Macroscopic quantum superposition states in Bose-Einstein condensates: Decoherence and many modes

Louis, Pearl J. Y.; Brydon, P. M. R.; Savage, C. M.

doi:10.1103/physreva.64.053613

Cited by 37 publications

(15 citation statements)

References 20 publications

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“…A double-well BEC can, in principle, be used to create a macroscopic superposition state (see, for example, [37][38][39][40][77][78][79][80][81][82][83]). The full Hamiltonian of this system is:…”

Section: Generating Macroscopic Superposition States With Double-wellmentioning

confidence: 99%

Exploring the unification of quantum theory and general relativity with a Bose–Einstein condensate

2019

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Despite almost a century's worth of study, it is still unclear how general relativity (GR) and quantum theory (QT) should be unified into a consistent theory. The conventional approach is to retain the foundational principles of QT, such as the superposition principle, and modify GR. This is referred to as 'quantizing gravity', resulting in a theory of 'quantum gravity'. The opposite approach is 'gravitizing QT' where we attempt to keep the principles of GR, such as the equivalence principle, and consider how this leads to modifications of QT. What we are most lacking in understanding which route to take, if either, is experimental guidance. Here we consider using a Bose-Einstein condensate (BEC) to search for clues. In particular, we study how a single BEC in a superposition of two locations could test a gravitizing QT proposal where wavefunction collapse emerges from a unified theory as an objective process, resolving the measurement problem of QT. Such a modification to QT due to general relativistic principles is testable near the Planck mass scale, which is much closer to experiments than the Planck length scale where quantum, general relativistic effects are traditionally anticipated in quantum gravity theories. Furthermore, experimental tests of this proposal should be simpler to perform than recently suggested experiments that would test the quantizing gravity approach in the Newtonian gravity limit by searching for entanglement between two massive systems that are both in a superposition of two locations.

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Section: Generating Macroscopic Superposition States With Double-wellmentioning

confidence: 99%

Exploring the unification of quantum theory and general relativity with a Bose–Einstein condensate

2019

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“…Two-sites Bose-Hubbard model. In the following we investigate the two-time correlation dynamics in a twosites Bose-Hubbard model in the presence of phase noise [27,[31][32][33][34][35][36][37][38][39][40][41][42]. The Hamiltonian is given by…”

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confidence: 99%

Two-Time Correlations Probing the Dynamics of Dissipative Many-Body Quantum Systems: Aging and Fast Relaxation

2015

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We use two-time correlation functions to study the complex dynamics of dissipative many-body quantum systems. In order to measure, understand, and categorize these correlations we extend the framework of the adiabatic elimination method. We show that, for the same parameters and times, two-time correlations can display two distinct behaviors depending on the observable considered: a fast exponential decay or a much slower dynamics. We exemplify these findings by studying strongly interacting bosons in a double well subjected to phase noise. While the single-particle correlations decay exponentially fast with time, the density-density correlations display slow aging dynamics. We also show that this slow relaxation regime is robust against particle losses. Additionally, we use the developed framework to show that the dynamic properties of dissipatively engineered states can be drastically different from their Hamiltonian counterparts.

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“…One difficulty to overcome in the experimental procedure is the precise control over the number of atoms in the junction, which should stay constant during the experiment. Atom losses may induce dephasing as discussed in [22]. On the other side, the time required for the unitary time evolution into the Schroedinger cat state is experimentally feasible as demonstrated already with the experiments in optical lattices [9].…”

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confidence: 88%

Number squeezing, quantum fluctuations, and oscillations in mesoscopic Bose Josephson junctions

2008

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Starting from a quantum two-mode Bose-Hubbard Hamiltonian we determine the ground state properties, momentum distribution and dynamical evolution for a Bose Josephson junction realized by an ultracold Bose gas in a double-well trap. Varying the well asymmetry we identify Mott-like regions of parameters where number fluctuations are suppressed and the interference fringes in the momentum distribution are strongly reduced. We also show how Schroedinger cat states, realized from an initially phase coherent state by a sudden rise of the barrier among the two wells, will give rise to a destructive interference in the time-dependent momentum distribution.PACS numbers: 03.75.Mn Superconductor Josephson junctions are a paradigmatic example of macroscopic quantum coherence. The underlying physical mechanism is the Josephson effect [1]: two superconductors connected by a weak link have coherent dynamical behavior determined by the relative macroscopic phase of the superconducting condensates. Josephson junctions have been used to discuss fundamental concepts in quantum mechanics [2], perform precision measurements [3], and are now promising candidates to implement quantum information devices [4]. One important feature of superconducting Josephson junctions is the possibility to precisely control and adjust the state of the system by varying external parameters, eg a gate-voltage or magnetic flux.Bose Josephson junctions have been only recently proposed [5], and realized experimentally [6], and many issues remain open. In the simplest configuration a Bose Josephson junction is realized by confining an ultracold Bose gas in a double-well potential. This configuration can be described using a two-mode model in which the bosons occupy the lowest level in each well. In the "classical" regime of large particle numbers and weak repulsive interactions the gas is well described by the Gross-Pitaevskii equation which, within the two-mode approximation, can be recast in the form of generalized Josephson equations for the time evolution of the relative phase and population imbalance among the two wells [5]. These equations differ from the original ones used for superconductor Josephson junctions [3] by the presence of a nonlinear coupling among the phase and populationimbalance variables. This term originates from bosonboson interactions in the mean-field approximation and gives rise to a rich dynamical behavior, displaying self trapping and π oscillations [5].In this Letter we focus on the mesoscopic "quantum" regime beyond the Gross-Pitaevskii equation, in the limit of strong interactions and/or smaller values of N . This gets within reach of current experiments [7]. As interactions are increased phase fluctuations become more and more important while number fluctuations are suppressed; the ground state of the system approaches a regime which can be viewed as a mesoscopic Mott insulator. During the time evolution the phase coherence first degrades ("phase diffusion" [8]), but, in a closed quantum system, periodically revives, as ...

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Macroscopic quantum superposition states in Bose-Einstein condensates: Decoherence and many modes

Cited by 37 publications

References 20 publications

Exploring the unification of quantum theory and general relativity with a Bose–Einstein condensate

Exploring the unification of quantum theory and general relativity with a Bose–Einstein condensate

Two-Time Correlations Probing the Dynamics of Dissipative Many-Body Quantum Systems: Aging and Fast Relaxation

Number squeezing, quantum fluctuations, and oscillations in mesoscopic Bose Josephson junctions

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