Dual-species Bose-Einstein condensate of {sup 87}Rb and {sup 133}Cs
McCarron, D. J.; Cho, H. W.; Jenkin, D. L.; Koeppinger, M. P.; Cornish, S. L.
2011-07-15
We report the formation of a dual-species Bose-Einstein condensate of {sup 87}Rb and {sup 133}Cs in the same trapping potential. Our method exploits the efficient sympathetic cooling of {sup 133}Cs via elastic collisions with {sup 87}Rb, initially in a magnetic quadrupole trap and subsequently in a levitated optical trap. The two condensates each contain up to 2x10{sup 4} atoms and exhibit a striking phase separation, revealing the mixture to be immiscible due to strong repulsive interspecies interactions. Sacrificing all the {sup 87}Rb during the cooling, we create single-species {sup 133}Cs condensates of up to 6x10{sup 4} atoms.
Generalized quantum measurements on a 87 Rb Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Murphree, Joseph D.; Hansen, Azure; Schultz, Justin T.; Jayaseelan, Maitreyi; Bigelow, Nicholas P.
2016-05-01
We investigate two applications of generalized measurements on a 87 Rb Bose-Einstein condensate (BEC). The first involves preparing the BEC in one of two non-orthogonal states constructed from a superposition of two atomic spin states. A positive-operator valued measure (POVM) for this system can be defined by three vectors in the 2D spin space. A two-photon Raman process rotates these vectors into a higher-dimensional space associating each with its own spin state, whose relative populations are measured using Stern-Gerlach imaging. This allows the possibility of unambiguously determining in which state the system was prepared. For the second application, a superposition of two spin states is used to put the BEC into one of three non-orthogonal states in the trine state configuration and measured using a POVM as before. Here an unambiguous measurement is impossible, but the POVM minimizes the error probability, improving upon the error probability associated with a traditional projective von Neumann measurement. Finally, incorporating orbital angular momentum states of the BEC allows for the possibility of extending these techniques into higher dimensions.
NASA Astrophysics Data System (ADS)
Wang, Fudong; Li, Xiaoke; Xiong, Dezhi; Wang, Dajun
2016-01-01
We have realized a dual-species Bose-Einstein condensate (BEC) of 23Na and 87Rb atoms and observed its immiscibility. Because of the favorable background intra- and inter-species scattering lengths, stable condensates can be obtained via efficient evaporative cooling and sympathetic cooling without the need for fine tuning of the interactions. Our system thus provides a clean platform for studying inter-species interactions-driven effects in superfluid mixtures. With a Feshbach resonance, we have successfully created double BECs with largely tunable inter-species interactions and studied the miscible-immiscible phase transition.
Efficient production of an 87Rb F = 2, mF = 2 Bose-Einstein condensate in a hybrid trap
NASA Astrophysics Data System (ADS)
Mishra, Hari Prasad; Flores, Adonis Silva; Vassen, Wim; Knoop, Steven
2015-02-01
We have realized Bose-Einstein condensation (BEC) of 87Rb in the F = 2, m F = 2 hyperfine substate in a hybrid trap, consisting of a quadrupole magnetic field and a single optical dipole beam. The symmetry axis of the quadrupole magnetic trap coincides with the optical beam axis, which gives stronger axial confinement than previous hybrid traps. After loading 2 × 106 atoms at 14 μK from a quadrupole magnetic trap into the hybrid trap, we perform efficient forced evaporation and reach the onset of BEC at a temperature of 0.5 μK and with 4 × 105 atoms. We also obtain thermal clouds of 1 × 106 atoms below 1 μK in a pure single beam optical dipole trap, by ramping down the magnetic field gradient after evaporative cooling in the hybrid trap.
Efficient production of an 87Rb F = 2, mF = 2 Bose-Einstein condensate in a hybrid trap
NASA Astrophysics Data System (ADS)
Prasad Mishra, Hari; Silva Flores, Adonis; Vassen, Wim; Knoop, Steven
2015-02-01
We have realized Bose-Einstein condensation (BEC) of 87Rb in the F = 2, mF = 2 hyperfine substate in a hybrid trap, consisting of a quadrupole magnetic field and a single optical dipole beam. The symmetry axis of the quadrupole magnetic trap coincides with the optical beam axis, which gives stronger axial confinement than previous hybrid traps. After loading 2 × 106 atoms at 14 μK from a quadrupole magnetic trap into the hybrid trap, we perform efficient forced evaporation and reach the onset of BEC at a temperature of 0.5 μK and with 4 × 105 atoms. We also obtain thermal clouds of 1 × 106 atoms below 1 μK in a pure single beam optical dipole trap, by ramping down the magnetic field gradient after evaporative cooling in the hybrid trap.
NASA Astrophysics Data System (ADS)
Nolli, Raffaele; Venturelli, Michela; Marmugi, Luca; Wickenbrock, Arne; Renzoni, Ferruccio
2016-08-01
We present a compact experimental apparatus for Bose-Einstein condensation of 87Rb in the |F = 2, mF = + 2> state. A pre-cooled atomic beam of 87Rb is obtained by using an unbalanced magneto-optical trap, allowing controlled transfer of trapped atoms from the first vacuum chamber to the science chamber. Here, atoms are transferred to a hybrid trap, as produced by overlapping a magnetic quadrupole trap with a far-detuned optical trap with crossed beam configuration, where forced radiofrequency evaporation is realized. The final evaporation leading to Bose-Einstein condensation is then performed by exponentially lowering the optical trap depth. Control and stabilization systems of the optical trap beams are discussed in detail. The setup reliably produces a pure condensate in the |F = 2, mF = + 2> state in 50 s, which includes 33 s loading of the science magneto-optical trap and 17 s forced evaporation.
Nolli, Raffaele; Venturelli, Michela; Marmugi, Luca; Wickenbrock, Arne; Renzoni, Ferruccio
2016-08-01
We present a compact experimental apparatus for Bose-Einstein condensation of (87)Rb in the |F = 2, mF = + 2〉 state. A pre-cooled atomic beam of (87)Rb is obtained by using an unbalanced magneto-optical trap, allowing controlled transfer of trapped atoms from the first vacuum chamber to the science chamber. Here, atoms are transferred to a hybrid trap, as produced by overlapping a magnetic quadrupole trap with a far-detuned optical trap with crossed beam configuration, where forced radiofrequency evaporation is realized. The final evaporation leading to Bose-Einstein condensation is then performed by exponentially lowering the optical trap depth. Control and stabilization systems of the optical trap beams are discussed in detail. The setup reliably produces a pure condensate in the |F = 2, mF = + 2〉 state in 50 s, which includes 33 s loading of the science magneto-optical trap and 17 s forced evaporation. PMID:27587095
Phuc, Nguyen Thanh; Kawaguchi, Yuki; Ueda, Masahito
2011-10-15
We investigate the effects of thermal and quantum fluctuations on the phase diagram of a spin-1 {sup 87}Rb Bose-Einstein condensate (BEC) under the quadratic Zeeman effect. Due to the large ratio of spin-independent to spin-dependent interactions of {sup 87}Rb atoms, the effect of noncondensed atoms on the condensate is much more significant than that in scalar BECs. We find that the condensate and spontaneous magnetization emerge at different temperatures when the ground state is in the broken-axisymmetry phase. In this phase, a magnetized condensate induces spin coherence of noncondensed atoms in different magnetic sublevels, resulting in temperature-dependent magnetization of the noncondensate. We also examine the effect of quantum fluctuations on the order parameter at absolute zero and find that the ground-state phase diagram is significantly altered by quantum depletion.
El-Sherbini, Th.M.
2005-03-17
This article gives a brief review of Bose-Einstein condensation. It is an exotic quantum phenomenon that was observed in dilute atomic gases for the first time in 1995. It exhibits a new state of matter in which a group of atoms behaves as a single particle. Experiments on this form of matter are relevant to many different areas of physics- from atomic clocks and quantum computing to super fluidity, superconductivity and quantum phase transition.
Topological objects in two-component Bose-Einstein condensates
Cho, Y. M.; Khim, Hyojoong; Zhang, Pengming
2005-12-15
We study the topological objects in two-component Bose-Einstein condensates. We compare two competing theories of two-component Bose-Einstein condensates, the popular Gross-Pitaevskii theory, and the recently proposed gauge theory of two-component Bose-Einstein condensate which has an induced vorticity interaction. We show that two theories produce very similar topological objects, in spite of the obvious differences in dynamics. Furthermore we show that the gauge theory of two-component Bose-Einstein condensates, with the U(1) gauge symmetry, is remarkably similar to the Skyrme theory. Just like the Skyrme theory this theory admits the non-Abelian vortex, the helical vortex, and the vorticity knot. We construct the lightest knot solution in two-component Bose-Einstein condensates numerically, and discuss how the knot can be constructed in the spin-(1/2) condensate of {sup 87}Rb atoms.
Approaching Bose-Einstein Condensation
ERIC Educational Resources Information Center
Ferrari, Loris
2011-01-01
Bose-Einstein condensation (BEC) is discussed at the level of an advanced course of statistical thermodynamics, clarifying some formal and physical aspects that are usually not covered by the standard pedagogical literature. The non-conventional approach adopted starts by showing that the continuum limit, in certain cases, cancels out the crucial…
Large atom number Bose-Einstein condensate machines
Streed, Erik W.; Chikkatur, Ananth P.; Gustavson, Todd L.; Boyd, Micah; Torii, Yoshio; Schneble, Dominik; Campbell, Gretchen K.; Pritchard, David E.; Ketterle, Wolfgang
2006-02-15
We describe experimental setups for producing large Bose-Einstein condensates of {sup 23}Na and {sup 87}Rb. In both, a high-flux thermal atomic beam is decelerated by a Zeeman slower and is then captured and cooled in a magneto-optical trap. The atoms are then transferred into a cloverleaf-style Ioffe-Pritchard magnetic trap and cooled to quantum degeneracy with radio-frequency-induced forced evaporation. Typical condensates contain 20x10{sup 6} atoms. We discuss the similarities and differences between the techniques used for producing large {sup 87}Rb and {sup 23}Na condensates in the context of nearly identical setups.
Bose-Einstein condensation at constant temperature
NASA Astrophysics Data System (ADS)
Erhard, M.; Schmaljohann, H.; Kronjäger, J.; Bongs, K.; Sengstock, K.
2004-09-01
We present an experimental approach to Bose-Einstein condensation by increasing the particle number of the system at almost constant temperature. In particular, the emergence of a new condensate is observed in multicomponent F=1 spinor condensates of Rb87 . Furthermore, we develop a simple rate-equation model for multicomponent Bose-Einstein condensate thermodynamics at finite temperature which well reproduces the measured effects.
Recent developments in Bose-Einstein condensation
Kalman, G.
1997-09-22
This paper contains viewgraphs on developments on Bose-Einstein condensation. Some topics covered are: strongly coupled coulomb systems; standard response functions of the first and second kind; dynamical mean field theory; quasi localized charge approximation; and the main equations.
Generalized Bose-Einstein Condensation
NASA Astrophysics Data System (ADS)
Mullin, William J.; Sakhel, Asaad R.
2012-02-01
Generalized Bose-Einstein condensation (GBEC) involves condensates appearing simultaneously in multiple states. We review examples of the three types in an ideal Bose gas with different geometries. In Type I there is a discrete number of quantum states each having macroscopic occupation; Type II has condensation into a continuous band of states, with each state having macroscopic occupation; in Type III each state is microscopically occupied while the entire condensate band is macroscopically occupied. We begin by discussing Type I or "normal" BEC into a single state for an isotropic harmonic oscillator potential. Other geometries and external potentials are then considered: the "channel" potential (harmonic in one dimension and hard-wall in the other), which displays Type II, the "cigar trap" (anisotropic harmonic potential), and the "Casimir prism" (an elongated box), the latter two having Type III condensations. General box geometries are considered in an appendix. We particularly focus on the cigar trap, which Van Druten and Ketterle first showed had a two-step condensation: a GBEC into a band of states at a temperature T c and another "one-dimensional" transition at a lower temperature T 1 into the ground state. In a thermodynamic limit in which the ratio of the dimensions of the anisotropic harmonic trap is kept fixed, T 1 merges with the upper transition, which then becomes a normal BEC. However, in the thermodynamic limit of Beau and Zagrebnov, in which the ratio of the boundary lengths increases exponentially, T 1 becomes fixed at the temperature of a true Type I phase transition. The effects of interactions on GBEC are discussed and we show that there is evidence that Type III condensation may have been observed in the cigar trap.
Diquark Bose-Einstein condensation
Nawa, K.; Nakano, E.; Yabu, H.
2006-08-01
Bose-Einstein condensation of composite diquarks in quark matter (the color superconductor phase) is discussed using the quasichemical equilibrium theory at a relatively low-density region near the deconfinement phase transition, where dynamical quark-pair fluctuations are assumed to be described as bosonic degrees of freedom (diquarks). A general formulation is given for the diquark formation and particle-antiparticle pair-creation processes in the relativistic framework, and some interesting properties are shown, which are characteristic for the relativistic many-body system. Behaviors of transition temperature and phase diagram of the quark-diquark matter are generally presented in model parameter space, and their asymptotic behaviors are also discussed. As an application to the color superconductivity, the transition temperatures and the quark and diquark density profiles are calculated in case with constituent/current quarks, where the diquark is in the bound/resonant state. We obtained T{sub C}{approx}60-80 MeV for constituent quarks and T{sub C}{approx}130 MeV for current quarks at a moderate density ({rho}{sub b}{approx}3{rho}{sub 0}). The method is also developed to include interdiquark interactions into the quasichemical equilibrium theory within a mean-field approximation, and it is found that a possible repulsive diquark-diquark interaction lowers the transition temperature by {approx}50%.
Dynamics of F=2 Spinor Bose-Einstein Condensates
NASA Astrophysics Data System (ADS)
Schmaljohann, H.; Erhard, M.; Kronjäger, J.; Kottke, M.; van Staa, S.; Cacciapuoti, L.; Arlt, J. J.; Bongs, K.; Sengstock, K.
2004-01-01
We experimentally investigate and analyze the rich dynamics in F=2 spinor Bose-Einstein condensates of 87Rb. An interplay between mean-field driven spin dynamics and hyperfine-changing losses in addition to interactions with the thermal component is observed. In particular, we measure conversion rates in the range of 10-12 cm3 s-1 for spin-changing collisions within the F=2 manifold and spin-dependent loss rates in the range of 10-13 cm3 s-1 for hyperfine-changing collisions. We observe polar behavior in the F=2 ground state of 87Rb, while we find the F=1 ground state to be ferromagnetic. We further see a magnetization for condensates prepared with nonzero total spin.
Bose-Einstein condensation. Twenty years after
Bagnato, V. S.; Frantzeskakis, D. J.; Kevrekidis, P. G.; Malomed, B. A.; Mihalache, D.
2015-02-23
The aim of this introductory article is two-fold. First, we aim to offer a general introduction to the theme of Bose-Einstein condensates, and briefly discuss the evolution of a number of relevant research directions during the last two decades. Second, we introduce and present the articles that appear in this Special Volume of Romanian Reports in Physics celebrating the conclusion of the second decade since the experimental creation of Bose-Einstein condensation in ultracold gases of alkali-metal atoms.
Quantum metrology with Bose-Einstein condensates
Boixo, Sergio; Datta, Animesh; Davis, Matthew J.; Flammia, Steven T.; Shaji, Anil; Tacla, Alexandre B.; Caves, Carlton M.
2009-04-13
We show how a generalized quantum metrology protocol can be implemented in a two-mode Bose-Einstein condensate of n atoms, achieving a sensitivity that scales better than 1/n and approaches 1/n{sup 3/2} for appropriate design of the condensate.
Soliton resonance in bose-einstein condensate
NASA Technical Reports Server (NTRS)
Zak, Michail; Kulikov, I.
2002-01-01
A new phenomenon in nonlinear dispersive systems, including a Bose-Einstein Condensate (BEC), has been described. It is based upon a resonance between an externally induced soliton and 'eigen-solitons' of the homogeneous cubic Schrodinger equation. There have been shown that a moving source of positive /negative potential induces bright /dark solitons in an attractive / repulsive Bose condensate.
Axions: Bose Einstein condensate or classical field?
NASA Astrophysics Data System (ADS)
Davidson, Sacha
2015-05-01
The axion is a motivated dark matter candidate, so it would be interesting to find features in Large Scale Structures specific to axion dark matter. Such features were proposed for a Bose Einstein condensate of axions, leading to confusion in the literature (to which I contributed) about whether axions condense due to their gravitational interactions. This note argues that the Bose Einstein condensation of axions is a red herring: the axion dark matter produced by the misalignment mechanism is already a classical field, which has the distinctive features attributed to the axion condensate (BE condensates are described as classical fields). This note also estimates that the rate at which axion particles condense to the field, or the field evaporates to particles, is negligible.
Bose-Einstein condensation of 84Sr.
Martinez de Escobar, Y N; Mickelson, P G; Yan, M; DeSalvo, B J; Nagel, S B; Killian, T C
2009-11-13
We report Bose-Einstein condensation of (84)Sr in an optical dipole trap. Efficient laser cooling on the narrow intercombination line and an ideal s-wave scattering length allow the creation of large condensates (N(0) approximately 3 x 10(5)) even though the natural abundance of this isotope is only 0.6%. Condensation is heralded by the emergence of a low-velocity component in time-of-flight images. PMID:20365965
Scanning Cryogenic Magnetometry with a Bose-Einstein Condensate
NASA Astrophysics Data System (ADS)
Lev, Benjamin; Straquadine, Joshua; Yang, Fan
2016-05-01
Microscopy techniques co-opted from nonlinear optics and high energy physics have complemented solid-state probes in elucidating exotic order manifest in condensed matter systems. We present a novel scanning magnetometer which adds the techniques of ultracold atomic physics to the condensed matter toolbox. Our device, the Scanning Quantum CRyogenic Atom Microscope (SQCRAMscope) uses a one-dimensional Bose-Einstein condensate of 87 Rb to image magnetic and electric fields near surfaces between room and cryogenic temperatures, and allows for rapid sample changes while retaining UHV compatibility for atomic experiments. We present our characterization of the spatial resolution and magnetic field sensitivity of the device, and discuss the advantages and applications of this magnetometry technique. In particular, we will discuss our plans for performing local transport measurements in technologically relevant materials such as Fe-based superconductors and topological insulators.
Scanning Cryogenic Magnetometry with a 1D Bose Einstein Condensate
NASA Astrophysics Data System (ADS)
Straquadine, Joshua; Yang, Fan; Lev, Benjamin
We present a novel scanning probe magnetometer suitable for cryogenic studies, in which the probe is a Bose-Einstein condensate of 87Rb. The system is designed for rapid sample changes and operation between 35 K and room temperature while remaining compatible with the UHV requirements of ultracold atom experiments. We demonstrate a spatial resolution (FWHM) of 2.6 μm and a repeatability of 1.9 +/- 1.0 nT. We also show that the system is operating close to the fundamental measurement limits set by photon shot noise and atom shot noise. Our scanning quantum cryogenic atom microscope is suitable for fundamental studies of transport and magnetism in condensed matter systems such as high-temperature superconductors and topological insulators. We discuss the advantages and applications of this magnetometry technique.
Efficient production of large {sup 39}K Bose-Einstein condensates
Campbell, Robert L. D.; Smith, Robert P.; Tammuz, Naaman; Beattie, Scott; Moulder, Stuart; Hadzibabic, Zoran
2010-12-15
We describe an experimental setup and the cooling procedure for producing {sup 39}K Bose-Einstein condensates of over 4x10{sup 5} atoms. Condensation is achieved via a combination of sympathetic cooling with {sup 87}Rb in a quadrupole-Ioffe-configuration (QUIC) magnetic trap and direct evaporation in a large-volume crossed optical dipole trap, where we exploit the broad Feshbach resonance at 402 G to tune the {sup 39}K interactions from weak and attractive to strong and repulsive. In the same apparatus we create quasipure {sup 87}Rb condensates of over 8x10{sup 5} atoms.
Bose-Einstein condensation in microgravity.
van Zoest, T; Gaaloul, N; Singh, Y; Ahlers, H; Herr, W; Seidel, S T; Ertmer, W; Rasel, E; Eckart, M; Kajari, E; Arnold, S; Nandi, G; Schleich, W P; Walser, R; Vogel, A; Sengstock, K; Bongs, K; Lewoczko-Adamczyk, W; Schiemangk, M; Schuldt, T; Peters, A; Könemann, T; Müntinga, H; Lämmerzahl, C; Dittus, H; Steinmetz, T; Hänsch, T W; Reichel, J
2010-06-18
Albert Einstein's insight that it is impossible to distinguish a local experiment in a "freely falling elevator" from one in free space led to the development of the theory of general relativity. The wave nature of matter manifests itself in a striking way in Bose-Einstein condensates, where millions of atoms lose their identity and can be described by a single macroscopic wave function. We combine these two topics and report the preparation and observation of a Bose-Einstein condensate during free fall in a 146-meter-tall evacuated drop tower. During the expansion over 1 second, the atoms form a giant coherent matter wave that is delocalized on a millimeter scale, which represents a promising source for matter-wave interferometry to test the universality of free fall with quantum matter. PMID:20558713
Beliaev theory of spinor Bose-Einstein condensates
Phuc, Nguyen Thanh; Kawaguchi, Yuki; Ueda, Masahito
2013-01-15
By generalizing the Green's function approach developed by Beliaev [S.T. Beliaev, Sov. Phys. JETP 7 (1958) 299; S.T. Beliaev, Sov. Phys. JETP 7 (1958) 289], we study effects of quantum fluctuations on the energy spectra of spin-1 spinor Bose-Einstein condensates, in particular, of a {sup 87}Rb condensate in the presence of an external magnetic field. We find that due to quantum fluctuations, the effective mass of magnons, which characterizes the quadratic dispersion relation of spin-wave excitations, increases compared with its mean-field value. The enhancement factor turns out to be the same for two distinct quantum phases: the ferromagnetic and polar phases, and it is a function of only the gas parameter. The lifetime of magnons in a spin-1 {sup 87}Rb spinor condensate is shown to be much longer than that of phonons due to the difference in their dispersion relations. We propose a scheme to measure the effective mass of magnons in a spinor Bose gas by utilizing the effect of magnons' nonlinear dispersion relation on the time evolution of the distribution of transverse magnetization. This type of measurement can be applied, for example, to precision magnetometry. - Highlights: Black-Right-Pointing-Pointer Second-order energy spectra for a spin-1 {sup 87}Rb spinor BEC under a quadratic Zeeman effect are found. Black-Right-Pointing-Pointer Effective mass of magnons increases due to quantum fluctuations. Black-Right-Pointing-Pointer Enhancement factor is the same for two quantum phases and also independent of external parameters. Black-Right-Pointing-Pointer Lifetime of magnons in a spin-1 {sup 87}Rb spinor BEC is much longer than that of phonons. Black-Right-Pointing-Pointer Experimental scheme to measure the effective mass of magnons is proposed.
Schrodinger Leopards in Bose-Einstein Condensates
NASA Astrophysics Data System (ADS)
Carr, Lincoln D.; Dounas-Frazer, Dimitri R.
2008-03-01
We present the complex quantum dynamics of vortices in Bose-Einstein condensates in a double well via exact diagonalization of a discretized Hamiltonian. When the barrier is high, vortices evolve into macroscopic superposition (NOON) states of a vortex in either well -- a Schrodinger cat with spots. Such Schrodinger leopard states are more robust than previously proposed NOON states, which only use two single particle modes of the double well potential.
Formation of molecules in an expanding Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Yurovsky, Vladimir; Ben-Reuven, Abraham
2004-05-01
A mean field theory [1] is extended to an inhomogeneous case of expanding hybrid atom-molecule Bose-Einstein condensates. This theory is applied to the recent MPI experiments [2] on ^87Rb demonstrating the formation of ultracold molecules due to Feshbach resonance. The subsequent dissociation of the molecules is treated using a non-mean-field parametric approximation [3]. The latter method is also used in determining optimal conditions for the formation of molecular BEC. [1] V. A. Yurovsky, A. Ben-Reuven, P. S. Julienne and C. J. Williams, Phys. Rev. A 60, R765 (1999); Phys. Rev. A 62, 043605 (2000). [2] S. Dürr, T. Volz, A. Marte, and G. Rempe, Phys. Rev. Lett. 92, 020406 (2004). [3] V. A. Yurovsky and A. Ben-Reuven, Phys. Rev. A 67, 043611 (2003).
Optical Devices for Cold Atoms and Bose-Einstein Condensates
Gaaloul, Naceur; Jaouadi, Amine; Telmini, Mourad; Pruvost, Laurence; Charron, Eric
2007-09-19
The manipulation of cold atoms with optical fields is a very promising technique for a variety of applications ranging from laser cooling and trapping to coherent atom transport and matter wave interferometry. Optical fields have also been proposed as interesting tools for quantum information processing with cold atoms. In this paper, we present a theoretical study of the dynamics of a cold {sup 87}Rb atomic cloud falling in the gravity field in the presence of two crossing dipole guides. The cloud is either deflected or split between the two branches of this guide. We explore the possibilities of optimization of this device and present preliminary results obtained in the case of zero-temperature dilute Bose-Einstein condensates.
Mechanocaloric and thermomechanical effects in Bose-Einstein-condensed systems
Marques, G.C.; Bagnato, V.S.; Muniz, S.R.; Spehler, D.
2004-05-01
In this paper we extend previous hydrodynamic equations, governing the motion of Bose-Einstein-condensed fluids, to include temperature effects. This allows us to analyze some differences between a normal fluid and a Bose-Einstein-condensed one. We show that, in close analogy with superfluid {sup 4}He, a Bose-Einstein-condensed fluid exhibits the mechanocaloric and thermomechanical effects. In our approach we can explain both effects without using the hypothesis that the Bose-Einstein-condensed fluid has zero entropy. Such ideas could be investigated in existing experiments.
Bose-Einstein Condensation of Yb atoms
Takasu, Y.; Maki, K.; Komori, K.; Takano, T.; Honda, K.; Kumakura, M.; Yabuzaki, T.; Takahashi, Y.
2005-05-05
We could recently achieve the Bose Einstein condensation (BEC) of Yb atoms. Yb differs from most of the elements that have previously been condensed, because it is a two-electron atom with the singlet S ground state. Furthermore the Bosonic isotopes of Yb, like 174Yb which we succeeded to condensate, has no nuclear spin, so that the ground state is completely spin-less state and hence insensitive to magnetic fields. Thus a new type of atom could join the group of atoms for BEC studies. We would like to report how we could achieve the BEC of Yb atoms.
Bose-Einstein Condensation of Strontium
Stellmer, Simon; Huang Bo; Grimm, Rudolf; Tey, Meng Khoon; Schreck, Florian
2009-11-13
We report on the attainment of Bose-Einstein condensation with ultracold strontium atoms. We use the {sup 84}Sr isotope, which has a low natural abundance but offers excellent scattering properties for evaporative cooling. Accumulation in a metastable state using a magnetic-trap, narrowline cooling, and straightforward evaporative cooling in an optical trap lead to pure condensates containing 1.5x10{sup 5} atoms. This puts {sup 84}Sr in a prime position for future experiments on quantum-degenerate gases involving atomic two-electron systems.
Bose-Einstein Condensation in Extended Microgravity
NASA Astrophysics Data System (ADS)
Scharringhausen, Marco; Quantus Team; Rasel, Ernst Maria
2012-07-01
The setup and the envisaged experiment timeline of the QUANTUS-III experiment onboard a sounding rocket to be started in the near future are presented. The major intention of QUANTUS-III is the stable generation of a number of Bose-Einstein condensates as a source for atom interferometry during several minutes of microgravity onboard the sounding rocket. Later missions aim at the realization of atom interferoemeters as precursor satellite missions. These condesates will be generated serially, allowing a large number of repeatable tests. Within such Bose-Einstein condensates, millions of atoms lose their identity and can be described by a single macroscopic wave function. During the expansion over several seconds, the atoms form a giant coherent matter wave that is delocalized on a millimeter scale, which represents a promising source for matter-wave interferometry to test the universality of free fall with quantum matter. Cold quantum gases and, in particular, Bose-Einstein condensates represent a new state of matter which is nowadays established in many laboratories. They offer unique insights into a broad range of fundamental physics as well as prospects for novel quantum sensors. Microgravity will substantially extend the science of quantum gases towards nowadays inaccessible regimes at lowest temperatures, to macroscopic dimensions, and to unequalled durations of unperturbed evolution of these distinguished quantum objects. Right now, the QUANTUS-III experiment is in the development phase, taking heritage from QUANTUS-I and QUANTUS-II. Major components of the engineering model are available. Boundary conditions of the rocket, requirements of the experiment and interface considerations are presented. This include laser stabilization, vacuum technology and magnetic shielding. The planned trajectory of the rocket will have an apogee of 200 - 300 km and a total microgravity time of 4 - 7 minutes, both depending on the total experiment mass.
Nonlinear interferometry with Bose-Einstein condensates
Tacla, Alexandre B.; Boixo, Sergio; Datta, Animesh; Shaji, Anil; Caves, Carlton M.
2010-11-15
We analyze a proposed experiment [Boixo et al., Phys. Rev. Lett. 101, 040403 (2008)] for achieving sensitivity scaling better than 1/N in a nonlinear Ramsey interferometer that uses a two-mode Bose-Einstein condensate (BEC) of N atoms. We present numerical simulations that confirm the analytical predictions for the effect of the spreading of the BEC ground-state wave function on the ideal 1/N{sup 3/2} scaling. Numerical integration of the coupled, time-dependent, two-mode Gross-Pitaevskii equations allows us to study the several simplifying assumptions made in the initial analytic study of the proposal and to explore when they can be justified. In particular, we find that the two modes share the same spatial wave function for a length of time that is sufficient to run the metrology scheme.
Rotating trapped Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Fetter, A. L.
2008-01-01
Trapped Bose-Einstein condensates (BECs) differ considerably from the standard textbook example of a uniform Bose gas. In an isotropic harmonic potential V( r) = ½ Mω2 r 2, the single-particle ground state introduces a new intrinsic scale of length [the ground-state size d = √ ℏ/( Mω)] and energy [the ground-state energy E 0 = frac{3} {2} ℏω]. When the trap rotates at a low angular velocity, the behavior of a single vortex illustrates the crucial role of discrete quantized vorticity. For more rapid rotation, the condensate contains a vortex array. The resulting centrifugal forces expand the condensate radially and shrink it axially; thus, the condensate becomes effectively two dimensional. If the external rotation speed approaches the frequency of the radial harmonic confining potential, the condensate enters the "lowest-Landau-level" regime, and a simple description again becomes possible. Eventually, the system is predicted to make a quantum phase transition to a highly correlated state analogous to the fractional quantum Hall states of electrons in a strong magnetic field.
Nonequilibrium Bose-Einstein condensation of hot magnons
Vannucchi, Fabio Stucchi; Vasconcellos, Aurea Rosas; Luzzi, Roberto
2010-10-01
We present an analysis of the emergence of a nonequilibrium Bose-Einstein-type condensation of magnons in radio-frequency pumped magnetic thin films, which has recently been experimentally observed. A complete description of all the nonequilibrium processes involved is given. It is demonstrated that the phenomenon is another example of the emergence of Bose-Einstein-type condensation in nonequilibrium many-boson systems embedded in a thermal bath, a phenomenon evidenced decades ago by the renowned late Herbert Froehlich.
Vortex Formation by Merging of Multiple Trapped Bose-Einstein Condensates
Scherer, David R.; Weiler, Chad N.; Neely, Tyler W.; Anderson, Brian P.
2007-03-16
We report observations of vortex formation by merging and interfering multiple {sup 87}Rb Bose-Einstein condensates (BECs) in a confining potential. In this experiment, a single harmonic potential well is partitioned into three sections by a barrier, enabling the simultaneous formation of three independent, uncorrelated BECs. The BECs may either automatically merge together during their growth, or for high-energy barriers, the BECs can be merged together by barrier removal after their formation. Either process may instigate vortex formation in the resulting BEC, depending on the initially indeterminate relative phases of the condensates and the merging rate.
Tojo, Satoshi; Taguchi, Yoshihisa; Masuyama, Yuta; Hayashi, Taro; Hirano, Takuya; Saito, Hiroki
2010-09-15
We investigate controlled phase separation of a binary Bose-Einstein condensate in the proximity of a mixed-spin-channel Feshbach resonance in the |F=1,m{sub F}=+1> and |F=2,m{sub F}=-1> states of {sup 87}Rb at a magnetic field of 9.10 G. Phase separation occurs on the lower-magnetic-field side of the Feshbach resonance while the two components overlap on the higher-magnetic-field side. The Feshbach resonance curve of the scattering length is obtained from the shape of the atomic cloud by comparison with the numerical analysis of coupled Gross-Pitaevskii equations.
Fractional-charge vortex in a spinor Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Gautam, Sandeep; Adhikari, S. K.
2016-01-01
We classify all possible fractional charge vortices of charge less than unity in spin-1 and spin-2 polar and cyclic Bose-Einstein condensates (BECs) with zero magnetization. Statics and dynamics of these vortices in quasi-two-dimensional spinor BECs are studied employing an accurate numerical solution and a Lagrange variational approximation. The results for density and collective-mode oscillation are illustrated using the fractional-charge BEC vortex of 23Na and 87Rb atoms with realistic interaction and trapping potential parameters.
Dynamics of a Cold Trapped Ion in a Bose-Einstein Condensate
Schmid, Stefan; Haerter, Arne; Denschlag, Johannes Hecker
2010-09-24
We investigate the interaction of a laser-cooled trapped ion (Ba{sup +} or Rb{sup +}) with an optically confined {sup 87}Rb Bose-Einstein condensate. The system features interesting dynamics of the ion and the atom cloud as determined by their collisions and their motion in their respective traps. Elastic as well as inelastic processes are observed and their respective cross sections are determined. We demonstrate that a single ion can be used to probe the density profile of an ultracold atom cloud.
Simple method for generating Bose-Einstein condensates in a weak hybrid trap
Zaiser, M.; Hartwig, J.; Schlippert, D.; Velte, U.; Winter, N.; Lebedev, V.; Ertmer, W.; Rasel, E. M.
2011-03-15
We report on a simple trapping scheme for the generation of Bose-Einstein condensates of {sup 87}Rb atoms. This scheme employs a near-infrared single-beam optical dipole trap combined with a weak magnetic quadrupole field as used for magneto-optical trapping to enhance the confinement in axial direction. Efficient forced evaporative cooling to the phase transition is achieved in this weak hybrid trap via reduction of the laser intensity of the optical dipole trap at constant magnetic field gradient.
Bose-Einstein-condensate heating by atomic losses
Dziarmaga, Jacek; Sacha, Krzysztof
2003-10-01
Atomic Bose-Einstein condensate is heated by atomic losses. The losses act as a heat reservoir for the condensate. The condensate is approaching a state of thermal equilibrium with a thermal depletion ranging from 1% for a uniform three-dimensional (3D) condensate to around 13% for a quasi-1D condensate in a harmonic trap.
BOOK REVIEW: Bose-Einstein Condensation
NASA Astrophysics Data System (ADS)
Jaksch, D.
2003-09-01
L Pitaevskii and S Stringari Oxford: Oxford University Press (2003) £55.50 (hardback), ISBN 0-19-850719-4 The Gross--Pitaevskii equation, named after one of the authors of the book, and its large number of applications for describing the properties of Bose--Einstein condensation (BEC) in trapped weakly interacting atomic gases, is the main topic of this book. In total the monograph comprises 18 chapters and is divided into two parts. Part I introduces the notion of BEC and superfluidity in general terms. The most important properties of the ideal and the weakly interacting Bose gas are described and the effects of nonuniformity due to an external potential at zero temperature are studied. The first part is then concluded with a summary of the properties of superfluid ^{4}He. In Part II the authors describe the theoretical aspects of BEC in harmonically trapped weakly interacting atomic gases. A short and rather rudimentary chapter on collisions and trapping of atomic gases which seems to be included for completeness only is followed by a detailed analysis of the ground state,\
Spin-dependent inelastic collisions in spin-2 Bose-Einstein condensates
Tojo, Satoshi; Hayashi, Taro; Tanabe, Tatsuyoshi; Hirano, Takuya; Kawaguchi, Yuki; Saito, Hiroki; Ueda, Masahito
2009-10-15
We studied spin-dependent two-body inelastic collisions in F=2 {sup 87}Rb Bose-Einstein condensates both experimentally and theoretically. The {sup 87}Rb condensates were confined in an optical trap and selectively prepared in various spin states in the F=2 manifold at a magnetic field of 3.0 G. The measured atom loss rates depend on the spin states of colliding atoms. We measured two fundamental loss coefficients for two-body inelastic collisions with total spins of 0 and 2. The loss coefficients determine the loss rates of all the spin pairs. The experimental results for mixtures of all spin combinations are in good agreement with numerical solutions of the Gross-Pitaevskii equations that include the effect of a magnetic field gradient.
Evidence of Bose-Einstein Condensation in solid helium
NASA Astrophysics Data System (ADS)
Chan, Moses H. W.
2005-03-01
The onset of superfluidity in liquid He-4 below 2.176K is associated with Bose-Einstein condensation where He-4 atoms condensed into a single momentum state and acquire quantum mechanical coherence over macroscopic length scales. Bose- Einstein condensation of alkali atoms in the vapor phase was achieved in 1995 and there is strong evidence for superfluidity in these systems. Perhaps counter to intuition, superfluid-like behavior is thought possible even in solid helium. Recent high Q torsional oscillator measurements found evidence of superflow in solid helium confined in porous media (1) and in bulk solid helium (2), indicating Bose-Einstein condensation very likely occurs in all three phases of matter. (1) E. Kim and M. H. W. Chan, Nature 427, 225 (2004) (2) E. Kim and M. H. W. Chan, Science 305, 1941 (2004).
Vortex formation in a fast rotating Bose-Einstein condensate
Ghosh, Tarun Kanti
2004-04-01
We study rotational motion of an interacting atomic Bose-Einstein condensate confined in a quadratic-plus-quartic potential. We calculate the lowest energy surface mode frequency and show that a symmetric trapped (harmonic and quartic) Bose-Einstein condensate breaks the rotational symmetry of the Hamiltonian when rotational frequency is greater than one-half of the lowest energy surface mode frequency. We argue that the formation of a vortex is not possible in a noninteracting as well as in an attractive Bose-Einstein condensate confined in a harmonic trap due to the absence of the spontaneous shape deformation, but it can occur which leads to the vortex formation if we add an additional quartic potential. Moreover, the spontaneous shape deformation and consequently the formation of a vortex in an attractive system depends on the strengths of the two-body interaction and the quartic potential.
Spin-orbit coupled Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Jimenez-Garcia, Karina
2011-05-01
Ultracold atoms are quantum systems under precise experimental control, ideal for realizing and characterizing novel artificial gauge fields. Our latest experiments with 87Rb Bose-Einstein condensates (BECs) have demonstrated and explored Abelian, both scalar and matrix valued, light-induced gauge potentials. We optically dressed our BECs with a pair of far detuned Raman lasers. The resulting dressed states are spin and momentum superpositions, and we adiabatically load the atoms into the lowest energy of these dressed states. The nature of the dressed states is experimentally tunable via the strength of the laser coupling and the detuning from Raman resonance, thereby introducing gauge fields into the Hamiltonian. I will discuss Spin-Orbit (SO) coupling, the interaction between a quantum particle's spin and its momentum. We experimentally realized SO coupling with equal contributions of Rashba and Dresselhaus coupling, which modified the interaction between the dressed spin states and resulted in a phase transition from a spatially spin- mixed state to a phase-separated state as a function of laser power. The location of this transition is in agreement with our calculations. Finally I conclude by focusing on our most recent progress on artificial gauge fields. This work was performed in collaboration with Y.-J. Lin, R. A. Williams, L. J. LeBlanc, M. Beeler, W. D. Phillips, J. V. Porto and I. B. Spielman. This work was supported by ONR; ARO with funds both from the DARPA OLE program and the Atomtronics MURI; the NSF through the Physics Frontier Center at JQI; and CONACYT.
NASA Astrophysics Data System (ADS)
Posso Trujillo, Katerine; Rasel, Ernst M.; Gaaloul, Naceur; Quantus Team
Preparation of Bose Einstein condensates in realistc trapping potentials for precision atom interferometry Theoretical studies of the ground state and the dynamical properties of Bose Einstein condensates (BECs) are typically realized by considering the ensemble as being initiaally trapped by a harmonic potential. Dramatic discrepancies were found by comparing numerical results of the long-time expansion of BECs after being released from the harmonic trap, and measurements of the free evolution and delta-kick cooling (DKC) of a 87Rb BEC on large timescales of up to 2 s in micro-gravity (micro-g) environment such as those performed in the QUANTUS project from our group. The modification in the dynamics of a 87Rb BEC with the application of DKC by using experimentally implemented trapping geometries and the effect of gravity have been studied. Three different configurations have been considered: atom chip-based potential, dipole trap and the time-averaged orbiting potential. Such discrepancies may be crucial in high precision atom interferometry experiments in micro-g and zero-g platforms in which the implementation of DKC is mandatory to achieve the long-expansion times required
Space-time curvature signatures in Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Matos, Tonatiuh; Gomez, Eduardo
2015-05-01
We derive a generalized Gross-Pitaevski (GP) equation for a Bose Einstein Condensate (BEC) immersed in a weak gravitational field starting from the covariant Complex Klein-Gordon field in a curved space-time. We compare it with the traditional GP equation where the gravitational field is added by hand as an external potential. We show that there is a small difference of order gz/c2 between them that could be measured in the future using Bose-Einstein Condensates. This represents the next order correction to the Newtonian gravity in a curved space-time.
Bose-Einstein Condensation: A Platform for Quantum Simulation Experiments
NASA Astrophysics Data System (ADS)
Yamamoto, Yoshihisa; Takahashi, Yoshiro
Bose-Einstein condensation (BEC) of dilute atomic gases and dense exciton-polaritons provides unique experimental platforms for the simulation of quantum many-body systems in various trap and lattice structures. Atomic BEC is suitable for exploration of the thermal equilibrium and steady state properties of isolated many-body systems, while exciton-polariton BEC is suitable for study of the nonequilibrium and transient properties of open dissipative many-body systems. In this chapter, we will review the fundamental properties of these distinct Bose-Einstein condensates to provide a basis for later discussions of various quantum simulation experiments using cold atoms and exciton-polaritons.
Quantum and thermal fluctuations of trapped Bose-Einstein condensates
Kruglov, V.I.; Collett, M.J.; Olsen, M.K.
2005-09-15
We quantize a semiclassical system defined by the Hamiltonian obtained from the asymptotic self-similar solution of the Gross-Pitaevskii equation for a trapped Bose-Einstein condensate with a linear gain term. On the basis of a Schroedinger equation derived in a space of ellipsoidal parameters, we analytically calculate the quantum mechanical and thermal variance in the ellipsoidal parameters for Bose-Einstein condensates in various shapes of trap. We show that, except for temperatures close to zero, dimensionless dispersions do not depend on the frequencies of the trap and they have the same dependence on dimensionless temperatures.
Impurities in Bose-Einstein Condensates: From Polaron to Soliton.
Shadkhoo, Shahriar; Bruinsma, Robijn
2015-09-25
We propose that impurities in a Bose-Einstein condensate which is coupled to a transversely laser-pumped multimode cavity form an experimentally accessible and analytically tractable model system for the study of impurities solvated in correlated liquids and the breakdown of linear-response theory [corrected]. As the strength of the coupling constant between the impurity and the Bose-Einstein condensate is increased, which is possible through Feshbach resonance methods, the impurity passes from a large to a small polaron state, and then to an impurity-soliton state. This last transition marks the breakdown of linear-response theory. PMID:26451565
Bose-Einstein condensation mechanism in economic system
NASA Astrophysics Data System (ADS)
Xu, Jianping
2015-06-01
This paper starts from modifying the kinetic exchange model and ends with making a parallel between economic crisis and the Bose-Einstein condensation. By introducing a parameter δ, we incorporate the time influence into the Bose-Einstein statistics. And δ is found to represent the technology level in an economy. δ's growth in time enlarges the rich and poor gap and induces economic crisis in free market despite the fact that average living standard is raised. Then we find the “δ-Te-Entropy” dilemma which features a strong implication of the second law of thermodynamics. The dilemma means when an economy is isolated the entropy grows and synergetically Te and δ grow inducing the Bose-Einstein condensation, i.e., economic crisis while for open economy the dilemma breaks. Then we raise the question: What would happen if the world economy as a whole became isolated with ultimately omnibearing globalization?
Long Time Convergence of the Bose-Einstein Condensation
NASA Astrophysics Data System (ADS)
Lu, Xuguang
2016-02-01
We study long time behavior of the Bose-Einstein condensation of measure-valued solutions F_t of the space homogeneous and velocity isotropic Boltzmann equation for Bose-Einstein particles at low temperature. We prove that if F_0≥ 0 is a non-singular Borel measure on R_{≥ 0} satisfying a very low temperature condition and that the ratio F_0([0,\\varepsilon ])/\\varepsilon ^{α } is sufficiently large for all \\varepsilon in (0, R] for some constants 0<α <1, R>0, then there exists a solution F_t of the equation on [0,+∞) with the initial datum F_0 such that F_t({0}) converges to the expected Bose-Einstein condensation as t→ +∞. We also show that such initial data F_0 exist extensively.
Quantum Phase Diffusion of a Bose-Einstein Condensate
Lewenstein, M.; You, L.
1996-10-01
We discuss the quantum properties of the Bose-Einstein condensate of a dilute gas of atoms in a trap. We show that the phase of the condensate undergoes quantum diffusion which can be detected in far off-resonant light scattering experiments. {copyright} {ital 1996 The American Physical Society.}
Symmetry and inert states of spin Bose-Einstein condensates
Yip, S.-K.
2007-02-15
We construct the list of all possible inert states of spin Bose-Einstein condensates for S{<=}4. In doing so, we also obtain their symmetry properties. These results are applied to classify line defects of spin condensates in zero magnetic field.
Theoretical studies of Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Das, Kunal Kashyap
This thesis is a theoretical study of Bose-Einstein Condensation (BEC) in harmonically-trapped, weakly-interacting dilute gases. The motivation for this study is the experimental realization of BEC in trapped alkali gases since 1995. The weak inter-particle interactions and diluteness of the gases allow for a fairly accurate mean-field treatment and justifies a discrete quasi-particle description as we use in this work. This thesis considers three specific topics in the rapidly growing field of BEC theory: (i) interference effects in BEC, (ii) interaction-induced energy shifts and damping of excitations of condensates and (iii) the properties of highly anisotropic condensates. The results are summarized here: i. We show that if two multiply occupied boson modes are in eigenstates of the Hermitian relative phase operator, then the visibility of fringes formed by the interference between the modes is necessarily less than unity. For large total occupation numbers the visibility V ≤ pi/4. States with definite relative phase and unit visibility do exist. They are related to coherent states and are not orthogonal (not eigenstates of a Hermitian phase operator). This visibility limitation may make it possible to investigate experimentally the physical role of the relative phase eigenstates in interference measurements on BEC. ii. We evaluate analytically the asymptotic energy shifts of the high energy Bogoliubov quasi-particle modes. In spherical geometry, those modes display a 1/ n dependence on their number of radial nodes n but only a weak dependence on their angular momenta l. We obtain similar results for cylindrical geometry. We derive an implicit equation for the widths or decay rates gamma of the modes from an assumption of exponential decay. We use the equation to do a detailed numerical study of the trends in the behavior of the widths as a function of temperature, energy, particle number and scattering lengths. In particular, we find that widths due to
Particle Correlations in Bose-Einstein Condensates
NASA Astrophysics Data System (ADS)
Jiang, Zhang
The impact of interparticle correlations on the behavior of Bose-Einstein Condensates (BECs) is discussed using two approaches. In the first approach, the wavefunction of a BEC is encoded in the N-particle sector of an extended "catalytic state". Going to a time-dependent interaction picture, we can organize the effective Hamiltonian by powers of N -1/2 . Requiring the terms of order N 1/2 to vanish, we get the Gross-Pitaevskii Equation. Going to the next order, N0, we obtain the number-conserving Bogoliubov approximation. Our approach allows one to stay in the Schrodinger picture and to apply many techniques from quantum optics. Moreover, it is easier to track different orders in the Hamiltonian and to generalize to the multi-component case. In the second approach, I consider a state of N = l x n bosons that is derived by symmetrizing the n-fold tensor product of an arbitrary l-boson state. Particularly, we are interested in the pure state case for l = 2, which we call the Pair-Correlated State (PCS). I show that PCS reproduces the number-conserving Bogoliubov approximation; moreover, it also works in the strong interaction regime where the Bogoliubov approximation fails. For the two-site Bose-Hubbard model, I find numerically that the error (measured by trace distance of the two-particle RDMs) of PCS is less than two percent over the entire parameter space, thus making PCS a bridge between the super uid and Mott insulating phases. Amazingly, the error of PCS does not increase, in the time-dependent case, as the system evolves for longer times. I derive both time-dependent and -independent equations for the ground state and the time evolution of the PCS ansatz. The time complexity of simulating PCS does not depend on N and is linear in the number of orbitals in use. Compared to other methods, e.g, the Jastrow wavefunction, the Gutzwiller wavefunction, and the multi-configurational time-dependent Hartree method, our approach does not require quantum Monte Carlo nor
Observation of Vortex Phase Singularities in Bose-Einstein Condensates
Inouye, S.; Gupta, S.; Rosenband, T.; Chikkatur, A. P.; Goerlitz, A.; Gustavson, T. L.; Leanhardt, A. E.; Pritchard, D. E.; Ketterle, W.
2001-08-20
We have observed phase singularities due to vortex excitation in Bose-Einstein condensates. Vortices were created by moving a laser beam through a condensate. They were observed as dislocations in the interference fringes formed by the stirred condensate and a second unperturbed condensate. The velocity dependence for vortex excitation and the time scale for re-establishing a uniform phase across the condensate were determined.
Bouncing motion and penetration dynamics in multicomponent Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Eto, Yujiro; Takahashi, Masahiro; Nabeta, Keita; Okada, Ryotaro; Kunimi, Masaya; Saito, Hiroki; Hirano, Takuya
2016-03-01
We investigate the dynamic properties of bouncing and penetration in colliding binary and ternary Bose-Einstein condensates comprised of different Zeeman or hyperfine states of 87Rb. Through the application of magnetic field gradient pulses, two- or three-component condensates in an optical trap are spatially separated and then made to collide. The subsequent evolutions are classified into two categories: repeated bouncing motion and mutual penetration after damped bounces. We experimentally observed mutual penetration for immiscible condensates, bouncing between miscible condensates, and domain formation for miscible condensates. From numerical simulations of the Gross-Pitaevskii equation, we find that the penetration time can be tuned by slightly changing the atomic interaction strengths.
Observation of Vortex Nucleation in a Rotating Two-Dimensional Lattice of Bose-Einstein Condensates
Williams, R. A.; Al-Assam, S.; Foot, C. J.
2010-02-05
We report the observation of vortex nucleation in a rotating optical lattice. A {sup 87}Rb Bose-Einstein condensate was loaded into a static two-dimensional lattice and the rotation frequency of the lattice was then increased from zero. We studied how vortex nucleation depended on optical lattice depth and rotation frequency. For deep lattices above the chemical potential of the condensate we observed a linear dependence of the number of vortices created with the rotation frequency, even below the thermodynamic critical frequency required for vortex nucleation. At these lattice depths the system formed an array of Josephson-coupled condensates. The effective magnetic field produced by rotation introduced characteristic relative phases between neighboring condensates, such that vortices were observed upon ramping down the lattice depth and recombining the condensates.
Bose-Einstein condensates: BECs from the fridge
NASA Astrophysics Data System (ADS)
Friedrich, Bretislav
2009-10-01
Large ensembles of atoms can be buffer-gas loaded into a magnetic trap and further evaporatively cooled all the way down to quantum degeneracy. The approach has now been shown to provide an alternative - and potentially general - route to Bose-Einstein condensation.
Feshbach resonance and growth of a Bose-Einstein condensate
Yuce, C.; Kilic, A.
2006-09-15
The Gross-Pitaevskii gain equation is used to model atom laser and Bose-Einstein condensation (BEC) fed by the surrounding thermal cloud. It is shown that the number of atoms continuously injected into BEC from the reservoir can be controlled by applying the external magnetic field via Feshbach resonance.
Bose-Einstein condensates from scalar field dark matter
Urena-Lopez, L. Arturo
2010-12-07
We review the properties of astrophysical and cosmological relevance that may arise from the bosonic nature of scalar field dark matter models. The key property is the formation of Bose-Einstein condensates, but we also consider the presence of non-empty excited states that may be relevant for the description of scalar field galaxy halos and the properties of rotation curves.
Entanglement Properties in Two-Component Bose-Einstein Condensate
NASA Astrophysics Data System (ADS)
Jiang, Di-You
2016-05-01
We investigate entanglement inseparability and bipartite entanglement of in two-component Bose-Einstein condensate in the presence of the nonlinear interatomic interaction, interspecies interaction. Entanglement inseparability and bipartite entanglement have the similar properties. More entanglement can be generated by adjusting the nonlinear interatomic interaction and control the time interval of the entanglement by adjusting interspecies interaction.
Stability of nonstationary states of spin-1 Bose-Einstein condensates
Maekelae, H.; Lundh, E.; Johansson, M.; Zelan, M.
2011-10-15
The stability of nonstationary states of homogeneous spin-1 Bose-Einstein condensates is studied by performing Bogoliubov analysis in a frame of reference where the state is stationary. In particular, the effect of an external magnetic field is examined. It is found that a nonzero magnetic field introduces instability in a {sup 23}Na condensate. The wavelengths of this instability can be controlled by tuning the strength of the magnetic field. In a {sup 87}Rb condensate this instability is present already at zero magnetic field. Furthermore, an analytical bound for the size of a stable condensate is found, and a condition for the validity of the single-mode approximation is presented. Realization of the system in a toroidal trap is discussed, and the full time development is simulated.
Bose-Einstein Condensation of {sup 84}Sr
Martinez de Escobar, Y. N.; Mickelson, P. G.; Yan, M.; DeSalvo, B. J.; Nagel, S. B.; Killian, T. C.
2009-11-13
We report Bose-Einstein condensation of {sup 84}Sr in an optical dipole trap. Efficient laser cooling on the narrow intercombination line and an ideal s-wave scattering length allow the creation of large condensates (N{sub 0}approx3x10{sup 5}) even though the natural abundance of this isotope is only 0.6%. Condensation is heralded by the emergence of a low-velocity component in time-of-flight images.
Thermal spin fluctuations in spinor Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Melé-Messeguer, M.; Juliá-Díaz, B.; Polls, A.; Santos, L.
2013-03-01
We study the thermal activation of spin fluctuations in dynamically stable spinor Bose-Einstein condensates. We analyze the specific cases of a nondipolar spin-1 condensate in the state m=0, where thermal activation results from spin-changing collisions, and of a chromium condensate in the maximally stretched state m=-3, where thermal spin fluctuations are due to dipole-induced spin relaxation. In both cases, we show that the low energy associated to the spinor physics may be employed for thermometry purposes down to extremely low temperatures, typically impossible to measure in Bose-Einstein condensates with the usual thermometric techniques. Moreover, the peculiar dependence of the system's entropy with the applied Zeeman energy opens a possible route for adiabatic cooling.
Controlling chaos in the Bose-Einstein condensate
Cong Fuzhong Wang Zhixia; Hua Hongtu; Pang Shichun; Tong Shouyu
2012-03-15
The spatial structure of the Bose-Einstein condensate (BEC) is investigated and spatially chaotic distributions of the condensates are revealed. By means of changing the s-wave scattering length with a Feshbach resonance, the chaotic behavior can be well controlled to enter into periodicity. Numerical simulation shows that there are different periodic orbits according to different s-wave scattering lengths only if the Lyapunov exponent of the system is negative.
Bose-Einstein condensation of {sup 86}Sr
Stellmer, Simon; Grimm, Rudolf; Tey, Meng Khoon; Schreck, Florian
2010-10-15
We report on the attainment of Bose-Einstein condensation of {sup 86}Sr. This isotope has a scattering length of about +800a{sub 0} and thus suffers from fast three-body losses. To avoid detrimental atom loss, evaporative cooling is performed at low densities around 3x10{sup 12} cm{sup -3} in a large volume optical dipole trap. We obtain almost pure condensates of 5x10{sup 3} atoms.
Beyond Spontaneously Broken Symmetry in Bose-Einstein Condensates
Mullin, W. J.; Laloee, F.
2010-04-16
Spontaneous symmetry breaking (SSB) for Bose-Einstein condensates cannot treat phase off-diagonal effects, and thus cannot explain Bell inequality violations. We describe another situation that is beyond a SSB treatment: an experiment where particles from two (possibly macroscopic) condensate sources are used for conjugate measurements of the relative phase and populations. Off-diagonal phase effects are characterized by a 'quantum angle' and observed via 'population oscillations', signaling quantum interference of macroscopically distinct states.
Optimization of evaporative cooling towards a large number of Bose-Einstein-condensed atoms
Yamashita, Makoto; Mukai, Tetsuya; Mukai, Takaaki; Koashi, Masato; Mitsunaga, Masaharu; Imoto, Nobuyuki
2003-02-01
We study the optimization of evaporative cooling in trapped bosonic atoms on the basis of quantum kinetic theory of a Bose gas. The optimized cooling trajectory for {sup 87}Rb atoms indicates that the acceleration of evaporative cooling around the transition point of Bose-Einstein condensation is very effective against loss of trapped atoms caused by three-body recombination. The number of condensed atoms is largely enhanced by the optimization, more than two orders of magnitude in our present calculation using relevant experimental parameters, as compared with the typical value given by the conventional evaporative cooling where the frequency of radio-frequency magnetic field is swept exponentially. In addition to this optimized cooling, it is also shown that highly efficient evaporative cooling can be achieved by an initial exponential and then a rapid linear sweep of frequency.
Impurity driven diffusion and destruction of solitons in quasi-1D Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Aycock, Lauren; Hurst, Hilary; Lu, Hsin-I.; Genkina, Dina; Spielman, Ian
2016-05-01
Current experimental research on solitons focuses on their collisions with each other and how dimensionality influences their stability and decay. Here, we investigate the effect of evenly distributed impurity atoms on soliton dynamics. We launch lone, long-lived solitons in highly elongated 87 Rb Bose-Einstein condensates (BECs) by phase imprinting and observe oscillations stable over many seconds. We compare these long-lived solitons to those launched in BECs containing a few percent of impurity-the same atomic species in a different Zeeman sublevel-controllably introduced just before evaporation to degeneracy. These impurities - evenly distributed throughout the condensate - dramatically decrease the soliton lifetime and enhance Brownian-like diffusion in the soliton's trajectory.
Time-orbiting potential trap for Bose-Einstein condensate interferometry
Reeves, J. M.; Garcia, O.; Deissler, B.; Baranowski, K. L.; Hughes, K. J.; Sackett, C. A.
2005-11-15
We describe an atom trap for Bose-Einstein condensates of {sup 87}Rb to be used in atom interferometry experiments. The trap is based on a time-orbiting potential waveguide. It supports the atoms against gravity while providing weak confinement to minimize interaction effects. We observe harmonic oscillation frequencies ({omega}{sub x},{omega}{sub y},{omega}{sub z}) as low as 2{pi}x(6.0,1.2,3.3) Hz. Up to 2x10{sup 4} condensate atoms have been loaded into the trap, at estimated temperatures as low as 850 pK. We anticipate that interferometer measurement times of 1 s or more should be achievable in this device.
Coherent magnon optics in a ferromagnetic spinor Bose-Einstein condensate.
Marti, G Edward; MacRae, Andrew; Olf, Ryan; Lourette, Sean; Fang, Fang; Stamper-Kurn, Dan M
2014-10-10
We measure the dispersion relation, gap, and magnetic moment of a magnon in the ferromagnetic F = 1 spinor Bose-Einstein condensate of (87)Rb. From the dispersion relation we measure an average effective mass 1.033(2)(stat)(10)(sys) times the atomic mass, as determined by interfering standing and running coherent magnon waves within the dense and trapped condensed gas. The measured mass is higher than theoretical predictions of mean-field and beyond-mean-field Beliaev theory for a bulk spinor Bose gas with s-wave contact interactions. We observe a magnon energy gap of h × 2.5(1)(stat)(2)(sys) Hz, which is consistent with the predicted effect of magnetic dipole-dipole interactions. These dipolar interactions may also account for the high magnon mass. The effective magnetic moment of -1.04(2)(stat)(8)(sys) times the atomic magnetic moment is consistent with mean-field theory. PMID:25375719
Entanglement entropy and mutual information in Bose-Einstein condensates
Ding Wenxin; Yang Kun
2009-07-15
In this paper we study the entanglement properties of free nonrelativistic Bose gases. At zero temperature, we calculate the bipartite block entanglement entropy of the system and find that it diverges logarithmically with the particle number in the subsystem. For finite temperatures, we study the mutual information between the two blocks. We first analytically study an infinite-range hopping model, then numerically study a set of long-range hopping models in one dimension that exhibit Bose-Einstein condensation. In both cases we find that a Bose-Einstein condensate, if present, makes a divergent contribution to the mutual information which is proportional to the logarithm of the number of particles in the condensate in the subsystem. The prefactor of the logarithmic divergent term is model dependent.
Electronic pumping of quasiequilibrium Bose-Einstein-condensed magnons.
Bender, Scott A; Duine, Rembert A; Tserkovnyak, Yaroslav
2012-06-15
We theoretically investigate spin transfer between a system of quasiequilibrated Bose-Einstein-condensed magnons in an insulator in direct contact with a conductor. While charge transfer is prohibited across the interface, spin transport arises from the exchange coupling between insulator and conductor spins. In a normal insulator phase, spin transport is governed solely by the presence of thermal and spin-diffusive gradients; the presence of Bose-Einstein condensation (BEC), meanwhile, gives rise to a temperature-independent condensate spin current. Depending on the thermodynamic bias of the system, spin may flow in either direction across the interface, engendering the possibility of a dynamical phase transition of magnons. We discuss the experimental feasibility of observing a BEC steady state (fomented by a spin Seebeck effect), which is contrasted to the more familiar spin-transfer-induced classical instabilities. PMID:23004301
Interferometry with Bose-Einstein condensates in microgravity.
Müntinga, H; Ahlers, H; Krutzik, M; Wenzlawski, A; Arnold, S; Becker, D; Bongs, K; Dittus, H; Duncker, H; Gaaloul, N; Gherasim, C; Giese, E; Grzeschik, C; Hänsch, T W; Hellmig, O; Herr, W; Herrmann, S; Kajari, E; Kleinert, S; Lämmerzahl, C; Lewoczko-Adamczyk, W; Malcolm, J; Meyer, N; Nolte, R; Peters, A; Popp, M; Reichel, J; Roura, A; Rudolph, J; Schiemangk, M; Schneider, M; Seidel, S T; Sengstock, K; Tamma, V; Valenzuela, T; Vogel, A; Walser, R; Wendrich, T; Windpassinger, P; Zeller, W; van Zoest, T; Ertmer, W; Schleich, W P; Rasel, E M
2013-03-01
Atom interferometers covering macroscopic domains of space-time are a spectacular manifestation of the wave nature of matter. Because of their unique coherence properties, Bose-Einstein condensates are ideal sources for an atom interferometer in extended free fall. In this Letter we report on the realization of an asymmetric Mach-Zehnder interferometer operated with a Bose-Einstein condensate in microgravity. The resulting interference pattern is similar to the one in the far field of a double slit and shows a linear scaling with the time the wave packets expand. We employ delta-kick cooling in order to enhance the signal and extend our atom interferometer. Our experiments demonstrate the high potential of interferometers operated with quantum gases for probing the fundamental concepts of quantum mechanics and general relativity. PMID:23496709
Bose-Einstein condensates and scalar fields; exploring the similitudes
NASA Astrophysics Data System (ADS)
Castellanos, E.; Macías, A.; Núñez, D.
2014-01-01
We analyze the the remarkable analogy between the classical Klein-Gordon equation for a test scalar field in a flat and also in a curved background, and the Gross-Pitaevskii equation for a Bose-Einstein condensate trapped by an external potential. We stress here that the solution associated with the Klein-Gordon equation (KG) in a flat space time has the same mathematical structure, under certain circumstances, to those obtained for the Gross-Pitaevskii equation, that is, a static soliton solution. Additionally, Thomas-Fermi approximation is applied to the 3-dimensional version of this equation, in order to calculate some thermodynamical properties of the system in curved a space-time back ground. Finally, we stress the fact that a gravitational background provides, in some cases, a kind of confining potential for the scalar field, allowing us to remarks even more the possible connection between scalar fields and the phenomenon of Bose-Einstein condensation.
Scalar field as a Bose-Einstein condensate?
Castellanos, Elías; Escamilla-Rivera, Celia; Macías, Alfredo; Núñez, Darío E-mail: cescamilla@mctp.mx E-mail: nunez@nucleares.unam.mx
2014-11-01
We discuss the analogy between a classical scalar field with a self-interacting potential, in a curved spacetime described by a quasi-bounded state, and a trapped Bose-Einstein condensate. In this context, we compare the Klein-Gordon equation with the Gross-Pitaevskii equation. Moreover, the introduction of a curved background spacetime endows, in a natural way, an equivalence to the Gross-Pitaevskii equation with an explicit confinement potential. The curvature also induces a position dependent self-interaction parameter. We exploit this analogy by means of the Thomas-Fermi approximation, commonly used to describe the Bose-Einstein condensate, in order to analyze the quasi bound scalar field distribution surrounding a black hole.
Interferometry with Bose-Einstein Condensates in Microgravity
NASA Astrophysics Data System (ADS)
Müntinga, H.; Ahlers, H.; Krutzik, M.; Wenzlawski, A.; Arnold, S.; Becker, D.; Bongs, K.; Dittus, H.; Duncker, H.; Gaaloul, N.; Gherasim, C.; Giese, E.; Grzeschik, C.; Hänsch, T. W.; Hellmig, O.; Herr, W.; Herrmann, S.; Kajari, E.; Kleinert, S.; Lämmerzahl, C.; Lewoczko-Adamczyk, W.; Malcolm, J.; Meyer, N.; Nolte, R.; Peters, A.; Popp, M.; Reichel, J.; Roura, A.; Rudolph, J.; Schiemangk, M.; Schneider, M.; Seidel, S. T.; Sengstock, K.; Tamma, V.; Valenzuela, T.; Vogel, A.; Walser, R.; Wendrich, T.; Windpassinger, P.; Zeller, W.; van Zoest, T.; Ertmer, W.; Schleich, W. P.; Rasel, E. M.
2013-03-01
Atom interferometers covering macroscopic domains of space-time are a spectacular manifestation of the wave nature of matter. Because of their unique coherence properties, Bose-Einstein condensates are ideal sources for an atom interferometer in extended free fall. In this Letter we report on the realization of an asymmetric Mach-Zehnder interferometer operated with a Bose-Einstein condensate in microgravity. The resulting interference pattern is similar to the one in the far field of a double slit and shows a linear scaling with the time the wave packets expand. We employ delta-kick cooling in order to enhance the signal and extend our atom interferometer. Our experiments demonstrate the high potential of interferometers operated with quantum gases for probing the fundamental concepts of quantum mechanics and general relativity.
Kinetic Evolution and Bose-Einstein Condensation in the Glasma
NASA Astrophysics Data System (ADS)
Liao, Jinfeng
2013-10-01
We study the evolution of a dense system of gluons, such as those produced in the early stages (the Glasma) of ultra-relativistic heavy ion collisions. We describe the approach to thermal equilibrium using the small angle approximation for gluon scattering in a Boltzmann equation that includes the effects of Bose statistics. Simple power counting arguments indicate that the gluon system as in the Glasma is over-occupied and driven towards the formation of a Bose-Einstein condensate. We derive and solve the transport equation for initial conditions that correspond to the overpopulated Glasma and present numerical evidence that such over-populated systems reach the onset of Bose-Einstein condensation in a finite time. The approach to condensation is characterized by a scaling behavior that we briefly analyze. Finally we analyze the effects of the inelastic, number changing, processes on the dynamical formation of the Bose-Einstein condensate by analytically deriving the 2 <--> 3 kernel under the collinear and small angle approximations and numerically solving it. References: J. Blaizot, J. Liao and L. McLerran, arXiv:1305.2119; X. Huang and J. Liao, arXiv:1303.7214; J. Blaizot, F. Gelis, J. Liao, L. McLerran and R. Venugopalan, arXiv:1107.5296. I thank the RIKEN BNL Research Center for partial support.
Symbiotic solitons in heteronuclear multicomponent Bose-Einstein condensates
Perez-Garcia, Victor M.; Beitia, Juan Belmonte
2005-09-15
We show that bright solitons exist in quasi-one-dimensional heteronuclear multicomponent Bose-Einstein condensates with repulsive self-interaction and attractive interspecies interaction. They are remarkably robust to perturbations of initial data and collisions and can be generated by the mechanism of modulational instability. Some possibilities for control and the behavior of the system in fully three-dimensional scenarios are also discussed.
Bose-Einstein-condensate interferometer with macroscopic arm separation
Garcia, O.; Deissler, B.; Hughes, K. J.; Reeves, J. M.; Sackett, C. A.
2006-09-15
A Michelson interferometer using Bose-Einstein condensates is demonstrated with coherence times of up to 44 ms and arm separations up to 180 {mu}m. This arm separation is larger than that observed for any previous atom interferometer. The device uses atoms weakly confined in a magnetic guide and the atomic motion is controlled using Bragg interactions with an off-resonant standing-wave laser beam.
Magnons as a Bose-Einstein Condensate in Nanocrystalline Gadolinium
Kaul, S. N.; Mathew, S. P.
2011-06-17
The recent observation [S. P. Mathew et al., J. Phys. Conf. Ser. 200, 072047 (2010)] of the anomalous softening of spin-wave modes at low temperatures in nanocrystalline gadolinium is interpreted as a Bose-Einstein condensation (BEC) of magnons. A self-consistent calculation, based on the BEC picture, is shown to closely reproduce the observed temperature variations of magnetization and specific heat at constant magnetic fields.
Spin-Mixing Interferometry with Bose-Einstein Condensates
NASA Astrophysics Data System (ADS)
Gabbrielli, Marco; Pezzè, Luca; Smerzi, Augusto
2015-10-01
Unstable spinor Bose-Einstein condensates are ideal candidates to create nonlinear three-mode interferometers. Our analysis goes beyond the standard SU(1,1) parametric approach and therefore provides the regime of parameters where sub-shot-noise sensitivities can be reached with respect to the input total average number of particles. Decoherence due to particle losses and finite detection efficiency are also considered.
Spin-Mixing Interferometry with Bose-Einstein Condensates.
Gabbrielli, Marco; Pezzè, Luca; Smerzi, Augusto
2015-10-16
Unstable spinor Bose-Einstein condensates are ideal candidates to create nonlinear three-mode interferometers. Our analysis goes beyond the standard SU(1,1) parametric approach and therefore provides the regime of parameters where sub-shot-noise sensitivities can be reached with respect to the input total average number of particles. Decoherence due to particle losses and finite detection efficiency are also considered. PMID:26550872
Inhibition of Coherence in Trapped Bose-Einstein Condensates
Imamoglu, A.; Lewenstein, M.
1997-03-01
We analyze the dependence of the collapse and revival of many-atom coherence of a trapped Bose-Einstein condensate on the trap potential, dimensionality of the gas, and atom number fluctuations. We show that in a class of experimentally relevant systems the collapse time vanishes in the limit of a large number of atoms, implying that the trapped Bose gas cannot sustain a well-defined quantum phase. {copyright} {ital 1997} {ital The American Physical Society}
Anisotropic Solitons in Dipolar Bose-Einstein Condensates
Tikhonenkov, I.; Vardi, A.; Malomed, B. A.
2008-03-07
Starting with a Gaussian variational ansatz, we predict anisotropic bright solitons in quasi-2D Bose-Einstein condensates consisting of atoms with dipole moments polarized perpendicular to the confinement direction. Unlike isotropic solitons predicted for the moments aligned with the confinement axis [Phys. Rev. Lett. 95, 200404 (2005)], no sign reversal of the dipole-dipole interaction is necessary to support the solitons. Direct 3D simulations confirm their stability.
Stable Hopf solitons in rotating Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Bidasyuk, Y. M.; Chumachenko, A. V.; Prikhodko, O. O.; Vilchinskii, S. I.; Weyrauch, M.; Yakimenko, A. I.
2015-11-01
We reveal that Hopf solitons can be stabilized in rotating atomic Bose-Einstein condensates. The Hopfion is a matter-wave vortex complex which carries two independent winding numbers. Such a topological solitonic structure results from a superfluid flow of atoms simultaneously quantized in poloidal and toroidal directions. In the framework of a dissipative mean-field model we observe different unstable evolution scenarios of the Hopfions. We demonstrate energetic and dynamical stability of the Hopf solitons under experimentally feasible conditions.
Fidelity Decay in Trapped Bose-Einstein Condensates
Manfredi, G.; Hervieux, P.-A.
2008-02-08
The quantum coherence of a Bose-Einstein condensate is studied using the concept of quantum fidelity (Loschmidt echo). The condensate is confined in an elongated anharmonic trap and subjected to a small random potential such as that created by a laser speckle. Numerical experiments show that the quantum fidelity stays constant until a critical time, after which it drops abruptly over a single trap oscillation period. The critical time depends logarithmically on the number of condensed atoms and on the perturbation amplitude. This behavior may be observable by measuring the interference fringes of two condensates evolving in slightly different potentials.
NASA Astrophysics Data System (ADS)
Wang, Deng-Shan; Han, Wei; Shi, Yuren; Li, Zaidong; Liu, Wu-Ming
2016-07-01
The spin-1 Bose-Einstein condensates trapped in a standing light wave can be described by three coupled Gross-Pitaevskii equations with a periodic potential. In this paper, nine families of stationary solutions without phase structures in the form of Jacobi elliptic functions are proposed, and their stabilities are analyzed by both linear stability analysis and dynamical evolutions. Taking the ferromagnetic 87Rb atoms and antiferromagnetic (polar) 23Na atoms as examples, we investigate the stability regions of the nine stationary solutions, which are given in term of elliptic modulus k. It is shown that for the same stationary solution the stability regions of condensates with antiferromagnetic (polar) spin-dependent interactions are larger than that of the condensates with ferromagnetic ones. The dn-dn-dn stationary solution is the most stable solution among the nine families of stationary solutions. Moreover, in the same standing light wave, the spin-1 Bose-Einstein condensates are more stable than the scalar Bose-Einstein condensate.
Controllable high bandwidth storage of optical information in a Bose-Einstein Condensate
NASA Astrophysics Data System (ADS)
Jayaseelan, Maitreyi; Schultz, Justin T.; Murphree, Joseph D.; Hansen, Azure; Bigelow, Nicholas P.
2016-05-01
The storage and retrieval of optical information has been of interest for a variety of applications including quantum information processing, quantum networks and quantum memories. Several schemes have been investigated and realized with weak, narrowband pulses, including techniques using EIT in solid state systems and both hot and cold atomic vapors. In contrast, we investigate the storage and manipulation of strong, high bandwidth pulses in a Bose-Einstein Condensate (BEC) of ultracold 87 Rb atoms. As a storage medium for optical pulses, BECs offer long storage times and preserve the coherence properties of the input information, suppressing unwanted thermal decoherence effects. We present numerical simulations of nanosecond pulses addressing a three-level lambda system on the D2 line of 87 Rb. The signal pulse is stored as a localized spin excitation in the condensate and can be moved or retrieved by reapplication of successive control pulses. The relative Rabi frequencies and areas of the pulses and the local atomic density in the condensate determine the storage location and readout of the signal pulse. Extending this scheme to use beams with a variety of spatial modes such as Hermite- and Laguerre-Gaussian modes offers an expanded alphabet for information storage.
Behaviour of Rotating Bose Einstein Condensates Under Shrinking
NASA Astrophysics Data System (ADS)
Zhai, Hui; Zhou, Qi
2005-01-01
When the repulsive interaction strength between atoms decreases, the size of a rotating Bose-Einstein condensate will consequently shrink. We find that the rotational frequency will increase during the shrinking of condensate, which is a quantum mechanical analogy to ballet dancing. Compared to a non-rotating condensate, the size of a rotating BEC will eventually be saturated at a finite value when the interaction strength is gradually reduced. We also calculate the vortex dynamics induced by the atomic current, and discuss the difference of vortex dynamics in this case and that observed in a recent experiment carried out by the JILA group [Phys. Rev. Lett. 90 (2003) 170405].
Controlling quasiparticle excitations in a trapped Bose-Einstein condensate
Woo, S.J.; Choi, S.; Bigelow, N.P.
2005-08-15
We describe an approach to quantum control of the quasiparticle excitations in a trapped Bose-Einstein condensate based on adiabatic and diabatic changes in the trap anisotropy. We describe our approach in the context of the Landau-Zener transition at the avoided crossings in the quasiparticle excitation spectrum. We find also that there can be population oscillation between different modes at the specific aspect ratios of the trapping potential at which the mode energies are almost degenerate. These effects may have implications in the expansion of an excited condensate as well as the dynamics of a moving condensate in an atomic waveguide with a varying width.
1 and 2 Dimensional Bose Einstein Condensates
NASA Astrophysics Data System (ADS)
Vogels, Johnny; Gorlitz, Axel; Raman, Chandra; Gustavson, Todd; Drndic, Marija; Leanhardt, Aaron; Abo-Shaeer, Jamil; Loew, Robert; Ketterle, Wolfgang
2001-05-01
We have created condensates in which the zero point motion exceeds the mean field enegy in either 2 (1D-condensate) or 1 dimension (2D-condensate). We describe the optical traps and magnetic traps being used, their limitations, and the regimes that are accessible. Some of our 1D condensates should have limited coherence properties (quasi-condensates).
Spinor condensate of {sup 87}Rb as a dipolar gas
Swislocki, Tomasz; Gajda, Mariusz; RzaPzewski, Kazimierz
2010-03-15
We consider a spinor condensate of {sup 87}Rb atoms in the F=1 hyperfine state confined in an optical dipole trap. Putting initially all atoms in the m{sub F}=0 component, we find that the system evolves toward a state of thermal equilibrium with kinetic energy equally distributed among all magnetic components. We show that this process is dominated by the dipolar interaction of magnetic spins rather than spin-mixing contact potential. Our results show that because of a dynamical separation of magnetic components, the spin-mixing dynamics in the {sup 87}Rb condensate is governed by the dipolar interaction which plays no role in a single-component rubidium system in a magnetic trap.
Winding up superfluid in a torus via Bose Einstein condensation
Das, Arnab; Sabbatini, Jacopo; Zurek, Wojciech H
2010-12-16
We simulate Bose-Einstein condensation at finite temperature in a ring employing stochastic Gross-Pitaevskii equation and show that cooling through the critical point can generate topologically stable quantized circulation of the newborn condensate around the ring. The resulting winding numbers exhibiting Gaussian distribution with dispersion following scaling behavior predicted by the Kibble-Zurek mechanism (KZM). This opens up possibilities for direct experimental study of the underlying phase transition and the basic principles of KZM extended to account for such circulations. We discuss the effect of inhomogeneity on the above phenomenon by considering the effect of tilting of the ring in the gravitational field.
Observation of Faraday Waves in a Bose-Einstein Condensate
NASA Astrophysics Data System (ADS)
Engels, Peter; Atherton, Collin; Hoefer, Mark
2007-06-01
Faraday waves in a cigar-shaped Bose-Einstein condensate are created. It is shown that periodically modulating the transverse confinement, and thus the nonlinear interactions in the BEC, excites small amplitude longitudinal oscillations through a parametric resonance. It is also demonstrated that even without the presence of a continuous drive, an initial transverse breathing mode excitation of the condensate leads to spontaneous pattern formation in the longitudinal direction. Finally, the effects of strongly driving the transverse breathing mode with large amplitude are investigated. In this case, impact-oscillator behavior and intriguing nonlinear dynamics, including the gradual emergence of multiple longitudinal modes, are observed.
Observation of Faraday Waves in a Bose-Einstein Condensate
NASA Astrophysics Data System (ADS)
Engels, P.; Atherton, C.; Hoefer, M. A.
2007-03-01
Faraday waves in a cigar-shaped Bose-Einstein condensate are created. It is shown that periodically modulating the transverse confinement, and thus the nonlinear interactions in the BEC, excites small amplitude longitudinal oscillations through a parametric resonance. It is also demonstrated that even without the presence of a continuous drive, an initial transverse breathing mode excitation of the condensate leads to spontaneous pattern formation in the longitudinal direction. Finally, the effects of strongly driving the transverse breathing mode with large amplitude are investigated. In this case, impact-oscillator behavior and intriguing nonlinear dynamics, including the gradual emergence of multiple longitudinal modes, are observed.
Parametric-squeezing amplification of Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Jäger, Georg; Berrada, Tarik; Schmiedmayer, Jörg; Schumm, Thorsten; Hohenester, Ulrich
2015-11-01
We theoretically investigate the creation of squeezed states of a Bose-Einstein condensate (BEC) trapped in a magnetic double-well potential. The number or phase squeezed states are created by modulating the tunnel coupling between the two wells periodically with twice the Josephson frequency, i.e., through parametric amplification. Simulations are performed with the multiconfigurational time-dependent Hartree method for bosons. We employ optimal control theory to bring the condensate to a complete halt at a final time, thus creating a highly squeezed state (squeezing factor of 0.12, ξS2=-18 dB) suitable for atom interferometry.
Superfluidity and Critical Velocities in Nonequilibrium Bose-Einstein Condensates
NASA Astrophysics Data System (ADS)
Wouters, Michiel; Carusotto, Iacopo
2010-07-01
We theoretically study the superfluidity properties of a nonequilibrium Bose-Einstein condensate of exciton polaritons in a semiconductor microcavity under incoherent pumping. The dynamics of the condensate is described at mean-field level in terms of a generalized Gross-Pitaevskii equation. The drag force on a small moving object and the onset of fringes in the density profile are shown to have a sharp threshold as a function of the velocity; a generalized Landau criterion is developed to explain this behavior in terms of the dispersion of elementary excitations. Metastability of supercurrents in multiply-connected geometries is shown to persist up to higher flow speeds.
Superfluidity and Critical Velocities in Nonequilibrium Bose-Einstein Condensates
Wouters, Michiel; Carusotto, Iacopo
2010-07-09
We theoretically study the superfluidity properties of a nonequilibrium Bose-Einstein condensate of exciton polaritons in a semiconductor microcavity under incoherent pumping. The dynamics of the condensate is described at mean-field level in terms of a generalized Gross-Pitaevskii equation. The drag force on a small moving object and the onset of fringes in the density profile are shown to have a sharp threshold as a function of the velocity; a generalized Landau criterion is developed to explain this behavior in terms of the dispersion of elementary excitations. Metastability of supercurrents in multiply-connected geometries is shown to persist up to higher flow speeds.
Nonlinear effects in interference of bose-einstein condensates
Liu; Wu; Niu
2000-03-13
Nonlinear effects in the interference of Bose-Einstein condensates are studied using exact solutions of the one-dimensional nonlinear Schrodinger equation, which is applicable when the lateral motion is confined or negligible. With the inverse scattering method, the interference pattern is studied as a scattering problem with the linear Schrodinger equation, whose potential is profiled by the initial density distribution of the condensates. Our theory not only provides an analytical framework for quantitative predictions for the one-dimensional case, it also gives an intuitive understanding of some mysterious features of the interference patterns observed in experiments and numerical simulations. PMID:11018868
Large magnetic storage ring for Bose-Einstein condensates
Arnold, A. S.; Garvie, C. S.; Riis, E.
2006-04-15
Cold atomic clouds and Bose-Einstein condensates have been stored in a 10 cm diameter vertically oriented magnetic ring. An azimuthal magnetic field enables low-loss propagation of atomic clouds over a total distance of 2 m, with a heating rate of less than 50 nK/s. The vertical geometry was used to split an atomic cloud into two counter-rotating clouds which were recombined after one revolution. The system will be ideal for studying condensate collisions and ultimately Sagnac interferometry.
Avoiding infrared catastrophes in trapped Bose-Einstein condensates
Kevrekidis, P.G.; Theocharis, G.; Frantzeskakis, D.J.; Trombettoni, A.
2004-08-01
This paper is concerned with the long-wavelength instabilities (infrared catastrophes) occurring in Bose-Einstein condensates (BECs). We examine the modulational instability in 'cigar-shaped' (one-dimensional) attractive BECs and the transverse instability of dark solitons in 'pancake' (two-dimensional) repulsive BECs. We suggest mechanisms, and give explicit estimates, on how to engineer the trapping conditions of the condensate to avoid such instabilities: the main result being that a tight enough trapping potential suppresses the instabilities present in the homogeneous limit. We compare the obtained estimates with numerical results and we highlight the relevant regimes of dynamical behavior.
Fragmentation of Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Mueller, Erich J.; Ho, Tin-Lun; Ueda, Masahito; Baym, Gordon
2006-09-01
We present the theory of bosonic systems with multiple condensates, providing a unified description of various model systems that are found in the literature. We discuss how degeneracies, interactions, and symmetries conspire to give rise to this unusual behavior. We show that as degeneracies multiply, so do the varieties of fragmentation, eventually leading to strongly correlated states with no trace of condensation.
Coherence and Squeezing of Bose-Einstein Condensates in Double Wells
NASA Astrophysics Data System (ADS)
Yi, Xiao-jie
2016-05-01
We investigate coherence and squeezing of a two-mode Bose-Einstein condensate trapped in a double-well potential. By analytically deriving the form of coherence and numerically calculating the squeezing parameter, we show that the coherence and the squeezing may be controlled by adjusting some parameters of the two-mode Bose-Einstein condensate.
Dirac Monopoles in a Bose-Einstein Condensate
NASA Astrophysics Data System (ADS)
Hall, David
2014-05-01
Over eighty years ago, Dirac established a theory of magnetic monopoles consistent with both classical electrodynamics and quantum mechanics. I will discuss Dirac's theory and a recent realization of its essential features, including a monopole, in the context of the synthetic electric and magnetic fields supported by a spinor Bose-Einstein condensate. This material is based upon work supported by the National Science Foundation under grants nos. PHY-0855475 and PHY-1205822, by the Academy of Finland through its Centres of Excellence Program (grant no. 251748) and grants nos. 135794, 272806 and 141015.
Observation of Solitonic Vortices in Bose-Einstein Condensates
NASA Astrophysics Data System (ADS)
Donadello, Simone; Serafini, Simone; Tylutki, Marek; Pitaevskii, Lev P.; Dalfovo, Franco; Lamporesi, Giacomo; Ferrari, Gabriele
2014-08-01
We observe solitonic vortices in an atomic Bose-Einstein condensate (BEC) after free expansion. Clear signatures of the nature of such defects are the twisted planar density depletion around the vortex line, observed in absorption images, and the double dislocation in the interference pattern obtained through homodyne techniques. Both methods allow us to determine the sign of the quantized circulation. Experimental observations agree with numerical simulations. These solitonic vortices are the decay product of phase defects of the BEC order parameter spontaneously created after a rapid quench across the BEC transition in a cigar-shaped harmonic trap and are shown to have a very long lifetime.
Analytic vortex dynamics in an annular Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Toikka, L. A.; Suominen, K.-A.
2016-05-01
We consider analytically the dynamics of an arbitrary number and configuration of vortices in an annular Bose-Einstein condensate obtaining expressions for the free energy and vortex precession rates to logarithmic accuracy. We also obtain lower bounds for the lifetime of a single vortex in the annulus. Our results enable a closed-form analytic treatment of vortex-vortex interactions in the annulus that is exact in the incompressible limit. The incompressible hydrodynamics that is developed here paves the way for more general analytical treatments of vortex dynamics in non-simply-connected geometries.
Rapidly rotating Bose-Einstein condensates in homogeneous traps
Correggi, M.; Rindler-Daller, T.; Yngvason, J.
2007-10-15
We extend the results of a previous paper on the Gross-Pitaevskii description of rotating Bose-Einstein condensates in two-dimensional traps to confining potentials of the form V(r)=r{sup s}, 2
Coherent Ratchets in Driven Bose-Einstein Condensates
Creffield, C. E.; Sols, F.
2009-11-13
We study the response of a Bose-Einstein condensate to an unbiased periodic driving potential. By controlling the space and time symmetries of the driving we show how a directed current can be induced, producing a coherent quantum ratchet. Weak driving induces a regular behavior, and space and time symmetries must both be broken to produce a current. For strong driving, the behavior becomes chaotic and the resulting effective irreversibility means that it is unnecessary to explicitly break time symmetry. Spatial asymmetry alone is then sufficient to produce the ratchet effect, even in the absence of interactions, and although the system remains completely coherent.
Quantum Mass Acquisition in Spinor Bose-Einstein Condensates
NASA Astrophysics Data System (ADS)
Phuc, Nguyen Thanh; Kawaguchi, Yuki; Ueda, Masahito
2014-12-01
Quantum mass acquisition, in which a massless (quasi)particle becomes massive due to quantum corrections, is predicted to occur in several subfields of physics. However, its experimental observation remains elusive since the emergent energy gap is too small. We show that a spinor Bose-Einstein condensate is an excellent candidate for the observation of such a peculiar phenomenon as the energy gap turns out to be 2 orders of magnitude larger than the zero-point energy. This extraordinarily large energy gap is a consequence of the dynamical instability. The propagation velocity of the resultant massive excitation mode is found to be decreased by the quantum corrections as opposed to phonons.
Kicked Bose-Einstein Condensates: in Search of Exponential Instability
NASA Astrophysics Data System (ADS)
Monteiro, T. S.; Rancon, A.; Ruostekoski, J.
Bose-Einstein condensates subject to short pulses ("kicks") from standing waves of light represent a nonlinear analogue of the well-known chaos paradigm, the quantum kicked rotor. We review briefly our current understanding of dynamical or exponential instability in weakly kicked BECs. Previous studies of the onset of dynamical instability associated it with some form of classical chaos. We show it is due to parametric instability: resonant driving of certain collective modes. We map the zones of instability and calculate the Liapunov exponents.
Early stage of superradiance from Bose-Einstein condensates
Buchmann, L. F.; Lambropoulos, P.; Nikolopoulos, G. M.; Zobay, O.
2010-08-15
We investigate the dynamics of matter and optical waves at the early stage of superradiant Rayleigh scattering from Bose-Einstein condensates. Our analysis is within a spatially dependent quantum model which is capable of providing analytic solutions for the operators of interest. The predictions of the present model are compared to the predictions of a closely related mean-field model, and we provide a procedure that allows one to calculate quantum expectation values by averaging over semiclassical solutions. The coherence properties of the outgoing scattered light are also analyzed, and it is shown that the corresponding correlation functions may provide detailed information about the internal dynamics of the system.
Dispersive Bottleneck Delaying Thermalization of Turbulent Bose-Einstein Condensates
Krstulovic, Giorgio; Brachet, Marc
2011-03-18
A new mechanism of thermalization involving a direct energy cascade is obtained in the truncated Gross-Pitaevskii dynamics. A long transient with partial thermalization at small scales is observed before the system reaches equilibrium. Vortices are found to disappear as a prelude to final thermalization. A bottleneck that produces spontaneous effective self-truncation and delays thermalization is characterized when large dispersive effects are present at the truncation wave number. Order of magnitude estimates indicate that self-truncation takes place in turbulent Bose-Einstein condensates. This effect should also be present in classical hydrodynamics and models of turbulence.
Collisions of Dark Solitons in Elongated Bose-Einstein Condensates
Stellmer, S.; Becker, C.; Soltan-Panahi, P.; Richter, E.-M.; Doerscher, S.; Baumert, M.; Kronjaeger, J.; Sengstock, K.; Bongs, K.
2008-09-19
We present experimental data showing the head-on collision of dark solitons generated in an elongated Bose-Einstein condensate. No discernable interaction can be recorded, in full agreement with the fundamental theoretical concepts of solitons as mutually transparent quasiparticles. Our soliton generation technique allows for the creation of solitons with different depths; hence, they can be distinguished and their trajectories be followed. Simulations of the 1D-Gross-Pitaevskii equation have been performed to compare the experiment with a mean-field description.
Bose-Einstein Condensation of Dark Matter Axions
Sikivie, P.; Yang, Q.
2009-09-11
We show that cold dark matter axions thermalize and form a Bose-Einstein condensate (BEC). We obtain the axion state in a homogeneous and isotropic universe, and derive the equations governing small axion perturbations. Because they form a BEC, axions differ from ordinary cold dark matter in the nonlinear regime of structure formation and upon entering the horizon. Axion BEC provides a mechanism for the production of net overall rotation in dark matter halos, and for the alignment of cosmic microwave anisotropy multipoles.
Geometrical Pumping with a Bose-Einstein Condensate
NASA Astrophysics Data System (ADS)
Lu, H.-I.; Schemmer, M.; Aycock, L. M.; Genkina, D.; Sugawa, S.; Spielman, I. B.
2016-05-01
We realized a quantum geometric "charge" pump for a Bose-Einstein condensate (BEC) in the lowest Bloch band of a novel bipartite magnetic lattice. Topological charge pumps in filled bands yield quantized pumping set by the global—topological—properties of the bands. In contrast, our geometric charge pump for a BEC occupying just a single crystal momentum state exhibits nonquantized charge pumping set by local—geometrical—properties of the band structure. Like topological charge pumps, for each pump cycle we observed an overall displacement (here, not quantized) and a temporal modulation of the atomic wave packet's position in each unit cell, i.e., the polarization.
Geometrical Pumping with a Bose-Einstein Condensate.
Lu, H-I; Schemmer, M; Aycock, L M; Genkina, D; Sugawa, S; Spielman, I B
2016-05-20
We realized a quantum geometric "charge" pump for a Bose-Einstein condensate (BEC) in the lowest Bloch band of a novel bipartite magnetic lattice. Topological charge pumps in filled bands yield quantized pumping set by the global-topological-properties of the bands. In contrast, our geometric charge pump for a BEC occupying just a single crystal momentum state exhibits nonquantized charge pumping set by local-geometrical-properties of the band structure. Like topological charge pumps, for each pump cycle we observed an overall displacement (here, not quantized) and a temporal modulation of the atomic wave packet's position in each unit cell, i.e., the polarization. PMID:27258857
Bose-Einstein condensation in binary mixture of Bose gases
Tran Huu Phat; Le Viet Hoa; Nguyen Tuan Anh Nguyen Van Long
2009-10-15
The Bose-Einstein condensation (BEC) in a binary mixture of Bose gases is studied by means of the Cornwall-Jackiw-Tomboulis (CJT) effective action approach. The equations of state (EoS) and various scenarios of phase transitions of the system are considered in detail, in particular, the numerical computations are carried out for symmetry restoration (SR), symmetry nonrestoration (SNR) and inverse symmetry breaking (ISB) for getting an insight into their physical nature. It is shown that due to the cross interaction between distinct components of mixture there occur two interesting phenomena: the high temperature BEC and the inverse BEC, which could be tested in experiments.
Observation of solitonic vortices in Bose-Einstein condensates.
Donadello, Simone; Serafini, Simone; Tylutki, Marek; Pitaevskii, Lev P; Dalfovo, Franco; Lamporesi, Giacomo; Ferrari, Gabriele
2014-08-01
We observe solitonic vortices in an atomic Bose-Einstein condensate (BEC) after free expansion. Clear signatures of the nature of such defects are the twisted planar density depletion around the vortex line, observed in absorption images, and the double dislocation in the interference pattern obtained through homodyne techniques. Both methods allow us to determine the sign of the quantized circulation. Experimental observations agree with numerical simulations. These solitonic vortices are the decay product of phase defects of the BEC order parameter spontaneously created after a rapid quench across the BEC transition in a cigar-shaped harmonic trap and are shown to have a very long lifetime. PMID:25148333
A Raman waveplate for spinor Bose-Einstein condensates.
Schultz, Justin T; Hansen, Azure; Bigelow, Nicholas P
2014-07-15
We demonstrate a waveplate for a pseudo-spin-1/2 Bose-Einstein condensate (BEC) using a two-photon Raman interaction. The angle of the waveplate is set by the relative phase of the optical fields, and the retardance is controlled by the pulse area. The waveplate allows us to image maps of the Stokes parameters of a BEC and thereby measure its relative ground-state phase. We demonstrate the waveplate by measuring the Stokes parameters of a coreless vortex. PMID:25121704
Cooling of a Bose-Einstein Condensate by Spin Distillation.
Naylor, B; Maréchal, E; Huckans, J; Gorceix, O; Pedri, P; Vernac, L; Laburthe-Tolra, B
2015-12-11
We propose and experimentally demonstrate a new cooling mechanism leading to purification of a Bose-Einstein condensate (BEC). Our scheme starts with a BEC polarized in the lowest energy spin state. Spin excited states are thermally populated by lowering the single particle energy gap set by the magnetic field. Then, these spin-excited thermal components are filtered out, which leads to an increase of the BEC fraction. We experimentally demonstrate such cooling for a spin 3 ^{52}Cr dipolar BEC. Our scheme should be applicable to Na or Rb, with the perspective to reach temperatures below 1 nK. PMID:26705630
Non-equilibrium dynamics in driven Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Feng, Lei; Clark, Logan W.; Ha, Li-Chung; Chin, Cheng
2016-05-01
We report recent progress on the study of non-equilibrium dynamics in Bose-Einstein condensates using the shaken optical lattice or optically controlled Feshbach resonances. In the shaken lattice at sufficient shaking amplitude we observe a quantum phase transition from ordinary condensates to pseudo-spinor 1/2 condensates containing discrete domains with effective ferromagnetic interactions. We study the temporal and spatial Kibble-Zurek scaling laws for the dependence of this domain structure on the quench rate across the transition. Furthermore, we observe long-range density correlations within the ferromagnetic condensate. With optically controlled Feshbach resonances we demonstrate control of the interaction strength between atoms at timescales as short as ten nanoseconds and length scales smaller than the condensate. We find that making interactions attractive within only one region of the gas induces localized collapse of the condensate.
Analogue gravitational phenomena in Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Finazzi, Stefano
2012-08-01
Analogue gravity is based on the simple observation that perturbations propagating in several physical systems can be described by a quantum field theory in a curved spacetime. While phenomena like Hawking radiation are hardly detectable in astrophysical black holes, these effects may be experimentally tested in analogue systems. In this Thesis, focusing on Bose-Einstein condensates, we present our recent results about analogue models of gravity from three main perspectives: as laboratory tests of quantum field theory in curved spacetime, for the techniques that they provide to address various issues in general relativity, and as toy models of quantum gravity. The robustness of Hawking-like particle creation is investigated in flows with a single black hole horizon. Furthermore, we find that condensates with two (white and black) horizons develop a dynamical instability known in general relativity as black hole laser effect. Using techniques borrowed from analogue gravity, we also show that warp drives, which are general relativistic spacetimes allowing faster-than-light travel, are unstable. Finally, the cosmological constant issue is investigated from an analogue gravity perspective and relativistic Bose-Einstein condensates are proposed as new analogue systems with novel interesting properties.
Dynamics of vortex dipoles in anisotropic Bose-Einstein condensates
Goodman, Roy H.; Kevrekidis, P. G.; Carretero-González, R.
2015-04-14
We study the motion of a vortex dipole in a Bose-Einstein condensate confined to an anisotropic trap. We focus on a system of ODEs describing the vortices' motion, which is in turn a reduced model of the Gross-Pitaevskii equation describing the condensate's motion. Using a sequence of canonical changes of variables, we reduce the dimension and simplify the equations of motion. In this study, we uncover two interesting regimes. Near a family of periodic orbits known as guiding centers, we find that the dynamics is essentially that of a pendulum coupled to a linear oscillator, leading to stochastic reversals inmore » the overall direction of rotation of the dipole. Near the separatrix orbit in the isotropic system, we find other families of periodic, quasi-periodic, and chaotic trajectories. In a neighborhood of the guiding center orbits, we derive an explicit iterated map that simplifies the problem further. Numerical calculations are used to illustrate the phenomena discovered through the analysis. Using the results from the reduced system, we are able to construct complex periodic orbits in the original, PDE, mean-field model for Bose-Einstein condensates, which corroborates the phenomenology observed in the reduced dynamical equations.« less
Dynamics of vortex dipoles in anisotropic Bose-Einstein condensates
Goodman, Roy H.; Kevrekidis, P. G.; Carretero-González, R.
2015-04-14
We study the motion of a vortex dipole in a Bose-Einstein condensate confined to an anisotropic trap. We focus on a system of ODEs describing the vortices' motion, which is in turn a reduced model of the Gross-Pitaevskii equation describing the condensate's motion. Using a sequence of canonical changes of variables, we reduce the dimension and simplify the equations of motion. In this study, we uncover two interesting regimes. Near a family of periodic orbits known as guiding centers, we find that the dynamics is essentially that of a pendulum coupled to a linear oscillator, leading to stochastic reversals in the overall direction of rotation of the dipole. Near the separatrix orbit in the isotropic system, we find other families of periodic, quasi-periodic, and chaotic trajectories. In a neighborhood of the guiding center orbits, we derive an explicit iterated map that simplifies the problem further. Numerical calculations are used to illustrate the phenomena discovered through the analysis. Using the results from the reduced system, we are able to construct complex periodic orbits in the original, PDE, mean-field model for Bose-Einstein condensates, which corroborates the phenomenology observed in the reduced dynamical equations.
Dissipative transport of a Bose-Einstein condensate
Dries, D.; Pollack, S. E.; Hitchcock, J. M.; Hulet, R. G.
2010-09-15
We investigate the effects of impurities, either correlated disorder or a single Gaussian defect, on the collective dipole motion of a Bose-Einstein condensate of {sup 7}Li in an optical trap. We find that this motion is damped at a rate dependent on the impurity strength, condensate center-of-mass velocity, and interatomic interactions. Damping in the Thomas-Fermi regime depends universally on the disordered potential strength scaled to the condensate chemical potential and the condensate velocity scaled to the speed of sound. The damping rate is comparatively small in the weakly interacting regime, and, in this case, is accompanied by strong condensate fragmentation. In situ and time-of-flight images of the atomic cloud provide evidence that this fragmentation is driven by dark soliton formation.
Numerical study of localized impurity in a Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Akram, Javed; Pelster, Axel
2016-03-01
Motivated by recent experiments, we investigate a single 133 Cs impurity in the center of a trapped 87 Rb Bose-Einstein condensate (BEC). Within a zero-temperature mean-field description we provide a one-dimensional physical intuitive model which involves two coupled differential equations for the condensate and the impurity wave function, which we solve numerically. With this we determine within the equilibrium phase diagram spanned by the intra- and interspecies coupling strength whether the impurity is localized at the trap center or expelled to the condensate border. In the former case we find that the impurity induces a bump or dip on the condensate for an attractive or a repulsive Rb-Cs interaction strength, respectively. Conversely, the condensate environment leads to an effective mass of the impurity which increases quadratically for small interspecies interaction strength. Afterwards, we investigate how the impurity imprint upon the condensate wave function evolves for two quench scenarios. At first we consider the case that the harmonic confinement is released. During the resulting time-of-flight expansion it turns out that the impurity-induced bump in the condensate wave function starts decaying marginally, whereas the dip decays with a characteristic time scale which decreases with increasing repulsive impurity-BEC interaction strength. Second, once the attractive or repulsive interspecies coupling constant is switched off, we find that white-shock waves or bisolitons emerge which both oscillate within the harmonic confinement with a characteristic frequency.
Thermalization of gluons with Bose-Einstein condensation.
Xu, Zhe; Zhou, Kai; Zhuang, Pengfei; Greiner, Carsten
2015-05-01
We study the thermalization of gluons far from thermal equilibrium in relativistic kinetic theory. The initial distribution of gluons is assumed to resemble that in the early stage of ultrarelativistic heavy ion collisions. Only elastic scatterings in static, nonexpanding gluonic matter are considered. At first we show that the occurrence of condensation in the limit of vanishing particle mass requires a general constraint for the scattering matrix element. Then the thermalization of gluons with Bose-Einstein condensation is demonstrated in a transport calculation. We see a continuously increasing overpopulation of low energy gluons, followed by a decrease to the equilibrium distribution, when the condensation occurs. The times of the completion of the gluon condensation and of the entropy production are calculated. These times scale inversely with the energy density. PMID:26000996
Internal Josephson oscillations for distinct momenta Bose-Einstein condensates
Lim, Lih-King; Troppenz, T.; Morais Smith, C.
2011-11-15
The internal Josephson oscillations between an atomic Bose-Einstein condensate (BEC) and a molecular one are studied for atoms in a square optical lattice subjected to a staggered gauge field. The system is described by a Bose-Hubbard model with complex and anisotropic hopping parameters that are different for each species, i.e., atoms and molecules. When the flux per plaquette for each species is small, the system oscillates between two conventional zero-momentum condensates. However, there is a regime of parameters in which Josephson oscillations between a vortex-carrying atomic condensate (finite momentum BEC) and a conventional zero-momentum molecular condensate may be realized. The experimental observation of the oscillations between these qualitatively distinct BEC's is possible with state-of-the-art Ramsey interference techniques.
Atom Interferometry on Sounding Rockets with Bose-Einstein Condensates
NASA Astrophysics Data System (ADS)
Seidel, Stephan T.; Becker, Dennis; Lachmann, Maike D.; Herr, Waldemar; Rasel, Ernst M.; Quantus Collaboration
2016-05-01
One of the fundamental postulates of our description of nature is the universality of free fall, stating that the force exerted upon an object due to gravity is independent of its constitution. A precise test of this assumption is the comparison of the free fall of two ultra-cold clouds of different atomic species via atom interferometry. Since the sensitivity of the measurement is proportional to the square of the propagation time in the interferometer, it can be increased by performing the experiments in microgravity. In order to fully utilize the potential of the experiments the usage of a Bose-Einstein-Condensate as the initial state is necessary, because it is characterized by a small initial size and a low expansion velocity. As a step towards the transfer of such a system into space three sounding rocket missions with atom interferometers are currently being prepared. The launch of the first mission, aimed at the first demonstration of a Bose-Einstein-Condensate in space and an atom interferometer based on it is planned for 2016 from ESRANGE, Sweden. It will be followed by two more missions that extend the scientific goals to the creation of degenerate mixtures and dual-species atom interferometry. This research is funded by the German Space Agency DLR under Grant Number DLR 50 1131-37.
Resistive flow in a weakly interacting Bose-Einstein condensate.
Jendrzejewski, F; Eckel, S; Murray, N; Lanier, C; Edwards, M; Lobb, C J; Campbell, G K
2014-07-25
We report the direct observation of resistive flow through a weak link in a weakly interacting atomic Bose-Einstein condensate. Two weak links separate our ring-shaped superfluid atomtronic circuit into two distinct regions, a source and a drain. Motion of these weak links allows for creation of controlled flow between the source and the drain. At a critical value of the weak link velocity, we observe a transition from superfluid flow to superfluid plus resistive flow. Working in the hydrodynamic limit, we observe a conductivity that is 4 orders of magnitude larger than previously reported conductivities for a Bose-Einstein condensate with a tunnel junction. Good agreement with zero-temperature Gross-Pitaevskii simulations and a phenomenological model based on phase slips indicate that the creation of excitations plays an important role in the resulting conductivity. Our measurements of resistive flow elucidate the microscopic origin of the dissipation and pave the way for more complex atomtronic devices. PMID:25105631
Effects of interaction on thermodynamics of a repulsive Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Bhattacharyya, Satadal; Das, Tapan Kumar; Chakrabarti, Barnali
2013-11-01
We report the effects of interaction on thermodynamic properties of a repulsive Bose-Einstein condensate confined in a harmonic trap by using the correlated potential harmonics expansion method. This many-body technique permits the use of a realistic interactomic interaction, which gives rise to the effective long-range interaction of the condensate in terms of the s-wave scattering length. We have computed temperature (T) dependence of the chemical potential, specific heat, condensate fraction, entropy, pressure, and the average energy per particle of a system containing a large number (A) of 87Rb atoms in the Joint Institute for Laboratory Astrophysics (JILA) trap. The repulsion among the interacting bosons results in a small but measurable drop of condensate fraction and critical temperature (Tc), compared to those of a noninteracting condensate. These are in agreement with the experiment. Although all thermodynamic quantities have a strong dependence on A and to a smaller extent on the interatomic interaction, our numerical calculation appears to show that a thermodynamic quantity per particle follows a universal behavior as a function of T/Tc. This shows the importance of Tc for all thermodynamic properties of the condensate. As expected, for T>Tc, these properties follow those of a trapped noncondensed Bose gas.
Static interfacial properties of Bose-Einstein-condensate mixtures
NASA Astrophysics Data System (ADS)
Indekeu, Joseph O.; Lin, Chang-You; Van Thu, Nguyen; Van Schaeybroeck, Bert; Phat, Tran Huu
2015-03-01
The interfacial profiles and interfacial tensions of phase-separated binary mixtures of Bose-Einstein condensates are studied theoretically. The two condensates are characterized by their respective healing lengths ξ1 and ξ2 and by the interspecies repulsive interaction K . An exact solution to the Gross-Pitaevskii (GP) equations is obtained for the special case ξ2/ξ1=1 /2 and K =3 /2 . Furthermore, applying a double-parabola approximation (DPA) to the energy density featured in GP theory allows us to define a DPA model, which is much simpler to handle than GP theory but nevertheless still captures the main physics. In particular, a compact analytic expression for the interfacial tension is derived that is useful for all ξ1,ξ2 , and K . An application to wetting phenomena is presented for condensates adsorbed at an optical wall. The wetting phase boundary obtained within the DPA model nearly coincides with the exact one in GP theory.
Kinetic approach to a relativistic Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Meistrenko, Alex; van Hees, Hendrik; Zhou, Kai; Greiner, Carsten
2016-03-01
We apply a Boltzmann approach to the kinetic regime of a relativistic Bose-Einstein condensate of scalar bosons by decomposing the one-particle distribution function in a condensate part and a nonzero momentum part of excited modes, leading to a coupled set of evolution equations which are then solved efficiently with an adaptive higher order Runge-Kutta scheme. We compare our results to the partonic cascade Monte Carlo simulation BAMPS for a critical but far from equilibrium case of massless bosons. Motivated by the color glass condensate initial conditions in QCD with a strongly overpopulated initial glasma state, we also discuss the time evolution starting from an overpopulated initial distribution function of massive scalar bosons. In this system a self-similar evolution of the particle cascade with a nonrelativistic turbulent scaling in the infrared sector is observed as well as a relativistic exponent for the direct energy cascade, confirming a weak wave turbulence in the ultraviolet region.
Atom interferometry with a weakly interacting Bose-Einstein condensate.
Fattori, M; D'Errico, C; Roati, G; Zaccanti, M; Jona-Lasinio, M; Modugno, M; Inguscio, M; Modugno, G
2008-02-29
We demonstrate the operation of an atom interferometer based on a weakly interacting Bose-Einstein condensate. We strongly reduce the interaction induced decoherence that usually limits interferometers based on trapped condensates by tuning the s-wave scattering length almost to zero via a magnetic Feshbach resonance. We employ a 39K condensate trapped in an optical lattice, where Bloch oscillations are forced by gravity. The fine-tuning of the scattering length down to 0.1 a_(0) and the micrometric sizes of the atomic sample make our system a very promising candidate for measuring forces with high spatial resolution. Our technique can be in principle extended to other measurement schemes opening new possibilities in the field of trapped atom interferometry. PMID:18352607
Atom Interferometry with a Weakly Interacting Bose-Einstein Condensate
Fattori, M.; D'Errico, C.; Roati, G.; Inguscio, M.; Modugno, G.; Zaccanti, M.; Jona-Lasinio, M.; Modugno, M.
2008-02-29
We demonstrate the operation of an atom interferometer based on a weakly interacting Bose-Einstein condensate. We strongly reduce the interaction induced decoherence that usually limits interferometers based on trapped condensates by tuning the s-wave scattering length almost to zero via a magnetic Feshbach resonance. We employ a {sup 39}K condensate trapped in an optical lattice, where Bloch oscillations are forced by gravity. The fine-tuning of the scattering length down to 0.1 a{sub 0} and the micrometric sizes of the atomic sample make our system a very promising candidate for measuring forces with high spatial resolution. Our technique can be in principle extended to other measurement schemes opening new possibilities in the field of trapped atom interferometry.
Moving impurity in an inhomogenous Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Mathew, Ranchu; Tiesinga, Eite
2016-05-01
We study the dynamics of a non-uniform Bose-Einstein condensate (BEC) under the influence of a moving weak point-like impurity. When the condensate density varies slowly compared to its healing length the critical velocity of the impurity, beyond which the condensate becomes unstable, can be calculated using the Local Density Approximation (LDA). This critical velocity corresponds to the smallest local sound speed. The LDA breaks down when the length scale of density variations is of the order of the healing length. We have calculated corrections to the critical velocity in this regime as an asymptotic expansion in the size of the BEC. We also discuss the experimental implications of our calculations by studying the stability of the atomic analogue of a Superconducting Quantum Interference Device (SQUID). The atom-SQUID consists of a BEC in a ring trap with rotating barrier. The impurity corresponds to imperfections in the ring trap.
Bose-Einstein condensation of alkaline earth atoms: ;{40}Ca.
Kraft, Sebastian; Vogt, Felix; Appel, Oliver; Riehle, Fritz; Sterr, Uwe
2009-09-25
We have achieved Bose-Einstein condensation of ;{40}Ca, the first for an alkaline earth element. The influence of elastic and inelastic collisions associated with the large ground-state s-wave scattering length of ;{40}Ca was measured. From these findings, an optimized loading and cooling scheme was developed that allowed us to condense about 2 x 10;{4} atoms after laser cooling in a two-stage magneto-optical trap and subsequent forced evaporation in a crossed dipole trap within less than 3 s. The condensation of an alkaline earth element opens novel opportunities for precision measurements on the narrow intercombination lines as well as investigations of molecular states at the ;{1}S-;{3}P asymptotes. PMID:19905493
Nonlinear waves in coherently coupled Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Congy, T.; Kamchatnov, A. M.; Pavloff, N.
2016-04-01
We consider a quasi-one-dimensional two-component Bose-Einstein condensate subject to a coherent coupling between its components, such as realized in spin-orbit coupled condensates. We study how nonlinearity modifies the dynamics of the elementary excitations. The spectrum has two branches, which are affected in different ways. The upper branch experiences a modulational instability, which is stabilized by a long-wave-short-wave resonance with the lower branch. The lower branch is stable. In the limit of weak nonlinearity and small dispersion it is described by a Korteweg-de Vries equation or by the Gardner equation, depending on the value of the parameters of the system.
Momentum-space engineering of gaseous Bose-Einstein condensates
Edwards, Mark; Benton, Brandon; Heward, Jeffrey; Clark, Charles W.
2010-12-15
We show how the momentum distribution of gaseous Bose-Einstein condensates can be shaped by applying a sequence of standing-wave laser pulses. We present a theory, whose validity was demonstrated in an earlier experiment [L. Deng et al., Phys. Rev. Lett. 83, 5407 (1999)], of the effect of a two-pulse sequence on the condensate wavefunction in momentum space. We generalize the previous result to the case of N pulses of arbitrary intensity separated by arbitrary intervals and show how these parameters can be engineered to produce a desired final momentum distribution. We find that several momentum distributions, important in atom-interferometry applications, can be engineered with high fidelity with two or three pulses.
Nonlocal Quantum Effects with Bose-Einstein Condensates
Laloee, F.; Mullin, W. J.
2007-10-12
We study theoretically the properties of two Bose-Einstein condensates in different spin states, represented by a double Fock state. Individual measurements of the spins of the particles are performed in transverse directions, giving access to the relative phase of the condensates. Initially, this phase is completely undefined, and the first measurements provide random results. But a fixed value of this phase rapidly emerges under the effect of the successive quantum measurements, giving rise to a quasiclassical situation where all spins have parallel transverse orientations. If the number of measurements reaches its maximum (the number of particles), quantum effects show up again, giving rise to violations of Bell type inequalities. The violation of Bell-Clauser-Horne-Shimony-Holt inequalities with an arbitrarily large number of spins may be comparable (or even equal) to that obtained with two spins.
Winding up superfluid in a torus via Bose Einstein condensation
NASA Astrophysics Data System (ADS)
Das, Arnab; Sabbatini, Jacopo; Zurek, Wojciech H.
2012-04-01
Phase transitions are usually treated as equilibrium phenomena, which yields telltale universality classes with scaling behavior of relaxation time and healing length. However, in second-order phase transitions relaxation time diverges near the critical point (``critical slowing down''). Therefore, every such transition traversed at a finite rate is a non-equilibrium process. Kibble-Zurek mechanism (KZM) captures this basic physics, predicting sizes of domains - fragments of broken symmetry - and the density of topological defects, long-lived relics of symmetry breaking that can survive long after the transition. To test KZM we simulate Bose-Einstein condensation in a ring using stochastic Gross-Pitaevskii equation and show that BEC formation can spontaneously generate quantized circulation of the newborn condensate. The magnitude of the resulting winding numbers and the time-lag of BEC density growth - both experimentally measurable - follow scalings predicted by KZM. Our results may also facilitate measuring the dynamical critical exponent for the BEC transition.
Emergence of classical rotation in superfluid Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
White, Angela; Hennessy, Tara; Busch, Thomas
2016-03-01
Phase transitions can modify quantum behavior on mesoscopic scales and give access to new and unusual quantum dynamics. Here we investigate the superfluid properties of a rotating two-component Bose-Einstein condensate as a function of changes in the interaction energy and in particular through the phase transition from miscibility to immiscibility. We show that the breaking of one of the hallmarks of superfluid flow, namely, the quantization condition on circulation, is continuous throughout an azimuthal phase-separation process and displays intriguing flow dynamics. We find that the resulting currents are stable for long times and possess a boundary between the two condensate components that exhibits classical solid-body rotation, despite the quantum nature of superfluid flow. To support this coexistence of classical and quantum behavior the system develops a unique velocity flow profile, which includes unusual radial flow in regions near the boundary.
Bose-Einstein condensation in liquid 4He under pressure
Glyde, Henry R; Omar Diallo, Souleymane; Azuah, Richard T; Kirichek, Oleg; Taylor, Jon W.
2011-01-01
We present neutron scattering measurements of Bose-Einstein condensation, the atomic momen- tum distribution and Final State effects in liquid 4He under pressure. The condensate fraction at low temperature is found to decrease from n0 = 7.25 0.75% at SVP (p 0) to n0 = 3.2 0.75% at pressure p = 24 bar. This indicates an n0 = 3.0% in the liquid at the liquid/solid co-existence line (p = 25.3 bar). The atomic momentum distribution n(k) has high occupation of low k states and differs significantly from a Gaussian (e.g. a classical n(k)). Both n(k) and the Final state function broaden with increasing pressure, reflecting the increased localization of the 4He in space under increased pressure.
Brugarino, Tommaso; Sciacca, Michele
2010-09-15
In this paper, we investigate the integrability of an inhomogeneous nonlinear Schroedinger equation, which has several applications in many branches of physics, as in Bose-Einstein condensates and fiber optics. The main issue deals with Painleve property (PP) and Liouville integrability for a nonlinear Schroedinger-type equation. Solutions of the integrable equation are obtained by means of the Darboux transformation. Finally, some applications on fiber optics and Bose-Einstein condensates are proposed (including Bose-Einstein condensates in three-dimensional in cylindrical symmetry).
D-brane solitons and boojums in field theory and Bose-Einstein condensates.
Kasamatsu, Kenichi; Takeuchi, Hiromitsu; Nitta, Muneto
2013-10-01
In certain field theoretical models, composite solitons consisting of a domain wall and vortex lines attached to the wall have been referred to as 'D-brane solitons'. We show that similar composite solitons can be realized in phase-separated two-component Bose-Einstein condensates. We discuss the similarities and differences between topological solitons in the Abelian-Higgs model and those in two-component Bose-Einstein condensates. On the basis of the formulation of gauge theory, we introduce the 'boojum charge' to characterize the D-brane soliton in Bose-Einstein condensates. PMID:24025586
Quantum noise, scaling, and domain formation in a spinor Bose-Einstein condensate
Mias, George I.; Girvin, S. M.; Cooper, Nigel R.
2008-02-15
In this paper we discuss Bose-Einstein spinor condensates for F=1 atoms in the context of {sup 87}Rb, as studied experimentally by the Stamper-Kurn group [L. E. Sadler et al., Nature (London) 443, 312 (2006)]. The dynamical quantum fluctuations of a sample that starts as a condensate of N atoms in a pure F=1, m{sub F}=0 state are described in analogy to the two-mode squeezing of quantum optics in terms of an su(1,1) algebra. In this system the initial m{sub F}=0 condensate acts as a source (pump) for the creation pairs of m{sub F}=1,-1 atoms. We show that even though the system as a whole is described by a pure state with zero entropy, the reduced density matrix for the m{sub F}=+1 degree of freedom, obtained by tracing out the m{sub F}=-1,0 degrees of freedom, corresponds to a thermal state. Furthermore, these quantum fluctuations of the initial dynamics of the system provide the seeds for the formation of domains of ferromagnetically aligned spins.
NASA Astrophysics Data System (ADS)
Gallemí, A.; Guilleumas, M.; Mayol, R.; Mateo, A. Muñoz
2016-03-01
We analyze the dynamics of Josephson vortex states in two-component Bose-Einstein condensates with Rashba-Dresselhaus spin-orbit coupling by using the Gross-Pitaevskii equation. In one dimension, both in homogeneous and harmonically trapped systems, we report on stationary states containing doubly charged, static Josephson vortices. In multidimensional systems, we find stable Josephson vortices in a regime of parameters typical of current experiments with 87Rb atoms. In addition, we discuss the instability regime of Josephson vortices in disk-shaped condensates, where the snake instability operates and vortex dipoles emerge. We study the rich dynamics that they exhibit in different regimes of the spin-orbit-coupled condensate depending on the orientation of the Josephson vortices.
Dynamics of macroscopic tunneling in elongated Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Dekel, G.; Farberovich, V.; Fleurov, V.; Soffer, A.
2010-06-01
We investigate macroscopic tunneling from an elongated quasi-one-dimensional trap, forming a “cigar-shaped” Bose-Einstein condensate (BEC). Using a recently developed formalism we get the leading analytical approximation for the right-hand side of the potential wall, i.e., outside the trap, and a formalism based on Wigner functions, for the left side of the potential wall, i.e., inside the BEC. We then present accomplished results of numerical calculations, which show a “blip” in the particle density traveling with an asymptotic shock velocity, as resulted from previous works on a dotlike trap but with significant differences from the latter. Inside the BEC a pattern of a traveling dispersive shock wave is revealed. In the attractive case, we find trains of bright solitons frozen near the boundary.
Neural networks using two-component Bose-Einstein condensates
Byrnes, Tim; Koyama, Shinsuke; Yan, Kai; Yamamoto, Yoshihisa
2013-01-01
The authors previously considered a method of solving optimization problems by using a system of interconnected network of two component Bose-Einstein condensates (Byrnes, Yan, Yamamoto New J. Phys. 13, 113025 (2011)). The use of bosonic particles gives a reduced time proportional to the number of bosons N for solving Ising model Hamiltonians by taking advantage of enhanced bosonic cooling rates. Here we consider the same system in terms of neural networks. We find that up to the accelerated cooling of the bosons the previously proposed system is equivalent to a stochastic continuous Hopfield network. This makes it clear that the BEC network is a physical realization of a simulated annealing algorithm, with an additional speedup due to bosonic enhancement. We discuss the BEC network in terms of neural network tasks such as learning and pattern recognition and find that the latter process may be accelerated by a factor of N. PMID:23989391
The Gross-Pitaevskii equation and Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Rogel-Salazar, J.
2013-03-01
The Gross-Pitaevskii equation (GPE) is discussed at the level of an advanced course on statistical physics. In the standard literature the GPE is usually obtained in the framework of the second quantization formalism, which in many cases goes beyond the material covered in many advanced undergraduate courses. In this paper, we motivate the derivation of the GPE in relationship to concepts from statistical physics, highlighting a number of applications from the dynamics of a Bose-Einstein condensate to the excitations of the gas cloud. This paper may be helpful for encouraging the discussion of modern developments in a statistical mechanics course, and can also be of use in other contexts such as mathematical physics and modelling. The paper is suitable for undergraduate and graduate students, as well as for general physicists.
Dynamics of nonautonomous rogue waves in Bose-Einstein condensate
Zhao, Li-Chen
2013-02-15
We study rogue waves of Bose-Einstein condensate (BEC) analytically in a time-dependent harmonic trap with a complex potential. Properties of the nonautonomous rogue waves are investigated analytically. It is reported that there are possibilities to 'catch' rogue waves through manipulating nonlinear interaction properly. The results provide many possibilities to manipulate rogue waves experimentally in a BEC system. - Highlights: Black-Right-Pointing-Pointer One more generalized rogue wave solutions are presented. Black-Right-Pointing-Pointer Present one possible way to catch a rouge wave. Black-Right-Pointing-Pointer Properties of rogue waves are investigated analytically for the first time. Black-Right-Pointing-Pointer Provide many possibilities to manipulate rogue waves in BEC.
Bell correlations in a Bose-Einstein condensate.
Schmied, Roman; Bancal, Jean-Daniel; Allard, Baptiste; Fadel, Matteo; Scarani, Valerio; Treutlein, Philipp; Sangouard, Nicolas
2016-04-22
Characterizing many-body systems through the quantum correlations between their constituent particles is a major goal of quantum physics. Although entanglement is routinely observed in many systems, we report here the detection of stronger correlations--Bell correlations--between the spins of about 480 atoms in a Bose-Einstein condensate. We derive a Bell correlation witness from a many-particle Bell inequality involving only one- and two-body correlation functions. Our measurement on a spin-squeezed state exceeds the threshold for Bell correlations by 3.8 standard deviations. Our work shows that the strongest possible nonclassical correlations are experimentally accessible in many-body systems and that they can be revealed by collective measurements. PMID:27102479
Bell correlations in a Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Schmied, Roman; Bancal, Jean-Daniel; Allard, Baptiste; Fadel, Matteo; Scarani, Valerio; Treutlein, Philipp; Sangouard, Nicolas
2016-04-01
Characterizing many-body systems through the quantum correlations between their constituent particles is a major goal of quantum physics. Although entanglement is routinely observed in many systems, we report here the detection of stronger correlations—Bell correlations—between the spins of about 480 atoms in a Bose-Einstein condensate. We derive a Bell correlation witness from a many-particle Bell inequality involving only one- and two-body correlation functions. Our measurement on a spin-squeezed state exceeds the threshold for Bell correlations by 3.8 standard deviations. Our work shows that the strongest possible nonclassical correlations are experimentally accessible in many-body systems and that they can be revealed by collective measurements.
Matter-wave recombiners for trapped Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Berrada, T.; van Frank, S.; Bücker, R.; Schumm, T.; Schaff, J.-F.; Schmiedmayer, J.; Julía-Díaz, B.; Polls, A.
2016-06-01
Interferometry with trapped atomic Bose-Einstein condensates (BECs) requires the development of techniques to recombine the two paths of the interferometer and map the accumulated phase difference to a measurable atom number difference. We have implemented and compared two recombining procedures in a double-well-based BEC interferometer. The first procedure utilizes the bosonic Josephson effect and controlled tunneling of atoms through the potential barrier, similar to laser light in an optical fiber coupler. The second one relies on the interference of the reflected and transmitted parts of the BEC wave function when impinging on the potential barrier, analogous to light impinging on a half-silvered mirror. Both schemes were implemented successfully, yielding an interferometric contrast of ˜20 % and 42% respectively. Building efficient matter-wave recombiners represents an important step towards the coherent manipulation of external quantum superposition states of BECs.
Quantum turbulence in trapped atomic Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Tsatsos, Marios C.; Tavares, Pedro E. S.; Cidrim, André; Fritsch, Amilson R.; Caracanhas, Mônica A.; dos Santos, F. Ednilson A.; Barenghi, Carlo F.; Bagnato, Vanderlei S.
2016-03-01
Turbulence, the complicated fluid behavior of nonlinear and statistical nature, arises in many physical systems across various disciplines, from tiny laboratory scales to geophysical and astrophysical ones. The notion of turbulence in the quantum world was conceived long ago by Onsager and Feynman, but the occurrence of turbulence in ultracold gases has been studied in the laboratory only very recently. Albeit new as a field, it already offers new paths and perspectives on the problem of turbulence. Herein we review the general properties of quantum gases at ultralow temperatures paying particular attention to vortices, their dynamics and turbulent behavior. We review the recent advances both from theory and experiment. We highlight, moreover, the difficulties of identifying and characterizing turbulence in gaseous Bose-Einstein condensates compared to ordinary turbulence and turbulence in superfluid liquid helium and spotlight future possible directions.
Knot Solitons in Spinor Bose-Einstein Condensates
NASA Astrophysics Data System (ADS)
Hall, David; Ray, Michael; Tiurev, Konstantin; Ruokokoski, Emmi; Gheorghe, Andrei Horia; Möttönen, Mikko
2016-05-01
Knots are familiar entities that appear at a captivating nexus of art, technology, mathematics and science. Following a lengthy period of theoretical investigation and development, they have recently attracted great experimental interest in classical contexts ranging from knotted DNA and nanostructures to vortex knots in fluids. We demonstrate here the controlled creation and detection of knot solitons in the quantum-mechanical order parameter of a spinor Bose-Einstein condensate. Images of the superfluid reveal the circular shape of the soliton core and its associated linked rings. Our observations of the knot soliton establish an experimental foundation for future studies of their stability, dynamics and applications within quantum systems. Supported in part by NSF Grant PHY-1205822.
Dynamics of macroscopic tunneling in elongated Bose-Einstein condensates
Dekel, G.; Farberovich, V.; Fleurov, V.; Soffer, A.
2010-06-15
We investigate macroscopic tunneling from an elongated quasi-one-dimensional trap, forming a 'cigar-shaped' Bose-Einstein condensate (BEC). Using a recently developed formalism we get the leading analytical approximation for the right-hand side of the potential wall, i.e., outside the trap, and a formalism based on Wigner functions, for the left side of the potential wall, i.e., inside the BEC. We then present accomplished results of numerical calculations, which show a 'blip' in the particle density traveling with an asymptotic shock velocity, as resulted from previous works on a dotlike trap but with significant differences from the latter. Inside the BEC a pattern of a traveling dispersive shock wave is revealed. In the attractive case, we find trains of bright solitons frozen near the boundary.
Stabilization of ring dark solitons in Bose-Einstein condensates
Wang, Wenlong; Kevrekidis, P. G.; Carretero-González, R.; Frantzeskakis, D. J.; Kaper, Tasso J.; Ma, Manjun
2015-09-14
Earlier work has shown that ring dark solitons in two-dimensional Bose-Einstein condensates are generically unstable. In this work, we propose a way of stabilizing the ring dark soliton via a radial Gaussian external potential. We investigate the existence and stability of the ring dark soliton upon variations of the chemical potential and also of the strength of the radial potential. Numerical results show that the ring dark soliton can be stabilized in a suitable interval of external potential strengths and chemical potentials. Furthermore, we also explore different proposed particle pictures considering the ring as a moving particle and find, where appropriate, results in very good qualitative and also reasonable quantitative agreement with the numerical findings.
Stabilization of ring dark solitons in Bose-Einstein condensates
Wang, Wenlong; Kevrekidis, P. G.; Carretero-González, R.; Frantzeskakis, D. J.; Kaper, Tasso J.; Ma, Manjun
2015-09-14
Earlier work has shown that ring dark solitons in two-dimensional Bose-Einstein condensates are generically unstable. In this work, we propose a way of stabilizing the ring dark soliton via a radial Gaussian external potential. We investigate the existence and stability of the ring dark soliton upon variations of the chemical potential and also of the strength of the radial potential. Numerical results show that the ring dark soliton can be stabilized in a suitable interval of external potential strengths and chemical potentials. Furthermore, we also explore different proposed particle pictures considering the ring as a moving particle and find, wheremore » appropriate, results in very good qualitative and also reasonable quantitative agreement with the numerical findings.« less
Bose-Einstein Condensates with Large Number of Vortices
Ho, Tin-Lun
2001-08-06
We show that as the number of vortices in a three dimensional Bose-Einstein condensate increases, the system reaches a ''quantum Hall'' regime where the density profile is a Gaussian in the xy plane and an inverted parabolic profile along z . The angular momentum of the system increases as the vortex lattice shrinks. However, Coriolis force prevents the unit cell of the vortex lattice from shrinking beyond a minimum size. Although the recent MIT experiment is not exactly in the quantum Hall regime, it is close enough for the present results to be used as a guide. The quantum Hall regime can be easily reached by moderate changes of the current experimental parameters.
Internal Josephson effects in spinor dipolar Bose-Einstein condensates
Yasunaga, Masashi; Tsubota, Makoto
2010-02-15
We theoretically study the internal Josephson effect, which is driven by spin-exchange interactions and magnetic dipole-dipole interactions, in a three-level system for spin-1 Bose-Einstein condensates, obtaining novel spin dynamics. We introduce single spatial mode approximations into the Gross-Pitaevskii equations and derive the Josephson-type equations, which are analogous to tunneling currents through three junctions between three superconductors. From an analogy with two interacting nonrigid pendulums, we identify unique varied oscillational modes, called the 0-{pi}, 0-running, running-running, 2n{pi} and running-2{pi}, single nonrigid pendulum, and two rigid pendulums phase modes. These Josephson modes in the three states are expected to be found in real atomic Bose gas systems.
Spatial structure of a collisionally inhomogeneous Bose-Einstein condensate
Li, Fei; Zhang, Dongxia; Rong, Shiguang; Xu, Ying
2013-11-15
The spatial structure of a collisionally inhomogeneous Bose-Einstein condensate (BEC) in an optical lattice is studied. A spatially dependent current with an explicit analytic expression is found in the case with a spatially dependent BEC phase. The oscillating amplitude of the current can be adjusted by a Feshbach resonance, and the intensity of the current depends heavily on the initial and boundary conditions. Increasing the oscillating amplitude of the current can force the system to pass from a single-periodic spatial structure into a very complex state. But in the case with a constant phase, the spatially dependent current disappears and the Melnikov chaotic criterion is obtained via a perturbative analysis in the presence of a weak optical lattice potential. Numerical simulations show that a strong optical lattice potential can lead BEC atoms to a state with a chaotic spatial distribution via a quasiperiodic route.
Optimal control of Bose-Einstein condensates in three dimensions
NASA Astrophysics Data System (ADS)
Mennemann, J.-F.; Matthes, D.; Weishäupl, R.-M.; Langen, T.
2015-11-01
Ultracold gases promise many applications in quantum metrology, simulation and computation. In this context, optimal control theory (OCT) provides a versatile framework for the efficient preparation of complex quantum states. However, due to the high computational cost, OCT of ultracold gases has so far mostly been applied to one-dimensional (1D) problems. Here, we realize computationally efficient OCT of the Gross-Pitaevskii equation to manipulate Bose-Einstein condensates in all three spatial dimensions. We study various realistic experimental applications where 1D simulations can only be applied approximately or not at all. Moreover, we provide a stringent mathematical footing for our scheme and carefully study the creation of elementary excitations and their minimization using multiple control parameters. The results are directly applicable to recent experiments and might thus be of immediate use in the ongoing effort to employ the properties of the quantum world for technological applications.
Quantum filaments in dipolar Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Wächtler, F.; Santos, L.
2016-06-01
Collapse in dipolar Bose-Einstein condensates may be arrested by quantum fluctuations. Due to the anisotropy of the dipole-dipole interactions, the dipole-driven collapse induced by soft excitations is compensated by the repulsive Lee-Huang-Yang contribution resulting from quantum fluctuations of hard excitations, in a similar mechanism as that recently proposed for Bose-Bose mixtures. The arrested collapse results in self-bound filamentlike droplets, providing an explanation for the intriguing results of recent dysprosium experiments. Arrested instability and droplet formation are general features directly linked to the nature of the dipole-dipole interactions, and should hence play an important role in all future experiments with strongly dipolar gases.
Cosmological constant: a lesson from Bose-Einstein condensates.
Finazzi, Stefano; Liberati, Stefano; Sindoni, Lorenzo
2012-02-17
The cosmological constant is one of the most pressing problems in modern physics. We address this issue from an emergent gravity standpoint, by using an analogue gravity model. Indeed, the dynamics of the emergent metric in a Bose-Einstein condensate can be described by a Poisson-like equation with a vacuum source term reminiscent of a cosmological constant. The direct computation of this term shows that in emergent gravity scenarios this constant may be naturally much smaller than the naive ground-state energy of the emergent effective field theory. This suggests that a proper computation of the cosmological constant would require a detailed understanding about how Einstein equations emerge from the full microscopic quantum theory. In this light, the cosmological constant appears as a decisive test bench for any quantum or emergent gravity scenario. PMID:22401190
Quantum mass acquisition in spinor Bose-Einstein condensates.
Phuc, Nguyen Thanh; Kawaguchi, Yuki; Ueda, Masahito
2014-12-01
Quantum mass acquisition, in which a massless (quasi)particle becomes massive due to quantum corrections, is predicted to occur in several subfields of physics. However, its experimental observation remains elusive since the emergent energy gap is too small. We show that a spinor Bose-Einstein condensate is an excellent candidate for the observation of such a peculiar phenomenon as the energy gap turns out to be 2 orders of magnitude larger than the zero-point energy. This extraordinarily large energy gap is a consequence of the dynamical instability. The propagation velocity of the resultant massive excitation mode is found to be decreased by the quantum corrections as opposed to phonons. PMID:25526104
Rydberg Electrons in a Bose-Einstein Condensate.
Wang, Jia; Gacesa, Marko; Côté, R
2015-06-19
We investigate a hybrid system composed of ultracold Rydberg atoms immersed in an atomic Bose-Einstein condensate (BEC). The coupling between Rydberg electrons and BEC atoms leads to excitations of phonons, the exchange of which induces a Yukawa interaction between Rydberg atoms. Because of the small electron mass, the effective charge associated with this quasiparticle-mediated interaction can be large. Its range, equal to the BEC healing length, is tunable using Feshbach resonances to adjust the scattering length between BEC atoms. We find that for small healing lengths, the distortion of the BEC can "image" the Rydberg electron wave function, while for large healing lengths the induced attractive Yukawa potentials between Rydberg atoms are strong enough to bind them. PMID:26196974
Ruostekoski, Janne; Dutton, Zachary
2005-12-15
We study controlled methods of preparing vortex configurations in atomic Bose-Einstein condensates and their use in the studies of fundamental vortex scattering, reconnection processes, and superfluid sound emission. We explore techniques of imprinting vortex rings by means of coherently driving internal atomic transitions with electromagnetic fields which exhibit singular phase profiles. In particular, we show that a vortex ring can be prepared by two focused co-propagating Gaussian laser beams. More complex vortex systems may also be imprinted by directly superposing simpler field configurations or by programming their phase profiles on optical holograms. We analyze specific examples of two merging vortex rings in a trapped two-species {sup 87}Rb gas. We calculate the radiated sound energy in the reconnection process and show that the vortex relaxation and the redistribution of sound energy can be controlled by the imprinting process. As another creation technique, we study engineering pairs of two-dimensional point vortices in the condensates using a 'light roadblock' in ultraslow light propagation. We show how this can be used to study vortex collisions in compressible superfluids and how these collisions result in energy dissipation via phonons and, sometimes, annihilation of vortex pairs.
Formation of granular structures in trapped Bose-Einstein condensates under oscillatory excitations
NASA Astrophysics Data System (ADS)
Yukalov, V. I.; Novikov, A. N.; Bagnato, V. S.
2014-09-01
We present experimental observations and numerical simulations of nonequilibrium spatial structures in a trapped Bose-Einstein condensate subject to oscillatory perturbations. In experiment, first, there appear collective excitations, followed by quantum vortices. Increasing the amount of the injected energy leads to the formation of vortex tangles representing quantum turbulence. We study what happens after the regime of quantum turbulence, with increasing further the amount of injected energy. In such a strongly nonequilibrium Bose-condensed system of trapped atoms, vortices become destroyed and there develops a new kind of spatial structure exhibiting essentially heterogeneous spatial density. The structure is reminiscent of fog consisting of high-density droplets, or grains, surrounded by the regions of low density. The grains are randomly distributed in space, where they move. They live for a sufficiently long time to be treated as a type of metastable object. Such structures have been observed in nonequilibrium trapped Bose gases of 87Rb, subject to the action of alternating fields. Here we present experimental results and support them by numerical simulation. The granular, or fog structure is essentially different from the state of wave turbulence that develops after increasing further the amount of injected energy.
Rapid Production of Bose-Einstein Condensates at a 1 Hz Rate
NASA Astrophysics Data System (ADS)
Farkas, Daniel; Ramirez-Serrano, Jaime; Salim, Evan
2013-05-01
The speed at which Bose-Einstein condensates (BECs) can be produced is a key metric for the performance of ultracold-atom inertial sensors, gravimeters, and magnetometers, where production cycle time of ultracold atoms determines sensor bandwidth. Here, we demonstrate production of 87Rb BECs at rates exceeding 1 Hz. Not only can we create a BEC from a hot vapor in less than one second, but we can continuously repeat the process for several cycles. Such speeds are possible because of the short evaporation times that result when atoms are confined in tight traps. In our case, we magnetically trap atoms with an atom chip that seals the top of one of ColdQuanta's RuBECi®vacuum cells. With RF evaporative cooling sequences as short as 450 ms, we attain nearly pure condensates of 2 × 104 atoms. In the future, the apparatus described here will be integrated into a portable system that houses all of the components needed to produce BECs (e.g. lasers, vacuum, electronics, imaging, etc.) in a volume less than 0.3 m3. This work was supported by the Office of Naval Research (SBIR contract N00014-10-C-0282).
Phase Separation and Dynamics of Trapped Two-component Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Proukakis, Np; Lee, Kl; Edmonds, M.; Liu, I.-K.; Jorgensen, Nb; Wacker, L.; Arlt, Jj
2016-05-01
Two-component Bose-Einstein condensates (BECs) are an attractive system to study the non-equilibrium dynamics of interacting quantum gases. We recently formulated a self-consistent kinetic model to study such systems at finite-temperature, where both components are partially-condensed. The BECs and the thermal atoms are coupled together through both the mean-field interactions and all possible collisional processes. We demonstrate the potential dominance of an energy-conserving exchange collision involving a BEC atom and a thermal atom from different components, and discuss the control of the hydrodynamicity through variations of temperature, trap frequencies and trap geometries. Numerically analysing the miscibility-immiscibility phase diagram for the trapped 87Rb-39K experimental system, we demonstrate deviations from the simple (homogeneous) interaction strength criterion (g122 /g11g22 = 1), with the transition boundary depending on the BEC atom numbers. We propose the experimental mapping of this boundary by monitoring the damping rate of the dipole oscillations, supported by detailed numerical simulations at zero and finite temperatures. Acknowledge: EPSRC (Grant No. EP/K03250X/1).
Black-hole lasing action in laboratory Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Wang, Yi-Hsieh; Jacobson, Ted; Edwards, Mark; Clark, Charles W.
2015-03-01
A recent experiment infers the the production of Hawking radiation in an analogue black-hole laser, which consists of a Bose-Einstein condensate of about 5,000 87Rb atoms in a trap with a translating potential step. In the co-moving reference frame the flow velocity of the condensate exceeds the sound speed in a region confined between two sonic points, the analogue black and white hole horizons. We report simulations of that experiment based on the zero-temperature Gross-Pitaevskii (GP) equation that are consistent with the reported experimental results. The simulations show exponential growth of oscillatory modes trapped between the horizons, with a power spectrum consistent with expectations from the Bogoliubov dispersion relation, which saturates after an initial period. Quantum Hawking radiation occurs spontaneously in the vacuum, but in the presence of a coherent state of phonons it takes on a classical form captured by the zero-temperature GP equation. The growth of the trapped modes results from repeated super-radiant scattering from the black hole horizon, associated with emission of Hawking radiation to the exterior that is not well-resolved in the simulation. Supported in part by NSF Grants PHY-1068761 and PHY-0822671 and the ARO Atomtronics MURI.
Black-hole lasing action in laboratory Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Wang, Yi-Hsieh; Jacobson, Ted; Edwards, Mark; Clark, Charles W.
2015-05-01
A recent experiment infers the the production of Hawking radiation in an analogue black-hole laser, which consists of a Bose-Einstein condensate of about 5,000 87Rb atoms in a trap with a translating potential step. In the co-moving reference frame the flow velocity of the condensate exceeds the sound speed in a region confined between two sonic points, the analogue black and white hole horizons. We report simulations of that experiment based on the zero-temperature Gross-Pitaevskii (GP) equation that are consistent with the reported experimental results. The simulations show exponential growth of oscillatory modes trapped between the horizons, with a power spectrum consistent with expectations from the Bogoliubov dispersion relation, which saturates after an initial period. Quantum Hawking radiation occurs spontaneously in the vacuum, but in the presence of a coherent state of phonons it takes on a classical form captured by the zero-temperature GP equation. The growth of the trapped modes results from repeated super-radiant scattering from the black hole horizon, associated with emission of Hawking radiation to the exterior that is not well-resolved in the simulation.
The effect of adiabaticity on strongly quenched Bose Einstein Condensates
NASA Astrophysics Data System (ADS)
Ling, Hong; Kain, Ben
2015-05-01
We study the properties of a Bose-Einstein condensate following a deep quench to a large scattering length during which the condensate fraction nc changes with time. We construct a closed set of equations that highlight the role of the adiabaticity or equivalently, dnc/dt, the rate change of nc, which is to induce an (imaginary) effective interaction between quasiparticles. We show analytically that such a system supports a steady state characterized by a constant condensate density and a steady but periodically changing momentum distribution, whose time average is described exactly by the generalized Gibbs ensemble. We discuss how the nc -induced effective interaction, which cannot be ignored on the grounds of the adiabatic approximation for modes near the gapless Goldstone mode, can significantly affect condensate populations and Tan's contact for a Bose gas that has undergone a deep quench. In particular, we find that even when the Bose gas is quenched to unitarity, nc(t) does not completely deplete, approaching, instead, to a steady state with a finite condensate fraction. ITAMP, Harvard-Smithsonian Center for Astrophysics; KITP, University of Santa Barbara.
Macroscopic entanglement between a Bose Einstein condensate and a superconducting loop.
Singh, Mandip
2009-02-16
We theoretically study macroscopic entanglement between a magnetically trapped Bose-Einstein condensate and a superconducting loop. We treat the superconducting loop in a quantum superposition of two different flux states coupling with the magnetic trap to generate macroscopic entanglement. The scheme also provides a platform to investigate interferometry with an entangled Bose Einstein condensate and to explore physics at the quantum-classical interface. PMID:19219163
Steady-state entanglement of a Bose-Einstein condensate and a nanomechanical resonator
Asjad, Muhammad; Saif, Farhan
2011-09-15
We analyze the steady-state entanglement between Bose-Einstein condensate trapped inside an optical cavity with a moving end mirror (nanomechanical resonator) driven by a single mode laser. The quantized laser field mediates the interaction between the Bose-Einstein condensate and nanomechanical resonator. In particular, we study the influence of temperature on the entanglement of the coupled system, and note that the steady-state entanglement is fragile with respect to temperature.
Measuring the heat capacity in a Bose-Einstein condensation using global variables
NASA Astrophysics Data System (ADS)
Shiozaki, R. F.; Telles, G. D.; Castilho, P.; Poveda-Cuevas, F. J.; Muniz, S. R.; Roati, G.; Romero-Rochin, V.; Bagnato, V. S.
2014-10-01
Phase transitions are well understood and generally followed by the behavior of the associated thermodynamic quantities, such as in the case of the λ -point superfluid transition of liquid He, which is observed in its heat capacity. In the case of a trapped Bose-Einstein condensate, the heat capacity cannot be directly measured. In this work, we present a technique capable of determining the global heat capacity from the density distribution of a weakly interacting gas trapped in an inhomogeneous potential. This approach represents an alternative to models based on the local density approximation. By defining a pair of global conjugate variables, we determine the total internal energy and its temperature derivative, the heat capacity. We then apply the technique to a trapped 87Rb BEC, and a λ -type transition dependent on the atom number is observed, and the deviations from the noninteracting, ideal gas case are discussed. Finally, we discuss the chances of using this method to study the heat capacity at T →0 .
Mechanisms of stimulated Hawking radiation in laboratory Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Wang, Yi-Hsieh; Jacobson, Ted; Edwards, Mark; Clark, Charles W.
2016-05-01
We simulate and reproduce the results of a recent experiment that reported observations of a sonic analog black hole laser in a Bose-Einstein condensate (BEC). In the experiment, a time-swept step potential was applied to a trapped cigar-shaped BEC of 87 Rb, thereby creating white hole (WH) and black hole (BH) event horizons. Exponential growth of a density wave in the WH-BH cavity and the emission of Hawking radiation were observed. We show that the solution of the time-dependent Gross-Pitaevskii equation gives good agreement with the experiment with no adjustable parameters. The Hawking radiation in this experiment is not self-amplifying, but is stimulated by a growing Bogoliubov-Čerenkov mode that is generated at the WH event horizon. We use scaling arguments to identify a class of feasible experiments that can provide more distinctive signatures of Hawking radiation and of the dominant Bogoliubov-Čerenkov mode that stimulates it. Work supported in part by the NSF Physics Frontier Center at JQI and by NSF Grants PHY-1407744 and PHY-1413768.
Squeezing and entanglement in a Bose-Einstein condensate.
Estève, J; Gross, C; Weller, A; Giovanazzi, S; Oberthaler, M K
2008-10-30
Entanglement, a key feature of quantum mechanics, is a resource that allows the improvement of precision measurements beyond the conventional bound attainable by classical means. This results in the standard quantum limit, which is reached in today's best available sensors of various quantities such as time and position. Many of these sensors are interferometers in which the standard quantum limit can be overcome by using quantum-entangled states (in particular spin squeezed states) at the two input ports. Bose-Einstein condensates of ultracold atoms are considered good candidates to provide such states involving a large number of particles. Here we demonstrate spin squeezed states suitable for atomic interferometry by splitting a condensate into a few parts using a lattice potential. Site-resolved detection of the atoms allows the measurement of the atom number difference and relative phase, which are conjugate variables. The observed fluctuations imply entanglement between the particles, a resource that would allow a precision gain of 3.8 dB over the standard quantum limit for interferometric measurements. PMID:18830245
Atomic interactions in precision interferometry using Bose-Einstein condensates
Jamison, Alan O.; Gupta, Subhadeep; Kutz, J. Nathan
2011-10-15
We present theoretical tools for predicting and reducing the effects of atomic interactions in Bose-Einstein condensate (BEC) interferometry experiments. To address mean-field shifts during free propagation, we derive a robust scaling solution that reduces the three-dimensional Gross-Pitaevskii equation to a set of three simple differential equations valid for any interaction strength. To model the other common components of a BEC interferometer--condensate splitting, manipulation, and recombination--we generalize the slowly varying envelope reduction, providing both analytic handles and dramatically improved simulations. Applying these tools to a BEC interferometer to measure the fine structure constant, {alpha}[S. Gupta, K. Dieckmann, Z. Hadzibabic, and D. E. Pritchard, Phys. Rev. Lett. 89, 140401 (2002)], we find agreement with the results of the original experiment and demonstrate that atomic interactions do not preclude measurement to better than part-per-billion accuracy, even for atomic species with relatively large scattering lengths. These tools help make BEC interferometry a viable choice for a broad class of precision measurements.
Interferometry with independently prepared Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Wasak, T.; Szańkowski, P.; Chwedeńczuk, J.
2015-04-01
Whenever the value of an unknown parameter θ is extracted from a series of experiments, the result is inevitably burdened by the uncertainty Δ θ . If the system that is the subject of measurement consists of unentangled particles, this uncertainty is bounded by the shot-noise limit. To overcome this limitation, it is necessary to use a properly entangled state, which is usually prepared in a dedicated procedure. We show that quantum correlations arising from the indistinguishability of bosons are a sufficient resource for the sub-shot-noise interferometry. To this end, we consider an interferometer, which operates on two independently prepared Bose-Einstein condensates with fluctuating numbers of particles. We calculate the sensitivity obtained from the measurement of the number of atoms and compare it with the ultimate achievable bound. Our main conclusion is that even in the presence of major atom number fluctuations, an interferometer operating on two independently prepared condensates can give very high precision. These observations indicate a new possibility for an interferometer operating below the shot-noise limit.
Winding up superfluid in a torus via Bose Einstein condensation
Das, Arnab; Sabbatini, Jacopo; Zurek, Wojciech H.
2012-01-01
Phase transitions are usually treated as equilibrium phenomena, which yields telltale universality classes with scaling behavior of relaxation time and healing length. However, in second-order phase transitions relaxation time diverges near the critical point (“critical slowing down”). Therefore, every such transition traversed at a finite rate is a non-equilibrium process. Kibble-Zurek mechanism (KZM) captures this basic physics, predicting sizes of domains – fragments of broken symmetry – and the density of topological defects, long-lived relics of symmetry breaking that can survive long after the transition. To test KZM we simulate Bose-Einstein condensation in a ring using stochastic Gross-Pitaevskii equation and show that BEC formation can spontaneously generate quantized circulation of the newborn condensate. The magnitude of the resulting winding numbers and the time-lag of BEC density growth – both experimentally measurable – follow scalings predicted by KZM. Our results may also facilitate measuring the dynamical critical exponent for the BEC transition. PMID:22500209
Bose-Einstein condensate in a rapidly rotating nonsymmetric trap
Fetter, Alexander L.
2010-03-15
A rapidly rotating Bose-Einstein condensate in a symmetric two-dimensional harmonic trap can be described with the lowest Landau-level set of single-particle states. The condensate wave function {psi}(x,y) is a Gaussian {proportional_to}exp(-r{sup 2}/2), multiplied by an analytic function f(z) of the complex variable z=x+iy. The criterion for a quantum phase transition to a non-superfluid correlated many-body state is usually expressed in terms of the ratio of the number of particles to the number of vortices. Here a similar description applies to a rapidly rotating nonsymmetric two-dimensional trap with arbitrary quadratic anisotropy ({omega}{sub x}{sup 2}<{omega}{sub y}{sup 2}). The corresponding condensate wave function {psi}(x,y) is a complex anisotropic Gaussian with a phase proportional to xy, multiplied by an analytic function f(z), where z=x+i{beta}{sub -}y is a stretched complex variable and 0{<=}{beta}{sub -{<=}}1 is a real parameter that depends on the trap anisotropy and the rotation frequency. Both in the mean-field Thomas-Fermi approximation and in the mean-field lowest Landau level approximation with many visible vortices, an anisotropic parabolic density profile minimizes the energy. An elongated condensate grows along the soft trap direction yet ultimately shrinks along the tight trap direction. The criterion for the quantum phase transition to a correlated state is generalized (1) in terms of N/L{sub z}, which suggests that a nonsymmetric trap should make it easier to observe this transition, or (2) in terms of a 'fragmented' correlated state, which suggests that a nonsymmetric trap should make it harder to observe this transition. An alternative scenario involves a crossover to a quasi one-dimensional condensate without visible vortices, as suggested by Aftalion et al., Phys. Rev. A 79, 011603(R) (2009).
Number-conserving master equation theory for a dilute Bose-Einstein condensate
Schelle, Alexej; Wellens, Thomas; Buchleitner, Andreas; Delande, Dominique
2011-01-15
We describe the transition of N weakly interacting atoms into a Bose-Einstein condensate within a number-conserving quantum master equation theory. Based on the separation of time scales for condensate formation and noncondensate thermalization, we derive a master equation for the condensate subsystem in the presence of the noncondensate environment under the inclusion of all two-body interaction processes. We numerically monitor the condensate particle number distribution during condensate formation, and derive a condition under which the unique equilibrium steady state of a dilute, weakly interacting Bose-Einstein condensate is given by a Gibbs-Boltzmann thermal state of N noninteracting atoms.
Countersuperflow in Binary Bose-Einstein Condensates with Rabi Coupling
NASA Astrophysics Data System (ADS)
Takeuchi, Hiromitsu; Usui, Ayaka
2014-05-01
Countersuperflow instability, dynamic instability of counterflow of miscible superfluids, was observed recently for the first time by Hamner et al.. In the experiment, a countersuperflow of miscible two-component Bose-Einstein condensates (BECs) was realized in a quasi-one-dimensional trap by applying a magnetic gradient, which leads to a force in opposite directions for each component. A countersuperflow becomes dynamically unstable if the relative velocity between two superfluids exceeds a critical value and the instability causes characteristic density patterns forming solitons in quasi-one-dimensional systems. Very recently, Hamner et al. performed the experiment in a similar situation where a two-component BEC is subject to inhomogeneous Rabi oscillations between two pseudospin components under a magnetic gradient. Motivated by the experiment, we investigated stability of countersuperflow with internal Josephson coupling, namely, Rabi coupling. We reveal the stability phase diagram of countersuperflow with Rabi coupling. This work was supported by JSPS KAKENHI Grant Numbers 25887042, 26870500 and the MEXT KAKENHI (No. 22103003).
Bose-Einstein condensation in low dimensional layered structures
NASA Astrophysics Data System (ADS)
Salas, Patricia; Solis, M. A.
2008-03-01
Bose-Einstein condensation critical temperature, among other thermodynamic properties are reported for an ideal boson gas inside layered structures created by trapping potential of the Kronig-Penney type. We start with a big box where we introduce the Kronig-Penney potential in three directions to get a honey comb of cubes of side a size and walls of variable penetrability (P=mV0ab/^2), with bosons instead of bees. We are able to reduce the dimensions of the cubes to simulate bosons inside quantum dots. The critical temperature, starting from that of an ideal boson gas inside the big box, decreases as the small cube wall impenetrability increases arriving to a tiny but different from zero when the penetrability is zero (P-->∞). We also calculate the internal energy and the specific heat, and compare them to the ones obtained for the case of the same Kronig-Penney potential in one direction (simulating layers), and two directions (nanotubes).
Rapidly rotating Bose-Einstein condensates in strongly anharmonic traps
Correggi, M.; Rindler-Daller, T.; Yngvason, J.
2007-04-15
We study a rotating Bose-Einstein condensate in a strongly anharmonic trap (flat trap with a finite radius) in the framework of two-dimensional Gross-Pitaevskii theory. We write the coupling constant for the interactions between the gas atoms as 1/{epsilon}{sup 2} and we are interested in the limit {epsilon}{yields}0 (Thomas-Fermi limit) with the angular velocity {omega} depending on {epsilon}. We derive rigorously the leading asymptotics of the ground state energy and the density profile when {omega} tends to infinity as a power of 1/{epsilon}. If {omega}({epsilon})={omega}{sub 0}/{epsilon} a ''hole'' (i.e., a region where the density becomes exponentially small as 1/{epsilon}{yields}{infinity}) develops for {omega}{sub 0} above a certain critical value. If {omega}({epsilon})>>1/{epsilon} the hole essentially exhausts the container and a ''giant vortex'' develops with the density concentrated in a thin layer at the boundary. While we do not analyze the detailed vortex structure we prove that rotational symmetry is broken in the ground state for const vertical bar log {epsilon} vertical bar <{omega}({epsilon}) < or approx. const/{epsilon}.
Exact analytical soliton solutions in dipolar Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Andreev, Pavel A.; Kuz'menkov, Leonid S.
2014-09-01
By applying the full potentials of the electric dipole interaction and the magnetic dipole interaction, and making corrections, we generalise the existing theory of dipolar Bose-Einstein condensates (BECs) with aligned dipoles, achieving a correct description of the dipole-dipole interactions. We show that the corrected theory is different for the electric and magnetic dipoles of BECs and can be presented in a local (non-integral) form. We apply our model to recapture fundamental results for linear and nonlinear waves in dipolar BECs. The bright, dark and grey solitons are well-known soliton solutions of the Gross-Pitaevskii equation for the attractive and repulsive BECs. We consider solitons in the dipolar BECs of the fully polarised particles, including both the magnetised and electrically polarised BECs. We show that these two kinds of dipolar BECs show different behavior in their collective excitations. This is related to the fact that the electric and the magnetic fields of the BECs satisfy different pairs of the Maxwell equations. Thus we consider the magnetic and electric dipolar BECs independently. We obtain the exact analytical solutions for the bright, dark, and grey solitons in the magnetised (electrically polarised) BECs when they propagate parallel and perpendicular to an external magnetic (or electric) field. Comparison of the spectrum of the linear collective excitations for the two kinds of the dipolar BECs is presented as well.
Quantum analogues of classical wakes in Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Stagg, George; Parker, Nick; Barenghi, Carlo
2014-11-01
We show that an elliptical obstacle moving through a Bose-Einstein condensate generates wakes of quantum vortices which resemble those of classical viscous flow past a cylinder or sphere. Initial steady symmetric wakes, similar to those observed in classical flow at low Reynolds number, lose their symmetry and form clusters of like-signed vortices, in analogy to the classical Bénard-von Kármán vortex street. The key ingredient to produce classical-like wakes is that vortices are generated at a sufficiently high rate that they undergo strong interactions with their neighbours (rather than being swept away). The role of ellipticity is to facilitate the interaction of the vortices and to reduce the critical velocity for vortex nucleation. Our findings, demonstrated numerically in both two and three dimensions, confirm the intuition that a sufficiently large number of quanta of circulation reproduce classical physics. The effects which we describe (dependence of the critical velocity and cluster size on the obstacle's size, velocity and ellipticity) are also relevant to the motion of objects (such as vibrating wires, grids and forks) in superfluid helium, as the obstacle's ellipticity plays a role which is analogous to rough boundaries.
Subsonic and Supersonic Effects in Bose-Einstein Condensate
NASA Technical Reports Server (NTRS)
Zak, Michail
2003-01-01
A paper presents a theoretical investigation of subsonic and supersonic effects in a Bose-Einstein condensate (BEC). The BEC is represented by a time-dependent, nonlinear Schroedinger equation that includes terms for an external confining potential term and a weak interatomic repulsive potential proportional to the number density of atoms. From this model are derived Madelung equations, which relate the quantum phase with the number density, and which are used to represent excitations propagating through the BEC. These equations are shown to be analogous to the classical equations of flow of an inviscid, compressible fluid characterized by a speed of sound (g/Po)1/2, where g is the coefficient of the repulsive potential and Po is the unperturbed mass density of the BEC. The equations are used to study the effects of a region of perturbation moving through the BEC. The excitations created by a perturbation moving at subsonic speed are found to be described by a Laplace equation and to propagate at infinite speed. For a supersonically moving perturbation, the excitations are found to be described by a wave equation and to propagate at finite speed inside a Mach cone.
Manipulating localized matter waves in multicomponent Bose-Einstein condensates.
Manikandan, K; Muruganandam, P; Senthilvelan, M; Lakshmanan, M
2016-03-01
We analyze vector localized solutions of two-component Bose-Einstein condensates (BECs) with variable nonlinearity parameters and external trap potentials through a similarity transformation technique which transforms the two coupled Gross-Pitaevskii equations into a pair of coupled nonlinear Schrödinger equations with constant coefficients under a specific integrability condition. In this analysis we consider three different types of external trap potentials: a time-independent trap, a time-dependent monotonic trap, and a time-dependent periodic trap. We point out the existence of different interesting localized structures; namely, rogue waves, dark- and bright-soliton rogue waves, and rogue-wave breatherlike structures for the above three cases of trap potentials. We show how the vector localized density profiles in a constant background get deformed when we tune the strength of the trap parameter. Furthermore, we investigate the nature of the trajectories of the nonautonomous rogue waves. We also construct the dark-dark rogue wave solution for the repulsive-repulsive interaction of two-component BECs and analyze the associated characteristics for the three different kinds of traps. We then deduce single-, two-, and three-composite rogue waves for three-component BECs and discuss the correlated characteristics when we tune the strength of the trap parameter for different trap potentials. PMID:27078349
Symmetry breaking and singularity structure in Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Commeford, K. A.; Garcia-March, M. A.; Ferrando, A.; Carr, Lincoln D.
2012-08-01
We determine the trajectories of vortex singularities that arise after a single vortex is broken by a discretely symmetric impulse in the context of Bose-Einstein condensates in a harmonic trap. The dynamics of these singularities are analyzed to determine the form of the imprinted motion. We find that the symmetry-breaking process introduces two effective forces: a repulsive harmonic force that causes the daughter trajectories to be ejected from the parent singularity and a Magnus force that introduces a torque about the axis of symmetry. For the analytical noninteracting case we find that the parent singularity is reconstructed from the daughter singularities after one period of the trapping frequency. The interactions between singularities in the weakly interacting system do not allow the parent vortex to be reconstructed. Analytic trajectories were compared to the actual minima of the wave function, showing less than 0.5% error for an impulse strength of v=0.00005. We show that these solutions are valid within the impulse regime for various impulse strengths using numerical integration of the Gross-Pitaevskii equation. We also show that the actual duration of the symmetry-breaking potential does not significantly change the dynamics of the system as long as the strength is below v=0.0005.
Shock Waves in a Bose-Einstein Condensate
NASA Technical Reports Server (NTRS)
Kulikov, Igor; Zak, Michail
2005-01-01
A paper presents a theoretical study of shock waves in a trapped Bose-Einstein condensate (BEC). The mathematical model of the BEC in this study is a nonlinear Schroedinger equation (NLSE) in which (1) the role of the wave function of a single particle in the traditional Schroedinger equation is played by a space- and time-dependent complex order parameter (x,t) proportional to the square root of the density of atoms and (2) the atoms engage in a repulsive interaction characterized by a potential proportional to | (x,t)|2. Equations that describe macroscopic perturbations of the BEC at zero temperature are derived from the NLSE and simplifying assumptions are made, leading to equations for the propagation of sound waves and the transformation of sound waves into shock waves. Equations for the speeds of shock waves and the relationships between jumps of velocity and density across shock fronts are derived. Similarities and differences between this theory and the classical theory of sound waves and shocks in ordinary gases are noted. The present theory is illustrated by solving the equations for the example of a shock wave propagating in a cigar-shaped BEC.
Manipulating localized matter waves in multicomponent Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Manikandan, K.; Muruganandam, P.; Senthilvelan, M.; Lakshmanan, M.
2016-03-01
We analyze vector localized solutions of two-component Bose-Einstein condensates (BECs) with variable nonlinearity parameters and external trap potentials through a similarity transformation technique which transforms the two coupled Gross-Pitaevskii equations into a pair of coupled nonlinear Schrödinger equations with constant coefficients under a specific integrability condition. In this analysis we consider three different types of external trap potentials: a time-independent trap, a time-dependent monotonic trap, and a time-dependent periodic trap. We point out the existence of different interesting localized structures; namely, rogue waves, dark- and bright-soliton rogue waves, and rogue-wave breatherlike structures for the above three cases of trap potentials. We show how the vector localized density profiles in a constant background get deformed when we tune the strength of the trap parameter. Furthermore, we investigate the nature of the trajectories of the nonautonomous rogue waves. We also construct the dark-dark rogue wave solution for the repulsive-repulsive interaction of two-component BECs and analyze the associated characteristics for the three different kinds of traps. We then deduce single-, two-, and three-composite rogue waves for three-component BECs and discuss the correlated characteristics when we tune the strength of the trap parameter for different trap potentials.
Early stage of Superradiance from Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Buchmann, Lukas
2011-05-01
We investigate the dynamics of matter and optical waves at the early stage of superradiant Rayleigh scattering from Bose-Einstein condensates, an instance of four-wave-mixing of matter and optical waves. Our analysis is within a spatially dependent model which treats the matter-waves as well as the optical end-fire modes quantum mechanically and is capable of providing analytic solutions for the operators of interest. In particular, we study the statistical properties of the outgoing scattered light which provide insight into the rich internal dynamics of the system at this early stage. Furthermore, we investigate coherence properties of pairs of counter propagating atomic sidemodes produced during the process. It is shown that these clouds exhibit long-range spatial coherence and strong nonclassical density cross-correlations due to entanglement between the clouds. These findings make this scheme a promising candidate for the production of highly directional nonclassically correlated atomic pulses. Our prediction of number difference squeezing between the clouds was observed in another instance of a four-wave mixing process using metastable helium. Work performed at IESL-FORTH in Crete, Greece
Tunable bistability in hybrid Bose-Einstein condensate optomechanics.
Yasir, Kashif Ammar; Liu, Wu-Ming
2015-01-01
Cavity-optomechanics, a rapidly developing area of research, has made a remarkable progress. A stunning manifestation of optomechanical phenomena is in exploiting the mechanical effects of light to couple the optical degree of freedom with mechanical degree of freedom. In this report, we investigate the controlled bistable dynamics of such hybrid optomechanical system composed of cigar-shaped Bose-Einstein condensate (BEC) trapped inside high-finesse optical cavity with one moving-end mirror and is driven by a single mode optical field. The numerical results provide evidence for controlled optical bistability in optomechanics using transverse optical field which directly interacts with atoms causing the coupling of transverse field with momentum side modes, exited by intra-cavity field. This technique of transverse field coupling is also used to control bistable dynamics of both moving-end mirror and BEC. The report provides an understanding of temporal dynamics of moving-end mirror and BEC with respect to transverse field. Moreover, dependence of effective potential of the system on transverse field has also been discussed. To observe this phenomena in laboratory, we have suggested a certain set of experimental parameters. These findings provide a platform to investigate the tunable behavior of novel phenomenon like electromagnetically induced transparency and entanglement in hybrid systems. PMID:26035206
Recent experiments with ring Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Eckel, S.; Kumar, A.; Anderson, N. W.; Campbell, G. K.
2016-05-01
Here, we present three recent results of our experiments with ring-shaped 23 Na Bose-Einstein condensates. First, we present results of the effect of temperature on the decay of persistent currents in the presence of a local, stationary perturbation, or weak link. When the weak link rotates, it can drive transitions between quantized persistent current states in the ring, that form hysteresis loops whose size depends strongly on temperature. We find that our data does not fit with a simple model of thermal activation. Second, we present a new method to measure the quantized persistent current state of the ring in a minimally-destructive way. This technique uses phonons as probes of the background flow through the Doppler effect. Finally, we present a set of experiments designed to reproduce the horizon problem in the early universe. Supersonic expansion of the ring creates causally-disconnected regions of BEC whose phase evolves at different rates. When the expansion stops and these regions are allowed to recombine, they form topological excitations. These excitations can be predicted using a simple theory that shows excellent agreement with the data.
Yamashita, Makoto; Mukai, Tetsuya
2003-12-01
The dynamics of evaporative cooling of magnetically trapped {sup 87}Rb atoms is studied on the basis of the quantum kinetic theory of a Bose gas. We carried out the quantitative calculations of the time evolution of conventional evaporative cooling where the frequency of the radio-frequency magnetic field is swept exponentially. This ''exponential-sweep cooling'' is known to become inefficient at the final stage of the cooling process due to a serious three-body recombination loss. We precisely examine how the growth of a Bose-Einstein condensate depends on the experimental parameters of evaporative cooling, such as the initial number of trapped atoms, the initial temperature, and the bias field of a magnetic trap. It is shown that three-body recombination drastically depletes the trapped {sup 87}Rb atoms as the system approaches the quantum degenerate region and the number of condensed atoms finally becomes insensitive to these experimental parameters. This result indicates that the final number of condensed atoms is well stabilized by a large nonlinear three-body loss against the fluctuations of experimental conditions in evaporative cooling.
Nonlinear Dynamics of Bose-Einstein Condensates with Long-Range Interactions
Wunner, G.; Cartarius, H.; Fabcic, T.; Koeberle, P.; Main, J.; Schwidder, T.
2008-11-13
The motto of this paper is: Let's face Bose-Einstein condensation through nonlinear dynamics. We do this by choosing variational forms of the condensate wave functions (of given symmetry classes), which convert the Bose-Einstein condensates via the time-dependent Gross-Pitaevskii equation into Hamiltonian systems that can be studied using the methods of nonlinear dynamics. We consider in particular cold quantum gases where long-range interactions between the neutral atoms are present, in addition to the conventional short-range contact interaction, viz. gravity-like interactions, and dipole-dipole interactions. The results obtained serve as a useful guide in the search for nonlinear dynamics effects in numerically exact quantum calculations for Bose-Einstein condensates. A main result is the prediction of the existence of stable islands as well as chaotic regions for excited states of dipolar condensates, which could be checked experimentally.
Direct evaporative cooling of 39K atoms to Bose-Einstein condensation
NASA Astrophysics Data System (ADS)
Landini, M.; Roy, S.; Roati, G.; Simoni, A.; Inguscio, M.; Modugno, G.; Fattori, M.
2012-09-01
We report the realization of a Bose-Einstein condensate of 39K atoms without the aid of an additional atomic coolant. Our route to Bose-Einstein condensation comprises sub-Doppler laser cooling of large atomic clouds with more than 1010 atoms and evaporative cooling in an optical dipole trap where the collisional cross section can be increased using magnetic Feshbach resonances. Large condensates with almost 106 atoms can be produced in less than 15 s. Our achievements eliminate the need for sympathetic cooling with Rb atoms, which was the usual route implemented until now due to the unfavorable collisional property of 39K. Our findings simplify the experimental setup for producing Bose-Einstein condensates of 39K atoms with tunable interactions, which have a wide variety of promising applications, including atom interferometry to studies on the interplay of disorder and interactions in quantum gases.
Properties of spin-orbit-coupled Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Zhang, Yongping; Mossman, Maren Elizabeth; Busch, Thomas; Engels, Peter; Zhang, Chuanwei
2016-06-01
The experimental and theoretical research of spin-orbit-coupled ultracold atomic gases has advanced and expanded rapidly in recent years. Here, we review some of the progress that either was pioneered by our own work, has helped to lay the foundation, or has developed new and relevant techniques. After examining the experimental accessibility of all relevant spin-orbit coupling parameters, we discuss the fundamental properties and general applications of spin-orbit-coupled Bose-Einstein condensates (BECs) over a wide range of physical situations. For the harmonically trapped case, we show that the ground state phase transition is a Dicke-type process and that spin-orbit-coupled BECs provide a unique platform to simulate and study the Dicke model and Dicke phase transitions. For a homogeneous BEC, we discuss the collective excitations, which have been observed experimentally using Bragg spectroscopy. They feature a roton-like minimum, the softening of which provides a potential mechanism to understand the ground state phase transition. On the other hand, if the collective dynamics are excited by a sudden quenching of the spin-orbit coupling parameters, we show that the resulting collective dynamics can be related to the famous Zitterbewegung in the relativistic realm. Finally, we discuss the case of a BEC loaded into a periodic optical potential. Here, the spin-orbit coupling generates isolated flat bands within the lowest Bloch bands whereas the nonlinearity of the system leads to dynamical instabilities of these Bloch waves. The experimental verification of this instability illustrates the lack of Galilean invariance in the system.
Observation of grand-canonical number statistics in a photon Bose-Einstein condensate.
Schmitt, Julian; Damm, Tobias; Dung, David; Vewinger, Frank; Klaers, Jan; Weitz, Martin
2014-01-24
We report measurements of particle number correlations and fluctuations of a photon Bose-Einstein condensate in a dye microcavity using a Hanbury Brown-Twiss experiment. The photon gas is coupled to a reservoir of molecular excitations, which serve as both heat bath and particle reservoir to realize grand-canonical conditions. For large reservoirs, we observe strong number fluctuations of the order of the total particle number extending deep into the condensed phase. Our results demonstrate that Bose-Einstein condensation under grand-canonical ensemble conditions does not imply second-order coherence. PMID:24484122
Ultraslow, stopped, and compressed light in Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Dutton, Zachary John
We present theoretical analysis and experimental results of methods to achieve and use ultraslow light (USL), stopped light, and compressed light in sodium Bose-Einstein condensates (BECs). We present applications of these methods to study and harness both the coherent and superfluid properties of BECs. A description of the propagation of probe and coupling laser fields in three-level Λ configuration atoms is presented in a semiclassical description. This formalism is used to derive how electromagnetically induced transparency (EIT) and USL arise. We present novel theoretical results on the effect a fourth level, and effects of nonlinearities associated with a strong probe. Experimental demonstration of ultraslow light is presented. A description which includes atomic motion in Bose-condensed samples of alkali atoms is developed in a mean field description and coupled Gross-Pitaevskii equations are derived. A numerical code which solves these equations is presented. An analytic and numerical analysis reveal the limits on ultraslow light and compressed light imposed by the external atomic dynamics. We then show that using USL and switching the coupling field off allows storage of the coherent probe pulse information (amplitude and phase) in the atomic fields. Switching the coupling beam back on writes the coherent information back onto the probe field. Experimental demonstration is presented. We present experimental data and theoretical analysis showing how stopping light in a BEC creates an atom laser with the highest reported phase space density flux to date. Alternatively, reviving the probe pulse after significant BEC dynamics can be used to process the information before it is written back onto the probe. Possible applications to quantum processing are discussed. We then present results on a light "roadblock", whereby blocking part of the coupling field spatially compresses probe pulses to sizes on the order of the condensate healing length. The compressed
Hidden vortices in a Bose-Einstein condensate in a rotating double-well potential
Wen Linghua; Xiong Hongwei; Wu Biao
2010-11-15
We study vortex formation in a Bose-Einstein condensate in a rotating double-well potential. In addition to the ordinary quantized vortices and elusive ghost vortices, 'hidden' vortices are found distributed along the central barrier. These hidden vortices are invisible like ghost vortices but carry angular momentum. Moreover, their core size is not given by the healing length, but is strongly influenced by the external potential. We find that the Feynman rule can be well satisfied only after including the hidden vortices. There is no critical rotation frequency for the formation of hidden vortices while there is one for the formation of ordinary visible vortices. Hidden vortices can be revealed in the free expansion of Bose-Einstein condensates. In addition, the hidden vortices in a Bose-Einstein condensate can appear in other external potentials, such as a rotating anisotropic toroidal trap.
Chaotic synchronization in Bose-Einstein condensate of moving optical lattices via linear coupling
NASA Astrophysics Data System (ADS)
Zhang, Zhi-Ying; Feng, Xiu-Qin; Yao, Zhi-Hai; Jia, Hong-Yang
2015-11-01
A systematic study of the chaotic synchronization of Bose-Einstein condensed body is performed using linear coupling method based on Lyapunov stability theory, Sylvester’s criterion, and Gerschgorin disc theorem. The chaotic synchronization of Bose-Einstein condensed body in moving optical lattices is realized by linear coupling. The relationship between the synchronization time and coupling coefficient is obtained. Both the single-variable coupling and double-variable coupling are effective. The results of numerical calculation prove that the chaotic synchronization of double-variable coupling is faster than that of single-variable coupling and small coupling coefficient can achieve the chaotic synchronization. Weak noise has little influence on synchronization effect, so the linear coupling technology is suitable for the chaotic synchronization of Bose-Einstein condensate. Project supported by the Industrial Technology Research and Development Special Project of Jilin Province, China (Grant No. 2013C46) and the Natural Science Foundation of Jilin Province, China (Grant No. 20101510).
Clark, Kevin B
2010-03-01
Fringe quantum biology theories often adopt the concept of Bose-Einstein condensation when explaining how consciousness, emotion, perception, learning, and reasoning emerge from operations of intact animal nervous systems and other computational media. However, controversial empirical evidence and mathematical formalism concerning decoherence rates of bioprocesses keep these frameworks from satisfactorily accounting for the physical nature of cognitive-like events. This study, inspired by the discovery that preferential attachment rules computed by complex technological networks obey Bose-Einstein statistics, is the first rigorous attempt to examine whether analogues of Bose-Einstein condensation precipitate learned decision making in live biological systems as bioenergetics optimization predicts. By exploiting the ciliate Spirostomum ambiguum's capacity to learn and store behavioral strategies advertising mating availability into heuristics of topologically invariant computational networks, three distinct phases of strategy use were found to map onto statistical distributions described by Bose-Einstein, Fermi-Dirac, and classical Maxwell-Boltzmann behavior. Ciliates that sensitized or habituated signaling patterns to emit brief periods of either deceptive 'harder-to-get' or altruistic 'easier-to-get' serial escape reactions began testing condensed on initially perceived fittest 'courting' solutions. When these ciliates switched from their first strategy choices, Bose-Einstein condensation of strategy use abruptly dissipated into a Maxwell-Boltzmann computational phase no longer dominated by a single fittest strategy. Recursive trial-and-error strategy searches annealed strategy use back into a condensed phase consistent with performance optimization. 'Social' decisions performed by ciliates showing no nonassociative learning were largely governed by Fermi-Dirac statistics, resulting in degenerate distributions of strategy choices. These findings corroborate
Control of a Bose-Einstein condensate by dissipation: Nonlinear Zeno effect
Shchesnovich, V. S.; Konotop, V. V.
2010-05-15
We show that controlled dissipation can be used as a tool for exploring fundamental phenomena and managing mesoscopic systems of cold atoms and Bose-Einstein condensates. Even the simplest boson-Josephson junction, that is, a Bose-Einstein condensate in a double-well trap, subjected to removal of atoms from one of the two potential minima allows one to observe such phenomena as the suppression of losses and the nonlinear Zeno effect. In such a system the controlled dissipation can be used to create desired macroscopic states and implement controlled switching among different quantum regimes.
Occupation Statistics of a Bose-Einstein Condensate for a Driven Landau-Zener Crossing
Smith-Mannschott, Katrina; Chuchem, Maya; Cohen, Doron; Hiller, Moritz; Kottos, Tsampikos
2009-06-12
We consider an atomic Bose-Einstein condensate loaded in a biased double-well trap with tunneling rate K and interatomic interaction U. The Bose-Einstein condensate is prepared such that all N atoms are in the left well. We drive the system by sweeping the potential difference E between the two wells. Depending on the interaction u=NU/K and the sweep rate E, we distinguish three dynamical regimes: adiabatic, diabatic, and sudden and consider the occupation statistics of the final state. The analysis goes beyond mean-field theory and is complemented by a semiclassical picture.
Engineered potentials in ultracold Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Campbell, Daniel L.
Bose-Einstein condensates (BECs) are a recent addition to the portfolio of quantum materials some of which have profound commercial and military applications e.g., superconductors, superfluids and light emitting diodes. BECs exist in the lowest motional modes of a trap and have the lowest temperatures achieved by mankind. With full control over the shape of the trap the experimentalist may explore an extremely diverse set of Hamiltonians which may be altered mid-experiment. These properties are particularly suited for realizing novel quantum systems. This thesis explores interaction-driven domain formation and the subsequent domain coarsening for two immiscible BEC components. Because quantum coherences associated with interactions in BECs can be derived from low energy scattering theory we compare our experimental results to both a careful simulation (performed by Brandon Anderson) and an analytical prediction. This result very carefully explores the question of how a metastable system relaxes at the extreme limit of low temperature. We also explore spin-orbit coupling (SOC) of a BEC which links the linear and discrete momentum transferable by two counterpropagating ''Raman'' lasers that resonantly couple the ground electronic states of our BECs. SOC is used similarly in condensed matter systems to describe coupling between charge carrier spin and crystal momentum and is a necessary component of the quantum spin Hall effect and topological insulators. SOC links the linear and discrete momentum transferable by two counterpropagating ''Raman'' lasers and a subset of the ground electronic states of our BEC. The phases of an effective 2-spin component spin-orbit coupling (SOC) in a spin-1 BEC are described in Lin et al. (2011). We measure the phase transition between two phases of a spin-1 BEC with SOC which cannot be mimicked by a spin-1/2 system. The order parameter that describes transitions between these two phases is insensitive to magnetic field fluctuations. I
Structure of vortex shedding past potential barriers moving in a Bose-Einstein condensate
Mironov, V. A.; Smirnov, A. I. Smirnov, L. A.
2010-05-15
The problem of excitation of a homogeneous Bose-Einstein condensate by axially symmetric potential barriers moving with respect to the condensate with both supersonic and subsonic velocities is considered in terms of the Gross-Pitaevskii equation. The specific features of the structure of the vortex shedding past the barriers are analyzed for both regimes of motion.
Bogoliubov theory of a Bose-Einstein condensate in the particle representation
Dziarmaga, Jacek; Sacha, Krzysztof
2003-03-01
In the number-conserving Bogoliubov theory of the Bose-Einstein condensate, the Bogoliubov transformation between quasiparticles and particles is nonlinear. We invert this nonlinear transformation and give a general expression for eigenstates of the Bogoliubov Hamiltonian in particle representation. The particle representation unveils the structure of a condensate multiparticle wave function. We give several examples to illustrate a general formalism.
On the occurrence and detectability of Bose-Einstein condensation in helium white dwarfs
Benvenuto, O.G.; Vito, M.A. De E-mail: adevito@fcaglp.unlp.edu.ar
2011-02-01
It has been recently proposed that helium white dwarfs may provide promising conditions for the occurrence of the Bose-Einstein condensation. The argument supporting this expectation is that in some conditions attained in the core of these objects, the typical De Broglie wavelength associated with helium nuclei is of the order of the mean distance between neighboring nuclei. In these conditions the system should depart from classical behavior showing quantum effects. As helium nuclei are bosons, they are expected to condense. In order to explore the possibility of detecting the Bose-Einstein condensation in the evolution of helium white dwarfs we have computed a set of models for a variety of stellar masses and values of the condensation temperature. We do not perform a detailed treatment of the condensation process but mimic it by suppressing the nuclei contribution to the equation of state by applying an adequate function. As the cooling of white dwarfs depends on average properties of the whole stellar interior, this procedure should be suitable for exploring the departure of the cooling process from that predicted by the standard treatment. We find that the Bose-Einstein condensation has noticeable, but not dramatic effects on the cooling process only for the most massive white dwarfs compatible with a helium dominated interior ( ≈ 0.50M{sub s}un) and very low luminosities (say, Log(L/L{sub s}un) < −4.0). These facts lead us to conclude that it seems extremely difficult to find observable signals of the Bose-Einstein condensation. Recently, it has been suggested that the population of helium white dwarfs detected in the globular cluster NGC 6397 is a good candidate for detecting signals of the Bose-Einstein condensation. We find that these stars have masses too low and are too bright to have an already condensed interior.
Cosmological perturbations during the Bose-Einstein condensation of dark matter
Freitas, R.C.; Gonçalves, S.V.B. E-mail: sergio.vitorino@pq.cnpq.br
2013-04-01
In the present work, we analyze the evolution of the scalar and tensorial perturbations and the quantities relevant for the physical description of the Universe, as the density contrast of the scalar perturbations and the gravitational waves energy density during the Bose-Einstein condensation of dark matter. The behavior of these parameters during the Bose-Einstein phase transition of dark matter is analyzed in details. To study the cosmological dynamics and evolution of scalar and tensorial perturbations in a Universe with and without cosmological constant we use both analytical and numerical methods. The Bose-Einstein phase transition modifies the evolution of gravitational waves of cosmological origin, as well as the process of large-scale structure formation.
The first experiments with Bose-Einstein condensation of rubidium-87
NASA Astrophysics Data System (ADS)
Ensher, Jason Remington
1999-10-01
Bose-Einstein Condensation (BEC) is the macroscopic occupation of the ground-state of a system of bosons that occurs when the extent of the wavefunctions of the particles is comparable to the interparticle spacing. Although predicted by Albert Einstein in 1924) BEC in a dilute system was observed only recently in an atomic vapor of 87Rb by our group in 1995. This thesis describes the first experiments to explore the properties of this new state of matter. In early experiments, we studied how interparticle interactions modify the ground-state wavefunction and mean energy. We observed phonon-like collective excitations of the condensate. We studied modes of different angular momenta and energies. Our observations of how the characteristics of the modes depend on interactions quantitatively supported the mean- field picture of the dilute BEC. Shortly thereafter, we developed thermometry and calorimetry to study the ground-state fraction and mean energy of the Bose gas as a function of temperature. The BEC transition temperature and the temperature dependence of the ground-state fraction are in good agreement with predictions for an ideal Bose gas. However, the measured mean energy is larger than that of the ideal gas below the transition. We observe a distinct change in the energy-temperature curve near the transition, which indicates a sharp feature in the specific heat. In an effort to produce larger condensates we constructed a double-MOT apparatus that became the third-generation machine at JILA to observe and study BEC. The new apparatus produces condensates five times more quickly than the original experiment, increasing the number of atoms in the condensate from several thousand to 1-2 million atoms. Using the improved apparatus, we studied the TOP (time-averaged orbiting potential) magnetic trap. An important, new observation is that the trap symmetry is affected by the sag due to gravity, an effect which can be exploited to create very harmonic, spherical
Quantum Entanglement and Spin Squeezing of Two Species Bose-Einstein Condensates
NASA Astrophysics Data System (ADS)
Li, Song-Song
2016-09-01
We investigate quantum entanglement and spin squeezing of two species Bose-Einstein condensates. By the rotating-wave approximation, we obtain the effective Hamiltonian and the wave function of the system. It's shown that more entanglement and squeezing may be achieved by increasing the population difference of particles.
Stability of Bose-Einstein condensates in two-dimensional optical lattices
Chen Zhu; Wu Biao
2010-04-15
Both Landau instability and dynamical instability of Bose-Einstein condensates in moving two-dimensional optical lattices are investigated numerically and analytically. Phase diagrams for both instabilities are obtained numerically for different system parameters. These phase diagrams show that the Landau instability does not depend on direction for weak lattices while the dynamic instability is direction dependent. These features are explained analytically.
NASA Astrophysics Data System (ADS)
Smyrnakis, J.; Magiropoulos, M.; Kavoulakis, G. M.; Jackson, A. D.
2013-01-01
We derive solitary-wave solutions within the mean-field approximation in quasi-one-dimensional binary mixtures of Bose-Einstein condensates under periodic boundary conditions, for the case of an effective repulsive interatomic interaction. The particular gray-bright solutions that give the global energy minima are determined. Their characteristics and the associated dispersion relation are derived.
Nonlinear Floquet solutions of two periodically driven Bose-Einstein condensates
Xie Qiongtao
2007-10-15
We investigate the effect of an external periodic driving on the self-trapping transitions of two weakly coupled Bose-Einstein condensates in a double-well potential. Exact nonlinear Floquet solutions are obtained when the driving parameters satisfy certain conditions. These solutions can give an analytic demonstration of the ac control of self-trapping transitions.
Comment on ``Feshbach resonance and growth of a Bose-Einstein condensate''
NASA Astrophysics Data System (ADS)
Wu, Lei; Jiang, Ren-Jie; Pei, Yu-Hua; Zhang, Jie-Fang
2007-03-01
Our analytical solution shows that the number of atoms continuously injected into Bose-Einstein condensate from the reservoir depends on the linear gain/loss coefficient, and cannot be controlled by applying the external magnetic field via Feshbach resonance reported by Yuce and Kilic [Phys. Rev. A 74, 033609 (2006)].
Comment on 'Feshbach resonance and growth of a Bose-Einstein condensate'
Wu, Lei; Jiang, Ren-Jie; Pei, Yu-hua; Zhang, Jie-Fang
2007-03-15
Our analytical solution shows that the number of atoms continuously injected into Bose-Einstein condensate from the reservoir depends on the linear gain/loss coefficient, and cannot be controlled by applying the external magnetic field via Feshbach resonance reported by Yuce and Kilic [Phys. Rev. A 74, 033609 (2006)].
Bogoliubov space of a Bose-Einstein condensate and quantum spacetime fluctuations
Rivas, J. I.; Camacho, A.; Goeklue, E.
2012-08-24
We analyze the role that metric fluctuations could have on the features of a Bose-Einstein condensate. Particularly, the Bogoliubov space associated to it is considered and it will be shown that the pressure and the speed of sound of the ground state define an expression allowing us to determine the average size of these fluctuations.
Bose-Einstein condensation in the presence of artificial spin-orbit interaction
Yip, S.-K.
2011-04-15
Bose-Einstein condensation in the presence of a synthetic spin-orbit interaction is considered, focusing on the case where a Dirac or Rashba potential is generated via a tripod scheme. We found that the ground states can be either plane-wave states or superpositions of them, each characterized by their unique density distributions.
Landau-Zener tunneling of Bose-Einstein condensates in an optical lattice
Konotop, V.V.; Kevrekidis, P.G.; Salerno, M.
2005-08-15
A theory of the nonsymmetric Landau-Zener tunneling of Bose-Einstein condensates in deep optical lattices is presented. It is shown that periodic exchange of matter between the bands is described by a set of linearly coupled nonlinear Schroedinger equations. The key role of the modulational instability in rendering the interband transitions irreversible is highlighted.
Detecting Bose-Einstein condensation of exciton-polaritons via electron transport
Chen, Y.-N.; Lambert, Neill; Nori, Franco
2009-12-15
We examine the Bose-Einstein condensation of exciton-polaritons in a semiconductor microcavity via an electrical current. We propose that by embedding a quantum dot p-i-n junction inside the cavity, the tunneling current through the device can reveal features of condensation due to a one-to-one correspondence of the photons to the condensate polaritons. Such a device can also be used to observe the phase interference of the order parameters from two condensates.
Interaction effects on number fluctuations in a Bose-Einstein condensate of light.
van der Wurff, E C I; de Leeuw, A-W; Duine, R A; Stoof, H T C
2014-09-26
We investigate the effect of interactions on condensate-number fluctuations in Bose-Einstein condensates. For a contact interaction we variationally obtain the equilibrium probability distribution for the number of particles in the condensate. To facilitate comparison with experiment, we also calculate the zero-time delay autocorrelation function g((2))(0) for different strengths of the interaction. Finally, we focus on the case of a condensate of photons and find good agreement with recent experiments. PMID:25302898
Antezza, Mauro; Stringari, Sandro; Pitaevskii, Lev P.
2004-11-01
We calculate the effect of the interaction between an optically active material and a Bose-Einstein condensate on the collective oscillations of the condensate. We provide explicit expressions for the frequency shift of the center-of-mass oscillation in terms of the potential generated by the substrate and of the density profile of the gas. The form of the potential is discussed in detail and various regimes (van der Waals-London, Casimir-Polder, and thermal regimes) are identified as a function of the distance of atoms from the surface. Numerical results for the frequency shifts are given for the case of a sapphire dielectric substrate interacting with a harmonically trapped condensate of {sup 87}Rb atoms. We find that at distances of 4-8 {mu}m, where thermal effects become visible, the relative frequency shifts produced by the substrate are of the order 10{sup -4} and hence accessible experimentally. The effects of nonlinearities due to the finite amplitude of the oscillation are explicitly discussed. Predictions are also given for the radial breathing mode.
Photon antibunching upon scattering by an atomic Bose-Einstein condensate
Ilichev, L. V. Chapovsky, P. L.
2010-05-15
Antibunching of photodetections from different modes is shown to arise when two quantized light modes are scattered by an atomic Bose-Einstein condensate. This effect appears because of the uncertainty in the position of the condensate wave function relative to the optical lattice formed by the light beams. It is shown how the information contained in the history of photodetections leads to a spatial localization of the condensate wave function.
Matter-Wave Interferometry with Phase Fluctuating Bose-Einstein Condensates
Jo, G.-B.; Choi, J.-H.; Christensen, C. A.; Lee, Y.-R.; Pasquini, T. A.; Ketterle, W.; Pritchard, D. E.
2007-12-14
Elongated Bose-Einstein condensates (BECs) exhibit strong spatial phase fluctuations even well below the BEC transition temperature. We demonstrate that atom interferometers using such condensates are robust against phase fluctuations; i.e., the relative phase of the split condensate is reproducible despite axial phase fluctuations. However, larger phase fluctuations limit the coherence time, especially in the presence of some asymmetries in the two wells of the interferometer.
Matter-wave interferometry with phase fluctuating Bose-Einstein condensates.
Jo, G-B; Choi, J-H; Christensen, C A; Lee, Y-R; Pasquini, T A; Ketterle, W; Pritchard, D E
2007-12-14
Elongated Bose-Einstein condensates (BECs) exhibit strong spatial phase fluctuations even well below the BEC transition temperature. We demonstrate that atom interferometers using such condensates are robust against phase fluctuations; i.e., the relative phase of the split condensate is reproducible despite axial phase fluctuations. However, larger phase fluctuations limit the coherence time, especially in the presence of some asymmetries in the two wells of the interferometer. PMID:18233429
Bose-Einstein Condensation in Semiconductors: The Key Role of Dark Excitons
NASA Astrophysics Data System (ADS)
Combescot, Monique; Betbeder-Matibet, Odile; Combescot, Roland
2007-10-01
Bose-Einstein condensation in semiconductors is controlled by the nonelementary-boson nature of excitons. Pauli exclusion between the fermionic components of composite excitons produces dramatic exchange couplings between bright and dark states. In microcavities, where bright excitons and photons form polaritons, they force the condensate to be linearly polarized, as observed. In bulk, they also force linear polarization, but of dark states, due to interband Coulomb scatterings. To evidence this dark condensate, indirect processes are thus needed.
On the nature of Bose-Einstein condensation enhanced by localization
Jaeck, Thomas; Pule, Joseph V.; Zagrebnov, Valentin A.
2010-10-15
In a previous paper we established that for the perfect Bose gas and the mean-field Bose gas with an external random or weak potential, whenever there is generalized Bose-Einstein condensation in the eigenstates of the single particle Hamiltonian, there is also generalized condensation in the kinetic-energy states. In these cases Bose-Einstein condensation is produced or enhanced by the external potential. In the present paper we establish a criterion for the absence of condensation in single kinetic-energy states and prove that this criterion is satisfied for a class of random potentials and weak potentials. This means that the condensate is spread over an infinite number of states with low kinetic-energy without any of them being macroscopically occupied.
Collective excitations of the hybrid atomic-molecular Bose-Einstein condensates
Gupta, Moumita; Dastidar, Krishna Rai
2010-06-15
We investigate the low-energy excitations of the spherically and axially trapped atomic Bose-Einstein condensate coupled to a molecular Bose gas by coherent Raman transitions. We apply the sum-rule approach of many-body response theory to derive the low-lying collective excitation frequencies of the hybrid atom-molecular system. The atomic and molecular ground-state densities obtained in Gross-Pitaevskii and modified Gross-Pitaevskii (including the higher order Lee-Huang-Yang term in interatomic interaction) approaches are used to find out the individual energy components and hence the excitation frequencies. We obtain different excitation energies for different angular momenta and study their characteristic dependence on the effective Raman detuning, the scattering length for atom-atom interaction, and the intensities of the coupling lasers. We show that the inclusion of the higher-order nonlinear interatomic interaction in modified Gross-Pitaevskii approach introduces significant corrections to the ground-state properties and the excitation frequencies both for axially and spherically trapped coupled {sup 87}Rb condensate system with the increase in the s-wave scattering length (for peak gas-parameter {>=}10{sup -3}). It has been shown that the excitation frequencies decrease with the increase in the effective Raman detuning as well as the s-wave scattering length, whereas excitation frequencies increase with the increase in the atom-molecular coupling strength. The frequencies in modified Gross-Pitaevskii approximation exhibit an upward trend after a certain value of scattering length and also largely deviate from the Gross-Pitaevskii results with the increase in s-wave scattering length. The strong dependence of excitation frequencies on the laser intensities used for Raman transitions manifests the role of atom-molecular coupling strength on the control of collective excitations. The collective excitation frequencies for the hybrid atom-molecular BEC differ
Oettl, Anton; Ritter, Stephan; Koehl, Michael; Esslinger, Tilman
2006-06-15
We present and characterize an experimental system in which we achieve the integration of an ultrahigh finesse optical cavity with a Bose-Einstein condensate (BEC). The conceptually novel design of the apparatus for the production of BECs features nested vacuum chambers and an in vacuo magnetic transport configuration. It grants large scale spatial access to the BEC for samples and probes via a modular and exchangeable ''science platform.'' We are able to produce {sup 87}Rb condensates of 5x10{sup 6} atoms and to output couple continuous atom lasers. The cavity is mounted on the science platform on top of a vibration isolation system. The optical cavity works in the strong coupling regime of cavity quantum electrodynamics and serves as a quantum optical detector for single atoms. This system enables us to study atom optics on a single particle level and to further develop the field of quantum atom optics. We describe the technological modules and the operation of the combined BEC cavity apparatus. Its performance is characterized by single atom detection measurements for thermal and quantum degenerate atomic beams. The atom laser provides a fast and controllable supply of atoms coupling with the cavity mode and allows for an efficient study of atom field interactions in the strong coupling regime. Moreover, the high detection efficiency for quantum degenerate atoms distinguishes the cavity as a sensitive and weakly invasive probe for cold atomic clouds.
Controlling chaos in a Bose-Einstein condensate loaded into a moving optical lattice potential
Wang Zhixia Zhang Xihe; Shen Ke
2008-11-15
The spatial structure of a Bose-Einstein condensate loaded into an optical lattice potential is investigated, and spatially chaotic distributions of the condensates are revealed. By means of changing of the s-wave scattering length with a Feshbach resonance, the chaotic behavior can be well controlled to enter into periodicity. Numerical simulation shows that there are different periodic orbits according to different s-wave scattering lengths only if the maximal Lyapunov exponent of the system is negative.
Javanainen, Juha
2010-05-15
We study theoretically an atomic Bose-Einstein condensate in a double-well trap, both quantum-mechanically and classically, under conditions such that in the classical model an unstable equilibrium dissolves into large-scale oscillations of the atoms between the potential wells. Quantum mechanics alone does not exhibit such nonlinear dynamics, but measurements of the atom numbers in the potential wells may nevertheless cause the condensate to behave essentially classically.
Capillary instability in a two-component Bose-Einstein condensate
Sasaki, Kazuki; Suzuki, Naoya; Saito, Hiroki
2011-05-15
Capillary instability and the resulting dynamics in an immiscible two-component Bose-Einstein condensate are investigated using the mean-field and Bogoliubov analyses. A long, cylindrical condensate surrounded by the other component is dynamically unstable against breakup into droplets due to the interfacial tension arising from the quantum pressure and interactions. A heteronuclear system confined in a cigar-shaped trap is proposed for realizing this phenomenon experimentally.
One-dimensional Bose-Einstein condensation of photons in a microtube
NASA Astrophysics Data System (ADS)
Kruchkov, Alex J.
2016-04-01
This paper introduces a quasiequilibrium one-dimensional Bose-Einstein condensation of photons trapped in a microtube. Light modes with a cutoff frequency (a photon's "mass") interact through different processes of absorption, emission, and scattering on molecules and atoms. In this paper we study the conditions for the one-dimensional condensation of light and the role of photon-photon interactions in the system. The technique in use is the Matsubara Green's functions formalism modified for the quasiequilibrium system under study.
Kelvin-Tkachenko waves of few-vortex arrays in trapped Bose-Einstein condensates
Simula, T. P.; Machida, K.
2010-12-15
We have calculated the low-lying elementary excitations of three-dimensional few-vortex arrays in trapped Bose-Einstein condensates. The number of different Kelvin-Tkachenko vortex wave branches found matches the number of vortices in the condensate. The lowest odd-parity modes exhibit superfluid gyroscopic vortex motion. Experimentally, these modes could be excited and observed individually or in connection with the formation and decay of quantum turbulence.
Fano Blockade by a Bose-Einstein Condensate in an Optical Lattice
Vicencio, Rodrigo A.; Brand, Joachim; Flach, Sergej
2007-05-04
We study the transport of atoms across a localized Bose-Einstein condensate in a one-dimensional optical lattice. For atoms scattering off the condensate, we predict total reflection as well as full transmission for certain parameter values on the basis of an exactly solvable model. The findings of analytical and numerical calculations are interpreted by a tunable Fano-like resonance and may lead to interesting applications for blocking and filtering atom beams.
Spin-orbit-coupled Bose-Einstein condensates in a one-dimensional optical lattice.
Hamner, C; Zhang, Yongping; Khamehchi, M A; Davis, Matthew J; Engels, P
2015-02-20
We investigate a spin-orbit-coupled Bose-Einstein condensate loaded into a translating optical lattice. We experimentally demonstrate the lack of Galilean invariance in the spin-orbit-coupled system, which leads to anisotropic behavior of the condensate depending on the direction of translation of the lattice. The anisotropy is theoretically understood by an effective dispersion relation. We experimentally confirm this theoretical picture by probing the dynamical instability of the system. PMID:25763940
Field effects on the vortex states in spin-orbit coupled Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Xu, Liang-Liang; Liu, Yong-Kai; Feng, Shiping; Yang, Shi-Jie
2016-06-01
Multi-quantum vortices can be created in the ground state of rotating Bose-Einstein condensates with spin-orbit couplings. We investigate the effects of external fields, either a longitudinal field or a transverse field, on the vortex states. We reveal that both fields can effectively reduce the number of vortices. In the latter case we further find that the condensate density packets are pushed away in the horizontal direction and the vortices finally disappear to form a plane wave phase.
Squeezing and Entanglement of Density Oscillations in a Bose-Einstein Condensate.
Wade, Andrew C J; Sherson, Jacob F; Mølmer, Klaus
2015-08-01
The dispersive interaction of atoms and a far-detuned light field allows nondestructive imaging of the density oscillations in Bose-Einstein condensates. Starting from a ground state condensate, we investigate how the measurement backaction leads to squeezing and entanglement of the quantized density oscillations. We show that properly timed, stroboscopic imaging and feedback can be used to selectively address specific eigenmodes and avoid excitation of nontargeted modes of the system. PMID:26296103
Magnon Kinetics and Bose-Einstein Condensation Studied in Phase Space
Demidov, V. E.; Dzyapko, O.; Buchmeier, M.; Demokritov, S. O.; Stockhoff, T.; Schmitz, G.; Melkov, G. A.
2008-12-19
Using a novel technique providing simultaneous resolution with respect to the wave vector and frequency of magnons, we observed the formation of a Bose-Einstein condensate documented by the narrowing of the magnon distribution in phase space. Based on the measured width of the distribution we determined the effective correlation length of the condensate, which appears to be anisotropic, reflecting the anisotropy of the magnon dispersion spectrum.
NASA Astrophysics Data System (ADS)
Trombettoni, A.; Smerzi, A.; Sodano, P.
2005-02-01
We investigate the possibility that Bose Einstein condensates, loaded on a 2D optical lattice, undergo—at finite temperature—a Berezinskii Kosterlitz Thouless transition. We show that—in an experimentally attainable range of parameters—a planar lattice of Bose Einstein condensates is described by the XY model at finite temperature. We demonstrate that the interference pattern of the expanding condensates provides the experimental signature of the Berezinskii Kosterlitz Thouless transition by showing that, near the critical temperature, the \\skew3\\vec{k}=0 component of the momentum distribution and the central peak of the atomic density profile sharply decrease. The finite-temperature transition for a 3D optical lattice is also discussed in this paper, and analogies with superconducting Josephson junction networks are stressed throughout the text.