Proposal for a motional-state Bell inequality test with ultracold atoms

Lewis-Swan, Robert J.; Kheruntsyan, K. V.

doi:10.1103/physreva.91.052114

Cited by 35 publications

(100 citation statements)

References 47 publications

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“…3(b). A value of jmj > n is necessary for any system to exhibit nonclassical (quantum) behavior, such as two-mode quadrature squeezing, Einstein-Podolsky-Rosen quadratureentanglement [57], and Bell inequality violation [58]. The fact that we measure values of jmj=n > 1 for all n (with jmj=n ≫ 1 for smallest n) is a further demonstration of the strong quantum nature of our system.…”

Section: Prl 118 240402 (2017) P H Y S I C a L R E V I E W L E T T Ementioning

confidence: 99%

Solving the Quantum Many-Body Problem via Correlations Measured with a Momentum Microscope

et al. 2017

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In quantum many-body theory, all physical observables are described in terms of correlation functions between particle creation or annihilation operators. Measurement of such correlation functions can therefore be regarded as an operational solution to the quantum many-body problem. Here, we demonstrate this paradigm by measuring multiparticle momentum correlations up to third order between ultracold helium atoms in an s-wave scattering halo of colliding Bose-Einstein condensates, using a quantum manybody momentum microscope. Our measurements allow us to extract a key building block of all higherorder correlations in this system-the pairing field amplitude. In addition, we demonstrate a record violation of the classical Cauchy-Schwarz inequality for correlated atom pairs and triples. Measuring multiparticle momentum correlations could provide new insights into effects such as unconventional superconductivity and many-body localization. DOI: 10.1103/PhysRevLett.118.240402 In quantum physics, fully understanding and characterizing complex systems, comprising a large (often macroscopic) number of interacting particles, is an extremely challenging problem. Solutions within the standard framework of (first-quantized) quantum mechanics generally require the knowledge of the full quantum many-body wave function. This necessitates an exponentially large amount of information to be encoded and simulated using the many-body Schrödinger equation. In an equivalent (second-quantized) quantum field theory formulation, the fundamental understanding of quantum many-body systems comes through the description of all physical observables via correlation functions between particle creation and annihilation operators. Here, the exponential complexity of the quantum many-body problem is converted into the need to know all possible multiparticle correlation functions, starting from two-, three-, and increasing to arbitrary N-particle (or higher-order) correlations.From an experimental viewpoint, an operational solution to the quantum many-body problem is therefore equivalent to measuring all multiparticle correlations. In certain cases, however, knowing only a specific set of (few-body or lower-order) correlations is sufficient to allow a solution of the many-body problem to be constructed. This was recently shown for phase correlations between two coupled one-dimensional (1D) Bose gases [1]. Apart from facilitating the description of physical observables, characterizing multiparticle correlations is important for introducing controlled approximations in many-body physics, such as the virial-and related cluster-expansion approaches that rely on truncation of the Bogolyubov-Born-GreenKirkwood-Yvon hierarchy [2,3] Correlations between multiple photons are also routinely used in numerous quantum optics experiments including ghost imaging [15,16], defining criteria for nonclassicality [17,18], analyzing entangled states generated by parametric down conversion [19], and characterizing single photon sources [20].Here, we demonstrate an e...

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Section: Prl 118 240402 (2017) P H Y S I C a L R E V I E W L E T T Ementioning

confidence: 99%

Solving the Quantum Many-Body Problem via Correlations Measured with a Momentum Microscope

et al. 2017

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“…Recent experiments using particles rather than photons have involved electrons [10], 87 Rb atoms trapped in optical tweezers [11], and helium atoms [12] where the beam splitter was a Bragg scattering optical grating. Each of the papers using matter waves rather than photons emphasizes that experiments developing coherent indistinguishable pairs of particles may be relevant in other areas such as quantum computing and information processing [13], highly sensitive force detection [14], quantum simulations [15], testing Bell inequalities with material observables [16], etc. Here we want to consider HOM-like interference with the use of Fock states of cold atoms undergoing simple tunneling in optical double (or multiple) potential wells in a method analogous to that experimentally used in Ref.…”

Section: Introductionmentioning

confidence: 99%

Interference effects in potential wells

Mullin

Laloë

2015

Phys. Rev. A

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We propose using an array of potential wells as an interferometer in which the beam splitters are provided by tunneling during an appropriate time through the barrier between wells. This arrangement allows demonstration of generalized Hong-Ou-Mandel effects with multiple particles traversing one or several beam splitters. Other interferometer effects can occur, including a violation of the Bell-Clauser-Horne-Shimony-Holt form of the Bell inequality. With interactions, one sees various effects, including so-called fermionization, collective tunneling, and self-trapping.

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“…While entanglement is usually detected using entanglement witnesses in many-body systems, first theoretical [3][4][5][6][7][8] and experimental [9] steps have been taken to test a Bell inequality on a many-body system. The interest is twofold.…”

Section: Introductionmentioning

confidence: 99%

“…To create quantum correlations between the spins, one can make use of elastic collisions in state-dependent potentials [28,29], giving rise to one-axis twisting as in Eq. (6). The spatial splitting is done by slowly raising a barrier in a state-independent potential as in Refs.…”

Section: Introductionmentioning

confidence: 99%

Optimal entanglement witnesses in a split spin-squeezed Bose-Einstein condensate

et al. 2017

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How do we detect quantum correlations in bipartite scenarios using a split many-body system and collective measurements on each party? We address this question by deriving entanglement witnesses using either only first-order or both first-and second-order moments of local collective spin components. In both cases, we derive optimal witnesses for spatially split spin-squeezed states in the presence of local white noise. We then compare the two optimal witnesses with respect to their resistance to various noise sources operating either at the preparation or at the detection level. We finally evaluate the statistics required to estimate the value of these witnesses when measuring a split spin-squeezed Bose-Einstein condensate. Our results can be seen as a step toward Bell tests with many-body systems.

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Proposal for a motional-state Bell inequality test with ultracold atoms

Cited by 35 publications

References 47 publications

Solving the Quantum Many-Body Problem via Correlations Measured with a Momentum Microscope

Solving the Quantum Many-Body Problem via Correlations Measured with a Momentum Microscope

Interference effects in potential wells

Optimal entanglement witnesses in a split spin-squeezed Bose-Einstein condensate

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