Witnessing bipartite entanglement sequentially by multiple observers

Bera, Anindita; Mal, Shiladitya; De, Aditi Sen; Sen, Ujjwal

doi:10.1103/physreva.98.062304

Cited by 88 publications

(94 citation statements)

References 47 publications

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“…The scenario of the present paper has also been studied for the related tasks of steering [18,22] and entanglement witnessing [23]. Since the presence of non-locality implies the possibility of steering and the presence of entanglement, our work shows that it is also possible to achieve both of these with arbitrarily many independent Bobs using only a single pair of entangled qubits.…”

Section: Discussionmentioning

confidence: 89%

“…Since the presence of non-locality implies the possibility of steering and the presence of entanglement, our work shows that it is also possible to achieve both of these with arbitrarily many independent Bobs using only a single pair of entangled qubits. This goes against some of the results in [18,22,23], and suggests that it is worth rethinking others that study the space of such correlations [24] or look at other Bell in-equalities [25] or more parties [26,27] after removing the assumption that both measurements used by each party have the same sharpness.…”

Section: Discussionmentioning

confidence: 98%

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Arbitrarily Many Independent Observers can Share the Nonlocality of a Single Maximally Entangled Qubit Pair

2020

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Alice and Bob each have half of a pair of entangled qubits. Bob measures his half and then passes his qubit to a second Bob who measures again and so on. The goal is to maximize the number of Bobs that can have an expected violation of the Clauser-Horne-Shimony-Holt (CHSH) Bell inequality with the single Alice. This scenario was introduced in [Phys. Rev. Lett. 114, 250401 (2015)] where the authors mentioned evidence that when the Bobs act independently and with unbiased inputs then at most two of them can expect to violate the CHSH inequality with Alice. Here we show that, contrary to this evidence, arbitrarily many independent Bobs can have an expected CHSH violation with the single Alice. Our proof is constructive and our measurement strategies can be generalized to work with a larger class of two-qubit states that includes all pure entangled two-qubit states. Since violation of a Bell inequality is necessary for device-independent tasks, our work represents a step towards an eventual understanding of the limitations on how much device-independent randomness can be robustly generated from a single pair of qubits.

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Section: Discussionmentioning

confidence: 89%

Section: Discussionmentioning

confidence: 98%

Arbitrarily Many Independent Observers can Share the Nonlocality of a Single Maximally Entangled Qubit Pair

2020

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“…Recently, quantum steering [15][16][17]] of a single system sequentially by multiple observers in the above scenario has also been demonstrated [18], going beyond monogamy constraint of quantum steering [19,20]. Sharing of entanglement by multiple observers measuring sequentially in the above scenario has been demonstrated [21]. Sharing of nonlocal advantage of quantum coherence [22] in the above scenario has also been presented recently [23].…”

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confidence: 99%

Sharing of tripartite nonlocality by multiple observers measuring sequentially at one side

Saha

Das

Sasmal

et al. 2019

Quantum Inf Process

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Standard tripartite nonlocality and genuine tripartite nonlocality can be detected by the violations of Mermin inequality and Svetlichny inequality, respectively. Since tripartite quantum nonlocality has novel applications in quantum information and quantum computation, it is important to investigate whether more than three observers can share tripartite nonlocality, simultaneously. In the present study we answer this question in the affirmative. In particular, we consider a scenario where three spin-1 2 particles are spatially separated and shared between Alice, Bob and multiple Charlies. Alice performs measurements on the first particle; Bob performs measurements on the second particle and multiple Charlies perform measurements on the third particle sequentially. In this scenario we investigate how many Charlies can simultaneously demonstrate standard tripartite nonlocality and genuine tripartite nonlocality with single Alice and single Bob. The interesting result revealed by the present study is that at most six Charlies can simultaneously demonstrate standard tripartite nonlocality with single Alice and single Bob. On the other hand, at most two Charlies can simultaneously demonstrate genuine tripartite nonlocality with single Alice and single Bob. Hence, the present study shows that standard tripartite nonlocality can be simultaneously shared by larger number of Charlies compared to genuine tripartite nonlocality in the aforementioned scenario, which implies that standard tripartite nonlocality is more effective than genuine tripartite nonlocality in the context of simultaneous sharing by multiple observers.

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“…This has also been experimentally demonstrated [10,11]. Moreover, shared quantum correlations have recently also been studied in other tasks such as entanglement witnessing [12], quantum steering [13,14] and a semidevice-independent setting [15][16][17][18].…”

Section: Introductionmentioning

confidence: 83%

Noise-robust preparation contextuality shared between any number of observers via unsharp measurements

Anwer

Wilson

Silva

et al. 2021

Quantum

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Multiple observers who independently harvest nonclassical correlations from a single physical system share the system's ability to enable quantum correlations. We show that any number of independent observers can share the preparation contextual outcome statistics enabled by state ensembles in quantum theory. Furthermore, we show that even in the presence of any amount of white noise, there exists quantum ensembles that enable such shared preparation contextuality. The findings are experimentally realised by applying sequential unsharp measurements to an optical qubit ensemble which reveals three shared demonstrations of preparation contextuality.

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Witnessing bipartite entanglement sequentially by multiple observers

Cited by 88 publications

References 47 publications

Arbitrarily Many Independent Observers can Share the Nonlocality of a Single Maximally Entangled Qubit Pair

Arbitrarily Many Independent Observers can Share the Nonlocality of a Single Maximally Entangled Qubit Pair

Sharing of tripartite nonlocality by multiple observers measuring sequentially at one side

Noise-robust preparation contextuality shared between any number of observers via unsharp measurements

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