Bell Correlations in Spin-Squeezed States of 500 000 Atoms

Engelsen, Nils J.; Krishnakumar, Rajiv; Hosten, Onur; Kasevich, Mark A.

doi:10.1103/physrevlett.118.140401

Cited by 77 publications

(91 citation statements)

References 29 publications

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“…So far, however, no violation of these inequalities could be observed experimentally since they require a single addressing of the constituent particles. This requirement have been lifted with the use of a Bell correlation witness (see below for details) which were used to demonstrate the presence of Bell correlations in many-body states [5][6][7]. This implies that if one could measure the constituent particle individually, then the observed correlations are strong enough to violate Bell inequalities presented in [2][3][4].…”

Section: Introductionmentioning

confidence: 99%

Bipartite nonlocality with a many-body system

et al. 2019

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We consider a bipartite scenario where two parties hold ensembles of 1/2-spins which can only be measured collectively. We give numerical arguments supporting the conjecture that in this scenario no Bell inequality can be violated for arbitrary numbers of spins if only first order moment observables are available. We then give a recipe to achieve a significant Bell violation with a split many-body system when this restriction is lifted. This highlights the strong requirements needed to detect bipartite quantum correlations in many-body systems device-independently.

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Section: Introductionmentioning

confidence: 99%

Bipartite nonlocality with a many-body system

et al. 2019

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“…These witnesses have triggered two experiments [9,11] which successfully detect the presence of Bell correlations in a many-body system under the assumption of Gaussian statistics [12,13]. The witness used in Refs.…”

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confidence: 99%

“…The witness used in Refs. [9,11] involves one-and two-body correlation functions and takes the form W ≥ 0, where the inequality is satisfied by measurements on states that are not Bell correlated. Observation of a negative value for W then leads to the conclusion that the measured system is Bell correlated.…”

mentioning

confidence: 99%

“…Let us mention that in Refs. [9,11], this finite statistics issue is circumvented by the addition of an assumption on the set of local states being tested. This has the effect of reducing the scope of the conclusion: the data reported in Refs.…”

mentioning

confidence: 99%

“…This has the effect of reducing the scope of the conclusion: the data reported in Refs. [9,11], are only able to exclude a subset of all non-Bell-correlated states (as pointed out in the references). Here, we show that such additional assumptions are not required in experiments on many-body systems, and thus argue that they should be avoided in the future.…”

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confidence: 99%

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Bell Correlations in a Many-Body System with Finite Statistics

et al. 2017

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A recent experiment reported the first violation of a Bell correlation witness in a many-body system [Science 352, 441 (2016)]. Following discussions in this Letter, we address here the question of the statistics required to witness Bell correlated states, i.e., states violating a Bell inequality, in such experiments. We start by deriving multipartite Bell inequalities involving an arbitrary number of measurement settings, two outcomes per party and one-and two-body correlators only. Based on these inequalities, we then build up improved witnesses able to detect Bell correlated states in many-body systems using two collective measurements only. These witnesses can potentially detect Bell correlations in states with an arbitrarily low amount of spin squeezing. We then establish an upper bound on the statistics needed to convincingly conclude that a measured state is Bell correlated.

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Quantum Magnetometer with Dual‐Coupling Optomechanics

Zhu

Liu

et al. 2022

Laser & Photonics Reviews

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An experimentally feasible magnetometer based on a dual‐coupling optomechanical system is proposed, where the radiation‐pressure coupling transduces the magnetic signal to the optical phase, and the quadratic optomechanical interaction induces a periodic squeezing effect. The latter not only amplifies the signal to be measured, but also accelerates the signal transducing rate characterized by an experimentally observable phase accumulation efficiency. In the vicinity of opto‐mechanical decoupled time, the ultimate bound to the estimability of magnetic signal is proportional to expfalse(−6rfalse)$\exp (-6r)$, and then the optimized accuracy of estimation can be enhanced nearly three orders with a controllable squeezing parameter r<1$r<1$. Moreover, this proposal is robust against the mechanical thermal noise, and the sensitivity of a specific measurement can reach to the order of 10−17normalTfalse(Hzfalse)−1${10}^{-17}\mathrm{T}{(\sqrt{\mathrm{Hz}})}^{-1}$ in the presence of dissipations and without ground state cooling of mechanical oscillator. The proposal fundamentally broadens the fields of quantum metrology and cavity optomechanics, with the potential application for on‐chip magnetic detection with high precision.

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Bell Correlations in Spin-Squeezed States of 500 000 Atoms

Cited by 77 publications

References 29 publications

Bipartite nonlocality with a many-body system

Bipartite nonlocality with a many-body system

Bell Correlations in a Many-Body System with Finite Statistics

Quantum Magnetometer with Dual‐Coupling Optomechanics

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