenges in chemistry is to develop predictive ability for the branching between energetically allowed chemical reaction pathways. Such predictive capability, coupled with a fundamental understanding of the important molecular interactions, is essential to the development and utilization of new fuels and the design of efficient combustion processes. Existing transition state and exact quantum theories successfully predict the branching between available product channels for systems in which each reaction coordinate can be adequately described by different paths along a single adiabatic potential energy surface. In particular, unimolecular dissociation following thermal, infrared multiphoton, or overtone excitation in the ground state yields a branching between energetically allowed product channels which can be successfully predicted by the application of statistical theories, i.e. the weakest bond breaks. (The predictions are particularly good for competing reactions in which when there is no saddle point along the reaction coordinates, as in simple bond fission reactions.) The predicted lack of bond selectivity results from the assumption of rapid internal vibrational energy redistribution and the implicit use of a single adiabatic Born-Oppenheimer potential energy surface for the reaction. However, the adiabatic approximation is not valid for the reaction of a wide variety of energetic materials and organic fuels; coupling between the electronic states of the reacting species play a a key role in determining the selectivity of the chemical reactions induced. The work described below investigated the central role played by coupling between electronic states in polyatomic molecules in determining the selective branching between energetically allowed fragmentation pathways in two key systems.
Adiabatic slice-selective excitation for surface coils.
Shen, J; Rothman, D L
1997-01-01
A novel RF pulse designed to perform a diabatic slice-selective excitation for surface coils (ASSESS) is proposed in which Bzero gradient is modulated in concert with RF frequency modulation. Within the selected slice, the principles of BIR4 pulses are employed to obtain well-defined, pure-phase and self-refocused spin rotation of arbitrary flip angles despite the presence of high B1 inhomogeneity produced by surface coils. Outside the slice, advantage is taken of the B1 field to dephase equilibrium magnetization to achieve slice selection or outer-volume suppression. This scheme should be useful for many localization techniques. Quaternion analysis of the overall propagator of the proposed pulse and numerical simulations using Bloch equations are performed. The pulse is tested experimentally on a phantom sample. PMID:9169211
Mitsouras, Dimitris; Mulkern, Robert V.; Rybicki, Frank J.
2006-01-01
Fast Spin Echo (FSE) trains elicited by non-selective “hard” refocusing radio frequency (RF) pulses have been proposed as a means to enable application of FSE methods for high resolution 3D magnetic resonance imaging (MRI). Hard-pulse FSE (HPFSE) trains offer short (3–4 ms) echo spacings, but are unfortunately limited to imaging the entire sample within the coil sensitivity thus requiring lengthy imaging times, consequently limiting clinical application. In this work we formulate and analyze two general purpose combinations of 3D HPFSE with Inner Volume (IV) MR imaging to circumvent this limitation. The first method employs a 2D selective RF excitation followed by the HPFSE train, and focuses on required properties of the spatial excitation profile with respect to limiting RF pulse duration in the 5–6 ms range. The second method employs two orthogonally selective 1D RF excitations (a 90x°– 180y° pair) to generate an echo from magnetization within the volume defined by their intersection. Subsequent echoes are formed via the HPFSE train, placing the focus of the method on (a) avoiding spurious echoes that may arise from transverse magnetization located outside the slab intersection when it is unavoidably affected by the non-selective refocusing pulses, and (b) avoiding signal losses due to the necessarily different spacing (in time) of the RF pulse applications. The performance of each method is experimentally measured using Carr-Purcell-Meiboom-Gill (CPMG) multi-echo imaging, enabling examination of the magnetization evolution throughout the echo train. The methods as implemented achieve 95% to 97% outer volume signal suppression, and higher suppression appears to be well within reach, by further refinement of the selective RF excitations. Example images of the human brain and spine are presented with each technique. We conclude that the SNR effciency of volume imaging in conjunction with the short echo spacing afforded by hard pulse trains enable high
Beguin, Laetitia; Courtieu, Jacques; Ziani, Latifa; Merlet, Denis
2006-12-01
This work presents a technique to simplify overcrowded proton spectra in chiral liquid crystal solvents using rotation of the sample near the magic angle, VASS, combined with homonuclear selective refocusing 2D NMR experiments, SERF. This methodology provides a powerful tool to visualise enantiomers out of unresolved proton spectra. A modified SERF sequence is presented where the resulting 2D spectrum can be phased to increase the resolution. Accurate enantiomeric excesses are determined that are not possible to measure on static samples. Two examples are presented. PMID:16991108
Quasi-adiabatic compression heating of selected foods
NASA Astrophysics Data System (ADS)
Landfeld, Ales; Strohalm, Jan; Halama, Radek; Houska, Milan
2011-03-01
The quasi-adiabatic temperature increase due to compression heating, during high-pressure (HP) processing (HPP), was studied using specially designed equipment. The temperature increase was evaluated as the difference in temperature, during compression, between atmospheric pressure and nominal pressure. The temperature was measured using a thermocouple in the center of a polyoxymethylene cup, which contained the sample. Fresh meat balls, pork meat pate, and tomato purée temperature increases were measured at three initial temperature levels between 40 and 80 °C. Nominal pressure was either 400 or 500 MPa. Results showed that the fat content had a positive effect on temperature increases. Empirical equations were developed to calculate the temperature increase during HPP at different initial temperatures for pressures of 400 and 500 MPa. This thermal effect data can be used for numerical modeling of temperature histories of foods during HP-assisted pasteurization or sterilization processes.
Butler, L.J.
1993-02-28
The adiabatic Born-Oppenheimer potential energy surface approximation is not valid for reaction of a wide variety of energetic materials and organic fuels; coupling between electronic states of reacting species plays a key role in determining the selectivity of the chemical reactions induced. This research program initially studies this coupling in (1) selective C-Br bond fission in 1,3- bromoiodopropane, (2) C-S:S-H bond fission branching in CH{sub 3}SH, and (3) competition between bond fission channels and H{sub 2} elimination in CH{sub 3}NH{sub 2}.
Broadband inversion for MAS NMR with single-sideband-selective adiabatic pulses
NASA Astrophysics Data System (ADS)
Pell, Andrew J.; Kervern, Gwendal; Emsley, Lyndon; Deschamps, Michaël; Massiot, Dominique; Grandinetti, Philip J.; Pintacuda, Guido
2011-01-01
We explain how and under which conditions it is possible to obtain an efficient inversion of an entire sideband family of several hundred kHz using low-power, sideband-selective adiabatic pulses, and we illustrate with some experimental results how this framework opens new avenues in solid-state NMR for manipulating spin systems with wide spinning-sideband (SSB) manifolds. This is achieved through the definition of the criteria of phase and amplitude modulation for designing an adiabatic inversion pulse for rotating solids. In turn, this is based on a framework for representing the Hamiltonian of the spin system in an NMR experiment under magic angle spinning (MAS). Following earlier ideas from Caravatti et al. [J. Magn. Reson. 55, 88 (1983)], the so-called "jolting frame" is used, which is the interaction frame of the anisotropic interaction giving rise to the SSB manifold. In the jolting frame, the shift modulation affecting the nuclear spin is removed, while the Hamiltonian corresponding to the RF field is frequency modulated and acquires a spinning-sideband pattern, specific for each crystallite orientation.
Super-resolved all-refocused image with a plenoptic camera
NASA Astrophysics Data System (ADS)
Wang, Xiang; Li, Lin; Hou, Guangqi
2015-12-01
This paper proposes an approach to produce the super-resolution all-refocused images with the plenoptic camera. The plenoptic camera can be produced by putting a micro-lens array between the lens and the sensor in a conventional camera. This kind of camera captures both the angular and spatial information of the scene in one single shot. A sequence of digital refocused images, which are refocused at different depth, can be produced after processing the 4D light field captured by the plenoptic camera. The number of the pixels in the refocused image is the same as that of the micro-lens in the micro-lens array. Limited number of the micro-lens will result in poor low resolution refocused images. Therefore, not enough details will exist in these images. Such lost details, which are often high frequency information, are important for the in-focus part in the refocused image. We decide to super-resolve these in-focus parts. The result of image segmentation method based on random walks, which works on the depth map produced from the 4D light field data, is used to separate the foreground and background in the refocused image. And focusing evaluation function is employed to determine which refocused image owns the clearest foreground part and which one owns the clearest background part. Subsequently, we employ single image super-resolution method based on sparse signal representation to process the focusing parts in these selected refocused images. Eventually, we can obtain the super-resolved all-focus image through merging the focusing background part and the focusing foreground part in the way of digital signal processing. And more spatial details will be kept in these output images. Our method will enhance the resolution of the refocused image, and just the refocused images owning the clearest foreground and background need to be super-resolved.
Refocusing properties of periodic magnetic fields
NASA Technical Reports Server (NTRS)
Stankiewicz, N.
1976-01-01
The use of depressed collectors for the efficient collection of spent beams from linear-beam microwave tubes depends on a refocusing procedure in which the space charge forces and transverse velocity components are reduced. The refocusing properties are evaluated of permanent magnet configurations whose axial fields are approximated by constant plateaus or linearly varying fields. The results provide design criteria and show that the refocusing properties can be determined from the plateau fields alone.
Enhanced quantum communication via optical refocusing
NASA Astrophysics Data System (ADS)
Lupo, Cosmo; Giovannetti, Vittorio; Pirandola, Stefano; Mancini, Stefano; Lloyd, Seth
2011-07-01
We consider the problem of quantum communication mediated by a passive optical refocusing system. The model captures the basic features of all those situations in which a signal is either refocused by a repeater for long-distance communication, or it is focused on a detector prior to the information decoding process. Introducing a general method for linear passive optical systems, we determine the conditions under which optical refocusing implies information transmission gain. Although the finite aperture of the repeater may cause loss of information, we show that the presence of the refocusing system can substantially enhance the rate of reliable communication with respect to the free-space propagation. We explicitly address the transferring of classical messages over the quantum channel, but the results can be easily extended to include the case of transferring quantum messages as well.
Adaptive Transthoracic Refocusing of Dual-Mode Ultrasound Arrays
Casper, Andrew J.; Wan, Yayun; Ebbini, Emad S.
2010-01-01
We present experimental validation results of an adaptive, image-based refocusing algorithm of dual-mode ultrasound arrays (DMUAs) in the presence of strongly scattering objects. This study is motivated by the need to develop noninvasive techniques for therapeutic targeting of tumors seated in organs where the therapeutic beam is partially obstructed by the ribcage, e.g., liver and kidney. We have developed an algorithm that takes advantage of the imaging capabilities of DMUAs to identify the ribs and the intercostals within the path of the therapeutic beam to produce a specified power deposition at the target while minimizing the exposure at the rib locations. This image-based refocusing algorithm takes advantage of the inherent registration between the imaging and therapeutic coordinate systems of DMUAs in the estimation of array directivity vectors at the target and rib locations. These directivity vectors are then used in solving a constrained optimization problem allowing for adaptive refocusing, directing the acoustical energy through the intercostals, and avoiding the rib locations. The experimental validation study utilized a 1-MHz, 64-element DMUA in focusing through a block of tissue-mimicking phantom [0.5 dB/(cm·MHz)] with embedded Plexiglas ribs. Single transmit focus (STF) images obtained with the DMUA were used for image-guided selection of the critical and target points to be used for adaptive refocusing. Experimental results show that the echogenicity of the ribs in STF images provide feedback on the reduction of power deposition at rib locations. This was confirmed by direct comparison of measured temperature rise and integrated backscatter at the rib locations. Direct temperature measurements also confirm the improved power deposition at the target and the reduction in power deposition at the rib locations. Finally, we have compared the quality of the image-based adaptive refocusing algorithm with a phase-conjugation solution obtained by direct
NASA Astrophysics Data System (ADS)
Stuerwald, S.; Schmitt, R.
2010-08-01
Digital holographic microscopy (DHM) is utilized for quantitative phase contrast microscopy in optical testing of reflective or transparent specimens and allows altering the focus numerically by propagating the complex wave. Especially for compensation of deformations or displacements and for long-term investigations of living cells, a reliable region selective numerical readjustment of the focus is of particular interest in digital holographic microscopy. Since this method is time consuming, a Halton point set with low discrepancy has been chosen. By this, the effective axial resolution can be enhanced numerically by post processing of complex wave fronts without narrowing the field of view leading to a loss of information around the focus plane by blurring. The concept of numerical parametric lenses is another key feature in DHM and used to correct aberrations in the reconstructed wave front caused by the setup. To reduce the number of parameters for parametric lenses, the polynomial basis by Forbes is applied for the needs of DHM. Both numerical approaches have been characterized and adapted to the requirements of DHM. The applicability is demonstrated by results of investigations of engineered surfaces and biological cells.
Zhu, He; Soher, Brian J; Ouwerkerk, Ronald; Schär, Michael; Barker, Peter B
2013-05-01
Two approaches to high-resolution SENSE-encoded magnetic resonance spectroscopic imaging (MRSI) of the human brain at 7 Tesla (T) with whole-slice coverage are described. Both sequences use high-bandwidth radiofrequency pulses to reduce chemical shift displacement artifacts, SENSE-encoding to reduce scan time, and dual-band water and lipid suppression optimized for 7 T. Simultaneous B0 and transmit B1 mapping was also used for both sequences to optimize field homogeneity using high-order shimming and determine optimum radiofrequency transmit level, respectively. One sequence ("Hahn-MRSI") used reduced flip angle (90°) refocusing pulses for lower radiofrequency power deposition, while the other sequence used adiabatic fast passage refocusing pulses for improved sensitivity and reduced signal dependence on the transmit-B1 level. In four normal subjects, adiabatic fast passage-MRSI showed a signal-to-noise ratio improvement of 3.2±0.5 compared to Hahn-MRSI at the same spatial resolution, pulse repetition time, echo time, and SENSE-acceleration factor. An interleaved two-slice Hahn-MRSI sequence is also demonstrated to be experimentally feasible. PMID:22692894
ERIC Educational Resources Information Center
Baird, Barbara J.
In anticipation of federal welfare reform, the Texas Department of Human Services developed and implemented the REFOCUS program, designed to enhance the economic self-sufficiency of English-as-a-Second-Language recipients of Aid to Families with Dependent Children (AFDC) through better use of existing education, job training, employment, and…
Refocusing Children's Services towards Prevention: Lessons from the Literature
ERIC Educational Resources Information Center
Axford, Nick; Little, Michael
2006-01-01
Increasingly, western developed countries are committed to improving prevention and early intervention strategies that address risks in all areas of children's lives. This article considers the "how" and "why" of such refocusing activity. Five sets of strategies for refocusing are described: developing and using local evidence; designing,…
Schick, F; Nägele, T; Klose, U; Lutz, O
1995-01-01
The quantitative assessment of lactic acid in tissue is an important goal for in vivo volume-selective NMR spectroscopy to aid in the noninvasive diagnosis of oxygen deficiency of other metabolic disorders. PRESS localized 1H spectra provide comparatively high signal-to-noise ratio from small volume elements in a single acquisition mode. The quantification of lactate after multipulse excitation is not trivial due to the J-coupling characteristics which do not occur for the substances serving as references. The influence of the timing scheme and of the quality of the refocusing pulses was systematically evaluated for the lactate resonances by volume-selective measurements. Gaussian pulses, Hanning-filtered sinc pulses, and numerically optimized RE-BURP-pulses were applied for refocusing the magnetization in the PRESS sequence and the effects on the lactate AX3 spin system were compared. For these pulses, sequence parameters are presented providing high sensitivity to lactate signals. Timing schemes are shown which provide good quantification of lactate, even in cases with B1-inhomogeneities or slight misadjustment of the transmitter amplitude. The combination of both echo times in the double-echo sequences clearly influences the signal characteristics of lactate at overall echo times near TE = 145 and 290 ms, which may result in pure in-phase magnetization for this weakly coupled homonuclear system. Numerically optimized refocusing pulses (RE-BURP) provided up to 50% higher signal ratio of the methyl protons of lactate to uncoupled nuclei than the often used Hanning-filtered sinc pulses. PMID:7739373
Refocusing criterion via sparsity measurements in digital holography.
Memmolo, Pasquale; Paturzo, Melania; Javidi, Bahram; Netti, Paolo A; Ferraro, Pietro
2014-08-15
Several automatic approaches have been proposed in the past to compute the refocus distance in digital holography (DH). However most of them are based on a maximization or minimization of a suitable amplitude image contrast measure, regarded as a function of the reconstruction distance parameter. Here we show that, by using the sparsity measure coefficient regarded as a refocusing criterion in the holographic reconstruction, it is possible to recover the focus plane and, at the same time, establish the degree of sparsity of digital holograms, when samples of the diffraction Fresnel propagation integral are used as a sparse signal representation. We employ a sparsity measurement coefficient known as Gini's index thus showing for the first time, to the best of our knowledge, its application in DH, as an effective refocusing criterion. Demonstration is provided for different holographic configurations (i.e., lens and lensless apparatus) and for completely different objects (i.e., a thin pure phase microscopic object as an in vitro cell, and macroscopic puppets) preparation. PMID:25121857
Wireless adiabatic power transfer
Rangelov, A.A.; Suchowski, H.; Silberberg, Y.; Vitanov, N.V.
2011-03-15
Research Highlights: > Efficient and robust mid-range wireless energy transfer between two coils. > The adiabatic energy transfer is analogous to adiabatic passage in quantum optics. > Wireless energy transfer is insensitive to any resonant constraints. > Wireless energy transfer is insensitive to noise in the neighborhood of the coils. - Abstract: We propose a technique for efficient mid-range wireless power transfer between two coils, by adapting the process of adiabatic passage for a coherently driven two-state quantum system to the realm of wireless energy transfer. The proposed technique is shown to be robust to noise, resonant constraints, and other interferences that exist in the neighborhood of the coils.
Adiabatically driven Brownian pumps.
Rozenbaum, Viktor M; Makhnovskii, Yurii A; Shapochkina, Irina V; Sheu, Sheh-Yi; Yang, Dah-Yen; Lin, Sheng Hsien
2013-07-01
We investigate a Brownian pump which, being powered by a flashing ratchet mechanism, produces net particle transport through a membrane. The extension of the Parrondo's approach developed for reversible Brownian motors [Parrondo, Phys. Rev. E 57, 7297 (1998)] to adiabatically driven pumps is given. We demonstrate that the pumping mechanism becomes especially efficient when the time variation of the potential occurs adiabatically fast or adiabatically slow, in perfect analogy with adiabatically driven Brownian motors which exhibit high efficiency [Rozenbaum et al., Phys. Rev. E 85, 041116 (2012)]. At the same time, the efficiency of the pumping mechanism is shown to be less than that of Brownian motors due to fluctuations of the number of particles in the membrane. PMID:23944411
NASA Technical Reports Server (NTRS)
Ramins, P.; Force, D. A.; Palmer, R. W.; Dayton, J. A., Jr.; Kosmahl, H. G.
1986-01-01
A computational procedure for the design of TWT-refocuser-MDC systems was used to design a short 'dynamic' refocusing system and highly efficient four-stage depressed collector for a 200-W 8-18-GHz TWT. The computations were carried out with advanced multidimensional computer programs which model the electron beam as a series of disks of charge and follow their trajectories from the RF input of the TWT, through the slow-wave structure and refocusing section, to their points of impact in the depressed collector. Secondary emission losses in the MDC were treated semiquantitatively by injecting a representative beam of secondary electrons into the MDC analysis at the point of impact of each primary beam. A comparison of computed and measured TWT and MDC performance showed very good agreement. The electrodes of the MDC were fabricated from a particular form of isotropic graphite that was selected for its low secondary electron yield, thermal expansion characteristics, ease of machinability and vacuum properties. This MDC was tested at CW for more than 1000 h with negligible degradation in TWT and MDC performances.
Parallelizable adiabatic gate teleportation
NASA Astrophysics Data System (ADS)
Nakago, Kosuke; Hajdušek, Michal; Nakayama, Shojun; Murao, Mio
2015-12-01
To investigate how a temporally ordered gate sequence can be parallelized in adiabatic implementations of quantum computation, we modify adiabatic gate teleportation, a model of quantum computation proposed by Bacon and Flammia [Phys. Rev. Lett. 103, 120504 (2009), 10.1103/PhysRevLett.103.120504], to a form deterministically simulating parallelized gate teleportation, which is achievable only by postselection. We introduce a twisted Heisenberg-type interaction Hamiltonian, a Heisenberg-type spin interaction where the coordinates of the second qubit are twisted according to a unitary gate. We develop parallelizable adiabatic gate teleportation (PAGT) where a sequence of unitary gates is performed in a single step of the adiabatic process. In PAGT, numeric calculations suggest the necessary time for the adiabatic evolution implementing a sequence of L unitary gates increases at most as O (L5) . However, we show that it has the interesting property that it can map the temporal order of gates to the spatial order of interactions specified by the final Hamiltonian. Using this property, we present a controlled-PAGT scheme to manipulate the order of gates by a control qubit. In the controlled-PAGT scheme, two differently ordered sequential unitary gates F G and G F are coherently performed depending on the state of a control qubit by simultaneously applying the twisted Heisenberg-type interaction Hamiltonians implementing unitary gates F and G . We investigate why the twisted Heisenberg-type interaction Hamiltonian allows PAGT. We show that the twisted Heisenberg-type interaction Hamiltonian has an ability to perform a transposed unitary gate by just modifying the space ordering of the final Hamiltonian implementing a unitary gate in adiabatic gate teleportation. The dynamics generated by the time-reversed Hamiltonian represented by the transposed unitary gate enables deterministic simulation of a postselected event of parallelized gate teleportation in adiabatic
Adiabatic cooling of antiprotons.
Gabrielse, G; Kolthammer, W S; McConnell, R; Richerme, P; Kalra, R; Novitski, E; Grzonka, D; Oelert, W; Sefzick, T; Zielinski, M; Fitzakerley, D; George, M C; Hessels, E A; Storry, C H; Weel, M; Müllers, A; Walz, J
2011-02-18
Adiabatic cooling is shown to be a simple and effective method to cool many charged particles in a trap to very low temperatures. Up to 3×10(6) p are cooled to 3.5 K-10(3) times more cold p and a 3 times lower p temperature than previously reported. A second cooling method cools p plasmas via the synchrotron radiation of embedded e(-) (with many fewer e(-) than p in preparation for adiabatic cooling. No p are lost during either process-a significant advantage for rare particles. PMID:21405511
Adiabatic Cooling of Antiprotons
Gabrielse, G.; Kolthammer, W. S.; McConnell, R.; Richerme, P.; Kalra, R.; Novitski, E.; Oelert, W.; Grzonka, D.; Sefzick, T.; Zielinski, M.; Fitzakerley, D.; George, M. C.; Hessels, E. A.; Storry, C. H.; Weel, M.; Muellers, A.; Walz, J.
2011-02-18
Adiabatic cooling is shown to be a simple and effective method to cool many charged particles in a trap to very low temperatures. Up to 3x10{sup 6} p are cooled to 3.5 K--10{sup 3} times more cold p and a 3 times lower p temperature than previously reported. A second cooling method cools p plasmas via the synchrotron radiation of embedded e{sup -} (with many fewer e{sup -} than p) in preparation for adiabatic cooling. No p are lost during either process--a significant advantage for rare particles.
Adiabatically implementing quantum gates
Sun, Jie; Lu, Songfeng Liu, Fang
2014-06-14
We show that, through the approach of quantum adiabatic evolution, all of the usual quantum gates can be implemented efficiently, yielding running time of order O(1). This may be considered as a useful alternative to the standard quantum computing approach, which involves quantum gates transforming quantum states during the computing process.
Entanglement and adiabatic quantum computation
NASA Astrophysics Data System (ADS)
Ahrensmeier, D.
2006-06-01
Adiabatic quantum computation provides an alternative approach to quantum computation using a time-dependent Hamiltonian. The time evolution of entanglement during the adiabatic quantum search algorithm is studied, and its relevance as a resource is discussed.
Filtered refocusing: a volumetric reconstruction algorithm for plenoptic-PIV
NASA Astrophysics Data System (ADS)
Fahringer, Timothy W.; Thurow, Brian S.
2016-09-01
A new algorithm for reconstruction of 3D particle fields from plenoptic image data is presented. The algorithm is based on the technique of computational refocusing with the addition of a post reconstruction filter to remove the out of focus particles. This new algorithm is tested in terms of reconstruction quality on synthetic particle fields as well as a synthetically generated 3D Gaussian ring vortex. Preliminary results indicate that the new algorithm performs as well as the MART algorithm (used in previous work) in terms of the reconstructed particle position accuracy, but produces more elongated particles. The major advantage to the new algorithm is the dramatic reduction in the computational cost required to reconstruct a volume. It is shown that the new algorithm takes 1/9th the time to reconstruct the same volume as MART while using minimal resources. Experimental results are presented in the form of the wake behind a cylinder at a Reynolds number of 185.
Adiabatic topological quantum computing
NASA Astrophysics Data System (ADS)
Cesare, Chris; Landahl, Andrew J.; Bacon, Dave; Flammia, Steven T.; Neels, Alice
2015-07-01
Topological quantum computing promises error-resistant quantum computation without active error correction. However, there is a worry that during the process of executing quantum gates by braiding anyons around each other, extra anyonic excitations will be created that will disorder the encoded quantum information. Here, we explore this question in detail by studying adiabatic code deformations on Hamiltonians based on topological codes, notably Kitaev's surface codes and the more recently discovered color codes. We develop protocols that enable universal quantum computing by adiabatic evolution in a way that keeps the energy gap of the system constant with respect to the computation size and introduces only simple local Hamiltonian interactions. This allows one to perform holonomic quantum computing with these topological quantum computing systems. The tools we develop allow one to go beyond numerical simulations and understand these processes analytically.
Bazzani, A.; Turchetti, G.; Benedetti, C.; Rambaldi, S.; Servizi, G.
2005-06-08
In a high intensity circular accelerator the synchrotron dynamics introduces a slow modulation in the betatronic tune due to the space-charge tune depression. When the transverse motion is non-linear due to the presence of multipolar effects, resonance islands move in the phase space and change their amplitude. This effect introduces the trapping and detrapping phenomenon and a slow diffusion in the phase space. We apply the neo-adiabatic theory to describe this diffusion mechanism that can contribute to halo formation.
MRSI via fully-refocused spatiotemporal encoding with polychromatic spectral pulses.
Zhang, Zhiyong; Frydman, Lucio
2015-10-01
A novel method for the rapid acquisition of quality multi-slice 2D images targeting a small number of spectroscopic resonances, is introduced and illustrated. The method exploits the robustness derived from recently proposed spatiotemporal encoding (SPEN) methods, when operating in the so-called "fully refocused" mode. Fully-refocused SPEN provides high-fidelity single-shot images thanks to its refocusing of all offset-derived effects throughout the course of the acquisition. This refocusing, however, prevents exploiting such robustness for spectroscopic imaging. We propose here a solution to this limitation, based on the use of polychromatic refocusing pulses. It is shown that if used to address a series of a priori known resonance positions, these pulses can lead to quality spectroscopic images in a small number of scans - generally equal or slightly larger than the number of targeted peaks. Such strategy is explored in combination with both fully-refocused SPEN and echo-planar-imaging (EPI) acquisitions. The expected SPEN advantages were observed in both phantom-based models, and in in vivo results of fat and water separation in mice at 7 T. PMID:26282060
MRSI via fully-refocused spatiotemporal encoding with polychromatic spectral pulses
NASA Astrophysics Data System (ADS)
Zhang, Zhiyong; Frydman, Lucio
2015-10-01
A novel method for the rapid acquisition of quality multi-slice 2D images targeting a small number of spectroscopic resonances, is introduced and illustrated. The method exploits the robustness derived from recently proposed spatiotemporal encoding (SPEN) methods, when operating in the so-called "fully refocused" mode. Fully-refocused SPEN provides high-fidelity single-shot images thanks to its refocusing of all offset-derived effects throughout the course of the acquisition. This refocusing, however, prevents exploiting such robustness for spectroscopic imaging. We propose here a solution to this limitation, based on the use of polychromatic refocusing pulses. It is shown that if used to address a series of a priori known resonance positions, these pulses can lead to quality spectroscopic images in a small number of scans - generally equal or slightly larger than the number of targeted peaks. Such strategy is explored in combination with both fully-refocused SPEN and echo-planar-imaging (EPI) acquisitions. The expected SPEN advantages were observed in both phantom-based models, and in in vivo results of fat and water separation in mice at 7 T.
Variable Curvature Mirrors for ELT Laser Guide Star refocusing systems
NASA Astrophysics Data System (ADS)
Challita, Zalpha; Hugot, Emmanuel; Ferrari, Marc; Madec, Fabrice; Le Mignant, David; Cuby, Jean-Gabriel
2011-09-01
The future generation of Extremely Large Telescopes will require a complex combination of technologies for adaptive optics (AO) systems assisted by laser guide stars (LGS). In this context, LGS defocusing is one of the system issues that can be tackled using active refocusing mirrors such as Variable Curvature Mirrors (VCM). Indeed, the distance from the LGS spot to the telescope pupil ranges from about 80 to 200 km, depending on the Sodium layer altitude and the elevation of the telescope, and induces a large defocusing at the LGS wave-front sensor focal plane. To compensate for that, we propose an original concept including a VCM specifically designed to keep a focused spot on the wave-front sensor: the mirror is made of a thin meniscus bend using a pressure applied on its back face. Due to the large defocusing, the LGS-VCM must be able to change its shape from F/12.5 to F/5, leading to more than 1 mm sag. The VCM benefits of a specific shape with a variable radial thickness distribution, allowing keeping an optical quality better than λ/5 over this very large range of deformation. The work presented here details the analytical development leading to the specific geometry of the active component, the results of finite element analysis and the expected performances in terms of surface error versus the range of refocalisation. Two prototypes have been manufactured to compare the real behaviour of the mirror and the simulations data. Results obtained on the prototypes show that the deformation of the VCM is very close to the simulation, and leads to a realistic concept.
NASA Astrophysics Data System (ADS)
Landahl, Andrew
2012-10-01
Quantum computers promise to exploit counterintuitive quantum physics principles like superposition, entanglement, and uncertainty to solve problems using fundamentally fewer steps than any conventional computer ever could. The mere possibility of such a device has sharpened our understanding of quantum coherent information, just as lasers did for our understanding of coherent light. The chief obstacle to developing quantum computer technology is decoherence--one of the fastest phenomena in all of physics. In principle, decoherence can be overcome by using clever entangled redundancies in a process called fault-tolerant quantum error correction. However, the quality and scale of technology required to realize this solution appears distant. An exciting alternative is a proposal called ``adiabatic'' quantum computing (AQC), in which adiabatic quantum physics keeps the computer in its lowest-energy configuration throughout its operation, rendering it immune to many decoherence sources. The Adiabatic Quantum Architectures In Ultracold Systems (AQUARIUS) Grand Challenge Project at Sandia seeks to demonstrate this robustness in the laboratory and point a path forward for future hardware development. We are building devices in AQUARIUS that realize the AQC architecture on up to three quantum bits (``qubits'') in two platforms: Cs atoms laser-cooled to below 5 microkelvin and Si quantum dots cryo-cooled to below 100 millikelvin. We are also expanding theoretical frontiers by developing methods for scalable universal AQC in these platforms. We have successfully demonstrated operational qubits in both platforms and have even run modest one-qubit calculations using our Cs device. In the course of reaching our primary proof-of-principle demonstrations, we have developed multiple spinoff technologies including nanofabricated diffractive optical elements that define optical-tweezer trap arrays and atomic-scale Si lithography commensurate with placing individual donor atoms with
Geometry of the Adiabatic Theorem
ERIC Educational Resources Information Center
Lobo, Augusto Cesar; Ribeiro, Rafael Antunes; Ribeiro, Clyffe de Assis; Dieguez, Pedro Ruas
2012-01-01
We present a simple and pedagogical derivation of the quantum adiabatic theorem for two-level systems (a single qubit) based on geometrical structures of quantum mechanics developed by Anandan and Aharonov, among others. We have chosen to use only the minimum geometric structure needed for the understanding of the adiabatic theorem for this case.…
NASA Technical Reports Server (NTRS)
Ramins, P.; Kosmahl, H. G.; Force, D. A.; Palmer, R. W.; Dayton, J. A., Jr.
1985-01-01
A computational procedure for the design of TWT-refocuser-MDC systems was used to design a short dynamic refocusing system and highly efficient four-stage depressed collector for a 200-W, 8- to 18-GHz, TWT. The computations were carried out with advanced, multidimensional computer programs which model the electron beam as a series of disks of charge and follow their trajectories from the RF input of the TWT, through the slow-wave structure and refocusing section, to their points of impact in the depressed collector. Secondary emission losses in the MDC were treated semi-quantitatively by injecting a representative beam of secondary electrons into the MDC analysis at the point of impact of each primary beam. A comparison of computed and measured TWT and MDC performance showed very good agreement. The electrodes of the MDC were fabricated from a particular form of isotropic graphite that was selected for its low secondary electron yield, ease of machinability, and vacuum properties. This MDC was tested (at CW) for more than 1000 hr with negligible degradation in TWT and MDC performances.
Refocus of constant velocity moving targets in synthetic aperture radar imagery
Jakowatz, C.V. Jr.; Wahl, D.E.; Eichel, P.H.
1998-04-01
The detection and refocus of moving targets in SAR imagery is of interest in a number of applications. In this paper the authors address the problem of refocusing a blurred signature that has by some means been identified as a moving target. They assume that the target vehicle velocity is constant, i.e., the motion is in a straight line with constant speed. The refocus is accomplished by application of a two-dimensional phase function to the phase history data obtained via Fourier transformation of an image chip that contains the blurred moving target data. By considering separately the phase effects of the range and cross-range components of the target velocity vector, they show how the appropriate phase correction term can be derived as a two-parameter function. They then show a procedure for estimating the two parameters, so that the blurred signature can be automatically refocused. The algorithm utilizes optimization of an image domain contrast metric. They present results of refocusing moving targets in real SAR imagery by this method.
Embedded FIR filter design for real-time refocusing using a standard plenoptic video camera
NASA Astrophysics Data System (ADS)
Hahne, Christopher; Aggoun, Amar
2014-03-01
A novel and low-cost embedded hardware architecture for real-time refocusing based on a standard plenoptic camera is presented in this study. The proposed layout design synthesizes refocusing slices directly from micro images by omitting the process for the commonly used sub-aperture extraction. Therefore, intellectual property cores, containing switch controlled Finite Impulse Response (FIR) filters, are developed and applied to the Field Programmable Gate Array (FPGA) XC6SLX45 from Xilinx. Enabling the hardware design to work economically, the FIR filters are composed of stored product as well as upsampling and interpolation techniques in order to achieve an ideal relation between image resolution, delay time, power consumption and the demand of logic gates. The video output is transmitted via High-Definition Multimedia Interface (HDMI) with a resolution of 720p at a frame rate of 60 fps conforming to the HD ready standard. Examples of the synthesized refocusing slices are presented.
Refocusing two-qubit-gate noise for trapped ions by composite pulses
NASA Astrophysics Data System (ADS)
Cohen, I.; Rotem, A.; Retzker, A.
2016-03-01
Amplitude noise, which inflicts a random two-qubit term, is one of the main obstacles preventing the implementation of a high-fidelity two-body gate below the fault-tolerance threshold. This noise is difficult to refocus as any refocusing technique could only tackle noise with frequency below the operation rate. Since the two-qubit-gate speed is normally the slowest rate in the system, it constitutes the last bottleneck toward an implementation of a gate below the fault-tolerant threshold. Here we propose to use composite pulses as a dynamical decoupling approach in order to reduce two-qubit-gate noise for trapped-ion systems. This is done by refocusing the building blocks of ultrafast entangling gates, where the amplitude noise is reduced to shot-to-shot noise. We present detailed simulations showing that the fault-tolerance threshold could be achieved using the proposed approach.
Design of refocusing system for a high-resolution space TDICCD camera with wide-field of view
NASA Astrophysics Data System (ADS)
Lv, Shiliang; Liu, Jinguo
2015-10-01
This paper describes the design and realization of a refocusing system for a space TDICCD camera of 2.2-meter focal length, which, features a three mirror anastigmatic(TMA) optical system along with 8 TDICCDs assemble at the focal plane, is high resolution and wide field of view. TDICCDs assemble is a kind of major method of acquiring wide field of view for space camera. In this way, the swath width reach 60km. First, the design of TMA optical system and its advantage of this space TDICCD camera was introduced; Then, the refocusing system as well as the technique of mechanical interleaving assemble for TDICCDs focal plane of this space camera was discussed in detail, At last, the refocusing system was measured. Experimental results indicated that the precision of the refocusing system is +/- 3.12μm(3σ), which satisfy the refocusing control system requirements of higher precision and stabilization.
Efficient hybrid tree-based stereo matching with applications to postcapture image refocusing.
Vu, Dung T; Chidester, Benjamin; Yang, Hongsheng; Do, Minh N; Lu, Jiangbo
2014-08-01
Estimating dense correspondence or depth information from a pair of stereoscopic images is a fundamental problem in computer vision, which finds a range of important applications. Despite intensive past research efforts in this topic, it still remains challenging to recover the depth information both reliably and efficiently, especially when the input images contain weakly textured regions or are captured under uncontrolled, real-life conditions. Striking a desired balance between computational efficiency and estimation quality, a hybrid minimum spanning tree-based stereo matching method is proposed in this paper. Our method performs efficient nonlocal cost aggregation at pixel-level and region-level, and then adaptively fuses the resulting costs together to leverage their respective strength in handling large textureless regions and fine depth discontinuities. Experiments on the standard Middlebury stereo benchmark show that the proposed stereo method outperforms all prior local and nonlocal aggregation-based methods, achieving particularly noticeable improvements for low texture regions. To further demonstrate the effectiveness of the proposed stereo method, also motivated by the increasing desire to generate expressive depth-induced photo effects, this paper is tasked next to address the emerging application of interactive depth-of-field rendering given a real-world stereo image pair. To this end, we propose an accurate thin-lens model for synthetic depth-of-field rendering, which considers the user-stroke placement and camera-specific parameters and performs the pixel-adapted Gaussian blurring in a principled way. Taking ~1.5 s to process a pair of 640×360 images in the off-line step, our system named Scribble2focus allows users to interactively select in-focus regions by simple strokes using the touch screen and returns the synthetically refocused images instantly to the user. PMID:24919201
NASA Technical Reports Server (NTRS)
Kosmahl, H. G. (Inventor)
1973-01-01
An electron beam device which extracts energy from an electron beam before the electrons of the beam are captured by a collector apparatus is described. The device produces refocusing of a spent electron beam by minimizing tranverse electron velocities in the beam where the electrons, having a multiplicity of axial velocities, are sorted at high efficiency by collector electrodes.
ERIC Educational Resources Information Center
Malloy, William
1997-01-01
Educators working to improve dropout prevention programs should closely examine the development of defensive overlays in children's world views. Efforts to neutralize defensive world views within existing dropout prevention initiatives should refocus efforts to be more holistic. Such neutralization may best succeed in small schools. (SM)
The Freedom Schools, the Civil Rights Movement, and Refocusing the Goals of American Education
ERIC Educational Resources Information Center
Hale, Jon N.
2011-01-01
This article examines the history of the 1964 Mississippi Freedom Schools to illustrate how integrating the Civil Rights Movement into the social studies curriculum refocuses the aims of American education on participatory democracy. Teaching the Civil Rights Movement and employing the teaching strategies used in the Freedom Schools leads to the…
A rapid magnetic resonance acoustic radiation force imaging sequence for ultrasonic refocusing
NASA Astrophysics Data System (ADS)
Mougenot, Charles; Pichardo, Samuel; Engler, Steven; Waspe, Adam; Constanciel Colas, Elodie; Drake, James M.
2016-08-01
Magnetic resonance guided acoustic radiation force imaging (MR-ARFI) is being used to correct for aberrations induced by tissue heterogeneities when using high intensity focusing ultrasound (HIFU). A compromise between published MR-ARFI adaptive solutions is proposed to achieve efficient refocusing of the ultrasound beam in under 10 min. In addition, an ARFI sequence based on an EPI gradient echo sequence was used to simultaneously monitor displacement and temperature with a large SNR and low distortion. This study was conducted inside an Achieva 3T clinical MRI using a Philips Sonalleve MR-HIFU system to emit a 1 ms pulsed sonication with duty cycle of 2.3% at 300 Wac inside a polymer phantom. Virtual elements defined by a Hadamard array with sonication patterns composed of 6 phase steps were used to characterize 64 groups of 4 elements to find the optimal phase of the 256 elements of the transducer. The 384 sonication patterns were acquired in 580 s to identify the set of phases that maximize the displacement at the focal point. Three aberrators (neonatal skull, 8 year old skull and a checkered pattern) were added to each sonication pattern to evaluate the performance of this refocusing algorithm (n = 4). These aberrators reduced the relative intensities to 95.3%, 69.6% and 25.5% for the neonatal skull, 8 year old skull, and checkered pattern virtual aberrators respectively. Using a 10 min refocusing algorithm, relative intensities of 101.6%, 91.3% and 93.3% were obtained. Better relative intensities of 103.9%, 94.3% and 101% were achieved using a 25 min refocusing algorithm. An average temperature increase of 4.2 °C per refocusing test was induced for the 10 min refocusing algorithm, resulting in a negligible thermal dose of 2 EM. A rapid refocusing of the beam can be achieved while keeping thermal effects to a minimum.
A rapid magnetic resonance acoustic radiation force imaging sequence for ultrasonic refocusing.
Mougenot, Charles; Pichardo, Samuel; Engler, Steven; Waspe, Adam; Colas, Elodie Constanciel; Drake, James M
2016-08-01
Magnetic resonance guided acoustic radiation force imaging (MR-ARFI) is being used to correct for aberrations induced by tissue heterogeneities when using high intensity focusing ultrasound (HIFU). A compromise between published MR-ARFI adaptive solutions is proposed to achieve efficient refocusing of the ultrasound beam in under 10 min. In addition, an ARFI sequence based on an EPI gradient echo sequence was used to simultaneously monitor displacement and temperature with a large SNR and low distortion. This study was conducted inside an Achieva 3T clinical MRI using a Philips Sonalleve MR-HIFU system to emit a 1 ms pulsed sonication with duty cycle of 2.3% at 300 Wac inside a polymer phantom. Virtual elements defined by a Hadamard array with sonication patterns composed of 6 phase steps were used to characterize 64 groups of 4 elements to find the optimal phase of the 256 elements of the transducer. The 384 sonication patterns were acquired in 580 s to identify the set of phases that maximize the displacement at the focal point. Three aberrators (neonatal skull, 8 year old skull and a checkered pattern) were added to each sonication pattern to evaluate the performance of this refocusing algorithm (n = 4). These aberrators reduced the relative intensities to 95.3%, 69.6% and 25.5% for the neonatal skull, 8 year old skull, and checkered pattern virtual aberrators respectively. Using a 10 min refocusing algorithm, relative intensities of 101.6%, 91.3% and 93.3% were obtained. Better relative intensities of 103.9%, 94.3% and 101% were achieved using a 25 min refocusing algorithm. An average temperature increase of 4.2 °C per refocusing test was induced for the 10 min refocusing algorithm, resulting in a negligible thermal dose of 2 EM. A rapid refocusing of the beam can be achieved while keeping thermal effects to a minimum. PMID:27401452
Adiabatic evolution of plasma equilibrium
Grad, H.; Hu, P. N.; Stevens, D. C.
1975-01-01
A new theory of plasma equilibrium is introduced in which adiabatic constraints are specified. This leads to a mathematically nonstandard structure, as compared to the usual equilibrium theory, in which prescription of pressure and current profiles leads to an elliptic partial differential equation. Topologically complex configurations require further generalization of the concept of adiabaticity to allow irreversible mixing of plasma and magnetic flux among islands. Matching conditions across a boundary layer at the separatrix are obtained from appropriate conservation laws. Applications are made to configurations with planned islands (as in Doublet) and accidental islands (as in Tokamaks). Two-dimensional, axially symmetric, helically symmetric, and closed line equilibria are included. PMID:16578729
Thibaudeau, Christophe; Remaud, Gérald; Silvestre, Virginie; Akoka, Serge
2010-07-01
(2)H/(1)H and (13)C/(12)C site-specific isotope ratios determined by NMR spectroscopy may be used to discriminate pharmaceutically active ingredients based on the synthetic process used in production. Extending the Site-specific Natural Isotope Fractionation NMR (SNIF-NMR) method to (13)C is highly beneficial for complex organic molecules when measurements of (2)H/(1)H ratios lead to poorly defined molecular fingerprints. The current NMR methodology to determine (13)C/(12)C site-specific isotope ratios suffers from poor sensitivity and long experimental times. In this work, several NMR pulse sequences based on polarization transfer were evaluated and optimized to measure precise quantitative (13)C NMR spectra within a short time. Adiabatic 180 degrees (1)H and (13)C pulses were incorporated into distortionless enhancement by polarization transfer (DEPT) and refocused insensitive nuclei enhanced by polarization transfer (INEPT) to minimize the influence of 180 degrees pulse imperfections and of off-resonance effects on the precision of the measured (13)C peak areas. The adiabatic DEPT sequence was applied to draw up a precise site-specific (13)C isotope profile of ibuprofen. A modified heteronuclear cross-polarization (HCP) experiment featuring (1)H and (13)C spin-locks with adiabatic 180 degrees pulses is also introduced. This sequence enables efficient magnetization transfer across a wide (13)C frequency range although not enough for an application in quantitative (13)C isotopic analysis. PMID:20527737
Pressure Oscillations in Adiabatic Compression
ERIC Educational Resources Information Center
Stout, Roland
2011-01-01
After finding Moloney and McGarvey's modified adiabatic compression apparatus, I decided to insert this experiment into my physical chemistry laboratory at the last minute, replacing a problematic experiment. With insufficient time to build the apparatus, we placed a bottle between two thick textbooks and compressed it with a third textbook forced…
Adiabatic dynamics of magnetic vortices
NASA Astrophysics Data System (ADS)
Papanicolaou, N.
1994-03-01
We formulate a reasonably detailed adiabatic conjecture concerning the dynamics of skew deflection of magnetic vortices in a field gradient, which is expected to be valid at sufficiently large values of the winding number. The conjecture is consistent with the golden rule used to describe the dynamics of realistic magnetic bubbles and is verified here numerically within the 2-D isotropic Heisenberg model.
Transitionless driving on adiabatic search algorithm
Oh, Sangchul; Kais, Sabre
2014-12-14
We study quantum dynamics of the adiabatic search algorithm with the equivalent two-level system. Its adiabatic and non-adiabatic evolution is studied and visualized as trajectories of Bloch vectors on a Bloch sphere. We find the change in the non-adiabatic transition probability from exponential decay for the short running time to inverse-square decay in asymptotic running time. The scaling of the critical running time is expressed in terms of the Lambert W function. We derive the transitionless driving Hamiltonian for the adiabatic search algorithm, which makes a quantum state follow the adiabatic path. We demonstrate that a uniform transitionless driving Hamiltonian, approximate to the exact time-dependent driving Hamiltonian, can alter the non-adiabatic transition probability from the inverse square decay to the inverse fourth power decay with the running time. This may open up a new but simple way of speeding up adiabatic quantum dynamics.
Transitionless driving on adiabatic search algorithm
NASA Astrophysics Data System (ADS)
Oh, Sangchul; Kais, Sabre
2014-12-01
We study quantum dynamics of the adiabatic search algorithm with the equivalent two-level system. Its adiabatic and non-adiabatic evolution is studied and visualized as trajectories of Bloch vectors on a Bloch sphere. We find the change in the non-adiabatic transition probability from exponential decay for the short running time to inverse-square decay in asymptotic running time. The scaling of the critical running time is expressed in terms of the Lambert W function. We derive the transitionless driving Hamiltonian for the adiabatic search algorithm, which makes a quantum state follow the adiabatic path. We demonstrate that a uniform transitionless driving Hamiltonian, approximate to the exact time-dependent driving Hamiltonian, can alter the non-adiabatic transition probability from the inverse square decay to the inverse fourth power decay with the running time. This may open up a new but simple way of speeding up adiabatic quantum dynamics.
Transitionless driving on adiabatic search algorithm.
Oh, Sangchul; Kais, Sabre
2014-12-14
We study quantum dynamics of the adiabatic search algorithm with the equivalent two-level system. Its adiabatic and non-adiabatic evolution is studied and visualized as trajectories of Bloch vectors on a Bloch sphere. We find the change in the non-adiabatic transition probability from exponential decay for the short running time to inverse-square decay in asymptotic running time. The scaling of the critical running time is expressed in terms of the Lambert W function. We derive the transitionless driving Hamiltonian for the adiabatic search algorithm, which makes a quantum state follow the adiabatic path. We demonstrate that a uniform transitionless driving Hamiltonian, approximate to the exact time-dependent driving Hamiltonian, can alter the non-adiabatic transition probability from the inverse square decay to the inverse fourth power decay with the running time. This may open up a new but simple way of speeding up adiabatic quantum dynamics. PMID:25494733
Studies in Chaotic adiabatic dynamics
Jarzynski, C.
1994-01-01
Chaotic adiabatic dynamics refers to the study of systems exhibiting chaotic evolution under slowly time-dependent equations of motion. In this dissertation the author restricts his attention to Hamiltonian chaotic adiabatic systems. The results presented are organized around a central theme, namely, that the energies of such systems evolve diffusively. He begins with a general analysis, in which he motivates and derives a Fokker-Planck equation governing this process of energy diffusion. He applies this equation to study the {open_quotes}goodness{close_quotes} of an adiabatic invariant associated with chaotic motion. This formalism is then applied to two specific examples. The first is that of a gas of noninteracting point particles inside a hard container that deforms slowly with time. Both the two- and three-dimensional cases are considered. The results are discussed in the context of the Wall Formula for one-body dissipation in nuclear physics, and it is shown that such a gas approaches, asymptotically with time, an exponential velocity distribution. The second example involves the Fermi mechanism for the acceleration of cosmic rays. Explicit evolution equations are obtained for the distribution of cosmic ray energies within this model, and the steady-state energy distribution that arises when this equation is modified to account for the injection and removal of cosmic rays is discussed. Finally, the author re-examines the multiple-time-scale approach as applied to the study of phase space evolution under a chaotic adiabatic Hamiltonian. This leads to a more rigorous derivation of the above-mentioned Fokker-Planck equation, and also to a new term which has relevance to the problem of chaotic adiabatic reaction forces (the forces acting on slow, heavy degrees of freedom due to their coupling to light, fast chaotic degrees).
Adiabatic quantum computing with phase modulated laser pulses
Goswami, Debabrata
2005-01-01
Implementation of quantum logical gates for multilevel systems is demonstrated through decoherence control under the quantum adiabatic method using simple phase modulated laser pulses. We make use of selective population inversion and Hamiltonian evolution with time to achieve such goals robustly instead of the standard unitary transformation language. PMID:17195865
NASA Astrophysics Data System (ADS)
Shao, Xiaopeng; Wu, Tengfei; Gong, Changmei
2013-11-01
We present a simulation method for studying turbid media in the optical field based on circular Gaussian distribution (CGD) model, by which the transmission matrix, representing the modulation of a turbid medium on the amplitude and the phase of incident light, can be generated directly and efficiently. As an application example, light refocusing through a turbid medium is realized employing the CGD model approach, combining with wavefront-phase modulation technique and Fresnel diffraction theory, which is applied to describe the light propagation between optical elements of the entire system. Simulation results based on this approach agree well with theoretical analysis for light refocusing, which can validate the feasibility of CGD model. This work can be used for exploring the potential applications of turbid media in the optical field further, especially for developing new microscopic imaging technologies beyond the diffraction limit.
NASA Technical Reports Server (NTRS)
Stankiewicz, N.
1974-01-01
Magnetic field configurations in which the axial component of the field decays linearly to a constant plateau field are evaluated for use in refocusing the output beam of linear beam microwave tubes. The slope of the decay and the value of the plateau field are parameters in this study. A uniform beam with a space charge force only in the radial direction is assumed, and the electron trajectories are computed for various classes. For a given magnetic configuration (slope and plateau value) the plateau length is calculated for a specified class and the rms deviation of the output angles for all classes is computed at the end of this plateau length. A minimum condition for a refocused beam is defined to be one in which the rms value of the output angles is less than the rms input. Many of the configurations satisfied this criteria and successfully reduced the rms value by half.
Refocusing from a plenoptic camera within seconds on a mobile phone
NASA Astrophysics Data System (ADS)
Gómez-Cárdenes, Ã.`scar; Marichal-Hernández, José G.; Rosa, Fernando L.; Lüke, Jonas P.; Fernández-Valdivia, Juan José; Rodríguez-Ramos, José M.
2014-05-01
Refocusing a plenoptic image by digital means and after the exposure has been thoroughly studied in the last years, but few efforts have been made in the direction of real time implementation in a constrained environment such as that provided by current mobile phones and tablets. In this work we address the aforementioned challenge demonstrating that a complete focal stack, comprising 31 refocused planes from a (256ff16)2 plenoptic image, can be achieved within seconds by a current SoC mobile phone platform. The election of an appropriate algorithm is the key to success. In a previous work we developed an algorithm, the fast approximate 4D:3D discrete Radon transform, that performs this task with linear time complexity where others obtain quadratic or linearithmic time complexity. Moreover, that algorithm does not requires complex number transforms, trigonometric calculus nor even multiplications nor oat numbers. Our algorithm has been ported to a multi core ARM chip on an off-the-shelf tablet running Android. A careful implementation exploiting parallelism at several levels has been necessary. The final implementation takes advantage of multi-threading in native code and NEON SIMD instructions. As a result our current implementation completes the refocusing task within seconds for a 16 megapixels image, much faster than previous attempts running on powerful PC platforms or dedicated hardware. The times consumed by the different stages of the digital refocusing are given and the strategies to achieve this result are discussed. Time results are given for a variety of environments within Android ecosystem, from the weaker/cheaper SoCs to the top of the line for 2013.
Quantum Adiabatic Algorithms and Large Spin Tunnelling
NASA Technical Reports Server (NTRS)
Boulatov, A.; Smelyanskiy, V. N.
2003-01-01
We provide a theoretical study of the quantum adiabatic evolution algorithm with different evolution paths proposed in this paper. The algorithm is applied to a random binary optimization problem (a version of the 3-Satisfiability problem) where the n-bit cost function is symmetric with respect to the permutation of individual bits. The evolution paths are produced, using the generic control Hamiltonians H (r) that preserve the bit symmetry of the underlying optimization problem. In the case where the ground state of H(0) coincides with the totally-symmetric state of an n-qubit system the algorithm dynamics is completely described in terms of the motion of a spin-n/2. We show that different control Hamiltonians can be parameterized by a set of independent parameters that are expansion coefficients of H (r) in a certain universal set of operators. Only one of these operators can be responsible for avoiding the tunnelling in the spin-n/2 system during the quantum adiabatic algorithm. We show that it is possible to select a coefficient for this operator that guarantees a polynomial complexity of the algorithm for all problem instances. We show that a successful evolution path of the algorithm always corresponds to the trajectory of a classical spin-n/2 and provide a complete characterization of such paths.
Robust adiabatic sum frequency conversion.
Suchowski, Haim; Prabhudesai, Vaibhav; Oron, Dan; Arie, Ady; Silberberg, Yaron
2009-07-20
We discuss theoretically and demonstrate experimentally the robustness of the adiabatic sum frequency conversion method. This technique, borrowed from an analogous scheme of robust population transfer in atomic physics and nuclear magnetic resonance, enables the achievement of nearly full frequency conversion in a sum frequency generation process for a bandwidth up to two orders of magnitude wider than in conventional conversion schemes. We show that this scheme is robust to variations in the parameters of both the nonlinear crystal and of the incoming light. These include the crystal temperature, the frequency of the incoming field, the pump intensity, the crystal length and the angle of incidence. Also, we show that this extremely broad bandwidth can be tuned to higher or lower central wavelengths by changing either the pump frequency or the crystal temperature. The detailed study of the properties of this converter is done using the Landau-Zener theory dealing with the adiabatic transitions in two level systems. PMID:19654679
Adiabaticity in open quantum systems
NASA Astrophysics Data System (ADS)
Venuti, Lorenzo Campos; Albash, Tameem; Lidar, Daniel A.; Zanardi, Paolo
2016-03-01
We provide a rigorous generalization of the quantum adiabatic theorem for open systems described by a Markovian master equation with time-dependent Liouvillian L (t ) . We focus on the finite system case relevant for adiabatic quantum computing and quantum annealing. Adiabaticity is defined in terms of closeness to the instantaneous steady state. While the general result is conceptually similar to the closed-system case, there are important differences. Namely, a system initialized in the zero-eigenvalue eigenspace of L (t ) will remain in this eigenspace with a deviation that is inversely proportional to the total evolution time T . In the case of a finite number of level crossings, the scaling becomes T-η with an exponent η that we relate to the rate of the gap closing. For master equations that describe relaxation to thermal equilibrium, we show that the evolution time T should be long compared to the corresponding minimum inverse gap squared of L (t ) . Our results are illustrated with several examples.
NASA Astrophysics Data System (ADS)
Li, Dafa
2016-05-01
The adiabatic theorem was proposed about 90 years ago and has played an important role in quantum physics. The quantitative adiabatic condition constructed from eigenstates and eigenvalues of a Hamiltonian is a traditional tool to estimate adiabaticity and has proven to be the necessary and sufficient condition for adiabaticity. However, recently the condition has become a controversial subject. In this paper, we list some expressions to estimate the validity of the adiabatic approximation. We show that the quantitative adiabatic condition is invalid for the adiabatic approximation via the Euclidean distance between the adiabatic state and the evolution state. Furthermore, we deduce general necessary and sufficient conditions for the validity of the adiabatic approximation by different definitions.
Adiabatic Wankel type rotary engine
NASA Technical Reports Server (NTRS)
Kamo, R.; Badgley, P.; Doup, D.
1988-01-01
This SBIR Phase program accomplished the objective of advancing the technology of the Wankel type rotary engine for aircraft applications through the use of adiabatic engine technology. Based on the results of this program, technology is in place to provide a rotor and side and intermediate housings with thermal barrier coatings. A detailed cycle analysis of the NASA 1007R Direct Injection Stratified Charge (DISC) rotary engine was performed which concluded that applying thermal barrier coatings to the rotor should be successful and that it was unlikely that the rotor housing could be successfully run with thermal barrier coatings as the thermal stresses were extensive.
Andronesi, Ovidiu C.; Ramadan, Saadallah; Mountford, Carolyn E.; Sorensen, A. Gregory
2011-01-01
Novel low-power adiabatic sequences are demonstrated for in-vivo localized two-dimensional (2D) correlated MR spectroscopy, such as COSY (Correlated Spectroscopy) and TOCSY (Total Correlated Spectroscopy). The design is based on three new elements for in-vivo 2D MRS: the use of gradient modulated constant adiabaticity GOIA-W(16,4) pulses for i) localization (COSY and TOCSY) and ii) mixing (TOCSY), and iii) the use of longitudinal mixing (z-filter) for magnetization transfer during TOCSY. GOIA-W(16,4) provides accurate signal localization, and more importantly, lowers the SAR for both TOCSY mixing and localization. Longitudinal mixing improves considerably (five-folds) the efficiency of TOCSY transfer. These are markedly different from previous 1D editing TOCSY sequences using spatially non-selective pulses and transverse mixing. Fully adiabatic (adiabatic mixing with adiabatic localization) and semi-adiabatic (adiabatic mixing with non-adiabatic localization) methods for 2D TOCSY are compared. Results are presented for simulations, phantoms, and in-vivo 2D spectra from healthy volunteers and patients with brain tumors obtained on 3T clinical platforms equipped with standard hardware. To the best of our knowledge this is the first demonstration of in-vivo adiabatic 2D TOCSY and fully adiabatic 2D COSY. It is expected that these methodological developments will advance the in-vivo applicability of multi(spectrally)dimensional MRS to reliably identify metabolic biomarkers. PMID:20890988
Refocusing of B-cell responses following a single amino acid substitution in an antigen
Chiesa, Marta Dalla; Martensen, Pia M; Simmons, Cameron; Porakishvili, Nino; Justesen, Just; Dougan, Gordon; Roitt, Ivan M; Delves, Peter J; Lund, Torben
2001-01-01
Intranasal immunization of BALB/c strain mice was carried out using baculovirus-derived human chorionic gonadotrophin (hCG) β-chain, together with Escherichia coli heat-labile enterotoxin. Gonadotrophin-reactive immunoglobulin A (IgA) was induced in a remote mucosal site, the lung, in addition to a systemic IgG response. The extensive sequence homology with luteinizing hormone (LH) results in the production of LH cross-reactive antibodies when holo-hCG is used as an immunogen. In contrast to wild-type hCGβ, a mutated hCGβ-chain containing an arginine to glutamic acid substitution at position 68 did not induce the production of antibodies which cross-react with LH. Furthermore, the epitopes utilized in the B-cell response to the mutated hCGβ shifted away from the immunodominant region of the parent wild-type molecule towards epitopes within the normally weakly immunogenic C terminus. This shift in epitope usage was also seen following intramuscular immunization of rabbits. Thus, a single amino acid change, which does not disrupt the overall structure of the molecule, refocuses the immune response away from a disadvantageous cross-reactive epitope region and towards a normally weakly immunogenic but antigen-unique area. Similar mutational strategies for epitope-refocusing may be applicable to other vaccine candidate molecules. PMID:11412304
A generic approach to post-column refocusing in liquid chromatography.
De Vos, Jelle; Desmet, Gert; Eeltink, Sebastiaan
2014-09-19
To increase detection sensitivity in liquid chromatography, a generic post-column refocusing strategy has been developed to enrich (target) analytes prior to detection. In this strategy, after separation on the analytical column, the analytes are led to a trap column preferably containing a stationary phase with strong retentive properties (e.g. silica C30). They are then eluted using a strong solvent in a backward-elution mode. A first key element of the proposed strategy is that the trapping time should be at least equal to the time the front of the remobilization solvent needs to cover the entire length of the trap column, divided by the ratio of the flow rates used for trapping and remobilization. This condition is independent of the retention properties of the analytes in the trapping and remobilization solvent. Another essential element is the addition of a third solvent (isopropanol in the present case) to the remobilization solvent to overcome viscous-fingering effects caused by the viscosity difference between the trap and the remobilization solvents. The potential of the proposed post-column refocusing strategy is demonstrated for an isocratic separation of KI (t0 marker), an antibiotic (sulfamethazine), and acetophenone as a case study. Using optimized remobilization conditions a maximum signal-enhancement factor of 8 was achieved. Higher enhancement factors using a remobilization solvent with slightly higher elution strength were prohibited by disturbances of the UV background signal. PMID:25127691
Coupled long-range carbon-hydrogen correlation experiment without refocusing delay
NASA Astrophysics Data System (ADS)
Krishnamurthy, V. V.; Nunlist, Rudi
In long-range carbon-hydrogen correlation experiments with standard heteronuclear shift correlation sequences cross-peak intensities can be severely attenuated due to modulation by "interfering" long-range couplings with other protons. Often cross peaks, even if the polarization transfer delay, Δ1, is optimized, can be missed due to the wrong choice of the refocusing delay, Δ2. A useful improvement is to eliminate the Δ2 delay and acquire without proton decoupling. A one-step low-pass J filter is introduced before evolution to suppress one-bond correlations and this sequence is compared to decoupled versions (the standard heteronuclear shift correlation sequence and the COLOC sequence with one-step low-pass J filter before evolution and a BIRD pulse midway through Δ2). Using rotenone as an example we show the advantages of removing the "refocusing" ("defocusing") delay and retaining 1H coupling in the F2 dimension. It is suggested that the decrease in S/ N (by a factor of 2 or less) is often not very significant compared to the danger of accidental missing of cross peaks due to the wrong choice of Δ2.
Degenerate adiabatic perturbation theory: Foundations and applications
NASA Astrophysics Data System (ADS)
Rigolin, Gustavo; Ortiz, Gerardo
2014-08-01
We present details and expand on the framework leading to the recently introduced degenerate adiabatic perturbation theory [Phys. Rev. Lett. 104, 170406 (2010), 10.1103/PhysRevLett.104.170406], and on the formulation of the degenerate adiabatic theorem, along with its necessary and sufficient conditions [given in Phys. Rev. A 85, 062111 (2012), 10.1103/PhysRevA.85.062111]. We start with the adiabatic approximation for degenerate Hamiltonians that paves the way to a clear and rigorous statement of the associated degenerate adiabatic theorem, where the non-Abelian geometric phase (Wilczek-Zee phase) plays a central role to its quantitative formulation. We then describe the degenerate adiabatic perturbation theory, whose zeroth-order term is the degenerate adiabatic approximation, in its full generality. The parameter in the perturbative power-series expansion of the time-dependent wave function is directly associated to the inverse of the time it takes to drive the system from its initial to its final state. With the aid of the degenerate adiabatic perturbation theory we obtain rigorous necessary and sufficient conditions for the validity of the adiabatic theorem of quantum mechanics. Finally, to illustrate the power and wide scope of the methodology, we apply the framework to a degenerate Hamiltonian, whose closed-form time-dependent wave function is derived exactly, and also to other nonexactly solvable Hamiltonians whose solutions are numerically computed.
NASA Astrophysics Data System (ADS)
Smeesters, L.; Belay, G. Y.; Ottevaere, H.; Meuret, Y.; Vervaeke, Michael; Van Erps, J.; Thienpont, H.
2014-09-01
Refocusing multi-channel imaging systems are nowadays commercially available only in bulky and expensive designs. Compact wafer-level multi-channel imaging systems have until now only been published without refocusing mechanisms, since classical refocusing concepts could not be integrated in a miniaturized configuration. This lack of refocusing capabilities limits the depth-of-field of these imaging designs and therefore their application in practical systems. We designed and characterized a wafer-level two-channel multi-resolution refocusing imaging system, based on an electrically tunable liquid lens and a design that can be realized with wafer-level mass-manufacturing techniques. One wide field-of-view channel (2x40°) gives a general image of the surroundings with a lower angular resolution (0.078°), whereas the high angular resolution channel (0.0098°) provides a detailed image of a small region of interest with a much narrower field-of-view (2x7.57°). The latter high resolution imaging channel contains the tunable lens and therefore the refocusing capability. The performances of this high resolution imaging channel were experimentally characterized in a proof-of-concept demonstrator. The experimental and simulated depth-of-field and resolving power correspond well. Moreover, we are able to obtain a depth-of-field from 0.25m until infinity, which is a significant improvement of the current state-of-the-art static multi-channel imaging systems, which show a depth-of-field from 9m until infinity. Both the high resolution and wide field-of-view imaging channels show a diffraction-limited image quality. The designed wafer-level two-channel imaging system can form the basis of an advanced three-dimensional stacked image sensor, where different image processing algorithms can be simultaneously applied to the different images on the image sensor.
Shortcut to adiabatic gate teleportation
NASA Astrophysics Data System (ADS)
Santos, Alan C.; Silva, Raphael D.; Sarandy, Marcelo S.
2016-01-01
We introduce a shortcut to the adiabatic gate teleportation model of quantum computation. More specifically, we determine fast local counterdiabatic Hamiltonians able to implement teleportation as a universal computational primitive. In this scenario, we provide the counterdiabatic driving for arbitrary n -qubit gates, which allows to achieve universality through a variety of gate sets. Remarkably, our approach maps the superadiabatic Hamiltonian HSA for an arbitrary n -qubit gate teleportation into the implementation of a rotated superadiabatic dynamics of an n -qubit state teleportation. This result is rather general, with the speed of the evolution only dictated by the quantum speed limit. In particular, we analyze the energetic cost for different Hamiltonian interpolations in the context of the energy-time complementarity.
De Vos, Jelle; Desmet, Gert; Eeltink, Sebastiaan
2016-07-15
We developed earlier the post-column refocusing strategy for isocratic separations, which employs trapping target analytes after an analytical separation and additionally focusing them using a strong remobilization solvent prior to detection, and have now extended it to high-speed gradient LC. A gradient separation of antibiotics and its metabolites, applying a linear aqueous acetonitrile gradient from 2 to 65% (v/v) ACN containing 0.1% FA in 10min, performed on an analytical column was selected as an application. Eluted heart-cut fractions were directed from the analytical silica C18 column to a trap column packed with Hypercarb particles. The remobilization of the target analytes was performed in back-flush mode using solvent mixtures tuned to maximize the solvent strength by mixing isopropanol into the remobilization solvent containing acetonitrile. Additionally, a viscosity-calibration experiment showed that the viscosity difference between trapping and remobilization solvents should be smaller than 0.15mPa·s to prevent viscous fingering. To keep the viscosity difference below this limit, during the gradient separation performed on the analytical column, the composition of the remobilization solvent was changed in time. An empirical equation is provided that allows for the selection of the optimal remobilization-solvent composition. To maximize the signal enhancement, the loading time of target analytes on the trap column should be optimized. Peak dispersion was further minimized by applying a flow rate that corresponded to the optimal van-Deemter flow rate of the trap column (20μL/min). Finally, decreasing the diameter of the trap column from 1mm to 0.3mm led to a significant enhancement of the detection sensitivity with more than one order of magnitude. Using an optimized trap configuration and elution/remobilization conditions, a signal enhancement of a factor of 14 was achieved for sulfaguanidine (early-eluting compound in the gradient separation) and 7
NASA Astrophysics Data System (ADS)
Domínguez, F. D.; González, C. E.; Segnorile, H. H.; Zamar, R. C.
2016-02-01
We study the quantum adiabatic decoherence of a multispin array, coupled with an environment of harmonic phonons, in the framework of the theory of open quantum systems. We follow the basic formal guidelines of the well-known spin-boson model, since in this framework it is possible to derive the time dependence of the reduced density matrix in the adiabatic time scale, without resorting to coarse-graining procedures. However, instead of considering a set of uncoupled spins interacting individually with the boson field, the observed system in our model is a network of weakly interacting spin pairs; the bath corresponds to lattice phonons, and the system-environment interaction is generated by the variation of the dipole-dipole energy due to correlated shifts of the spin positions, produced by the phonons. We discuss the conditions that the model must meet in order to fit within the adiabatic regime. By identifying the coupling of the dipole-dipole spin interaction with the low-frequency acoustic modes as the source of decoherence, we calculate the decoherence function of the reduced spin density matrix in closed way, and estimate the decoherence rate of a typical element of the reduced density matrix in one- and three-dimensional models of the spin array. Using realistic values for the various parameters of the model we conclude that the dipole-phonon mechanism can be particularly efficient to degrade multispin coherences, when the number of active spins involved in a given coherence is high. The model provides insight into the microscopic irreversible spin dynamics involved in the buildup of quasiequilibrium states and in the coherence leakage during refocusing experiments in nuclear magnetic resonance of crystalline solids.
Quantum gates with controlled adiabatic evolutions
NASA Astrophysics Data System (ADS)
Hen, Itay
2015-02-01
We introduce a class of quantum adiabatic evolutions that we claim may be interpreted as the equivalents of the unitary gates of the quantum gate model. We argue that these gates form a universal set and may therefore be used as building blocks in the construction of arbitrary "adiabatic circuits," analogously to the manner in which gates are used in the circuit model. One implication of the above construction is that arbitrary classical boolean circuits as well as gate model circuits may be directly translated to adiabatic algorithms with no additional resources or complexities. We show that while these adiabatic algorithms fail to exhibit certain aspects of the inherent fault tolerance of traditional quantum adiabatic algorithms, they may have certain other experimental advantages acting as quantum gates.
On a Nonlinear Model in Adiabatic Evolutions
NASA Astrophysics Data System (ADS)
Sun, Jie; Lu, Song-Feng
2016-08-01
In this paper, we study a kind of nonlinear model of adiabatic evolution in quantum search problem. As will be seen here, for this problem, there always exists a possibility that this nonlinear model can successfully solve the problem, while the linear model can not. Also in the same setting, when the overlap between the initial state and the final stare is sufficiently large, a simple linear adiabatic evolution can achieve O(1) time efficiency, but infinite time complexity for the nonlinear model of adiabatic evolution is needed. This tells us, it is not always a wise choice to use nonlinear interpolations in adiabatic algorithms. Sometimes, simple linear adiabatic evolutions may be sufficient for using. Supported by the National Natural Science Foundation of China under Grant Nos. 61402188 and 61173050. The first author also gratefully acknowledges the support from the China Postdoctoral Science Foundation under Grant No. 2014M552041
Moore, Jay; Colón, Raul D; Tadanki, Sasidhar; Waddell, Kevin W
2014-08-01
The application of low magnetic fields to heteronuclear NMR has expanded recently alongside the emergence of methods for achieving near unity polarization of spin ensembles, independent of magnetic field strength. The parahydrogen induced hyperpolarization methods in particular, often use a hybrid arrangement where a high field spectrometer is used to detect or image polarized molecules that have been conjured on a separate, dedicated polarizer instrument operating at fields in the mT regime where yields are higher. For controlling polarizer chemistry, spare TTL channels of portable NMR spectrometers can be used to pulse program reaction timings in synchrony with heteronuclear RF transformations. The use of a spectrometer as a portable polarizer control module has the advantage of allowing detection in situ, simplifying the process of optimizing polarization yields prior to in vivo experimental trials. Suitable heteronuclear spectrometers compatible with this application are becoming more common, but are still sparsely available in comparison to a large existing infrastructure of single channel NMR consoles. With the goal of expanding the range of these systems to multinuclear applications, the feasibility of rotating a pair of heteronuclear spins ((13)C and (1)H) at 12mT was investigated in this study. Nonlinear phase and amplitude modulated waveforms designed to simultaneously refocus magnetization at 128kHz ((13)C) and 510kHz ((1)H) were generated numerically with optimal control. Although precise quantitative comparisons were not attempted due to limitations of the experimental setup, signals refocused at heteronuclear frequencies with this PANORAMIC approach (Precession And Nutation for Observing Rotation At Multiple Intervals about the Carrier) yielded amplitudes comparable to signals which were refocused using traditional block pulses on heteronuclear channels. Using this PANORAMIC approach to heteronuclear NMR at low field would reduce expense as well as
Steam bottoming cycle for an adiabatic diesel engine
NASA Technical Reports Server (NTRS)
Poulin, E.; Demier, R.; Krepchin, I.; Walker, D.
1984-01-01
Steam bottoming cycles using adiabatic diesel engine exhaust heat which projected substantial performance and economic benefits for long haul trucks were studied. Steam cycle and system component variables, system cost, size and performance were analyzed. An 811 K/6.90 MPa state of the art reciprocating expander steam system with a monotube boiler and radiator core condenser was selected for preliminary design. The costs of the diesel with bottoming system (TC/B) and a NASA specified turbocompound adiabatic diesel with aftercooling with the same total output were compared, the annual fuel savings less the added maintenance cost was determined to cover the increase initial cost of the TC/B system in a payback period of 2.3 years. Steam bottoming system freeze protection strategies were developed, technological advances required for improved system reliability are considered and the cost and performance of advanced systes are evaluated.
Adiabatic Compression of Oxygen: Real Fluid Temperatures
NASA Technical Reports Server (NTRS)
Barragan, Michelle; Wilson, D. Bruce; Stoltzfus, Joel M.
2000-01-01
The adiabatic compression of oxygen has been identified as an ignition source for systems operating in enriched oxygen atmospheres. Current practice is to evaluate the temperature rise on compression by treating oxygen as an ideal gas with constant heat capacity. This paper establishes the appropriate thermodynamic analysis for the common occurrence of adiabatic compression of oxygen and in the process defines a satisfactory equation of state (EOS) for oxygen. It uses that EOS to model adiabatic compression as isentropic compression and calculates final temperatures for this system using current approaches for comparison.
Heating and cooling in adiabatic mixing process
NASA Astrophysics Data System (ADS)
Zhou, Jing; Cai, Zi; Zou, Xu-Bo; Guo, Guang-Can
2010-12-01
We study the effect of interaction on the temperature change in the process of adiabatic mixing of two components of Fermi gases using the real-space Bogoliubov-de Gennes method. We find that in the process of adiabatic mixing, the competition between the adiabatic expansion and the attractive interaction makes it possible to cool or heat the system depending on the strength of the interaction and the initial temperature of the system. The changes of the temperature in a bulk system and in a trapped system are investigated.
A re-examination of spent beam refocusing for high-efficiency helix TWT's and small MDC's
NASA Technical Reports Server (NTRS)
Ramins, Peter; Peet, Shelly; Force, Dale A.
1988-01-01
The usefulness of the concept of spent-beam refocusing in optimizing the performance of low- and medium-power helix TWTs (traveling-wave tubes) equipped with small multistage depressed collectors (MDCs) is examined. Several direct comparisons of the performance of individually optimized TWT-MDC combinations with and without controlled beam expansion and recollimation are presented. The collector efficiency of a number of representative space and airborne TWT-MDCs, which do not use refocusing, is compared to a measure of quality (standard of excellence) established by an examination of irrecoverable MDC losses. The results suggest that the application of the traditional concept of spent-beam refocusing to most helix TWTs that are equipped with small MDCs in order to obtain maximum efficiency is not required (or even desired). Two effects combine to obviate the need for refocusing: 1) the unexpanded beam more nearly meets the `point source' ideal at the input to the small MDC, and 2) the larger space-charge spreading and the slightly larger (but manageable) injection angles of the unexpanded beam can reduce the amount of backstreaming current and the attendant loss in efficiency.
Refocusing core intuitions: A concretizing role for analogy in conceptual change
NASA Astrophysics Data System (ADS)
Brown, David E.
1993-12-01
This article outlines a theoretical framework for viewing students' conceptions and the effect of analogies on students' conceptions. There are several points involved in this perspective: (a) Components of students' conceptions can be considered to be at various levels - verbal-symbolic knowledge, conscious models, implicit models, and core intuitions. (b) Components at the deeper, less articulated levels (especially core intuitions) are particularly entrenched. (c) Conceptual change in cases involving core intuitions can be considered to be the adjustment of attributive clusters for a class of situations. (d) In order to change the attributive cluster for a target situation, the target must be enriched with new concrete entities or features, providing nuclei for the reattribution of agency. (e) Analogies can help with this reattribution or refocusing by helping the student enrich his or her representation of the target situation.
Refocusing of ground moving targets for range migration algorithm in FMCW SAR
NASA Astrophysics Data System (ADS)
Cheng, Pu; Xin, Qin; Wan, Jianwei; Wang, Zhan
2015-10-01
Frequency-Modulated Continuous-Wave Synthetic Aperture Radar (FMCW SAR) is a promising compact remote imaging sensor. Its detection and refocusing of the ground moving targets is discussed in this paper in order to provide FMCW SAR system with simultaneous moving targets indication application. A moving target indication method by focusing is derived and presented. This method is derived based on range migration algorithm taking into account the moving target range cell walk. To discriminate the target optimally, the concept of relative motion is extended to FMCW SAR. Due to continuous transmitting and receiving at all time, the standard "stop-go" approximation is not valid here. By searching the relative velocity, the moving target can be focused accurately, equivalent as a fixed target focused in squint mode. The maximum output corresponds to the best matched parameters. Thus the matched targets are detected and the others suppressed.
Multisurface Adiabatic Reactive Molecular Dynamics.
Nagy, Tibor; Yosa Reyes, Juvenal; Meuwly, Markus
2014-04-01
Adiabatic reactive molecular dynamics (ARMD) simulation method is a surface-crossing algorithm for modeling chemical reactions in classical molecular dynamics simulations using empirical force fields. As the ARMD Hamiltonian is time dependent during crossing, it allows only approximate energy conservation. In the current work, the range of applicability of conventional ARMD is explored, and a new multisurface ARMD (MS-ARMD) method is presented, implemented in CHARMM and applied to the vibrationally induced photodissociation of sulfuric acid (H2SO4) in the gas phase. For this, an accurate global potential energy surface (PES) involving 12 H2SO4 and 4 H2O + SO3 force fields fitted to MP2/6-311G++(2d,2p) reference energies is employed. The MS-ARMD simulations conserve total energy and feature both intramolecular H-transfer reactions and water elimination. An analytical treatment of the dynamics in the crossing region finds that conventional ARMD can approximately conserve total energy for limiting cases. In one of them, the reduced mass of the system is large, which often occurs for simulations of solvated biomolecular systems. On the other hand, MS-ARMD is a general approach for modeling chemical reactions including gas-phase, homogeneous, heterogeneous, and enzymatic catalytic reactions while conserving total energy in atomistic simulations. PMID:26580356
High-speed, digitally refocused retinal imaging with line-field parallel swept source OCT
NASA Astrophysics Data System (ADS)
Fechtig, Daniel J.; Kumar, Abhishek; Ginner, Laurin; Drexler, Wolfgang; Leitgeb, Rainer A.
2015-03-01
MHz OCT allows mitigating undesired influence of motion artifacts during retinal assessment, but comes in state-of-the-art point scanning OCT at the price of increased system complexity. By changing the paradigm from scanning to parallel OCT for in vivo retinal imaging the three-dimensional (3D) acquisition time is reduced without a trade-off between speed, sensitivity and technological requirements. Furthermore, the intrinsic phase stability allows for applying digital refocusing methods increasing the in-focus imaging depth range. Line field parallel interferometric imaging (LPSI) is utilizing a commercially available swept source, a single-axis galvo-scanner and a line scan camera for recording 3D data with up to 1MHz A-scan rate. Besides line-focus illumination and parallel detection, we mitigate the necessity for high-speed sensor and laser technology by holographic full-range imaging, which allows for increasing the imaging speed by low sampling of the optical spectrum. High B-scan rates up to 1kHz further allow for implementation of lable-free optical angiography in 3D by calculating the inter B-scan speckle variance. We achieve a detection sensitivity of 93.5 (96.5) dB at an equivalent A-scan rate of 1 (0.6) MHz and present 3D in vivo retinal structural and functional imaging utilizing digital refocusing. Our results demonstrate for the first time competitive imaging sensitivity, resolution and speed with a parallel OCT modality. LPSI is in fact currently the fastest OCT device applied to retinal imaging and operating at a central wavelength window around 800 nm with a detection sensitivity of higher than 93.5 dB.
Adiabatic limits on Riemannian Heisenberg manifolds
Yakovlev, A A
2008-02-28
An asymptotic formula is obtained for the distribution function of the spectrum of the Laplace operator, in the adiabatic limit for the foliation defined by the orbits of an invariant flow on a compact Riemannian Heisenberg manifold. Bibliography: 21 titles.
Experimental demonstration of composite adiabatic passage
NASA Astrophysics Data System (ADS)
Schraft, Daniel; Halfmann, Thomas; Genov, Genko T.; Vitanov, Nikolay V.
2013-12-01
We report an experimental demonstration of composite adiabatic passage (CAP) for robust and efficient manipulation of two-level systems. The technique represents a altered version of rapid adiabatic passage (RAP), driven by composite sequences of radiation pulses with appropriately chosen phases. We implement CAP with radio-frequency pulses to invert (i.e., to rephase) optically prepared spin coherences in a Pr3+:Y2SiO5 crystal. We perform systematic investigations of the efficiency of CAP and compare the results with conventional π pulses and RAP. The data clearly demonstrate the superior features of CAP with regard to robustness and efficiency, even under conditions of weakly fulfilled adiabaticity. The experimental demonstration of composite sequences to support adiabatic passage is of significant relevance whenever a high efficiency or robustness of coherent excitation processes need to be maintained, e.g., as required in quantum information technology.
An Adiabatic Architecture for Linear Signal Processing
NASA Astrophysics Data System (ADS)
Vollmer, M.; Götze, J.
2005-05-01
Using adiabatic CMOS logic instead of the more traditional static CMOS logic can lower the power consumption of a hardware design. However, the characteristic differences between adiabatic and static logic, such as a four-phase clock, have a far reaching influence on the design itself. These influences are investigated in this paper by adapting a systolic array of CORDIC devices to be implemented adiabatically. We present a means to describe adiabatic logic in VHDL and use it to define the systolic array with precise timing and bit-true calculations. The large pipeline bubbles that occur in a naive version of this array are identified and removed to a large degree. As an example, we demonstrate a parameterization of the CORDIC array that carries out adaptive RLS filtering.
General conditions for quantum adiabatic evolution
Comparat, Daniel
2009-07-15
Adiabaticity occurs when, during its evolution, a physical system remains in the instantaneous eigenstate of the Hamiltonian. Unfortunately, existing results, such as the quantum adiabatic theorem based on a slow down evolution [H({epsilon}t),{epsilon}{yields}0], are insufficient to describe an evolution driven by the Hamiltonian H(t) itself. Here we derive general criteria and exact bounds, for the state and its phase, ensuring an adiabatic evolution for any Hamiltonian H(t). As a corollary, we demonstrate that the commonly used condition of a slow Hamiltonian variation rate, compared to the spectral gap, is indeed sufficient to ensure adiabaticity but only when the Hamiltonian is real and nonoscillating (for instance, containing exponential or polynomial but no sinusoidal functions)
Adiabatic invariance of oscillons/I -balls
NASA Astrophysics Data System (ADS)
Kawasaki, Masahiro; Takahashi, Fuminobu; Takeda, Naoyuki
2015-11-01
Real scalar fields are known to fragment into spatially localized and long-lived solitons called oscillons or I -balls. We prove the adiabatic invariance of the oscillons/I -balls for a potential that allows periodic motion even in the presence of non-negligible spatial gradient energy. We show that such a potential is uniquely determined to be the quadratic one with a logarithmic correction, for which the oscillons/I -balls are absolutely stable. For slightly different forms of the scalar potential dominated by the quadratic one, the oscillons/I -balls are only quasistable, because the adiabatic charge is only approximately conserved. We check the conservation of the adiabatic charge of the I -balls in numerical simulation by slowly varying the coefficient of logarithmic corrections. This unambiguously shows that the longevity of oscillons/I -balls is due to the adiabatic invariance.
Symmetry of the Adiabatic Condition in the Piston Problem
ERIC Educational Resources Information Center
Anacleto, Joaquim; Ferreira, J. M.
2011-01-01
This study addresses a controversial issue in the adiabatic piston problem, namely that of the piston being adiabatic when it is fixed but no longer so when it can move freely. It is shown that this apparent contradiction arises from the usual definition of adiabatic condition. The issue is addressed here by requiring the adiabatic condition to be…
Steam bottoming cycle for an adiabatic diesel engine
Poulin, E.; Demler, R.; Krepchin, I.; Walker, D.
1984-03-01
A study of steam bottoming cycles using adiabatic diesel engine exhaust heat projected substantial performance and economic benefits for long haul trucks. A parametric analysis of steam cycle and system component variables, system cost, size and performance was conducted. An 811 K/6.90 MPa state-of-the-art reciprocating expander steam system with a monotube boiler and radiator core condenser was selected for preliminary design. When applied to a NASA specified turbo-charged adiabatic diesel the bottoming system increased the diesel output by almost 18%. In a comparison of the costs of the diesel with bottoming system (TC/B) and a NASA specified turbocompound adiabatic diesel with after-cooling with the same total output, the annual fuel savings less the added maintenance cost was determined to cover the increased initial cost of the TC/B system in a payback period of 2.3 years. Also during this program steam bottoming system freeze protection strategies were developed, technological advances required for improved system reliability were considered and the cost and performance of advanced systems were evaluated.
NMR implementation of adiabatic SAT algorithm using strongly modulated pulses.
Mitra, Avik; Mahesh, T S; Kumar, Anil
2008-03-28
NMR implementation of adiabatic algorithms face severe problems in homonuclear spin systems since the qubit selective pulses are long and during this period, evolution under the Hamiltonian and decoherence cause errors. The decoherence destroys the answer as it causes the final state to evolve to mixed state and in homonuclear systems, evolution under the internal Hamiltonian causes phase errors preventing the initial state to converge to the solution state. The resolution of these issues is necessary before one can proceed to implement an adiabatic algorithm in a large system where homonuclear coupled spins will become a necessity. In the present work, we demonstrate that by using "strongly modulated pulses" (SMPs) for the creation of interpolating Hamiltonian, one can circumvent both the problems and successfully implement the adiabatic SAT algorithm in a homonuclear three qubit system. This work also demonstrates that the SMPs tremendously reduce the time taken for the implementation of the algorithm, can overcome problems associated with decoherence, and will be the modality in future implementation of quantum information processing by NMR. PMID:18376911
NMR implementation of adiabatic SAT algorithm using strongly modulated pulses
NASA Astrophysics Data System (ADS)
Mitra, Avik; Mahesh, T. S.; Kumar, Anil
2008-03-01
NMR implementation of adiabatic algorithms face severe problems in homonuclear spin systems since the qubit selective pulses are long and during this period, evolution under the Hamiltonian and decoherence cause errors. The decoherence destroys the answer as it causes the final state to evolve to mixed state and in homonuclear systems, evolution under the internal Hamiltonian causes phase errors preventing the initial state to converge to the solution state. The resolution of these issues is necessary before one can proceed to implement an adiabatic algorithm in a large system where homonuclear coupled spins will become a necessity. In the present work, we demonstrate that by using "strongly modulated pulses" (SMPs) for the creation of interpolating Hamiltonian, one can circumvent both the problems and successfully implement the adiabatic SAT algorithm in a homonuclear three qubit system. This work also demonstrates that the SMPs tremendously reduce the time taken for the implementation of the algorithm, can overcome problems associated with decoherence, and will be the modality in future implementation of quantum information processing by NMR.
Graph isomorphism and adiabatic quantum computing
NASA Astrophysics Data System (ADS)
Gaitan, Frank; Clark, Lane
2014-02-01
In the graph isomorphism (GI) problem two N-vertex graphs G and G' are given and the task is to determine whether there exists a permutation of the vertices of G that preserves adjacency and transforms G →G'. If yes, then G and G' are said to be isomorphic; otherwise they are nonisomorphic. The GI problem is an important problem in computer science and is thought to be of comparable difficulty to integer factorization. In this paper we present a quantum algorithm that solves arbitrary instances of GI and which also provides an approach to determining all automorphisms of a given graph. We show how the GI problem can be converted to a combinatorial optimization problem that can be solved using adiabatic quantum evolution. We numerically simulate the algorithm's quantum dynamics and show that it correctly (i) distinguishes nonisomorphic graphs; (ii) recognizes isomorphic graphs and determines the permutation(s) that connect them; and (iii) finds the automorphism group of a given graph G. We then discuss the GI quantum algorithm's experimental implementation, and close by showing how it can be leveraged to give a quantum algorithm that solves arbitrary instances of the NP-complete subgraph isomorphism problem. The computational complexity of an adiabatic quantum algorithm is largely determined by the minimum energy gap Δ (N) separating the ground and first-excited states in the limit of large problem size N ≫1. Calculating Δ (N) in this limit is a fundamental open problem in adiabatic quantum computing, and so it is not possible to determine the computational complexity of adiabatic quantum algorithms in general, nor consequently, of the specific adiabatic quantum algorithms presented here. Adiabatic quantum computing has been shown to be equivalent to the circuit model of quantum computing, and so development of adiabatic quantum algorithms continues to be of great interest.
Accurate adiabatic correction in the hydrogen molecule
Pachucki, Krzysztof; Komasa, Jacek
2014-12-14
A new formalism for the accurate treatment of adiabatic effects in the hydrogen molecule is presented, in which the electronic wave function is expanded in the James-Coolidge basis functions. Systematic increase in the size of the basis set permits estimation of the accuracy. Numerical results for the adiabatic correction to the Born-Oppenheimer interaction energy reveal a relative precision of 10{sup −12} at an arbitrary internuclear distance. Such calculations have been performed for 88 internuclear distances in the range of 0 < R ⩽ 12 bohrs to construct the adiabatic correction potential and to solve the nuclear Schrödinger equation. Finally, the adiabatic correction to the dissociation energies of all rovibrational levels in H{sub 2}, HD, HT, D{sub 2}, DT, and T{sub 2} has been determined. For the ground state of H{sub 2} the estimated precision is 3 × 10{sup −7} cm{sup −1}, which is almost three orders of magnitude higher than that of the best previous result. The achieved accuracy removes the adiabatic contribution from the overall error budget of the present day theoretical predictions for the rovibrational levels.
Accurate adiabatic correction in the hydrogen molecule
NASA Astrophysics Data System (ADS)
Pachucki, Krzysztof; Komasa, Jacek
2014-12-01
A new formalism for the accurate treatment of adiabatic effects in the hydrogen molecule is presented, in which the electronic wave function is expanded in the James-Coolidge basis functions. Systematic increase in the size of the basis set permits estimation of the accuracy. Numerical results for the adiabatic correction to the Born-Oppenheimer interaction energy reveal a relative precision of 10-12 at an arbitrary internuclear distance. Such calculations have been performed for 88 internuclear distances in the range of 0 < R ⩽ 12 bohrs to construct the adiabatic correction potential and to solve the nuclear Schrödinger equation. Finally, the adiabatic correction to the dissociation energies of all rovibrational levels in H2, HD, HT, D2, DT, and T2 has been determined. For the ground state of H2 the estimated precision is 3 × 10-7 cm-1, which is almost three orders of magnitude higher than that of the best previous result. The achieved accuracy removes the adiabatic contribution from the overall error budget of the present day theoretical predictions for the rovibrational levels.
Symmetry-Protected Quantum Adiabatic Transistors
NASA Astrophysics Data System (ADS)
Williamson, Dominic J.; Bartlett, Stephen D.
2014-03-01
An essential development in the history of computing was the invention of the transistor as it allowed logic circuits to be implemented in a robust and modular way. The physical characteristics of semiconductor materials were the key to building these devices. We aim to present an analogous development for quantum computing by showing that quantum adiabatic transistors (as defined by Flammia et al.) are built upon the essential qualities of symmetry-protected (SP) quantum ordered phases in one dimension. Flammia et al. and Renes et al. have demonstrated schemes for universal adiabatic quantum computation using quantum adiabatic transistors described by interacting spin chain models with specifically chosen Hamiltonian terms. We show that these models can be understood as specific examples of the generic situation in which all SP phases lead to quantum computation on encoded edge degrees of freedom by adiabatically traversing a symmetric phase transition into a trivial symmetric phase. This point of view is advantageous as it allows us to readily see that the computational properties of a quantum adiabatic transistor arise from a phase of matter rather than due to carefully tuned interactions.
Vashaee, S; Newling, B; Balcom, B J
2015-12-01
Band selective adiabatic inversion radio frequency pulses were employed for multi-slice T2 distribution measurements in porous media samples. Multi-slice T2 measurement employing longitudinal Hadamard encoding has an inherent sensitivity advantage over slice-by-slice local T2 measurements. The slice selection process is rendered largely immune to B1 variation by employing hyperbolic secant adiabatic inversion pulses, which simultaneously invert spins in several well-defined slices. While Hadamard encoding is well established for local spectroscopy, the current work is the first use of Hadamard encoding for local T2 measurement. PMID:26580063
NASA Astrophysics Data System (ADS)
Vashaee, S.; Newling, B.; Balcom, B. J.
2015-12-01
Band selective adiabatic inversion radio frequency pulses were employed for multi-slice T2 distribution measurements in porous media samples. Multi-slice T2 measurement employing longitudinal Hadamard encoding has an inherent sensitivity advantage over slice-by-slice local T2 measurements. The slice selection process is rendered largely immune to B1 variation by employing hyperbolic secant adiabatic inversion pulses, which simultaneously invert spins in several well-defined slices. While Hadamard encoding is well established for local spectroscopy, the current work is the first use of Hadamard encoding for local T2 measurement.
NASA Astrophysics Data System (ADS)
Ford, Logan; Bajpayee, Abhishek; Techet, Alexandra
2015-11-01
3D particle image velocimetry (PIV) is becoming a popular technique to study biological flows. PIV images that contain fish or other animals around which flow is being studied, need to be appropriately masked in order to remove the animal body from the 3D reconstructed volumes prior to calculating particle displacement vectors. Presented here is a machine learning and synthetic aperture (SA) refocusing based approach for more accurate masking of fish from reconstructed intensity fields for 3D PIV purposes. Using prior knowledge about the 3D shape and appearance of the fish along with SA refocused images at arbitrarily oriented focal planes, the location and orientation of a fish in a reconstructed volume can be accurately determined. Once the location and orientation of a fish in a volume is determined, it can be masked out.
NASA Astrophysics Data System (ADS)
Chen, Ying; Chen, Song; Zhong, Jianhui; Chen, Zhong
2015-05-01
This paper presents a phase evolution rewinding algorithm for correcting the geometric and intensity distortions in single-shot spatiotemporally encoded (SPEN) MRI with acquisition of asymmetric self-refocused echo trains. Using the field map calculated from the phase distribution of the source image, the off-resonance induced phase errors are successfully rewound through deconvolution. The alias-free partial Fourier transform reconstruction helps improve the signal-to-noise ratio of the field maps and the output images. The effectiveness of the proposed algorithm was validated through 7 T MRI experiments on a lemon, a water phantom, and in vivo rat head. SPEN imaging was evaluated using rapid acquisition by sequential excitation and refocusing (RASER) which produces uniform T2 weighting. The results indicate that the new technique can more robustly deal with the cases in which the images obtained with conventional single-shot spin-echo EPI are difficult to be restored due to serious field variations.
Development and performance of the EAGLE active optics LGS WFS refocusing system
NASA Astrophysics Data System (ADS)
Madec, Fabrice; Le Mignant, David; Chardin, Elodie; Hugot, Emmanuel; Mazzanti, Silvio; Gimenez, Jean-Luc; Ferrari, Marc; Moreaux, Gabriel; Vives, Sébastien; Cuby, Jean-Gabriel
2010-07-01
We designed, developed, and tested a Variable Curvature Mirror (VCM) as an active refocusing system for the Laser Guide Star (LGS) Wave Front Sensor (WFS) of the E-ELT EAGLE instrument [1]. This paper is the second of two from our team on this R&D activity: Hugot et al. this conf. [2] presented the mirror design and performance simulations. Here, we report on the fabrication integration, testing and performance of the VCM system. During this activity, we developed all necessary parts for the VCM system: a metallic mirror, its housing and mounts, a computer-controlled pressure system, an internal metrology, a testbench etc. The functional testing of the VCM system is successful: we can control the internal pressure to less than 1 mBar, and measure the mirror displacement with a 100 nm accuracy. The mirror displacement is a near-linear and well-simulated function of internal pressure for the desired range of focus. The intrinsic optical quality of the mirror meniscus is well within the specifications. Once mounted in its housing, we observe additional mechanical constraints for the current design that generate optical aberrations. We measured the amplitude of the Zernike modes, and we showed that the axisymetric terms display a variation trend very similar to simulations, with amplitude close to simulations. All these results are very promising for a design of focus compensation without any moving part.
J-refocused coherence transfer spectroscopic imaging at 7 T in human brain.
Pan, J W; Avdievich, N; Hetherington, H P
2010-11-01
Short echo spectroscopy is commonly used to minimize signal modulation due to J-evolution of the cerebral amino acids. However, short echo acquisitions suffer from high sensitivity to macromolecules which make accurate baseline determination difficult. In this report, we describe implementation at 7 T of a double echo J-refocused coherence transfer sequence at echo time (TE) of 34 msec to minimize J-modulation of amino acids while also decreasing interfering macromolecule signals. Simulation of the pulse sequence at 7 T shows excellent resolution of glutamate, glutamine, and N-acetyl aspartate. B(1) sufficiency at 7 T for the double echo acquisition is achieved using a transceiver array with radiofrequency (RF) shimming. Using an alternate RF distribution to minimize receiver phase cancellation in the transceiver, accurate phase determination for the coherence transfer is achieved with rapid single scan calibration. This method is demonstrated in spectroscopic imaging mode with n = 5 healthy volunteers resulting in metabolite values consistent with literature and in a patient with epilepsy. PMID:20648684
Noehren, Brian; Andersen, Anders; Feiweier, Thorsten; Damon, Bruce; Hardy, Peter
2014-01-01
Purpose To compare the precision of measuring the pennation angle and fiber length in the Vastus Lateralis (VL) using two distinctly different diffusion tensor imaging sequences. Materials and Methods We imaged the thigh of ten normal subjects on a 3T MR imager with twice refocused spin echo (TRSE) and stimulated echo (STEAM) DTI-MRI techniques. Both techniques took the same total acquisition time, employed the same diffusion weighting and gradient directions. Using the diffusion tensor images produced by each sequence muscle fiber bundles were tracked from the aponeurosis by following the first eigenvector of the diffusion tensor. From these tracks we calculated the pennation angle and fiber length. Results The STEAM acquisition resulted in significantly higher SNR, lower ADC, higher FA values and longer fibers than the TRSE. Although no difference in the pennation angle between the two acquisitions was found, the TRSE sequence had a significantly greater within subject dispersion in the pennation angle of tracked fibers which may indicate a reduction in the coherence of fiber bundles. Conclusion Diffusion tensor imaging of muscle using a STEAM acquisition resulted in significant improvements in the SNR and FA, resulting in tracking a larger number of muscle fiber bundles over longer distances and with less within subject dispersion. PMID:24554376
Multi-Contrast Imaging and Digital Refocusing on a Mobile Microscope with a Domed LED Array
Phillips, Zachary F.; D'Ambrosio, Michael V.; Tian, Lei; Rulison, Jared J.; Patel, Hurshal S.; Sadras, Nitin; Gande, Aditya V.; Switz, Neil A.; Fletcher, Daniel A.; Waller, Laura
2015-01-01
We demonstrate the design and application of an add-on device for improving the diagnostic and research capabilities of CellScope—a low-cost, smartphone-based point-of-care microscope. We replace the single LED illumination of the original CellScope with a programmable domed LED array. By leveraging recent advances in computational illumination, this new device enables simultaneous multi-contrast imaging with brightfield, darkfield, and phase imaging modes. Further, we scan through illumination angles to capture lightfield datasets, which can be used to recover 3D intensity and phase images without any hardware changes. This digital refocusing procedure can be used for either 3D imaging or software-only focus correction, reducing the need for precise mechanical focusing during field experiments. All acquisition and processing is performed on the mobile phone and controlled through a smartphone application, making the computational microscope compact and portable. Using multiple samples and different objective magnifications, we demonstrate that the performance of our device is comparable to that of a commercial microscope. This unique device platform extends the field imaging capabilities of CellScope, opening up new clinical and research possibilities. PMID:25969980
Multi-Contrast Imaging and Digital Refocusing on a Mobile Microscope with a Domed LED Array.
Phillips, Zachary F; D'Ambrosio, Michael V; Tian, Lei; Rulison, Jared J; Patel, Hurshal S; Sadras, Nitin; Gande, Aditya V; Switz, Neil A; Fletcher, Daniel A; Waller, Laura
2015-01-01
We demonstrate the design and application of an add-on device for improving the diagnostic and research capabilities of CellScope--a low-cost, smartphone-based point-of-care microscope. We replace the single LED illumination of the original CellScope with a programmable domed LED array. By leveraging recent advances in computational illumination, this new device enables simultaneous multi-contrast imaging with brightfield, darkfield, and phase imaging modes. Further, we scan through illumination angles to capture lightfield datasets, which can be used to recover 3D intensity and phase images without any hardware changes. This digital refocusing procedure can be used for either 3D imaging or software-only focus correction, reducing the need for precise mechanical focusing during field experiments. All acquisition and processing is performed on the mobile phone and controlled through a smartphone application, making the computational microscope compact and portable. Using multiple samples and different objective magnifications, we demonstrate that the performance of our device is comparable to that of a commercial microscope. This unique device platform extends the field imaging capabilities of CellScope, opening up new clinical and research possibilities. PMID:25969980
Nonadiabatic exchange dynamics during adiabatic frequency sweeps
NASA Astrophysics Data System (ADS)
Barbara, Thomas M.
2016-04-01
A Bloch equation analysis that includes relaxation and exchange effects during an adiabatic frequency swept pulse is presented. For a large class of sweeps, relaxation can be incorporated using simple first order perturbation theory. For anisochronous exchange, new expressions are derived for exchange augmented rotating frame relaxation. For isochronous exchange between sites with distinct relaxation rate constants outside the extreme narrowing limit, simple criteria for adiabatic exchange are derived and demonstrate that frequency sweeps commonly in use may not be adiabatic with regard to exchange unless the exchange rates are much larger than the relaxation rates. Otherwise, accurate assessment of the sensitivity to exchange dynamics will require numerical integration of the rate equations. Examples of this situation are given for experimentally relevant parameters believed to hold for in-vivo tissue. These results are of significance in the study of exchange induced contrast in magnetic resonance imaging.
Adiabatic approximation for the density matrix
NASA Astrophysics Data System (ADS)
Band, Yehuda B.
1992-05-01
An adiabatic approximation for the Liouville density-matrix equation which includes decay terms is developed. The adiabatic approximation employs the eigenvectors of the non-normal Liouville operator. The approximation is valid when there exists a complete set of eigenvectors of the non-normal Liouville operator (i.e., the eigenvectors span the density-matrix space), the time rate of change of the Liouville operator is small, and an auxiliary matrix is nonsingular. Numerical examples are presented involving efficient population transfer in a molecule by stimulated Raman scattering, with the intermediate level of the molecule decaying on a time scale that is fast compared with the pulse durations of the pump and Stokes fields. The adiabatic density-matrix approximation can be simply used to determine the density matrix for atomic or molecular systems interacting with cw electromagnetic fields when spontaneous emission or other decay mechanisms prevail.
Extensive Adiabatic Invariants for Nonlinear Chains
NASA Astrophysics Data System (ADS)
Giorgilli, Antonio; Paleari, Simone; Penati, Tiziano
2012-09-01
We look for extensive adiabatic invariants in nonlinear chains in the thermodynamic limit. Considering the quadratic part of the Klein-Gordon Hamiltonian, by a linear change of variables we transform it into a sum of two parts in involution. At variance with the usual method of introducing normal modes, our constructive procedure allows us to exploit the complete resonance, while keeping the extensive nature of the system. Next we construct a nonlinear approximation of an extensive adiabatic invariant for a perturbation of the discrete nonlinear Schrödinger model. The fluctuations of this quantity are controlled via Gibbs measure estimates independent of the system size, for a large set of initial data at low specific energy. Finally, by numerical calculations we show that our adiabatic invariant is well conserved for times much longer than predicted by our first order theory, with fluctuation much smaller than expected according to standard statistical estimates.
Anderson localization makes adiabatic quantum optimization fail
Altshuler, Boris; Krovi, Hari; Roland, Jérémie
2010-01-01
Understanding NP-complete problems is a central topic in computer science (NP stands for nondeterministic polynomial time). This is why adiabatic quantum optimization has attracted so much attention, as it provided a new approach to tackle NP-complete problems using a quantum computer. The efficiency of this approach is limited by small spectral gaps between the ground and excited states of the quantum computer’s Hamiltonian. We show that the statistics of the gaps can be analyzed in a novel way, borrowed from the study of quantum disordered systems in statistical mechanics. It turns out that due to a phenomenon similar to Anderson localization, exponentially small gaps appear close to the end of the adiabatic algorithm for large random instances of NP-complete problems. This implies that unfortunately, adiabatic quantum optimization fails: The system gets trapped in one of the numerous local minima. PMID:20616043
2011-01-01
Purpose To theoretically develop and experimentally validate a formulism based on a fractional order calculus (FC) diffusion model to characterize anomalous diffusion in brain tissues measured with a twice-refocused spin-echo (TRSE) pulse sequence. Materials and Methods The FC diffusion model is the fractional order generalization of the Bloch-Torrey equation. Using this model, an analytical expression was derived to describe the diffusion-induced signal attenuation in a TRSE pulse sequence. To experimentally validate this expression, a set of diffusion-weighted (DW) images was acquired at 3 Tesla from healthy human brains using a TRSE sequence with twelve b-values ranging from 0 to 2,600 s/mm2. For comparison, DW images were also acquired using a Stejskal-Tanner diffusion gradient in a single-shot spin-echo echo planar sequence. For both datasets, a Levenberg-Marquardt fitting algorithm was used to extract three parameters: diffusion coefficient D, fractional order derivative in space β, and a spatial parameter μ (in units of μm). Using adjusted R-squared values and standard deviations, D, β and μ values and the goodness-of-fit in three specific regions of interest (ROI) in white matter, gray matter, and cerebrospinal fluid were evaluated for each of the two datasets. In addition, spatially resolved parametric maps were assessed qualitatively. Results The analytical expression for the TRSE sequence, derived from the FC diffusion model, accurately characterized the diffusion-induced signal loss in brain tissues at high b-values. In the selected ROIs, the goodness-of-fit and standard deviations for the TRSE dataset were comparable with the results obtained from the Stejskal-Tanner dataset, demonstrating the robustness of the FC model across multiple data acquisition strategies. Qualitatively, the D, β, and μ maps from the TRSE dataset exhibited fewer artifacts, reflecting the improved immunity to eddy currents. Conclusion The diffusion-induced signal
Spontaneous emission in stimulated Raman adiabatic passage
Ivanov, P. A.; Vitanov, N. V.; Bergmann, K.
2005-11-15
This work explores the effect of spontaneous emission on the population transfer efficiency in stimulated Raman adiabatic passage (STIRAP). The approach uses adiabatic elimination of weakly coupled density matrix elements in the Liouville equation, from which a very accurate analytic approximation is derived. The loss of population transfer efficiency is found to decrease exponentially with the factor {omega}{sub 0}{sup 2}/{gamma}, where {gamma} is the spontaneous emission rate and {omega}{sub 0} is the peak Rabi frequency. The transfer efficiency increases with the pulse delay and reaches a steady value. For large pulse delay and large spontaneous emission rate STIRAP degenerates into optical pumping.
Adiabatic Hyperspherical Analysis of Realistic Nuclear Potentials
NASA Astrophysics Data System (ADS)
Daily, K. M.; Kievsky, Alejandro; Greene, Chris H.
2015-12-01
Using the hyperspherical adiabatic method with the realistic nuclear potentials Argonne V14, Argonne V18, and Argonne V18 with the Urbana IX three-body potential, we calculate the adiabatic potentials and the triton bound state energies. We find that a discrete variable representation with the slow variable discretization method along the hyperradial degree of freedom results in energies consistent with the literature. However, using a Laguerre basis results in missing energy, even when extrapolated to an infinite number of basis functions and channels. We do not include the isospin T = 3/2 contribution in our analysis.
On black hole spectroscopy via adiabatic invariance
NASA Astrophysics Data System (ADS)
Jiang, Qing-Quan; Han, Yan
2012-12-01
In this Letter, we obtain the black hole spectroscopy by combining the black hole property of adiabaticity and the oscillating velocity of the black hole horizon. This velocity is obtained in the tunneling framework. In particular, we declare, if requiring canonical invariance, the adiabatic invariant quantity should be of the covariant form Iadia = ∮pi dqi. Using it, the horizon area of a Schwarzschild black hole is quantized independently of the choice of coordinates, with an equally spaced spectroscopy always given by ΔA = 8 π lp2 in the Schwarzschild and Painlevé coordinates.
Complexity of the Quantum Adiabatic Algorithm
NASA Technical Reports Server (NTRS)
Hen, Itay
2013-01-01
The Quantum Adiabatic Algorithm (QAA) has been proposed as a mechanism for efficiently solving optimization problems on a quantum computer. Since adiabatic computation is analog in nature and does not require the design and use of quantum gates, it can be thought of as a simpler and perhaps more profound method for performing quantum computations that might also be easier to implement experimentally. While these features have generated substantial research in QAA, to date there is still a lack of solid evidence that the algorithm can outperform classical optimization algorithms.
Adiabatic approximation for nucleus-nucleus scattering
Johnson, R.C.
2005-10-14
Adiabatic approximations to few-body models of nuclear scattering are described with emphasis on reactions with deuterons and halo nuclei (frozen halo approximation) as projectiles. The different ways the approximation should be implemented in a consistent theory of elastic scattering, stripping and break-up are explained and the conditions for the theory's validity are briefly discussed. A formalism which links few-body models and the underlying many-body system is outlined and the connection between the adiabatic and CDCC methods is reviewed.
Selection of Simultaneous Coherence Pathways with Gradient Pulses
NASA Astrophysics Data System (ADS)
Ross, A.; Czisch, M.; Holak, T. A.
A simple modification of a refocused INEPT sequence is described that produces single lines from multiplets of the heteronuclear coupled spin systems. Weighted selection of more than one coherence-transfer pathway is accomplished by pulsed field gradients in a single-scan experiment. Applications involve line selections in heteronuclear multiplets and the determination of relaxation times for selected coherences.
Adiabatic Compression in a Fire Syringe.
ERIC Educational Resources Information Center
Hayn, Carl H.; Baird, Scott C.
1985-01-01
Suggests using better materials in fire syringes to obtain more effective results during demonstrations which show the elevation in temperature upon a very rapid (adiabatic) compression of air. Also describes an experiment (using ignition temperatures) which introduces students to the use of thermocouples for high temperature measurements. (DH)
Apparatus to Measure Adiabatic and Isothermal Processes.
ERIC Educational Resources Information Center
Lamb, D. W.; White, G. M.
1996-01-01
Describes a simple manual apparatus designed to serve as an effective demonstration of the differences between isothermal and adiabatic processes for the general or elementary physics student. Enables students to verify Boyle's law for slow processes and identify the departure from this law for rapid processes and can also be used to give a clear…
Communication: Adiabatic and non-adiabatic electron-nuclear motion: Quantum and classical dynamics
NASA Astrophysics Data System (ADS)
Albert, Julian; Kaiser, Dustin; Engel, Volker
2016-05-01
Using a model for coupled electronic-nuclear motion we investigate the range from negligible to strong non-adiabatic coupling. In the adiabatic case, the quantum dynamics proceeds in a single electronic state, whereas for strong coupling a complete transition between two adiabatic electronic states takes place. It is shown that in all coupling regimes the short-time wave-packet dynamics can be described using ensembles of classical trajectories in the phase space spanned by electronic and nuclear degrees of freedom. We thus provide an example which documents that the quantum concept of non-adiabatic transitions is not necessarily needed if electronic and nuclear motion is treated on the same footing.
Golnik, Karl; Mayorga, Eduardo; Spivey, Bruce; Ritch, Robert; Gauthier, Tina-Marie
2012-01-01
The International Council of Ophthalmology (ICO) is a global organization with a regional focus. Working in partnership with supranational and ICO member societies, the ICO is building a "World Alliance for Sight" to improve access to the highest-quality eye care worldwide. Designed to preserve and restore vision on an international scale, the ICO initiative, "Refocusing Ophthalmic Education," enhances ophthalmic education of residents, subspecialists, medical students, and allied eye care personnel by redefining the most effective ways to teach and in creating beneficial educational opportunities. The "Teaching the Teachers" program helps ophthalmic educators incorporate more effective methods of training and continuing professional development to meet societal needs, achieved in part through regional courses for residency program directors; symposia, and keynote talks presented by ICO's World Ophthalmology Educational Colloquium, Conferences for Ophthalmic Educators, and ophthalmic surgical competency rubrics. Recognizing that standardized curricula are essential for consistent ophthalmic education, the ICO has developed a curricular framework whereby goals, expectations, knowledge base, competencies, and technical training are delineated. The ICO is defining worldwide models of team training and compiling best practice, which will include training-program accreditation to ensure improvement in the education of ophthalmologists. International Council of Ophthalmology Web-based teaching courses, a Webinar Network, and a technology blog further support information and communication technologies for teaching and learning. At the ICO's Center for Ophthalmic Educators (educators.icoph.org), trainers will find valuable teaching resources in multiple languages as well as ways to share ideas and collaborate with peers and other ophthalmic educators. PMID:26107594
The dynamic instability of adiabatic blast waves
NASA Technical Reports Server (NTRS)
Ryu, Dongsu; Vishniac, Ethan T.
1991-01-01
Adiabatic blastwaves, which have a total energy injected from the center E varies as t(sup q) and propagate through a preshock medium with a density rho(sub E) varies as r(sup -omega) are described by a family of similarity solutions. Previous work has shown that adiabatic blastwaves with increasing or constant postshock entropy behind the shock front are susceptible to an oscillatory instability, caused by the difference between the nature of the forces on the two sides of the dense shell behind the shock front. This instability sets in if the dense postshock layer is sufficiently thin. The stability of adiabatic blastwaves with a decreasing postshock entropy is considered. Such blastwaves, if they are decelerating, always have a region behind the shock front which is subject to convection. Some accelerating blastwaves also have such region, depending on the values of q, omega, and gamma where gamma is the adiabatic index. However, since the shock interface stabilizes dynamically induced perturbations, blastwaves become convectively unstable only if the convective zone is localized around the origin or a contact discontinuity far from the shock front. On the other hand, the contact discontinuity of accelerating blastwaves is subject to a strong Rayleigh-Taylor instability. The frequency spectra of the nonradial, normal modes of adiabatic blastwaves have been calculated. The results have been applied to the shocks propagating through supernovae envelopes. It is shown that the metal/He and He/H interfaces are strongly unstable against the Rayleigh-Taylor instability. This instability will induce mixing in supernovae envelopes. In addition the implications of this work for the evolution of planetary nebulae is discussed.
Adiabatic circuits: converter for static CMOS signals
NASA Astrophysics Data System (ADS)
Fischer, J.; Amirante, E.; Bargagli-Stoffi, A.; Schmitt-Landsiedel, D.
2003-05-01
Ultra low power applications can take great advantages from adiabatic circuitry. In this technique a multiphase system is used which consists ideally of trapezoidal voltage signals. The input signals to be processed will often come from a function block realized in static CMOS. The static rectangular signals must be converted for the oscillating multiphase system of the adiabatic circuitry. This work shows how to convert the input signals to the proposed pulse form which is synchronized to the appropriate supply voltage. By means of adder structures designed for a 0.13µm technology in a 4-phase system there will be demonstrated, which additional circuits are necessary for the conversion. It must be taken into account whether the data arrive in parallel or serial form. Parallel data are all in one phase and therefore it is advantageous to use an adder structure with a proper input stage, e.g. a Carry Lookahead Adder (CLA). With a serial input stage it is possible to read and to process four signals during one cycle due to the adiabatic 4-phase system. Therefore input signals with a frequency four times higher than the adiabatic clock frequency can be used. This reduces the disadvantage of the slow clock period typical for adiabatic circuits. By means of an 8 bit Ripple Carry Adder (8 bit RCA) the serial reading will be introduced. If the word width is larger than 4 bits the word can be divided in 4 bit words which are processed in parallel. This is the most efficient way to minimize the number of input lines and pads. At the same time a high throughput is achieved.
The dynamic instability of adiabatic blast waves
NASA Astrophysics Data System (ADS)
Ryu, Dongsu; Vishniac, Ethan T.
1991-02-01
Adiabatic blastwaves, which have a total energy injected from the center E varies as tq and propagate through a preshock medium with a density rhoE varies as r-omega are described by a family of similarity solutions. Previous work has shown that adiabatic blastwaves with increasing or constant postshock entropy behind the shock front are susceptible to an oscillatory instability, caused by the difference between the nature of the forces on the two sides of the dense shell behind the shock front. This instability sets in if the dense postshock layer is sufficiently thin. The stability of adiabatic blastwaves with a decreasing postshock entropy is considered. Such blastwaves, if they are decelerating, always have a region behind the shock front which is subject to convection. Some accelerating blastwaves also have such region, depending on the values of q, omega, and gamma where gamma is the adiabatic index. However, since the shock interface stabilizes dynamically induced perturbations, blastwaves become convectively unstable only if the convective zone is localized around the origin or a contact discontinuity far from the shock front. On the other hand, the contact discontinuity of accelerating blastwaves is subject to a strong Rayleigh-Taylor instability. The frequency spectra of the nonradial, normal modes of adiabatic blastwaves have been calculated. The results have been applied to the shocks propagating through supernovae envelopes. It is shown that the metal/He and He/H interfaces are strongly unstable against the Rayleigh-Taylor instability. This instability will induce mixing in supernovae envelopes. In addition the implications of this work for the evolution of planetary nebulae is discussed.
The dynamic instability of adiabatic blastwaves
NASA Astrophysics Data System (ADS)
Ryu, Dongsu; Vishniac, Ethan T.
1990-05-01
Adiabatic blastwaves, which have a total energy injected from the center E varies as t(sup q) and propagate through a preshock medium with a density rho(sub E) varies as r(sup -omega) are described by a family of similarity solutions. Previous work has shown that adiabatic blastwaves with increasing or constant postshock entropy behind the shock front are susceptible to an oscillatory instability, caused by the difference between the nature of the forces on the two sides of the dense shell behind the shock front. This instability sets in if the dense postshock layer is sufficiently thin. The stability of adiabatic blastwaves with a decreasing postshock entropy is considered. Such blastwaves, if they are decelerating, always have a region behind the shock front which is subject to convection. Some accelerating blastwaves also have such region, depending on the values of q, omega, and gamma where gamma is the adiabatic index. However, since the shock interface stabilizes dynamically induced perturbations, blastwaves become convectively unstable only if the convective zone is localized around the origin or a contact discontinuity far from the shock front. On the other hand, the contact discontinuity of accelerating blastwaves is subject to a strong Rayleigh-Taylor instability. The frequency spectra of the nonradial, normal modes of adiabatic blastwaves have been calculated. The results have been applied to the shocks propagating through supernovae envelopes. It is shown that the metal/He and He/H interfaces are strongly unstable against the Rayleigh-Taylor instability. This instability will induce mixing in supernovae envelopes. In addition the implications of this work for the evolution of planetary nebulae is discussed.
Adiabatic burst evaporation from bicontinuous nanoporous membranes
Ichilmann, Sachar; Rücker, Kerstin; Haase, Markus; Enke, Dirk
2015-01-01
Evaporation of volatile liquids from nanoporous media with bicontinuous morphology and pore diameters of a few 10 nm is an ubiquitous process. For example, such drying processes occur during syntheses of nanoporous materials by sol–gel chemistry or by spinodal decomposition in the presence of solvents as well as during solution impregnation of nanoporous hosts with functional guests. It is commonly assumed that drying is endothermic and driven by non-equilibrium partial pressures of the evaporating species in the gas phase. We show that nearly half of the liquid evaporates in an adiabatic mode involving burst-like liquid-to-gas conversions. During single adiabatic burst evaporation events liquid volumes of up to 107 μm3 are converted to gas. The adiabatic liquid-to-gas conversions occur if air invasion fronts get unstable because of the built-up of high capillary pressures. Adiabatic evaporation bursts propagate avalanche-like through the nanopore systems until the air invasion fronts have reached new stable configurations. Adiabatic cavitation bursts thus compete with Haines jumps involving air invasion front relaxation by local liquid flow without enhanced mass transport out of the nanoporous medium and prevail if the mean pore diameter is in the range of a few 10 nm. The results reported here may help optimize membrane preparation via solvent-based approaches, solution-loading of nanopore systems with guest materials as well as routine use of nanoporous membranes with bicontinuous morphology and may contribute to better understanding of adsorption/desorption processes in nanoporous media. PMID:25926406
Adiabatic evolution of an irreversible two level system
Kvitsinsky, A.; Putterman, S. )
1991-05-01
The adiabatic dynamics of a two level atom with spontaneous decay is studied. The existence of a complex adiabatic phase shift is established: The real part being the usual Berry's phase. A closed-form expression for this phase and the adiabatic transition amplitudes is obtained. Incorporation of a finite preparation time for the initial state yields a new asymptotic form for the adiabatic transition amplitudes which is significantly different from the standard Landau--Zener--Dykhne formula.
Protecting and accelerating adiabatic passage with time-delayed pulse sequences.
Sampedro, Pablo; Chang, Bo Y; Sola, Ignacio R
2016-05-21
Using numerical simulations of two-photon electronic absorption with femtosecond pulses in Na2 we show that: (i) it is possible to avoid the characteristic saturation or dumped Rabi oscillations in the yield of absorption by time-delaying the laser pulses; (ii) it is possible to accelerate the onset of adiabatic passage by using the vibrational coherence starting in a wave packet; and (iii) it is possible to prepare the initial wave packet in order to achieve full state-selective transitions with broadband pulses. The findings can be used, for instance, to achieve ultrafast adiabatic passage by light-induced potentials and understand its intrinsic robustness. PMID:27125342
NASA Astrophysics Data System (ADS)
Chen, Jingwei; Wei, L. F.
2015-10-01
We show that a set of universal quantum gates could be implemented robustly in a circuit QED system by using Stark-chirped rapid adiabatic passage (SCRAP) technique. Under the adiabatic limit we find that the population transfers could be deterministically passaged from one selected quantum states to the others, and thus the desired quantum gates can be implemented. The proposed SCRAP-based gates are insensitive to the details of the operations and thus relax the designs of the applied pulses, operational imperfections, and the decoherence of the system.
Transient Particle Energies in Shortcuts to Adiabatic Expansions of Harmonic Traps.
Cui, Yang-Yang; Chen, Xi; Muga, J G
2016-05-19
The expansion of a harmonic potential that holds a quantum particle may be realized without any final particle excitation but much faster than adiabatically via "shortcuts to adiabaticity" (STA). While ideally the process time can be reduced to zero, practical limitations and constraints impose minimal finite times for the externally controlled time-dependent frequency protocols. We examine the role of different time-averaged energies (total, kinetic, potential, nonadiabatic) and of the instantaneous power in characterizing or selecting different protocols. Specifically, we prove a virial theorem for STA processes, set minimal energies (or times) for given times (or energies), and discuss their realizability by means of Dirac impulses or otherwise. PMID:26237328
Controlled Rapid Adiabatic Passage in a V-Type System
NASA Astrophysics Data System (ADS)
Song, Yunheung; Lee, Han-Gyeol; Jo, Hanlae; Ahn, Jaewook
2016-05-01
In chirped rapid adiabatic passage (RAP), chirp sign determines the final state to which the complete population transfer (CPT) occurs in a three-level V-type system. In this study, we show that laser intensity can be alternatively used as a control means in RAP, when the laser pulse is chirped and of a spectral hole resonant to one of the excited states. We verified such excitation selectivity in the experiment performed as-shaped femtosecond laser pulses interacting with the lowest three levels (5S, 5 P1/2, and 5 P3/2) of atomic rubidium. The successful demonstration implies that this intensity-dependent RAP in conjunction with laser beam profile programming may allow excitation selectivity for atoms or ions arranged in space.
NASA Astrophysics Data System (ADS)
Merk, D.; Deneke, H.; Pospichal, B.; Seifert, P.
2016-01-01
Cloud properties from both ground-based as well as from geostationary passive satellite observations have been used previously for diagnosing aerosol-cloud interactions. In this investigation, a 2-year data set together with four selected case studies are analyzed with the aim of evaluating the consistency and limitations of current ground-based and satellite-retrieved cloud property data sets. The typically applied adiabatic cloud profile is modified using a sub-adiabatic factor to account for entrainment within the cloud. Based on the adiabatic factor obtained from the combination of ground-based cloud radar, ceilometer and microwave radiometer, we demonstrate that neither the assumption of a completely adiabatic cloud nor the assumption of a constant sub-adiabatic factor is fulfilled (mean adiabatic factor 0.63 ± 0.22). As cloud adiabaticity is required to estimate the cloud droplet number concentration but is not available from passive satellite observations, an independent method to estimate the adiabatic factor, and thus the influence of mixing, would be highly desirable for global-scale analyses. Considering the radiative effect of a cloud described by the sub-adiabatic model, we focus on cloud optical depth and its sensitivities. Ground-based estimates are here compared vs. cloud optical depth retrieved from the Meteosat SEVIRI satellite instrument resulting in a bias of -4 and a root mean square difference of 16. While a synergistic approach based on the combination of ceilometer, cloud radar and microwave radiometer enables an estimate of the cloud droplet concentration, it is highly sensitive to radar calibration and to assumptions about the moments of the droplet size distribution. Similarly, satellite-based estimates of cloud droplet concentration are uncertain. We conclude that neither the ground-based nor satellite-based cloud retrievals applied here allow a robust estimate of cloud droplet concentration, which complicates its use for the study of
Non-adiabatic perturbations in multi-component perfect fluids
Koshelev, N.A.
2011-04-01
The evolution of non-adiabatic perturbations in models with multiple coupled perfect fluids with non-adiabatic sound speed is considered. Instead of splitting the entropy perturbation into relative and intrinsic parts, we introduce a set of symmetric quantities, which also govern the non-adiabatic pressure perturbation in models with energy transfer. We write the gauge invariant equations for the variables that determine on a large scale the non-adiabatic pressure perturbation and the rate of changes of the comoving curvature perturbation. The analysis of evolution of the non-adiabatic pressure perturbation has been made for several particular models.
Adiabatic Far Field Sub-Diffraction Imaging
Cang, Hu; Salandrino, Alessandro; Wang, Yuan; Zhang, Xiang
2015-01-01
The limited resolution of a conventional optical imaging system stems from the fact that the fine feature information of an object is carried by evanescent waves, which exponentially decay in space thus cannot reach the imaging plane. We introduce here a new concept of adiabatic lens, which utilizes a geometrically conformal surface to mediate the interference of slowly decompressed electromagnetic waves at far field to form images. The decompression is satisfying an adiabatic condition, and by bridging the gap between far field and near field, it allows far field optical systems to project an image of the near field features directly. Using these designs, we demonstrated the magnification can be up to 20 times and it is possible to achieve sub-50nm imaging resolution in visible. Our approach provides a means to extend the domain of geometrical optics to a deep sub-wavelength scale. PMID:26258769
Shortcuts to adiabaticity from linear response theory.
Acconcia, Thiago V; Bonança, Marcus V S; Deffner, Sebastian
2015-10-01
A shortcut to adiabaticity is a finite-time process that produces the same final state as would result from infinitely slow driving. We show that such shortcuts can be found for weak perturbations from linear response theory. With the help of phenomenological response functions, a simple expression for the excess work is found-quantifying the nonequilibrium excitations. For two specific examples, i.e., the quantum parametric oscillator and the spin 1/2 in a time-dependent magnetic field, we show that finite-time zeros of the excess work indicate the existence of shortcuts. Finally, we propose a degenerate family of protocols, which facilitates shortcuts to adiabaticity for specific and very short driving times. PMID:26565209
Arbitrary qudit gates by adiabatic passage
NASA Astrophysics Data System (ADS)
Rousseaux, B.; Guérin, S.; Vitanov, N. V.
2013-03-01
We derive an adiabatic technique that implements the most general SU(d) transformation in a quantum system of d degenerate states, featuring a qudit. This technique is based on the factorization of the SU(d) transformation into d generalized quantum Householder reflections, each of which is implemented by a two-shot stimulated Raman adiabatic passage with appropriate static phases. The energy of the lasers needed to synthesize a single Householder reflection is shown to be remarkably constant as a function of d. This technique is directly applicable to a linear trapped ion system with d+1 ions. We implement the quantum Fourier transform numerically in a qudit with d=4 (defined as a quartit) as an example.
Trapped Ion Quantum Computation by Adiabatic Passage
Feng Xuni; Wu Chunfeng; Lai, C. H.; Oh, C. H.
2008-11-07
We propose a new universal quantum computation scheme for trapped ions in thermal motion via the technique of adiabatic passage, which incorporates the advantages of both the adiabatic passage and the model of trapped ions in thermal motion. Our scheme is immune from the decoherence due to spontaneous emission from excited states as the system in our scheme evolves along a dark state. In our scheme the vibrational degrees of freedom are not required to be cooled to their ground states because they are only virtually excited. It is shown that the fidelity of the resultant gate operation is still high even when the magnitude of the effective Rabi frequency moderately deviates from the desired value.
Adiabatic Quantum Optimization for Associative Memory Recall
NASA Astrophysics Data System (ADS)
Seddiqi, Hadayat; Humble, Travis
2014-12-01
Hopfield networks are a variant of associative memory that recall patterns stored in the couplings of an Ising model. Stored memories are conventionally accessed as fixed points in the network dynamics that correspond to energetic minima of the spin state. We show that memories stored in a Hopfield network may also be recalled by energy minimization using adiabatic quantum optimization (AQO). Numerical simulations of the underlying quantum dynamics allow us to quantify AQO recall accuracy with respect to the number of stored memories and noise in the input key. We investigate AQO performance with respect to how memories are stored in the Ising model according to different learning rules. Our results demonstrate that AQO recall accuracy varies strongly with learning rule, a behavior that is attributed to differences in energy landscapes. Consequently, learning rules offer a family of methods for programming adiabatic quantum optimization that we expect to be useful for characterizing AQO performance.
Quantum adiabatic evolution with energy degeneracy levels
NASA Astrophysics Data System (ADS)
Zhang, Qi
2016-01-01
A classical-kind phase-space formalism is developed to address the tiny intrinsic dynamical deviation from what is predicted by Wilczek-Zee theorem during quantum adiabatic evolution on degeneracy levels. In this formalism, the Hilbert space and the aggregate of degenerate eigenstates become the classical-kind phase space and a high-dimensional subspace in the phase space, respectively. Compared with the previous analogous study by a different method, the current result is qualitatively different in that the first-order deviation derived here is always perpendicular to the degeneracy subspace. A tripod-scheme Hamiltonian with two degenerate dark states is employed to illustrate the adiabatic deviation with degeneracy levels.
Shortcuts to adiabaticity from linear response theory
NASA Astrophysics Data System (ADS)
Acconcia, Thiago V.; Bonança, Marcus V. S.; Deffner, Sebastian
2015-10-01
A shortcut to adiabaticity is a finite-time process that produces the same final state as would result from infinitely slow driving. We show that such shortcuts can be found for weak perturbations from linear response theory. With the help of phenomenological response functions, a simple expression for the excess work is found—quantifying the nonequilibrium excitations. For two specific examples, i.e., the quantum parametric oscillator and the spin 1/2 in a time-dependent magnetic field, we show that finite-time zeros of the excess work indicate the existence of shortcuts. Finally, we propose a degenerate family of protocols, which facilitates shortcuts to adiabaticity for specific and very short driving times.
Adiabatic quantum optimization for associative memory recall
Seddiqi, Hadayat; Humble, Travis S.
2014-12-22
Hopfield networks are a variant of associative memory that recall patterns stored in the couplings of an Ising model. Stored memories are conventionally accessed as fixed points in the network dynamics that correspond to energetic minima of the spin state. We show that memories stored in a Hopfield network may also be recalled by energy minimization using adiabatic quantum optimization (AQO). Numerical simulations of the underlying quantum dynamics allow us to quantify AQO recall accuracy with respect to the number of stored memories and noise in the input key. We investigate AQO performance with respect to how memories are storedmore » in the Ising model according to different learning rules. Our results demonstrate that AQO recall accuracy varies strongly with learning rule, a behavior that is attributed to differences in energy landscapes. Consequently, learning rules offer a family of methods for programming adiabatic quantum optimization that we expect to be useful for characterizing AQO performance.« less
Adiabatic quantum optimization for associative memory recall
Seddiqi, Hadayat; Humble, Travis S.
2014-12-22
Hopfield networks are a variant of associative memory that recall patterns stored in the couplings of an Ising model. Stored memories are conventionally accessed as fixed points in the network dynamics that correspond to energetic minima of the spin state. We show that memories stored in a Hopfield network may also be recalled by energy minimization using adiabatic quantum optimization (AQO). Numerical simulations of the underlying quantum dynamics allow us to quantify AQO recall accuracy with respect to the number of stored memories and noise in the input key. We investigate AQO performance with respect to how memories are stored in the Ising model according to different learning rules. Our results demonstrate that AQO recall accuracy varies strongly with learning rule, a behavior that is attributed to differences in energy landscapes. Consequently, learning rules offer a family of methods for programming adiabatic quantum optimization that we expect to be useful for characterizing AQO performance.
Shortcuts to adiabaticity from linear response theory
Acconcia, Thiago V.; Bonança, Marcus V. S.; Deffner, Sebastian
2015-10-23
A shortcut to adiabaticity is a finite-time process that produces the same final state as would result from infinitely slow driving. We show that such shortcuts can be found for weak perturbations from linear response theory. Moreover, with the help of phenomenological response functions, a simple expression for the excess work is found—quantifying the nonequilibrium excitations. For two specific examples, i.e., the quantum parametric oscillator and the spin 1/2 in a time-dependent magnetic field, we show that finite-time zeros of the excess work indicate the existence of shortcuts. We finally propose a degenerate family of protocols, which facilitates shortcuts to adiabaticity for specific and very short driving times.
Shortcuts to adiabaticity from linear response theory
Acconcia, Thiago V.; Bonança, Marcus V. S.; Deffner, Sebastian
2015-10-23
A shortcut to adiabaticity is a finite-time process that produces the same final state as would result from infinitely slow driving. We show that such shortcuts can be found for weak perturbations from linear response theory. Moreover, with the help of phenomenological response functions, a simple expression for the excess work is found—quantifying the nonequilibrium excitations. For two specific examples, i.e., the quantum parametric oscillator and the spin 1/2 in a time-dependent magnetic field, we show that finite-time zeros of the excess work indicate the existence of shortcuts. We finally propose a degenerate family of protocols, which facilitates shortcuts tomore » adiabaticity for specific and very short driving times.« less
Adiabatic Quantization of Andreev Quantum Billiard Levels
NASA Astrophysics Data System (ADS)
Silvestrov, P. G.; Goorden, M. C.; Beenakker, C. W.
2003-03-01
We identify the time T between Andreev reflections as a classical adiabatic invariant in a ballistic chaotic cavity (Lyapunov exponent λ), coupled to a superconductor by an N-mode constriction. Quantization of the adiabatically invariant torus in phase space gives a discrete set of periods Tn, which in turn generate a ladder of excited states ɛnm=(m+1/2)πℏ/Tn. The largest quantized period is the Ehrenfest time T0=λ-1ln(N. Projection of the invariant torus onto the coordinate plane shows that the wave functions inside the cavity are squeezed to a transverse dimension W/(N), much below the width W of the constriction.
Adiabatic state preparation study of methylene
Veis, Libor Pittner, Jiří
2014-06-07
Quantum computers attract much attention as they promise to outperform their classical counterparts in solving certain type of problems. One of them with practical applications in quantum chemistry is simulation of complex quantum systems. An essential ingredient of efficient quantum simulation algorithms are initial guesses of the exact wave functions with high enough fidelity. As was proposed in Aspuru-Guzik et al. [Science 309, 1704 (2005)], the exact ground states can in principle be prepared by the adiabatic state preparation method. Here, we apply this approach to preparation of the lowest lying multireference singlet electronic state of methylene and numerically investigate preparation of this state at different molecular geometries. We then propose modifications that lead to speeding up the preparation process. Finally, we decompose the minimal adiabatic state preparation employing the direct mapping in terms of two-qubit interactions.
Adiabatic Quantum Simulation of Quantum Chemistry
Babbush, Ryan; Love, Peter J.; Aspuru-Guzik, Alán
2014-01-01
We show how to apply the quantum adiabatic algorithm directly to the quantum computation of molecular properties. We describe a procedure to map electronic structure Hamiltonians to 2-body qubit Hamiltonians with a small set of physically realizable couplings. By combining the Bravyi-Kitaev construction to map fermions to qubits with perturbative gadgets to reduce the Hamiltonian to 2-body, we obtain precision requirements on the coupling strengths and a number of ancilla qubits that scale polynomially in the problem size. Hence our mapping is efficient. The required set of controllable interactions includes only two types of interaction beyond the Ising interactions required to apply the quantum adiabatic algorithm to combinatorial optimization problems. Our mapping may also be of interest to chemists directly as it defines a dictionary from electronic structure to spin Hamiltonians with physical interactions. PMID:25308187
Pulse sequences in photoassociation via adiabatic passage
NASA Astrophysics Data System (ADS)
Li, Xuan; Dupre, William; Parker, Gregory A.
2012-07-01
We perform a detailed study of pulse sequences in a photoassociation via adiabatic passage (PAP) process to transfer population from an ensemble of ultracold atomic clouds to a vibrationally cold molecular state. We show that an appreciable final population of ultracold NaCs molecules can be achieved with optimized pulses in either the ‘counter-intuitive’ (tP > tS) or ‘intuitive’ (tP < tS) PAP pulse sequences, with tP and tS denoting the temporal centers of the pump and Stokes pulses, respectively. By investigating the dependence of the reactive yield on pulse sequences, in a wide range of tP-tS, we show that there is not a fundamental preference to either pulse sequence in a PAP process. We explain this no-sequence-preference phenomenon by analyzing a multi-bound model so that an analogy can be drawn to the conventional stimulated Raman adiabatic passage.
Grassroots efforts pursue alcohol policy reform: refocusing upstream in New Mexico.
Stivers, C
1994-01-01
ORGANIZATION SETTING. The New Mexico Alcohol Issues Consortium (NMAIC) originated in January 1989 as a grassroots effort to focus on the reduction of driving-while-intoxicated (DWI) in New Mexico. It was the brainchild of three state health department officials and grew to include in its membership representatives from education, medicine, law enforcement, neighborhood associations, business, and local and state government. RATIONALE. New Mexico ranks at or near the top in several alcohol-related statistics, including motor vehicle fatalities, cirrhosis, and alcoholism. Furthermore, the 'alcohol environment' in New Mexico included the allowance for the purchase of alcoholic beverages at drive-up windows, lax enforcement of DWI laws, and even state legislators with DWI records. Theoretical bases upon which NMAIC goals and strategies were based include the public health model, the public health/dynamic systems, model of alcohol and other drug use, and 'refocusing upstream,' all of which give attention to the environment as a determinant of health status. IMPLEMENTATION. While the NMAIC's activities addressed a variety of alcohol-related problems in New Mexico, the bulk of the organization's efforts for four years were directed toward increasing the excise tax on alcohol, either as a statewide measure or via county-level local option referenda. Strategies which were enacted to support this legislative activity included collaboration with other programs and organizations with similar DWI-prevention goals, and staged media events to solicit public support. IMPACT. In four years, the NMAIC had established itself as a credible organization which was successful in publicly and systematically challenging existing alcohol policies in New Mexico. The NMAIC was also instrumental in empowering individuals and communities to speak and act against the alcohol problems in their own communities. Finally, during the 1993 New Mexico Legislative Session, a bill was passed which
Adiabatic charging of nickel-hydrogen batteries
NASA Technical Reports Server (NTRS)
Lurie, Chuck; Foroozan, S.; Brewer, Jeff; Jackson, Lorna
1995-01-01
Battery management during prelaunch activities has always required special attention and careful planning. The transition from nickel-cadium to nickel-hydrogen batteries, with their high self discharge rate and lower charge efficiency, as well as longer prelaunch scenarios, has made this aspect of spacecraft battery management even more challenging. The AXAF-I Program requires high battery state of charge at launch. The use of active cooling, to ensure efficient charging, was considered and proved to be difficult and expensive. Alternative approaches were evaluated. Optimized charging, in the absence of cooling, appeared promising and was investigated. Initial testing was conducted to demonstrate the feasibility of the 'Adiabatic Charging' approach. Feasibility was demonstrated and additional testing performed to provide a quantitative, parametric data base. The assumption that the battery is in an adiabatic environment during prelaunch charging is a conservative approximation because the battery will transfer some heat to its surroundings by convective air cooling. The amount is small compared to the heat dissipated during battery overcharge. Because the battery has a large thermal mass, substantial overcharge can occur before the cells get too hot to charge efficiently. The testing presented here simulates a true adiabatic environment. Accordingly the data base may be slightly conservative. The adiabatic charge methodology used in this investigation begins with stabilizing the cell at a given starting temperature. The cell is then fully insulated on all sides. Battery temperature is carefully monitored and the charge terminated when the cell temperature reaches 85 F. Charging has been evaluated with starting temperatures from 55 to 75 F.
Advanced Adiabatic Demagnetization Refrigerators for Continuous Cooling
NASA Technical Reports Server (NTRS)
Chu, Paul C. W.
2004-01-01
The research at Houston was focused on optimizing the design of superconducting magnets for advanced adiabatic demagnetization refrigerators (ADRs), assessing the feasibility of using high temperature superconducting (HTS) magnets in ADRs in the future, and developing techniques to deposit HTS thin and thick films on high strength, low thermal conductivity substrates for HTS magnet leads. Several approaches have been tested for the suggested superconducting magnets.
Computer Code For Turbocompounded Adiabatic Diesel Engine
NASA Technical Reports Server (NTRS)
Assanis, D. N.; Heywood, J. B.
1988-01-01
Computer simulation developed to study advantages of increased exhaust enthalpy in adiabatic turbocompounded diesel engine. Subsytems of conceptual engine include compressor, reciprocator, turbocharger turbine, compounded turbine, ducting, and heat exchangers. Focus of simulation of total system is to define transfers of mass and energy, including release and transfer of heat and transfer of work in each subsystem, and relationship among subsystems. Written in FORTRAN IV.
Siphon flows in isolated magnetic flux tubes. II - Adiabatic flows
NASA Technical Reports Server (NTRS)
Montesinos, Benjamin; Thomas, John H.
1989-01-01
This paper extends the study of steady siphon flows in isolated magnetic flux tubes surrounded by field-free gas to the case of adiabatic flows. The basic equations governing steady adiabatic siphon flows in a thin, isolated magnetic flux tube are summarized, and qualitative features of adiabatic flows in elevated, arched flux tubes are discussed. The equations are then cast in nondimensional form and the results of numerical computations of adiabatic siphon flows in arched flux tubes are presented along with comparisons between isothermal and adiabatic flows. The effects of making the interior of the flux tube hotter or colder than the surrounding atmosphere at the upstream footpoint of the arch is considered. In this case, is it found that the adiabatic flows are qualitatively similar to the isothermal flows, with adiabatic cooling producing quantitative differences. Critical flows can produce a bulge point in the rising part of the arch and a concentration of magnetic flux above the bulge point.
Random matrix model of adiabatic quantum computing
Mitchell, David R.; Adami, Christoph; Lue, Waynn; Williams, Colin P.
2005-05-15
We present an analysis of the quantum adiabatic algorithm for solving hard instances of 3-SAT (an NP-complete problem) in terms of random matrix theory (RMT). We determine the global regularity of the spectral fluctuations of the instantaneous Hamiltonians encountered during the interpolation between the starting Hamiltonians and the ones whose ground states encode the solutions to the computational problems of interest. At each interpolation point, we quantify the degree of regularity of the average spectral distribution via its Brody parameter, a measure that distinguishes regular (i.e., Poissonian) from chaotic (i.e., Wigner-type) distributions of normalized nearest-neighbor spacings. We find that for hard problem instances - i.e., those having a critical ratio of clauses to variables - the spectral fluctuations typically become irregular across a contiguous region of the interpolation parameter, while the spectrum is regular for easy instances. Within the hard region, RMT may be applied to obtain a mathematical model of the probability of avoided level crossings and concomitant failure rate of the adiabatic algorithm due to nonadiabatic Landau-Zener-type transitions. Our model predicts that if the interpolation is performed at a uniform rate, the average failure rate of the quantum adiabatic algorithm, when averaged over hard problem instances, scales exponentially with increasing problem size.
Adiabatic heating in impulsive solar flares
NASA Technical Reports Server (NTRS)
Maetzler, C.; Bai, T.; Crannell, C. J.; Frost, K. J.
1978-01-01
A study is made of adiabatic heating in two impulsive solar flares on the basis of dynamic X-ray spectra in the 28-254 keV range, H-alpha, microwave, and meter-wave radio observations. It is found that the X-ray spectra of the events are like those of thermal bremsstrahlung from single-temperature plasmas in the 10-60 keV range if photospheric albedo is taken into account. The temperature-emission correlation indicates adiabatic compression followed by adiabatic expansion and that the electron distribution remains isotropic. H-alpha data suggest compressive energy transfer. The projected areas and volumes of the flares are estimated assuming that X-ray and microwave emissions are produced in a single thermal plasma. Electron densities of about 10 to the 9th/cu cm are found for homogeneous, spherically symmetric sources. It is noted that the strong self-absorption of hot-plasma gyrosynchrotron radiation reveals low magnetic field strengths.
Aspects of adiabatic population transfer and control
NASA Astrophysics Data System (ADS)
Demirplak, Mustafa
This thesis explores two different questions. The first question we answer is how to restore a given population transfer scenario given that it works efficiently in the adiabatic limit but fails because of lack of intensity and/or short duration. We derive a very simple algorithm to do this and apply it to both toy and realistic models. Two results emerge from this study. While the mathematical existence of the programme is certain it might not always be physically desirable. The restoration of adiabaticity is phase sensitive. The second question that is answered in this thesis is not how to invent new control paradigms, but rather what would happen to them in the presence of stochastic perturbers. We first use a phenomenological model to study the effect of stochastic dephasing on population transfer by stimulated Raman adiabatic passage. The results of this Monte Carlo calculation are qualitatively explained with a perturbation theoretical result in the dressed state basis. The reliability of our phenomenological model is questioned through a more rigorous hybrid quantal-classical simulation of controlled population transfer in HCl in Ar.
Non-adiabatic effect on quantum pumping
NASA Astrophysics Data System (ADS)
Uchiyama, Chikako
2014-03-01
We study quantum pumping for an anharmonic junction model which interacts with two kinds of bosonic environments. We provide an expression for the quantum pumping under a piecewise modulation of environmental temperatures with including non-adiabatic effect under Markovian approximation. The obtained formula is an extension of the one expressed with the geometrical phase(Phys. Rev. Lett. 104,170601 (2010)). This extension shows that the quantum pumping depends on the initial condition of the anharmonic junction just before the modulation, as well as the characteristic environmental parameters such as interaction strength and cut-off frequencies of spectral density other than the conditions of modulation. We clarify that the pumping current including non-adiabatic effect can be larger than that under the adiabatic condition. This means that we can find the optimal condition of the current by adjusting these parameters. (The article has been submitted as http://arxiv.org/submit/848201 and will be appeared soon.) This work is supported by a Grant-in-Aid for Scientific Research (B) (KAKENHI 25287098).
An adiabatic approximation for grain alignment theory
NASA Astrophysics Data System (ADS)
Roberge, W. G.
1997-10-01
The alignment of interstellar dust grains is described by the joint distribution function for certain `internal' and `external' variables, where the former describe the orientation of the axes of a grain with respect to its angular momentum, J, and the latter describe the orientation of J relative to the interstellar magnetic field. I show how the large disparity between the dynamical time-scales of the internal and external variables - which is typically 2-3 orders of magnitude - can be exploited to simplify calculations of the required distribution greatly. The method is based on an `adiabatic approximation' which closely resembles the Born-Oppenheimer approximation in quantum mechanics. The adiabatic approximation prescribes an analytic distribution function for the `fast' dynamical variables and a simplified Fokker-Planck equation for the `slow' variables which can be solved straightforwardly using various techniques. These solutions are accurate to O(epsilon), where epsilon is the ratio of the fast and slow dynamical time-scales. As a simple illustration of the method, I derive an analytic solution for the joint distribution established when Barnett relaxation acts in concert with gas damping. The statistics of the analytic solution agree with the results of laborious numerical calculations which do not exploit the adiabatic approximation.
An Adiabatic Approximation for Grain Alignment Theory
NASA Astrophysics Data System (ADS)
Roberge, W. G.
1997-12-01
The alignment of interstellar dust grains is described by the joint distribution function for certain ``internal'' and ``external'' variables, where the former describe the orientation of a grain's axes with respect to its angular momentum, J, and the latter describe the orientation of J relative to the interstellar magnetic field. I show how the large disparity between the dynamical timescales of the internal and external variables--- which is typically 2--3 orders of magnitude--- can be exploited to greatly simplify calculations of the required distribution. The method is based on an ``adiabatic approximation'' which closely resembles the Born-Oppenheimer approximation in quantum mechanics. The adiabatic approximation prescribes an analytic distribution function for the ``fast'' dynamical variables and a simplified Fokker-Planck equation for the ``slow'' variables which can be solved straightforwardly using various techniques. These solutions are accurate to cal {O}(epsilon ), where epsilon is the ratio of the fast and slow dynamical timescales. As a simple illustration of the method, I derive an analytic solution for the joint distribution established when Barnett relaxation acts in concert with gas damping. The statistics of the analytic solution agree with the results of laborious numerical calculations which do not exploit the adiabatic approximation.
Coherently controlled adiabatic passage to multiple continuum channels
Thanopulos, Ioannis; Shapiro, Moshe
2006-09-15
We present a solution to the multichannel quantum control problem, where selective and complete population transfer from an initial bound state to M energetically degenerate continuum channels is achieved under loss-free conditions. The control is affected by adiabatic passage proceeding via N bound intermediate states, where even in the presence of real loss from these states, the control efficiency remains significant, about 40-50%. We illustrate the viability of the method by computationally controlling the CH{sub 3}(v)+I*({sup 2}P{sub 1/2})<-CH{sub 3}I{yields}CH{sub 3}(v)+I({sup 2}P{sub 3/2}) multichannel photodissociation process.
Multiphoton Raman Atom Optics with Frequency-Swept Adiabatic Passage
NASA Astrophysics Data System (ADS)
Kotru, Krish; Butts, David; Kinast, Joseph; Stoner, Richard
2016-05-01
Light-pulse atom interferometry is a promising candidate for future inertial navigators, gravitational wave detectors, and measurements of fundamental physical constants. The sensitivity of this technique, however, is often limited by the small momentum separations created between interfering atom wave packets (typically ~ 2 ℏk) . We address this issue using light-pulse atom optics derived from stimulated Raman transitions and frequency-swept adiabatic rapid passage (ARP). In experiments, these Raman ARP atom optics have generated up to 30 ℏk photon recoil momenta in an acceleration-sensitive atom interferometer, thereby enhancing the phase shift per unit acceleration by a factor of 15. Since this approach forgoes evaporative cooling and velocity selection, it could enable large-area atom interferometry at higher data rates, while also lowering the atom shot-noise-limited measurement uncertainty.
Phase avalanches in near-adiabatic evolutions
Vertesi, T.; Englman, R.
2006-02-15
In the course of slow, nearly adiabatic motion of a system, relative changes in the slowness can cause abrupt and high magnitude phase changes, ''phase avalanches,'' superimposed on the ordinary geometric phases. The generality of this effect is examined for arbitrary Hamiltonians and multicomponent (>2) wave packets and is found to be connected (through the Blaschke term in the theory of analytic signals) to amplitude zeros in the lower half of the complex time plane. Motion on a nonmaximal circle on the Poincare-sphere suppresses the effect. A spectroscopic transition experiment can independently verify the phase-avalanche magnitudes.
Adiabatic chaos in the spin orbit problem
NASA Astrophysics Data System (ADS)
Benettin, Giancarlo; Guzzo, Massimiliano; Marini, Valerio
2008-05-01
We provide evidences that the angular momentum of a symmetric rigid body in a spin orbit resonance can perform large scale chaotic motions on time scales which increase polynomially with the inverse of the oblateness of the body. This kind of irregular precession appears as soon as the orbit of the center of mass is non-circular and the angular momentum of the body is far from the principal directions with minimum (maximum) moment of inertia. We also provide a quantitative explanation of these facts by using the theory of adiabatic invariants, and we provide numerical applications to the cases of the 1:1 and 1:2 spin orbit resonances.
Experimental breaking of an adiabatic invariant
NASA Astrophysics Data System (ADS)
Notte, J.; Fajans, J.; Chu, R.; Wurtele, J. S.
1993-06-01
When a cylindrical pure electron plasma is displaced from the center of the trap, it performs a bulk circular orbital motion known as the l=1 diocotron mode. The slow application of a perturbing potential to a patch on the trap wall distorts the orbit into a noncircular closed path. Experiments and a simple theoretical model indicate that the area by the loop is an adiabatic invariant. Detailed studies are made of the breaking of the invariant when perturbations are rapidly applied. When the perturbation is applied with discontinuous time derivatives, the invariant breaking greatly exceeds the predictions of the standard theory for smooth perturbations.
Adiabatic passage in the presence of noise
NASA Astrophysics Data System (ADS)
Noel, T.; Dietrich, M. R.; Kurz, N.; Shu, G.; Wright, J.; Blinov, B. B.
2012-02-01
We report on an experimental investigation of rapid adiabatic passage (RAP) in a trapped barium ion system. RAP is implemented on the transition from the 6S1/2 ground state to the metastable 5D5/2 level by applying a laser at 1.76 μm. We focus on the interplay of laser frequency noise and laser power in shaping the effectiveness of RAP, which is commonly assumed to be a robust tool for high-efficiency population transfer. However, we note that reaching high state transfer fidelity requires a combination of small laser linewidth and large Rabi frequency.
Adiabatic demagnetization refrigerator for space use
NASA Technical Reports Server (NTRS)
Serlemitsos, A. T.; Warner, B. A.; Castles, S.; Breon, S. R.; San Sebastian, M.; Hait, T.
1990-01-01
An Adiabatic Demagnetization Refrigerator (ADR) for space use is under development at NASA's Goddard Space Flight Center (GSFC). The breadboard ADR operated at 100 mK for 400 minutes. Some significant changes to that ADR, designed to eliminate shortcomings revealed during tests, are reported. To increase thermal contact, the ferric ammonium sulfate crystals were grown directly on gold-plated copper wires which serve as the thermal bus. The thermal link to the X-ray sensors was also markedly improved. To speed up the testing required to determine the best design parameters for the gas gap heat switch, the new heat switch has a modular design and is easy to disassemble.
An adiabatic demagnetization refrigerator for infrared bolometers
NASA Technical Reports Server (NTRS)
Britt, R. D.; Richards, P. L.
1981-01-01
Adiabatic demagnetization refrigerators have been built and installed in small portable liquid helium cryostats to test the feasibility of this method of cooling infrared bolometric detectors to temperatures below 0.3 K. Performance has been achieved which suggests that bolometer temperatures of 0.2 K can be maintained for periods of approximately 60 hours. Applications to sensitive infrared detection from ground-based telescopes and space satellites are discussed. Design data are given which permit the evaluation of refrigerator performance for a variety of design parameters.
Generalized Ramsey numbers through adiabatic quantum optimization
NASA Astrophysics Data System (ADS)
Ranjbar, Mani; Macready, William G.; Clark, Lane; Gaitan, Frank
2016-06-01
Ramsey theory is an active research area in combinatorics whose central theme is the emergence of order in large disordered structures, with Ramsey numbers marking the threshold at which this order first appears. For generalized Ramsey numbers r(G, H), the emergent order is characterized by graphs G and H. In this paper we: (i) present a quantum algorithm for computing generalized Ramsey numbers by reformulating the computation as a combinatorial optimization problem which is solved using adiabatic quantum optimization; and (ii) determine the Ramsey numbers r({{T}}m,{{T}}n) for trees of order m,n = 6,7,8 , most of which were previously unknown.
Decoherence in a scalable adiabatic quantum computer
Ashhab, S.; Johansson, J. R.; Nori, Franco
2006-11-15
We consider the effects of decoherence on Landau-Zener crossings encountered in a large-scale adiabatic-quantum-computing setup. We analyze the dependence of the success probability--i.e., the probability for the system to end up in its new ground state--on the noise amplitude and correlation time. We determine the optimal sweep rate that is required to maximize the success probability. We then discuss the scaling of decoherence effects with increasing system size. We find that those effects can be important for large systems, even if they are small for each of the small building blocks.
Local entanglement generation in the adiabatic regime
Cliche, M.; Veitia, Andrzej
2010-09-15
We study entanglement generation in a pair of qubits interacting with an initially correlated system. Using time-independent perturbation theory and the adiabatic theorem, we show conditions under which the qubits become entangled as the joint system evolves into the ground state of the interacting theory. We then apply these results to the case of qubits interacting with a scalar quantum field. We study three different variations of this setup; a quantum field subject to Dirichlet boundary conditions, a quantum field interacting with a classical potential, and a quantum field that starts in a thermal state.
Geometry of an adiabatic passage at a level crossing
Cholascinski, Mateusz
2005-06-15
We discuss adiabatic quantum phenomena at a level crossing. Given a path in the parameter space which passes through a degeneracy point, we find a criterion which determines whether the adiabaticity condition can be satisfied. For paths that can be traversed adiabatically we also derive a differential equation which specifies the time dependence of the system parameters, for which transitions between distinct energy levels can be neglected. We also generalize the well-known geometric connections to the case of adiabatic paths containing arbitrarily many level-crossing points and degenerate levels.
Geometrical representation of sum frequency generation and adiabatic frequency conversion
NASA Astrophysics Data System (ADS)
Suchowski, Haim; Oron, Dan; Arie, Ady; Silberberg, Yaron
2008-12-01
We present a geometrical representation of the process of sum frequency generation in the undepleted pump approximation, in analogy with the known optical Bloch equations. We use this analogy to propose a technique for achieving both high efficiency and large bandwidth in sum frequency conversion using the adiabatic inversion scheme. The process is analogous with rapid adiabatic passage in NMR, and adiabatic constraints are derived in this context. This adiabatic frequency conversion scheme is realized experimentally using an aperiodically poled potassium titanyl phosphate (KTP) device, where we achieved high efficiency signal-to-idler conversion over a bandwidth of 140nm .
On the Role of Prior Probability in Adiabatic Quantum Algorithms
NASA Astrophysics Data System (ADS)
Sun, Jie; Lu, Songfeng; Yang, Liping
2016-03-01
In this paper, we study the role of prior probability on the efficiency of quantum local adiabatic search algorithm. The following aspects for prior probability are found here: firstly, only the probabilities of marked states affect the running time of the adiabatic evolution; secondly, the prior probability can be used for improving the efficiency of the adiabatic algorithm; thirdly, like the usual quantum adiabatic evolution, the running time for the case of multiple solution states where the number of marked elements are smaller enough than the size of the set assigned that contains them can be significantly bigger than that of the case where the assigned set only contains all the marked states.
Nonadiabatic Transitions in Adiabatic Rapid Passage
NASA Astrophysics Data System (ADS)
Lu, T.; Miao, X.; Metcalf, H.
2006-05-01
Optical forces much larger than the ordinary radiative force can be achieved on a two-level atom by multiple repetitions of adiabatic rapid passage sweeps with counterpropagating light beams. Chirped light pulses drive the atom-laser system up a ladder of dressed state energy sheets on sequential trajectories, thereby decreasing the atomic kinetic energy. Nonadiabatic transitions between the energy sheets must be avoided for this process to be effective. We have calculated the nonadiabatic transition probability for various chirped light pulses numerically. These results were compared to the first Demkov-Kunike model and the well-known Landau-Zener model. In addition, an analytical form of the nonadiabatic transition probability has been found for linearly chirped pulses and an approximate form for generic symmetric finite-time pulses has been found for the entire parameter space using the technique of unitary integration. From this, the asymptotic transition probability in the adiabatic limit was derived. T. Lu, X. Miao, and H. Metcalf, Phys., Rev. A 71 061405(R) (2005). Yu. Demkov and M. Kunike, Vestn. Leningr. Univ. Fis. Khim., 16, 39 (1969); K.-A. Suominen and B. Garraway, Phys. Rev. A45, 374 (1992)
Effect of the Heat Pipe Adiabatic Region.
Brahim, Taoufik; Jemni, Abdelmajid
2014-04-01
The main motivation of conducting this work is to present a rigorous analysis and investigation of the potential effect of the heat pipe adiabatic region on the flow and heat transfer performance of a heat pipe under varying evaporator and condenser conditions. A two-dimensional steady-state model for a cylindrical heat pipe coupling, for both regions, is presented, where the flow of the fluid in the porous structure is described by Darcy-Brinkman-Forchheimer model which accounts for the boundary and inertial effects. The model is solved numerically by using the finite volumes method, and a fortran code was developed to solve the system of equations obtained. The results show that a phase change can occur in the adiabatic region due to temperature gradient created in the porous structure as the heat input increases and the heat pipe boundary conditions change. A recirculation zone may be created at the condenser end section. The effect of the heat transfer rate on the vapor radial velocities and the performance of the heat pipe are discussed. PMID:24895467
Adiabatic cooling of solar wind electrons
NASA Technical Reports Server (NTRS)
Sandbaek, Ornulf; Leer, Egil
1992-01-01
In thermally driven winds emanating from regions in the solar corona with base electron densities of n0 not less than 10 exp 8/cu cm, a substantial fraction of the heat conductive flux from the base is transfered into flow energy by the pressure gradient force. The adiabatic cooling of the electrons causes the electron temperature profile to fall off more rapidly than in heat conduction dominated flows. Alfven waves of solar origin, accelerating the basically thermally driven solar wind, lead to an increased mass flux and enhanced adiabatic cooling. The reduction in electron temperature may be significant also in the subsonic region of the flow and lead to a moderate increase of solar wind mass flux with increasing Alfven wave amplitude. In the solar wind model presented here the Alfven wave energy flux per unit mass is larger than that in models where the temperature in the subsonic flow is not reduced by the wave, and consequently the asymptotic flow speed is higher.
Inertial effects in adiabatically driven flashing ratchets
NASA Astrophysics Data System (ADS)
Rozenbaum, Viktor M.; Makhnovskii, Yurii A.; Shapochkina, Irina V.; Sheu, Sheh-Yi; Yang, Dah-Yen; Lin, Sheng Hsien
2014-05-01
We study analytically the effect of a small inertial correction on the properties of adiabatically driven flashing ratchets. Parrondo's lemma [J. M. R. Parrondo, Phys. Rev. E 57, 7297 (1998), 10.1103/PhysRevE.57.7297] is generalized to include the inertial term so as to establish the symmetry conditions allowing directed motion (other than in the overdamped massless case) and to obtain a high-temperature expansion of the motion velocity for arbitrary potential profiles. The inertial correction is thus shown to enhance the ratchet effect at all temperatures for sawtooth potentials and at high temperatures for simple potentials described by the first two harmonics. With the special choice of potentials represented by at least the first three harmonics, the correction gives rise to the motion reversal in the high-temperature region. In the low-temperature region, inertia weakens the ratchet effect, with the exception of the on-off model, where diffusion is important. The directed motion adiabatically driven by potential sign fluctuations, though forbidden in the overdamped limit, becomes possible due to purely inertial effects in neither symmetric nor antisymmetric potentials, i.e., not for commonly used sawtooth and two-sinusoid profiles.
Adiabatic Mass Loss Model in Binary Stars
NASA Astrophysics Data System (ADS)
Ge, H. W.
2012-07-01
Rapid mass transfer process in the interacting binary systems is very complicated. It relates to two basic problems in the binary star evolution, i.e., the dynamically unstable Roche-lobe overflow and the common envelope evolution. Both of the problems are very important and difficult to be modeled. In this PhD thesis, we focus on the rapid mass loss process of the donor in interacting binary systems. The application to the criterion of dynamically unstable mass transfer and the common envelope evolution are also included. Our results based on the adiabatic mass loss model could be used to improve the binary evolution theory, the binary population synthetic method, and other related aspects. We build up the adiabatic mass loss model. In this model, two approximations are included. The first one is that the energy generation and heat flow through the stellar interior can be neglected, hence the restructuring is adiabatic. The second one is that he stellar interior remains in hydrostatic equilibrium. We model this response by constructing model sequences, beginning with a donor star filling its Roche lobe at an arbitrary point in its evolution, holding its specific entropy and composition profiles fixed. These approximations are validated by the comparison with the time-dependent binary mass transfer calculations and the polytropic model for low mass zero-age main-sequence stars. In the dynamical time scale mass transfer, the adiabatic response of the donor star drives it to expand beyond its Roche lobe, leading to runaway mass transfer and the formation of a common envelope with its companion star. For donor stars with surface convection zones of any significant depth, this runaway condition is encountered early in mass transfer, if at all; but for main sequence stars with radiative envelopes, it may be encountered after a prolonged phase of thermal time scale mass transfer, so-called delayed dynamical instability. We identify the critical binary mass ratio for the
ERIC Educational Resources Information Center
Beamer, Catharine, Comp.
A bibliography of sources on women and American history at the Mt. San Antonio College Library (Walnut, California) has been compiled. It has five sections: (1) general history (works reflecting the contributions of women as historians as well as portraying their roles in the history of the United States from the early colonial days to the…
Adiabatic principles in atom-diatom collisional energy transfer
Hovingh, W.J.
1993-01-01
This work describes the application of numerical methods to the solution of the time dependent Schroedinger equation for non-reactive atom-diatom collisions in which only one of the degrees of freedom has been removed. The basic method involves expanding the wave function in a basis set in two of the diatomic coordinates in a body-fixed frame (with respect to the triatomic complex) and defining the coefficients in that expansion as functions on a grid in the collision coordinate. The wave function is then propagated in time using a split operator method. The bulk of this work is devoted to the application of this formalism to the study of internal rotational predissociation in NeHF, in which quasibound states of the triatom predissociate through the transfer of energy from rotation of the diatom into translational energy in the atom-diatom separation coordinate. The author analyzes the computed time dependent wave functions to calculate the lifetimes for several quasibound states; these are in agreement with time independent quantum calculations using the same potential. Moreover, the time dependent behavior of the wave functions themselves sheds light on the dynamics of the predissociation processes. Finally, the partial cross sections of the products in those processes is determined with multiple exit channels. These show strong selectivity in the orbital angular momentum of the outgoing fragments, which the author explains with an adiabatic channel interpretation of the wave function's dynamics. The author also suggests that the same formalism might profitably be used to investigate the quantum dynamics of [open quotes]quasiresonant vibration-rotation transfer[close quotes], in which remarkably strong propensity rules in certain inelastic atom-diatom collision arise from classical adiabatic invariance theory.
NASA Technical Reports Server (NTRS)
Dayton, J. A., Jr.; Kosmahl, H. G.; Ramins, P.; Stankiewicz, N.
1981-01-01
A comparison of analytical and experimental results is presented for a high performance dual-mode helix TWT, equipped with multistage depressed collectors (MDC), and operated over conditions ranging from saturation to the linear regime. The computations are carried out with advanced multidimensional computer programs which model the electron beam as a series of disks or rings of charge and follow their trajectories from the RF input of the TWT, through the slow-wave structure, through the refocusing system, to their points of impact in the depressed collector. TWT performance, collector efficiency, and collector current distribution are computed and compared with measurements. Very good agreement is obtained between computed and measured TWT performance and collector efficiencies. The analytical techniques were subsequently applied to the design of a smaller MDC of nearly equal efficiency.
Adiabat-shaping in indirect drive inertial confinement fusion
NASA Astrophysics Data System (ADS)
Baker, K. L.; Robey, H. F.; Milovich, J. L.; Jones, O. S.; Smalyuk, V. A.; Casey, D. T.; MacPhee, A. G.; Pak, A.; Celliers, P. M.; Clark, D. S.; Landen, O. L.; Peterson, J. L.; Berzak-Hopkins, L. F.; Weber, C. R.; Haan, S. W.; Döppner, T. D.; Dixit, S.; Giraldez, E.; Hamza, A. V.; Jancaitis, K. S.; Kroll, J. J.; Lafortune, K. N.; MacGowan, B. J.; Moody, J. D.; Nikroo, A.; Widmayer, C. C.
2015-05-01
Adiabat-shaping techniques were investigated in indirect drive inertial confinement fusion experiments on the National Ignition Facility as a means to improve implosion stability, while still maintaining a low adiabat in the fuel. Adiabat-shaping was accomplished in these indirect drive experiments by altering the ratio of the picket and trough energies in the laser pulse shape, thus driving a decaying first shock in the ablator. This decaying first shock is designed to place the ablation front on a high adiabat while keeping the fuel on a low adiabat. These experiments were conducted using the keyhole experimental platform for both three and four shock laser pulses. This platform enabled direct measurement of the shock velocities driven in the glow-discharge polymer capsule and in the liquid deuterium, the surrogate fuel for a DT ignition target. The measured shock velocities and radiation drive histories are compared to previous three and four shock laser pulses. This comparison indicates that in the case of adiabat shaping the ablation front initially drives a high shock velocity, and therefore, a high shock pressure and adiabat. The shock then decays as it travels through the ablator to pressures similar to the original low-adiabat pulses when it reaches the fuel. This approach takes advantage of initial high ablation velocity, which favors stability, and high-compression, which favors high stagnation pressures.
Quantum adiabatic algorithm for factorization and its experimental implementation.
Peng, Xinhua; Liao, Zeyang; Xu, Nanyang; Qin, Gan; Zhou, Xianyi; Suter, Dieter; Du, Jiangfeng
2008-11-28
We propose an adiabatic quantum algorithm capable of factorizing numbers, using fewer qubits than Shor's algorithm. We implement the algorithm in a NMR quantum information processor and experimentally factorize the number 21. In the range that our classical computer could simulate, the quantum adiabatic algorithm works well, providing evidence that the running time of this algorithm scales polynomially with the problem size. PMID:19113467
Adiabat-shaping in indirect drive inertial confinement fusion
Baker, K. L.; Robey, H. F.; Milovich, J. L.; Jones, O. S.; Smalyuk, V. A.; Casey, D. T.; MacPhee, A. G.; Pak, A.; Celliers, P. M.; Clark, D. S.; Landen, O. L.; Peterson, J. L.; Berzak-Hopkins, L. F.; Weber, C. R.; Haan, S. W.; Döppner, T. D.; Dixit, S.; Hamza, A. V.; Jancaitis, K. S.; Kroll, J. J.; and others
2015-05-15
Adiabat-shaping techniques were investigated in indirect drive inertial confinement fusion experiments on the National Ignition Facility as a means to improve implosion stability, while still maintaining a low adiabat in the fuel. Adiabat-shaping was accomplished in these indirect drive experiments by altering the ratio of the picket and trough energies in the laser pulse shape, thus driving a decaying first shock in the ablator. This decaying first shock is designed to place the ablation front on a high adiabat while keeping the fuel on a low adiabat. These experiments were conducted using the keyhole experimental platform for both three and four shock laser pulses. This platform enabled direct measurement of the shock velocities driven in the glow-discharge polymer capsule and in the liquid deuterium, the surrogate fuel for a DT ignition target. The measured shock velocities and radiation drive histories are compared to previous three and four shock laser pulses. This comparison indicates that in the case of adiabat shaping the ablation front initially drives a high shock velocity, and therefore, a high shock pressure and adiabat. The shock then decays as it travels through the ablator to pressures similar to the original low-adiabat pulses when it reaches the fuel. This approach takes advantage of initial high ablation velocity, which favors stability, and high-compression, which favors high stagnation pressures.
Kinetic Theory Derivation of the Adiabatic Law for Ideal Gases.
ERIC Educational Resources Information Center
Sobel, Michael I.
1980-01-01
Discusses how the adiabatic law for ideal gases can be derived from the assumption of a Maxwell-Boltzmann (or any other) distribution of velocities--in contrast to the usual derivations from thermodynamics alone, and the higher-order effect that leads to one-body viscosity. An elementary derivation of the adiabatic law is given. (Author/DS)
The Adiabatic Invariance of the Action Variable in Classical Dynamics
ERIC Educational Resources Information Center
Wells, Clive G.; Siklos, Stephen T. C.
2007-01-01
We consider one-dimensional classical time-dependent Hamiltonian systems with quasi-periodic orbits. It is well known that such systems possess an adiabatic invariant which coincides with the action variable of the Hamiltonian formalism. We present a new proof of the adiabatic invariance of this quantity and illustrate our arguments by means of…
Adiabatic theory for anisotropic cold molecule collisions
Pawlak, Mariusz; Shagam, Yuval; Narevicius, Edvardas; Moiseyev, Nimrod
2015-08-21
We developed an adiabatic theory for cold anisotropic collisions between slow atoms and cold molecules. It enables us to investigate the importance of the couplings between the projection states of the rotational motion of the atom about the molecular axis of the diatom. We tested our theory using the recent results from the Penning ionization reaction experiment {sup 4}He(1s2s {sup 3}S) + HD(1s{sup 2}) → {sup 4}He(1s{sup 2}) + HD{sup +}(1s) + e{sup −} [Lavert-Ofir et al., Nat. Chem. 6, 332 (2014)] and demonstrated that the couplings have strong effect on positions of shape resonances. The theory we derived provides cross sections which are in a very good agreement with the experimental findings.
Quantum Adiabatic Optimization and Combinatorial Landscapes
NASA Technical Reports Server (NTRS)
Smelyanskiy, V. N.; Knysh, S.; Morris, R. D.
2003-01-01
In this paper we analyze the performance of the Quantum Adiabatic Evolution (QAE) algorithm on a variant of Satisfiability problem for an ensemble of random graphs parametrized by the ratio of clauses to variables, gamma = M / N. We introduce a set of macroscopic parameters (landscapes) and put forward an ansatz of universality for random bit flips. We then formulate the problem of finding the smallest eigenvalue and the excitation gap as a statistical mechanics problem. We use the so-called annealing approximation with a refinement that a finite set of macroscopic variables (verses only energy) is used, and are able to show the existence of a dynamic threshold gamma = gammad, beyond which QAE should take an exponentially long time to find a solution. We compare the results for extended and simplified sets of landscapes and provide numerical evidence in support of our universality ansatz.
An adiabatic demagnetization refrigerator for SIRTF
NASA Technical Reports Server (NTRS)
Timbie, P. T.; Bernstein, G. M.; Richards, P. L.
1989-01-01
An adiabatic demagnetization refrigerator (ADR) has been proposed to cool bolometric infrared detectors on the multiband imaging photometer of the Space Infrared Telescope Facility (SIRTF). One such refrigerator has been built which uses a ferric ammonium alum salt pill suspended by nylon threads in a 3-T solenoid. The resonant modes of this suspension are above 100 Hz. The heat leak to the salt pill is less than 0.5 microW. The system has a hold time at 0.1K of more than 12 h. The cold stage temperature is regulated with a feedback loop that controls the magnetic field. A second, similar refrigerator is being built at a SIRTF prototype to fly on a ballon-borne telescope. It will use a ferromagnetic shield. The possibility of using a high-Tc solenoid-actuated heat switch is also discussed.
Design of a spaceworthy adiabatic demagnetization refrigerator
NASA Technical Reports Server (NTRS)
Serlemitsos, A. T.; Kunes, E.; Sansebastian, M.
1992-01-01
A spaceworthy adiabatic demagnetization refrigerator (ADR) under development at NASA-Goddard is presented. A baseline model heat switch was tested extensively with an on/off ratio of about 10,000 and a parasitic heat leak of 10 micro-W. Data obtained from the breadboard models were used to design an ADR with improved structural integrity. The core of the ADR is the salt pill which consists of the paramagnetic salt crystal and the thermal bus. When a magnetic field is applied to the salt it forces the alignment of the magnetic moments, thereby decreasing the entropy of the salt. Preliminary tests results showed a net crystal mass of 680 g instead of the expected 740 g, which indicate that there are gaps in the salt pill. A partial fix was accomplished by sealing helium gas in the salt pill at a pressure of 2 bar, which improved the thermal contact during salt magnetization, at about 2 K.
Differential topology of adiabatically controlled quantum processes
NASA Astrophysics Data System (ADS)
Jonckheere, Edmond A.; Rezakhani, Ali T.; Ahmad, Farooq
2013-03-01
It is shown that in a controlled adiabatic homotopy between two Hamiltonians, H 0 and H 1, the gap or "anti-crossing" phenomenon can be viewed as the development of cusps and swallow tails in the region of the complex plane where two critical value curves of the quadratic map associated with the numerical range of H 0 + i H 1 come close. The "near crossing" in the energy level plots happens to be a generic situation, in the sense that a crossing is a manifestation of the quadratic numerical range map being unstable in the sense of differential topology. The stable singularities that can develop are identified and it is shown that they could occur near the gap, making those singularities of paramount importance. Various applications, including the quantum random walk, are provided to illustrate this theory.
Reversible logic gate using adiabatic superconducting devices
Takeuchi, N.; Yamanashi, Y.; Yoshikawa, N.
2014-01-01
Reversible computing has been studied since Rolf Landauer advanced the argument that has come to be known as Landauer's principle. This principle states that there is no minimum energy dissipation for logic operations in reversible computing, because it is not accompanied by reductions in information entropy. However, until now, no practical reversible logic gates have been demonstrated. One of the problems is that reversible logic gates must be built by using extremely energy-efficient logic devices. Another difficulty is that reversible logic gates must be both logically and physically reversible. Here we propose the first practical reversible logic gate using adiabatic superconducting devices and experimentally demonstrate the logical and physical reversibility of the gate. Additionally, we estimate the energy dissipation of the gate, and discuss the minimum energy dissipation required for reversible logic operations. It is expected that the results of this study will enable reversible computing to move from the theoretical stage into practical usage. PMID:25220698
Entropy in Adiabatic Regions of Convection Simulations
NASA Astrophysics Data System (ADS)
Tanner, Joel D.; Basu, Sarbani; Demarque, Pierre
2016-05-01
One of the largest sources of uncertainty in stellar models is caused by the treatment of convection in stellar envelopes. One-dimensional stellar models often make use of the mixing length or equivalent approximations to describe convection, all of which depend on various free parameters. There have been attempts to rectify this by using 3D radiative-hydrodynamic simulations of stellar convection, and in trying to extract an equivalent mixing length from the simulations. In this Letter, we show that the entropy of the deeper, adiabatic layers in these simulations can be expressed as a simple function of {log}g and {log}{T}{{eff}}, which holds potential for calibrating stellar models in a simple and more general manner.
Symmetry-protected adiabatic quantum transistors
NASA Astrophysics Data System (ADS)
Williamson, Dominic J.; Bartlett, Stephen D.
2015-05-01
Adiabatic quantum transistors (AQT) allow quantum logic gates to be performed by applying a large field to a quantum many-body system prepared in its ground state, without the need for local control. The basic operation of such a device can be viewed as driving a spin chain from a symmetry-protected (SP) phase to a trivial phase. This perspective offers an avenue to generalize the AQT and to design several improvements. The performance of quantum logic gates is shown to depend only on universal symmetry properties of a SP phase rather than any fine tuning of the Hamiltonian, and it is possible to implement a universal set of logic gates in this way by combining several different types of SP matter. Such SP AQTs are argued to be robust to a range of relevant noise processes.
Number Partitioning via Quantum Adiabatic Computation
NASA Technical Reports Server (NTRS)
Smelyanskiy, Vadim N.; Toussaint, Udo; Clancy, Daniel (Technical Monitor)
2002-01-01
We study both analytically and numerically the complexity of the adiabatic quantum evolution algorithm applied to random instances of combinatorial optimization problems. We use as an example the NP-complete set partition problem and obtain an asymptotic expression for the minimal gap separating the ground and exited states of a system during the execution of the algorithm. We show that for computationally hard problem instances the size of the minimal gap scales exponentially with the problem size. This result is in qualitative agreement with the direct numerical simulation of the algorithm for small instances of the set partition problem. We describe the statistical properties of the optimization problem that are responsible for the exponential behavior of the algorithm.
Geometric Adiabatic Transport in Quantum Hall States
NASA Astrophysics Data System (ADS)
Klevtsov, S.; Wiegmann, P.
2015-08-01
We argue that in addition to the Hall conductance and the nondissipative component of the viscous tensor, there exists a third independent transport coefficient, which is precisely quantized. It takes constant values along quantum Hall plateaus. We show that the new coefficient is the Chern number of a vector bundle over moduli space of surfaces of genus 2 or higher and therefore cannot change continuously along the plateau. As such, it does not transpire on a sphere or a torus. In the linear response theory, this coefficient determines intensive forces exerted on electronic fluid by adiabatic deformations of geometry and represents the effect of the gravitational anomaly. We also present the method of computing the transport coefficients for quantum Hall states.
Geometric Adiabatic Transport in Quantum Hall States.
Klevtsov, S; Wiegmann, P
2015-08-21
We argue that in addition to the Hall conductance and the nondissipative component of the viscous tensor, there exists a third independent transport coefficient, which is precisely quantized. It takes constant values along quantum Hall plateaus. We show that the new coefficient is the Chern number of a vector bundle over moduli space of surfaces of genus 2 or higher and therefore cannot change continuously along the plateau. As such, it does not transpire on a sphere or a torus. In the linear response theory, this coefficient determines intensive forces exerted on electronic fluid by adiabatic deformations of geometry and represents the effect of the gravitational anomaly. We also present the method of computing the transport coefficients for quantum Hall states. PMID:26340197
Adiabatic connection at negative coupling strengths
Seidl, Michael; Gori-Giorgi, Paola
2010-01-15
The adiabatic connection of density functional theory (DFT) for electronic systems is generalized here to negative values of the coupling strength alpha (with attractive electrons). In the extreme limit alpha->-infinity a simple physical solution is presented and its implications for DFT (as well as its limitations) are discussed. For two-electron systems (a case in which the present solution can be calculated exactly), we find that an interpolation between the limit alpha->-infinity and the opposite limit of infinitely strong repulsion (alpha->+infinity) yields a rather accurate estimate of the second-order correlation energy E{sub c}{sup GL2}[rho] for several different densities rho, without using virtual orbitals. The same procedure is also applied to the Be isoelectronic series, analyzing the effects of near degeneracy.
Adiabatic theory for anisotropic cold molecule collisions.
Pawlak, Mariusz; Shagam, Yuval; Narevicius, Edvardas; Moiseyev, Nimrod
2015-08-21
We developed an adiabatic theory for cold anisotropic collisions between slow atoms and cold molecules. It enables us to investigate the importance of the couplings between the projection states of the rotational motion of the atom about the molecular axis of the diatom. We tested our theory using the recent results from the Penning ionization reaction experiment (4)He(1s2s (3)S) + HD(1s(2)) → (4)He(1s(2)) + HD(+)(1s) + e(-) [Lavert-Ofir et al., Nat. Chem. 6, 332 (2014)] and demonstrated that the couplings have strong effect on positions of shape resonances. The theory we derived provides cross sections which are in a very good agreement with the experimental findings. PMID:26298122
Sliding seal materials for adiabatic engines
NASA Technical Reports Server (NTRS)
Lankford, J.
1985-01-01
The sliding friction coefficients and wear rates of promising carbide, oxide, and nitride materials were measured under temperature, environmental, velocity, loading conditions that are representative of the adiabatic engine environment. In order to provide guidance needed to improve materials for this application, the program stressed fundamental understanding of the mechanisms involved in friction and wear. Microhardness tests were performed on the candidate materials at elevated temperatures, and in atmospheres relevant to the piston seal application, and optical and electron microscopy were used to elucidate the micromechanisms of wear following wear testing. X-ray spectroscopy was used to evaluate interface/environment interactions which seemed to be important in the friction and wear process. Electrical effects in the friction and wear processes were explored in order to evaluate the potential usefulness of such effects in modifying the friction and wear rates in service. However, this factor was found to be of negligible significance in controlling friction and wear.
Adiabatically-tapered fiber mode multiplexers.
Yerolatsitis, S; Gris-Sánchez, I; Birks, T A
2014-01-13
Simple all-fiber three-mode multiplexers were made by adiabatically merging three dissimilar single-mode cores into one multimode core. This was achieved by collapsing air holes in a photonic crystal fiber and (in a separate device) by fusing and tapering separate telecom fibers in a fluorine-doped silica capillary. In each case the LP01 mode and both LP11 modes were individually excited from three separate input cores, with losses below 0.3 and 0.7 dB respectively and mode purities exceeding 10 dB. Scaling to more modes is challenging, but would be assisted by using single-mode fibers with a smaller ratio of cladding to core diameter. PMID:24515021
The HAWC and SAFIRE Adiabatic Demagnetization Refrigerators
NASA Technical Reports Server (NTRS)
Tuttle, Jim; Shirron, Peter; DiPirro, Michael; Jackson, Michael; Behr, Jason; Kunes, Evan; Hait, Tom; Krebs, Carolyn (Technical Monitor)
2001-01-01
The High-Resolution Airborne Wide-band Camera (HAWC) and Submillimeter and Far Infrared Experiment (SAFIRE) are far-infrared experiments which will fly on the Stratospheric Observatory for Infrared Astronomy (SOFIA) aircraft. HAWC's detectors will operate at 0.2 Kelvin, while those of SAFIRE will be at 0.1 Kelvin. Each instrument will include an adiabatic demagnetization refrigerator (ADR) to cool its detector stage from the liquid helium bath temperature (HAWC's at 4.2 Kelvin and SAFIRE's pumped to about 1.3 Kelvin) to its operating temperature. Except for the magnets used to achieve the cooling and a slight difference in the heat switch design, the two ADRs are nearly identical. We describe the ADR design and present the results of performance testing.
An integrated programming and development environment for adiabatic quantum optimization
NASA Astrophysics Data System (ADS)
Humble, T. S.; McCaskey, A. J.; Bennink, R. S.; Billings, J. J.; DʼAzevedo, E. F.; Sullivan, B. D.; Klymko, C. F.; Seddiqi, H.
2014-01-01
Adiabatic quantum computing is a promising route to the computational power afforded by quantum information processing. The recent availability of adiabatic hardware has raised challenging questions about how to evaluate adiabatic quantum optimization (AQO) programs. Processor behavior depends on multiple steps to synthesize an adiabatic quantum program, which are each highly tunable. We present an integrated programming and development environment for AQO called Jade Adiabatic Development Environment (JADE) that provides control over all the steps taken during program synthesis. JADE captures the workflow needed to rigorously specify the AQO algorithm while allowing a variety of problem types, programming techniques, and processor configurations. We have also integrated JADE with a quantum simulation engine that enables program profiling using numerical calculation. The computational engine supports plug-ins for simulation methodologies tailored to various metrics and computing resources. We present the design, integration, and deployment of JADE and discuss its potential use for benchmarking AQO programs by the quantum computer science community.
An Integrated Development Environment for Adiabatic Quantum Programming
Humble, Travis S; McCaskey, Alex; Bennink, Ryan S; Billings, Jay Jay; D'Azevedo, Eduardo; Sullivan, Blair D; Klymko, Christine F; Seddiqi, Hadayat
2014-01-01
Adiabatic quantum computing is a promising route to the computational power afforded by quantum information processing. The recent availability of adiabatic hardware raises the question of how well quantum programs perform. Benchmarking behavior is challenging since the multiple steps to synthesize an adiabatic quantum program are highly tunable. We present an adiabatic quantum programming environment called JADE that provides control over all the steps taken during program development. JADE captures the workflow needed to rigorously benchmark performance while also allowing a variety of problem types, programming techniques, and processor configurations. We have also integrated JADE with a quantum simulation engine that enables program profiling using numerical calculation. The computational engine supports plug-ins for simulation methodologies tailored to various metrics and computing resources. We present the design, integration, and deployment of JADE and discuss its use for benchmarking adiabatic quantum programs.
Non-adiabatic molecular dynamics with complex quantum trajectories. II. The adiabatic representation
NASA Astrophysics Data System (ADS)
Zamstein, Noa; Tannor, David J.
2012-12-01
We present a complex quantum trajectory method for treating non-adiabatic dynamics. Each trajectory evolves classically on a single electronic surface but with complex position and momentum. The equations of motion are derived directly from the time-dependent Schrödinger equation, and the population exchange arises naturally from amplitude-transfer terms. In this paper the equations of motion are derived in the adiabatic representation to complement our work in the diabatic representation [N. Zamstein and D. J. Tannor, J. Chem. Phys. 137, 22A517 (2012)], 10.1063/1.4739845. We apply our method to two benchmark models introduced by John Tully [J. Chem. Phys. 93, 1061 (1990)], 10.1063/1.459170, and get very good agreement with converged quantum-mechanical calculations. Specifically, we show that decoherence (spatial separation of wavepackets on different surfaces) is already contained in the equations of motion and does not require ad hoc augmentation.
Non-adiabatic molecular dynamics with complex quantum trajectories. II. The adiabatic representation
Zamstein, Noa; Tannor, David J.
2012-12-14
We present a complex quantum trajectory method for treating non-adiabatic dynamics. Each trajectory evolves classically on a single electronic surface but with complex position and momentum. The equations of motion are derived directly from the time-dependent Schroedinger equation, and the population exchange arises naturally from amplitude-transfer terms. In this paper the equations of motion are derived in the adiabatic representation to complement our work in the diabatic representation [N. Zamstein and D. J. Tannor, J. Chem. Phys. 137, 22A517 (2012)]. We apply our method to two benchmark models introduced by John Tully [J. Chem. Phys. 93, 1061 (1990)], and get very good agreement with converged quantum-mechanical calculations. Specifically, we show that decoherence (spatial separation of wavepackets on different surfaces) is already contained in the equations of motion and does not require ad hoc augmentation.
Non-adiabatic perturbations in Ricci dark energy model
Karwan, Khamphee; Thitapura, Thiti E-mail: nanodsci2523@hotmail.com
2012-01-01
We show that the non-adiabatic perturbations between Ricci dark energy and matter can grow both on superhorizon and subhorizon scales, and these non-adiabatic perturbations on subhorizon scales can lead to instability in this dark energy model. The rapidly growing non-adiabatic modes on subhorizon scales always occur when the equation of state parameter of dark energy starts to drop towards -1 near the end of matter era, except that the parameter α of Ricci dark energy equals to 1/2. In the case where α = 1/2, the rapidly growing non-adiabatic modes disappear when the perturbations in dark energy and matter are adiabatic initially. However, an adiabaticity between dark energy and matter perturbations at early time implies a non-adiabaticity between matter and radiation, this can influence the ordinary Sachs-Wolfe (OSW) effect. Since the amount of Ricci dark energy is not small during matter domination, the integrated Sachs-Wolfe (ISW) effect is greatly modified by density perturbations of dark energy, leading to a wrong shape of CMB power spectrum. The instability in Ricci dark energy is difficult to be alleviated if the effects of coupling between baryon and photon on dark energy perturbations are included.
Dynamics of Charged Particles in an Adiabatic Thermal Beam Equilibrium
NASA Astrophysics Data System (ADS)
Chen, Chiping; Wei, Haofei
2010-11-01
Charged-particle motion is studied in the self-electric and self-magnetic fields of a well-matched, intense charged-particle beam and an applied periodic solenoidal magnetic focusing field. The beam is assumed to be in a state of adiabatic thermal equilibrium. The phase space is analyzed and compared with that of the well-known Kapchinskij-Vladimirskij (KV)-type beam equilibrium. It is found that the widths of nonlinear resonances in the adiabatic thermal beam equilibrium are narrower than those in the KV-type beam equilibrium. Numerical evidence is presented, indicating almost complete elimination of chaotic particle motion in the adiabatic thermal beam equilibrium.
Complete population inversion of Bose particles by an adiabatic cycle
NASA Astrophysics Data System (ADS)
Tanaka, Atushi; Cheon, Taksu
2016-04-01
We show that an adiabatic cycle excites Bose particles confined in a one-dimensional box. During the adiabatic cycle, a wall described by a δ-shaped potential is applied and its strength and position are slowly varied. When the system is initially prepared in the ground state, namely, in the zero-temperature equilibrium state, the adiabatic cycle brings all Bosons into the first excited one-particle state, leaving the system in a nonequilibrium state. The absorbed energy during the cycle is proportional to the number of Bosons.
Dephasing effects on stimulated Raman adiabatic passage in tripod configurations
Lazarou, C.; Vitanov, N. V.
2010-09-15
We present an analytic description of the effects of dephasing processes on stimulated Raman adiabatic passage in a tripod quantum system. To this end, we develop an effective two-level model. Our analysis makes use of the adiabatic approximation in the weak dephasing regime. An effective master equation for a two-level system formed by two dark states is derived, where analytic solutions are obtained by utilizing the Demkov-Kunike model. From these, it is found that the fidelity for the final coherent superposition state decreases exponentially for increasing dephasing rates. Depending on the pulse ordering and for adiabatic evolution, the pulse delay can have an inverse effect.
T1-weighted MRI as a substitute to CT for refocusing planning in MR-guided focused ultrasound
NASA Astrophysics Data System (ADS)
Wintermark, Max; Tustison, Nicholas J.; Elias, William J.; Patrie, James T.; Xin, Wenjun; Demartini, Nicholas; Eames, Matt; Sumer, Suna; Lau, Benison; Cupino, Alan; Snell, John; Hananel, Arik; Kassell, Neal; Aubry, Jean-Francois
2014-07-01
Precise focusing is essential for transcranial MRI-guided focused ultrasound (TcMRgFUS) to minimize collateral damage to non-diseased tissues and to achieve temperatures capable of inducing coagulative necrosis at acceptable power deposition levels. CT is usually used for this refocusing but requires a separate study (CT) ahead of the TcMRgFUS procedure. The goal of this study was to determine whether MRI using an appropriate sequence would be a viable alternative to CT for planning ultrasound refocusing in TcMRgFUS. We tested three MRI pulse sequences (3D T1 weighted 3D volume interpolated breath hold examination (VIBE), proton density weighted 3D sampling perfection with applications optimized contrasts using different flip angle evolution and 3D true fast imaging with steady state precision T2-weighted imaging) on patients who have already had a CT scan performed. We made detailed measurements of the calvarial structure based on the MRI data and compared those so-called ‘virtual CT’ to detailed measurements of the calvarial structure based on the CT data, used as a reference standard. We then loaded both standard and virtual CT in a TcMRgFUS device and compared the calculated phase correction values, as well as the temperature elevation in a phantom. A series of Bland-Altman measurement agreement analyses showed T1 3D VIBE as the optimal MRI sequence, with respect to minimizing the measurement discrepancy between the MRI derived total skull thickness measurement and the CT derived total skull thickness measurement (mean measurement discrepancy: 0.025; 95% CL (-0.22-0.27) p = 0.825). The T1-weighted sequence was also optimal in estimating skull CT density and skull layer thickness. The mean difference between the phase shifts calculated with the standard CT and the virtual CT reconstructed from the T1 dataset was 0.08 ± 1.2 rad on patients and 0.1 ± 0.9 rad on phantom. Compared to the real CT, the MR-based correction showed a 1 °C drop on the maximum
Design of the PIXIE Adiabatic Demagnetization Refrigerators
NASA Technical Reports Server (NTRS)
Shirron, Peter J.; Kimball, Mark Oliver; Fixsen, Dale J.; Kogut, Alan J.; Li, Xiaoyi; DiPirro, Michael
2012-01-01
The Primordial Inflation Explorer (PIXIE) is a proposed mission to densely map the polarization of the cosmic microwave background. It will operate in a scanning mode from a sun-synchronous orbit, using low temperature detectors (at 0.1 K) and located inside a teslescope that is cooled to approximately 2.73 K - to match the background temperature. A mechanical cryocooler operating at 4.5 K establishes a low base temperature from which two adiabatic demagnetization refrigerator (ADR) assemblies will cool the telescope and detectors. To achieve continuous scanning capability, the ADRs must operate continuously. Complicating the design are two factors: 1) the need to systematically vary the temperature of various telescope components in order to separate the small polarization signal variations from those that may arise from temperature drifts and changing gradients within the telescope, and 2) the orbital and monthly variations in lunar irradiance into the telescope barrels. These factors require the telescope ADR to reject quasi-continuous heat loads of 2-3 millwatts, while maintaining a peak heat reject rate of less than 12 milliwatts. The detector heat load at 0.1 K is comparatively small at 1-2 microwatts. This paper will describe the 3-stage and 2-stage continuous ADRs that will be used to meet the cooling power and temperature stability requirements of the PIXIE detectors and telescope.
Design of the PIXIE adiabatic demagnetization refrigerators
NASA Astrophysics Data System (ADS)
Shirron, Peter J.; Kimball, Mark O.; Fixsen, Dale J.; Kogut, Alan J.; Li, Xiaoyi; DiPirro, Michael J.
2012-04-01
The Primordial Inflation Explorer (PIXIE) is a proposed mission to densely map the polarization of the cosmic microwave background. It will operate in a scanning mode from a sun-synchronous orbit, using low temperature detectors (at 0.1 K) and located inside a telescope that is cooled to approximately 2.73 K - to match the background temperature. A mechanical cryocooler operating at 4.5 K establishes a low base temperature from which two adiabatic demagnetization refrigerator (ADR) assemblies will cool the telescope and detectors. To achieve continuous scanning capability, the ADRs must operate continuously. Complicating the design are two factors: (1) the need to systematically vary the temperature of various telescope components in order to separate the small polarization signal variations from those that may arise from temperature drifts and changing gradients within the telescope, and (2) the orbital and monthly variations in lunar irradiance into the telescope barrels. These factors require the telescope ADR to reject quasi-continuous heat loads of 2-3 mW, while maintaining a peak heat reject rate of less than 12 mW. The detector heat load at 0.1 K is comparatively small at 1-2 μW. This paper will describe the 3-stage and 2-stage continuous ADRs that will be used to meet the cooling power and temperature stability requirements of the PIXIE detectors and telescope.
Graph isomorphism and adiabatic quantum computing
NASA Astrophysics Data System (ADS)
Gaitan, Frank; Clark, Lane
2014-03-01
In the Graph Isomorphism (GI) problem two N-vertex graphs G and G' are given and the task is to determine whether there exists a permutation of the vertices of G that preserves adjacency and maps G --> G'. If yes (no), then G and G' are said to be isomorphic (non-isomorphic). The GI problem is an important problem in computer science and is thought to be of comparable difficulty to integer factorization. We present a quantum algorithm that solves arbitrary instances of GI, and which provides a novel approach to determining all automorphisms of a graph. The algorithm converts a GI instance to a combinatorial optimization problem that can be solved using adiabatic quantum evolution. Numerical simulation of the algorithm's quantum dynamics shows that it correctly distinguishes non-isomorphic graphs; recognizes isomorphic graphs; and finds the automorphism group of a graph. We also discuss the algorithm's experimental implementation and show how it can be leveraged to solve arbitrary instances of the NP-Complete Sub-Graph Isomorphism problem.
Adiabatic Quantum Computation with Neutral Atoms
NASA Astrophysics Data System (ADS)
Biedermann, Grant
2013-03-01
We are implementing a new platform for adiabatic quantum computation (AQC)[2] based on trapped neutral atoms whose coupling is mediated by the dipole-dipole interactions of Rydberg states. Ground state cesium atoms are dressed by laser fields in a manner conditional on the Rydberg blockade mechanism,[3,4] thereby providing the requisite entangling interactions. As a benchmark we study a Quadratic Unconstrained Binary Optimization (QUBO) problem whose solution is found in the ground state spin configuration of an Ising-like model. In collaboration with Lambert Parazzoli, Sandia National Laboratories; Aaron Hankin, Center for Quantum Information and Control (CQuIC), University of New Mexico; James Chin-Wen Chou, Yuan-Yu Jau, Peter Schwindt, Cort Johnson, and George Burns, Sandia National Laboratories; Tyler Keating, Krittika Goyal, and Ivan Deutsch, Center for Quantum Information and Control (CQuIC), University of New Mexico; and Andrew Landahl, Sandia National Laboratories. This work was supported by the Laboratory Directed Research and Development program at Sandia National Laboratories
Adiabatic Quantum Algorithm for Search Engine Ranking
NASA Astrophysics Data System (ADS)
Garnerone, Silvano; Zanardi, Paolo; Lidar, Daniel A.
2012-06-01
We propose an adiabatic quantum algorithm for generating a quantum pure state encoding of the PageRank vector, the most widely used tool in ranking the relative importance of internet pages. We present extensive numerical simulations which provide evidence that this algorithm can prepare the quantum PageRank state in a time which, on average, scales polylogarithmically in the number of web pages. We argue that the main topological feature of the underlying web graph allowing for such a scaling is the out-degree distribution. The top-ranked log(n) entries of the quantum PageRank state can then be estimated with a polynomial quantum speed-up. Moreover, the quantum PageRank state can be used in “q-sampling” protocols for testing properties of distributions, which require exponentially fewer measurements than all classical schemes designed for the same task. This can be used to decide whether to run a classical update of the PageRank.
NASA Astrophysics Data System (ADS)
Schmitz, D.; Siewert, F.; Zeschke, T.
2015-02-01
The effect of progress in surface finishing of optical components on the collimated-beam properties of soft x-ray beamlines at synchrotron radiation facilities is demonstrated: a stripe pattern, experimentally observed in the 2D intensity profile of beamlines with optical components manufactured 10-15 years ago, would be strongly attenuated if the existing refocusing mirror was replaced by an ultra-precise mirror manufactured with state-of-the-art of today surface finishing techniques. The observed stripe pattern is not caused by diffraction because its period length did not change with photon energy. Instead it can be explained with geometrical optics and is due to the height profile of the refocusing mirror which has been independently measured with a long trace profiler and used as an input in our raytracing simulations.
Adiabatic quantum pump in a zigzag graphene nanoribbon junction
NASA Astrophysics Data System (ADS)
Zhang, Lin
2015-11-01
The adiabatic electron transport is theoretically studied in a zigzag graphene nanoribbon (ZGNR) junction with two time-dependent pumping electric fields. By modeling a ZGNR p-n junction and applying the Keldysh Green’s function method, we find that a pumped charge current is flowing in the device at a zero external bias, which mainly comes from the photon-assisted tunneling process and the valley selection rule in an even-chain ZGNR junction. The pumped charge current and its ON and OFF states can be efficiently modulated by changing the system parameters such as the pumping frequency, the pumping phase difference, and the Fermi level. A ferromagnetic ZGNR device is also studied to generate a pure spin current and a fully polarized spin current due to the combined spin pump effect and the valley valve effect. Our finding might pave the way to manipulate the degree of freedom of electrons in a graphene-based electronic device. Project supported by the National Natural Science Foundation of China (Grant No. 110704033), the Natural Science Foundation of Jiangsu Province, China (Grant No. BK2010416), and the Natural Science Foundation for Colleges and Universities in Jiangsu Province, China (Grant No. 13KJB140005).
Adiabaticity and spectral splits in collective neutrino transformations
Raffelt, Georg G.; Smirnov, Alexei Yu.
2007-12-15
Neutrinos streaming off a supernova core transform collectively by neutrino-neutrino interactions, leading to 'spectral splits' where an energy E{sub split} divides the transformed spectrum sharply into parts of almost pure but different flavors. We present a detailed description of the spectral-split phenomenon which is conceptually and quantitatively understood in an adiabatic treatment of neutrino-neutrino effects. Central to this theory is a self-consistency condition in the form of two sum rules (integrals over the neutrino spectra that must equal certain conserved quantities). We provide explicit analytic and numerical solutions for various neutrino spectra. We introduce the concept of the adiabatic reference frame and elaborate on the relative adiabatic evolution. Violating adiabaticity leads to the spectral split being 'washed out'. The sharpness of the split appears to be represented by a surprisingly universal function.
Acceleration of adiabatic quantum dynamics in electromagnetic fields
Masuda, Shumpei; Nakamura, Katsuhiro
2011-10-15
We show a method to accelerate quantum adiabatic dynamics of wave functions under electromagnetic field (EMF) by developing the preceding theory [Masuda and Nakamura, Proc. R. Soc. London Ser. A 466, 1135 (2010)]. Treating the orbital dynamics of a charged particle in EMF, we derive the driving field which accelerates quantum adiabatic dynamics in order to obtain the final adiabatic states in any desired short time. The scheme is consolidated by describing a way to overcome possible singularities in both the additional phase and driving potential due to nodes proper to wave functions under EMF. As explicit examples, we exhibit the fast forward of adiabatic squeezing and transport of excited Landau states with nonzero angular momentum, obtaining the result consistent with the transitionless quantum driving applied to the orbital dynamics in EMF.
Adiabatic and isocurvature perturbation projections in multi-field inflation
NASA Astrophysics Data System (ADS)
Gordon, Chris; Saffin, Paul M.
2013-08-01
Current data are in good agreement with the predictions of single field inflation. However, the hemispherical asymmetry, seen in the cosmic microwave background data, may hint at a potential problem. Generalizing to multi-field models may provide one possible explanation. A useful way of modeling perturbations in multi-field inflation is to investigate the projection of the perturbation along and perpendicular to the background fields' trajectory. These correspond to the adiabatic and isocurvature perturbations. However, it is important to note that in general there are no corresponding adiabatic and isocurvature fields. The purpose of this article is to highlight the distinction between a field redefinition and a perturbation projection. We provide a detailed derivation of the evolution of the isocurvature perturbation to show that no assumption of an adiabatic or isocurvature field is needed. We also show how this evolution equation is consistent with the field covariant evolution equations for the adiabatic perturbation in the flat field space limit.
Startup of the RFP in a quasi-adiabatic mode
Caramana, E.J.
1980-01-01
The equations describing the purely adiabatic formation of the reversed-field pinch are solved. This method of formation in principle remedies the problem of flux consumption during the startup phase of this device.
Ultrafast stimulated Raman parallel adiabatic passage by shaped pulses
Dridi, G.; Guerin, S.; Hakobyan, V.; Jauslin, H. R.; Eleuch, H.
2009-10-15
We present a general and versatile technique of population transfer based on parallel adiabatic passage by femtosecond shaped pulses. Their amplitude and phase are specifically designed to optimize the adiabatic passage corresponding to parallel eigenvalues at all times. We show that this technique allows the robust adiabatic population transfer in a Raman system with the total pulse area as low as 3{pi}, corresponding to a fluence of one order of magnitude below the conventional stimulated Raman adiabatic passage process. This process of short duration, typically picosecond and subpicosecond, is easily implementable with the modern pulse shaper technology and opens the possibility of ultrafast robust population transfer with interesting applications in quantum information processing.
Quantum Monte Carlo simulations of tunneling in quantum adiabatic optimization
NASA Astrophysics Data System (ADS)
Brady, Lucas T.; van Dam, Wim
2016-03-01
We explore to what extent path-integral quantum Monte Carlo methods can efficiently simulate quantum adiabatic optimization algorithms during a quantum tunneling process. Specifically we look at symmetric cost functions defined over n bits with a single potential barrier that a successful quantum adiabatic optimization algorithm will have to tunnel through. The height and width of this barrier depend on n , and by tuning these dependencies, we can make the optimization algorithm succeed or fail in polynomial time. In this article we compare the strength of quantum adiabatic tunneling with that of path-integral quantum Monte Carlo methods. We find numerical evidence that quantum Monte Carlo algorithms will succeed in the same regimes where quantum adiabatic optimization succeeds.
Ashall, Vanessa; Millar, Kate
2013-09-01
Humane endpoints are a core refinement concept in animal experimentation. This paper identifies an urgent requirement for individuals and institutions to refocus on humane endpoints as part of the transposition of Directive 2010/63/EU into the national laws of the Member States, and to go beyond their legal construction when setting new guidance or applying humane endpoints in practice. It will be argued that requirements for humane endpoints within the Directive appear not to promote recent advances in best practice, but seem reliant on a narrow and potentially outdated definition of the term. We describe progress that has been made in encouraging change in the construction and application of humane endpoints, and suggest that Directive 2010/63/EU does not sufficiently acknowledge the conceptual complexity of this refinement strategy. For example, a useful development representing recent consensual views of best practice has been proposed by an EU consortium (in 2012). A complex approach to humane endpoints may place additional demands on institutions and raise challenges that would, unfortunately, not need to be overcome in order to remain within the Directive's current requirements regarding humane endpoints. We argue that there is now a need for a practical tool to help structure appropriate ethical reflection during research planning and experimentation, in order to facilitate best practice in the application of this important refinement concept. PMID:24168135
Nonadiabatic transitions in finite-time adiabatic rapid passage
NASA Astrophysics Data System (ADS)
Lu, T.; Miao, X.; Metcalf, H.
2007-06-01
To apply the adiabatic rapid passage process repetitively [T. Lu, X. Miao, and H. Metcalf, Phys. Rev. A 71, 061405(R) (2005)], the nonadiabatic transition probability of a two-level atom subject to chirped light pulses over a finite period of time needs to be calculated. Using a unitary first-order perturbation method in the rotating adiabatic frame, an approximate formula has been derived for such transition probabilities in the entire parameter space of the pulses.
Realization of adiabatic Aharonov-Bohm scattering with neutrons
NASA Astrophysics Data System (ADS)
Sjöqvist, Erik; Almquist, Martin; Mattsson, Ken; Gürkan, Zeynep Nilhan; Hessmo, Björn
2015-11-01
The adiabatic Aharonov-Bohm (AB) effect is a manifestation of the Berry phase acquired when some slow variables take a planar spin around a loop. While the effect has been observed in molecular spectroscopy, direct measurement of the topological phase shift in a scattering experiment has been elusive in the past. Here, we demonstrate an adiabatic AB effect by explicit simulation of the dynamics of unpolarized very slow neutrons that scatter on a long straight current-carrying wire.
Shortcuts to adiabaticity for non-Hermitian systems
Ibanez, S.; Martinez-Garaot, S.; Torrontegui, E.; Muga, J. G.; Chen Xi
2011-08-15
Adiabatic processes driven by non-Hermitian, time-dependent Hamiltonians may be sped up by generalizing inverse engineering techniques based on counter-diabatic (transitionless driving) algorithms or on dynamical invariants. We work out the basic theory and examples described by two-level Hamiltonians: the acceleration of rapid adiabatic passage with a decaying excited level and of the dynamics of a classical particle on an expanding harmonic oscillator.
NASA Astrophysics Data System (ADS)
Kakita, Veera Mohana Rao; Kupče, Eriks; Bharatam, Jagadeesh
2015-02-01
Unambiguous measurement of homonuclear scalar couplings (J) in multi-spin scalar network systems is not straightforward. Further, the direct measurement of J-couplings is obscured in solid-state samples due to the dipolar and chemical shift anisotropy (CSA)-dominated line broadening, even under the magic angle spinning (MAS). We present a new multiple frequency selective spin-echo method based on Hadamard matrix encoding, for simultaneous measurement of multiple homonuclear scalar couplings (J) in the solid-state. In contrast to the Hadamard encoded selective excitation schemes known for the solution-state, herein the selectivity is achieved during refocusing period. The Hadamard encoded refocusing scheme concurrently allows to create the spin-spin commutation property between number of spin-pairs of choice in uniformly labelled molecules, which, therefore avoids (1) the repetition of the double selective refocusing experiments for each spin-pair and (2) the synthesis of expensive selective labelled molecules. The experimental scheme is exemplified for determining 1JCC and 3JCC values in 13C6L-Histidine.HCl molecule, which are found to be in excellent agreement with those measured in conventional double frequency selective refocusing mode as well as in the solution-state. This method can be simply extended to 2D/3D pulse schemes and be applied to small bio-molecular solids.
Kakita, Veera Mohana Rao; Kupče, Eriks; Bharatam, Jagadeesh
2015-02-01
Unambiguous measurement of homonuclear scalar couplings (J) in multi-spin scalar network systems is not straightforward. Further, the direct measurement of J-couplings is obscured in solid-state samples due to the dipolar and chemical shift anisotropy (CSA)-dominated line broadening, even under the magic angle spinning (MAS). We present a new multiple frequency selective spin-echo method based on Hadamard matrix encoding, for simultaneous measurement of multiple homonuclear scalar couplings (J) in the solid-state. In contrast to the Hadamard encoded selective excitation schemes known for the solution-state, herein the selectivity is achieved during refocusing period. The Hadamard encoded refocusing scheme concurrently allows to create the spin-spin commutation property between number of spin-pairs of choice in uniformly labelled molecules, which, therefore avoids (1) the repetition of the double selective refocusing experiments for each spin-pair and (2) the synthesis of expensive selective labelled molecules. The experimental scheme is exemplified for determining (1)JCC and (3)JCC values in (13)C6l-Histidine.HCl molecule, which are found to be in excellent agreement with those measured in conventional double frequency selective refocusing mode as well as in the solution-state. This method can be simply extended to 2D/3D pulse schemes and be applied to small bio-molecular solids. PMID:25554944
Thermal explosion hazards on 18650 lithium ion batteries with a VSP2 adiabatic calorimeter.
Jhu, Can-Yong; Wang, Yih-Wen; Shu, Chi-Min; Chang, Jian-Chuang; Wu, Hung-Chun
2011-08-15
Thermal abuse behaviors relating to adiabatic runaway reactions in commercial 18650 lithium ion batteries (LiCoO(2)) are being studied in an adiabatic calorimeter, vent sizing package 2 (VSP2). We select four worldwide battery producers, Sony, Sanyo, Samsung and LG, and tested their Li-ion batteries, which have LiCoO(2) cathodes, to determine their thermal instabilities and adiabatic runaway features. The charged (4.2V) and uncharged (3.7 V) 18650 Li-ion batteries are tested using a VSP2 with a customized stainless steel test can to evaluate their thermal hazard characteristics, such as the initial exothermic temperature (T(0)), the self-heating rate (dT/dt), the pressure rise rate (dP/dt), the pressure-temperature profiles and the maximum temperature (T(max)) and pressure (P(max)). The T(max) and P(max) of the charged Li-ion battery during the runaway reaction reach 903.0°C and 1565.9 psig (pound-force per square inch gauge), respectively. This result leads to a thermal explosion, and the heat of reaction is 26.2 kJ. The thermokinetic parameters of the reaction of LiCoO(2) batteries are also determined using the Arrhenius model. The thermal reaction mechanism of the Li-ion battery (pack) proved to be an important safety concern for energy storage. Additionally, use of the VSP2 to classify the self-reactive ratings of the various Li-ion batteries demonstrates a new application of the adiabatic calorimetric methodology. PMID:21612866
Energy R and D in the Industrialized World: Retrenchment and Refocusing
JJ Dooley; PJ Runci; E Luiten
1999-11-01
This report presents preliminary findings from an ongoing research project examining trends in energy R&D investments in selected industrialized countries (The United States, Japan, Germany, the Netherlands, and the European Union). Its underlying purpose is to assess the adequacy of current energy R&D, in terms of investment levels and programmatic scope considering the likely energy technology demands associated with international efforts to address global climate change. It finds that, while overall levels of public and private investment in all forms of R&D have risen significantly across the countries studied, investments in energy R&D have declined in real terms. Causes of the observed decline might include the ongoing deregulation of the energy industries, the absence of acute energy crises, and shifts in domestic social and policy priorities in the post-Cold War period. In addition, it finds noteworthy shifts within industrialized countries' energy R&D investment portfolios. In most countries, nuclear R&D has declined (by more than 90% in key countries such as the U.S. and Germany) while the remaining R&D resources are shifting toward shorter-term projects, most notably in the energy efficiency area. Research on carbon sequestration, hydrogen production, and fuel cells is gaining in prominence public sector energy R&D, often displacing traditional fossil energy R&D projects. Future research associated with this project will include the preparation of reports on several additional industrialized countries, including the United Kingdom, France, Italy, Canada, and Switzerland. Collectively, the small set of countries addressed in this project account for over 95% of the world's energy R&D.
Zhang, Rongchun; Mroue, Kamal H; Ramamoorthy, Ayyalusamy
2016-05-01
Heteronuclear cross polarization (CP) has been commonly used to enhance the sensitivity of dilute low-γ nuclei in almost all solid-state NMR experiments. However, CP relies on heteronuclear dipolar couplings, and therefore the magnetization transfer efficiency becomes inefficient when the dipolar couplings are weak, as is often the case for mobile components in solids. Here, we demonstrate methods that combine CP with heteronuclear Overhauser effect (referred to as CP-NOE) or with refocused-INEPT (referred to as CP-RINEPT) to overcome the efficiency limitation of CP and enhance the signal-to-noise ratio (S/N) for mobile components. Our experimental results reveal that, compared to the conventional CP, significant S/N ratio enhancement can be achieved for resonances originating from mobile components, whereas the resonance signals associated with rigid groups are not significantly affected due to their long spin-lattice relaxation times. In fact, the S/N enhancement factor is also dependent on the temperature, CP contact time as well as on the system under investigation. Furthermore, we also demonstrate that CP-RINEPT experiment can be successfully employed to independently detect mobile and rigid signals in a single experiment without affecting the data collection time. However, the resolution of CP spectrum obtained from the CP-RINEPT experiment could be slightly compromised by the mandatory use of continuous wave (CW) decoupling during the acquisition of signals from rigid components. In addition, CP-RINEPT experiment can be used for spectral editing utilizing the difference in dynamics of different regions of a molecule and/or different components present in the sample, and could also be useful for the assignment of resonances from mobile components in poorly resolved spectra. Therefore, we believe that the proposed approaches are beneficial for the structural characterization of multiphase and heterogeneous systems, and could be used as a building block in
NASA Astrophysics Data System (ADS)
Zhang, Rongchun; Mroue, Kamal H.; Ramamoorthy, Ayyalusamy
2016-05-01
Heteronuclear cross polarization (CP) has been commonly used to enhance the sensitivity of dilute low-γ nuclei in almost all solid-state NMR experiments. However, CP relies on heteronuclear dipolar couplings, and therefore the magnetization transfer efficiency becomes inefficient when the dipolar couplings are weak, as is often the case for mobile components in solids. Here, we demonstrate methods that combine CP with heteronuclear Overhauser effect (referred to as CP-NOE) or with refocused-INEPT (referred to as CP-RINEPT) to overcome the efficiency limitation of CP and enhance the signal-to-noise ratio (S/N) for mobile components. Our experimental results reveal that, compared to the conventional CP, significant S/N ratio enhancement can be achieved for resonances originating from mobile components, whereas the resonance signals associated with rigid groups are not significantly affected due to their long spin-lattice relaxation times. In fact, the S/N enhancement factor is also dependent on the temperature, CP contact time as well as on the system under investigation. Furthermore, we also demonstrate that CP-RINEPT experiment can be successfully employed to independently detect mobile and rigid signals in a single experiment without affecting the data collection time. However, the resolution of CP spectrum obtained from the CP-RINEPT experiment could be slightly compromised by the mandatory use of continuous wave (CW) decoupling during the acquisition of signals from rigid components. In addition, CP-RINEPT experiment can be used for spectral editing utilizing the difference in dynamics of different regions of a molecule and/or different components present in the sample, and could also be useful for the assignment of resonances from mobile components in poorly resolved spectra. Therefore, we believe that the proposed approaches are beneficial for the structural characterization of multiphase and heterogeneous systems, and could be used as a building block in
Hobson, M. J.
1981-11-01
The objective of this study was to perform a conceptual engineering design and evaluation study and to develop a design for an adiabatic CAES system using water-compensated hard rock caverns for compressed air storage. The conceptual plant design was to feature underground containment for thermal energy storage and water-compensated hard rock caverns for high pressure air storage. Other design constraints included the selection of turbomachinery designs that would require little development and would therefore be available for near-term plant construction and demonstration. The design was to be based upon the DOE/EPRI/PEPCO-funded 231 MW/unit conventional CAES plant design prepared for a site in Maryland. This report summarizes the project, its findings, and the recommendations of the study team; presents the development and optimization of the plant heat cycle and the selection and thermal design of the thermal energy storage system; discusses the selection of turbomachinery and estimated plant performance and operational capability; describes the control system concept; and presents the conceptual design of the adiabatic CAES plant, the cost estimates and economic evaluation, and an assessment of technical and economic feasibility. Particular areas in the plant design requiring further development or investigation are discussed. It is concluded that the adiabatic concept appears to be the most attractive candidate for utility application in the near future. It is operationally viable, economically attractive compared with competing concerns, and will require relatively little development before the construction of a plant can be undertaken. It is estimated that a utility could start the design of a demonstration plant in 2 to 3 years if research regarding TES system design is undertaken in a timely manner. (LCL)
Adiabatic condition and the quantum hitting time of Markov chains
Krovi, Hari; Ozols, Maris; Roland, Jeremie
2010-08-15
We present an adiabatic quantum algorithm for the abstract problem of searching marked vertices in a graph, or spatial search. Given a random walk (or Markov chain) P on a graph with a set of unknown marked vertices, one can define a related absorbing walk P{sup '} where outgoing transitions from marked vertices are replaced by self-loops. We build a Hamiltonian H(s) from the interpolated Markov chain P(s)=(1-s)P+sP{sup '} and use it in an adiabatic quantum algorithm to drive an initial superposition over all vertices to a superposition over marked vertices. The adiabatic condition implies that, for any reversible Markov chain and any set of marked vertices, the running time of the adiabatic algorithm is given by the square root of the classical hitting time. This algorithm therefore demonstrates a novel connection between the adiabatic condition and the classical notion of hitting time of a random walk. It also significantly extends the scope of previous quantum algorithms for this problem, which could only obtain a full quadratic speedup for state-transitive reversible Markov chains with a unique marked vertex.
Large-Area Atom Interferometry with Frequency-Swept Raman Adiabatic Passage.
Kotru, Krish; Butts, David L; Kinast, Joseph M; Stoner, Richard E
2015-09-01
We demonstrate light-pulse atom interferometry with large-momentum-transfer atom optics based on stimulated Raman transitions and frequency-swept adiabatic rapid passage. Our atom optics have produced momentum splittings of up to 30 photon recoil momenta in an acceleration-sensitive interferometer for laser cooled atoms. We experimentally verify the enhancement of phase shift per unit acceleration and characterize interferometer contrast loss. By forgoing evaporative cooling and velocity selection, this method lowers the atom shot-noise-limited measurement uncertainty and enables large-area atom interferometry at higher data rates. PMID:26382675
Implementation of a quantum adiabatic algorithm for factorization on two qudits
Zobov, V. E. Ermilov, A. S.
2012-06-15
Implementation of an adiabatic quantum algorithm for factorization on two qudits with the number of levels d{sub 1} and d{sub 2} is considered. A method is proposed for obtaining a time-dependent effective Hamiltonian by means of a sequence of rotation operators that are selective with respect to the transitions between neighboring levels of a qudit. A sequence of RF magnetic field pulses is obtained, and a factorization of the numbers 35, 21, and 15 is numerically simulated on two quadrupole nuclei with spins 3/2 (d{sub 1} = 4) and 1 (d{sub 2} = 3).
Baranowski, M; Woźniak-Braszak, A; Jurga, K
2016-01-01
The paper presents the benefits of using fast adiabatic passage for the study of molecular dynamics in the solid state heteronuclear systems in the laboratory frame. A homemade pulse spectrometer operating at the frequency of 30.2MHz and 28.411MHz for protons and fluorines, respectively, has been enhanced with microcontroller direct digital synthesizer DDS controller [1-4]. This work briefly describes how to construct a low-cost and easy-to-assemble adiabatic extension set for homemade and commercial spectrometers based on recently very popular Arduino shields. The described set was designed for fast adiabatic generation. Timing and synchronization problems are discussed. The cross-relaxation experiments with different initial states of the two spin systems have been performed. Contrary to our previous work [5] where the steady-state NOE experiments were conducted now proton spins (1)H are polarized in the magnetic field B0 while fluorine spins (19)F are perturbed by selective saturation for a short time and then the system is allowed to evolve for a period in the absence of a saturating field. The adiabatic passage application leads to a reversal of magnetization of fluorine spins and increases the amplitude of the signal. PMID:26705906
NASA Astrophysics Data System (ADS)
Baranowski, M.; Woźniak-Braszak, A.; Jurga, K.
2016-01-01
The paper presents the benefits of using fast adiabatic passage for the study of molecular dynamics in the solid state heteronuclear systems in the laboratory frame. A homemade pulse spectrometer operating at the frequency of 30.2 MHz and 28.411 MHz for protons and fluorines, respectively, has been enhanced with microcontroller direct digital synthesizer DDS controller [1-4]. This work briefly describes how to construct a low-cost and easy-to-assemble adiabatic extension set for homemade and commercial spectrometers based on recently very popular Arduino shields. The described set was designed for fast adiabatic generation. Timing and synchronization problems are discussed. The cross-relaxation experiments with different initial states of the two spin systems have been performed. Contrary to our previous work [5] where the steady-state NOE experiments were conducted now proton spins 1H are polarized in the magnetic field B0 while fluorine spins 19F are perturbed by selective saturation for a short time and then the system is allowed to evolve for a period in the absence of a saturating field. The adiabatic passage application leads to a reversal of magnetization of fluorine spins and increases the amplitude of the signal.
Integrated polarization rotator/converter by stimulated Raman adiabatic passage.
Xiong, Xiao; Zou, Chang-Ling; Ren, Xi-Feng; Guo, Guang-Can
2013-07-15
We proposed a polarization rotator inspired by stimulated Raman adiabatic passage model from quantum optics, which is composed of a signal waveguide and an ancillary waveguide. The two orthogonal modes in signal waveguide and the oblique mode in ancillary waveguide form a Λ-type three-level system. By controlling the width of signal waveguide and the gap between two waveguides, adiabatic conversion between two orthogonal modes can be realized in the signal waveguide. With such adiabatic passage, polarization conversion is completed within 150 μm length, with the efficiencies over 99% for both conversions between horizontal polarization and vertical polarization. In addition, such a polarization rotator is quite robust against fabrication error, allowing a wide range of tolerances for the rotator geometric parameters. Our work is not only significative to photonic simulations of coherent quantum phenomena with engineered photonic waveguides, but also enlightens the practical applications of these phenomena in optical device designs. PMID:23938558
Adiabatic compressibility of myoglobin. Effect of axial ligand and denaturation.
Leung, W P; Cho, K C; Lo, Y M; Choy, C L
1986-03-01
An ultrasonic technique has been employed to study the adiabatic compressibility of three metmyoglobin derivatives (aquomet-, fluoromet- and azidometmyoglobin) at neutral pH, and aquometmyoglobin as a function of pH in the frequency range of 1-10 MHz at 20 degrees C. No difference was observed in the adiabatic compressibility of the various derivatives. This indicates that the binding of different axial ligands to myoglobin does not affect significantly the conformational fluctuations of the protein. The finding is consistent with the results of the hydrogen exchange rate experiment, indicating that both types of measurements are useful for the study of protein dynamics. Upon acid-induced denaturation, the adiabatic compressibility of myoglobin drops from 5.3 X 10(-12) cm2/dyn to 0.5 X 10(-12) cm2/dyn. Plausible reasons for such a decrease are discussed. PMID:3947645
Effect of dephasing on stimulated Raman adiabatic passage
Ivanov, P.A.; Vitanov, N.V.; Bergmann, K.
2004-12-01
This work explores the effect of phase relaxation on the population transfer efficiency in stimulated Raman adiabatic passage (STIRAP). The study is based on the Liouville equation, which is solved analytically in the adiabatic limit. The transfer efficiency of STIRAP is found to decrease exponentially with the dephasing rate; this effect is stronger for shorter pulse delays and weaker for larger delays, since the transition time is found to be inversely proportional to the pulse delay. Moreover, it is found that the transfer efficiency of STIRAP in the presence of dephasing does not depend on the peak Rabi frequencies at all, as long as they are sufficiently large to enforce adiabatic evolution; hence increasing the field intensity cannot reduce the dephasing losses. It is shown also that for any dephasing rate, the final populations of the initial state and the intermediate state are equal. For strong dephasing all three populations tend to (1/3)
Interaction-induced adiabatic cooling for antiferromagnetism in optical lattices
Dare, A.-M.; Raymond, L.; Albinet, G.; Tremblay, A.-M. S.
2007-08-01
In the experimental context of cold-fermion optical lattices, we discuss the possibilities to approach the pseudogap or ordered phases by manipulating the scattering length or the strength of the laser-induced lattice potential. Using the two-particle self-consistent approach, as well as quantum Monte Carlo simulations, we provide isentropic curves for the two- and three-dimensional Hubbard models at half-filling. These quantitative results are important for practical attempts to reach the ordered antiferromagnetic phase in experiments on optical lattices of two-component fermions. We find that adiabatically turning on the interaction in two dimensions to cool the system is not very effective. In three dimensions, adiabatic cooling to the antiferromagnetic phase can be achieved in such a manner, although the cooling efficiency is not as high as initially suggested by dynamical mean-field theory. Adiabatic cooling by turning off the repulsion beginning at strong coupling is possible in certain cases.
Adiabatic Quantum Programming: Minor Embedding With Hard Faults
Klymko, Christine F; Sullivan, Blair D; Humble, Travis S
2013-01-01
Adiabatic quantum programming defines the time-dependent mapping of a quantum algorithm into the hardware or logical fabric. An essential programming step is the embedding of problem-specific information into the logical fabric to define the quantum computational transformation. We present algorithms for embedding arbitrary instances of the adiabatic quantum optimization algorithm into a square lattice of specialized unit cells. Our methods are shown to be extensible in fabric growth, linear in time, and quadratic in logical footprint. In addition, we provide methods for accommodating hard faults in the logical fabric without invoking approximations to the original problem. These hard fault-tolerant embedding algorithms are expected to prove useful for benchmarking the adiabatic quantum optimization algorithm on existing quantum logical hardware. We illustrate this versatility through numerical studies of embeddabilty versus hard fault rates in square lattices of complete bipartite unit cells.
Shortcuts to adiabaticity in a time-dependent box
Campo, A. del; Boshier, M. G.
2012-01-01
A method is proposed to drive an ultrafast non-adiabatic dynamics of an ultracold gas trapped in a time-dependent box potential. The resulting state is free from spurious excitations associated with the breakdown of adiabaticity, and preserves the quantum correlations of the initial state up to a scaling factor. The process relies on the existence of an adiabatic invariant and the inversion of the dynamical self-similar scaling law dictated by it. Its physical implementation generally requires the use of an auxiliary expulsive potential. The method is extended to a broad family of interacting many-body systems. As illustrative examples we consider the ultrafast expansion of a Tonks-Girardeau gas and of Bose-Einstein condensates in different dimensions, where the method exhibits an excellent robustness against different regimes of interactions and the features of an experimentally realizable box potential. PMID:22970340
Pressure sensitivity of adiabatic shear banding in metals
NASA Astrophysics Data System (ADS)
Hanina, E.; Rittel, D.; Rosenberg, Z.
2007-01-01
Adiabatic shear banding (ASB) is a dynamic failure mode characterized by large plastic strains in a narrow localized band. ASB occurs at high strain rates (ɛ˙⩾103s-1), under adiabatic conditions leading to a significant temperature rise inside the band [H. Tresca, Annales du Conservatoire des Arts et Métiers 4, (1879); Y. L. Bai and B. Dodd, Adiabatic Shear Localization-Occurrence, Theories, and Applications (Pergamon, Oxford, 1992); M. A. Meyers, Dynamic Behavior of Materials (Wiley, New York, 1994).; and J. J. Lewandowski and L. M. Greer, Nat. Mater. 5, 15 (2006)]. Large hydrostatic pressures are experienced in many dynamic applications involving ASB formation (e.g., ballistic penetration, impact, and machining). The relationship between hydrostatic pressure and ASB development remains an open question, although its importance has been often noted. This letter reports original experimental results indicating a linear relationship between the (normalized) dynamic deformation energy and the (normalized) hydrostatic pressure.
Adiabatic quantum programming: minor embedding with hard faults
NASA Astrophysics Data System (ADS)
Klymko, Christine; Sullivan, Blair D.; Humble, Travis S.
2013-11-01
Adiabatic quantum programming defines the time-dependent mapping of a quantum algorithm into an underlying hardware or logical fabric. An essential step is embedding problem-specific information into the quantum logical fabric. We present algorithms for embedding arbitrary instances of the adiabatic quantum optimization algorithm into a square lattice of specialized unit cells. These methods extend with fabric growth while scaling linearly in time and quadratically in footprint. We also provide methods for handling hard faults in the logical fabric without invoking approximations to the original problem and illustrate their versatility through numerical studies of embeddability versus fault rates in square lattices of complete bipartite unit cells. The studies show that these algorithms are more resilient to faulty fabrics than naive embedding approaches, a feature which should prove useful in benchmarking the adiabatic quantum optimization algorithm on existing faulty hardware.
Non Adiabatic Evolution of Elliptical Galaxies by Dynamical Friction
NASA Astrophysics Data System (ADS)
Arena, S. E.; Bertin, G.; Liseikina, T.; Pegoraro, F.
2007-05-01
Many astrophysical problems, ranging from structure formation in cosmology to dynamics of elliptical galaxies, refer to slow processes of evolution of essentially collisionless self-gravitating systems. In order to determine the relevant quasi-equilibrium configuration at time t from given initial conditions, it is often argued that such slow evolution may be approximated in terms of adiabatic evolution, for the calculation of which efficient semi--analytical techniques are available. Here we focus on the slow process of evolution, induced by dynamical friction of a host stellar system on a minority component of "satellites", to determine to what extent an adiabatic description might be applied. The study is realized by means of N--body simulations of the evolution of the total system (the stellar system plus the minority component), in a controlled numerical environment. In particular, we compare the evolution from initial to final configurations of the system subject to dynamical friction with that of the same system evolved adiabatically (in the absence of dynamical friction). We consider two classes of galaxy models characterized by significantly different density and pressure anisotropy profiles. We demonstrate that, for the examined process, the evolution driven by dynamical friction is significantly different from the adiabatic case, not only quantitatively, but also qualitatively. The two classes of galaxy models considered in this investigation exhibit generally similar trends in evolution, with one exception: concentrated models reach a final total density profile, in the internal region, shallower than the initial one, while galaxy models with a broad core show the opposite behaviour. The evolution of elliptical galaxies induced by dynamical friction is a slow process but it is not adiabatic. The results of our investigation should be taken as a warning against the indiscriminate use of adiabatic growth prescriptions in studies of the structure of