Influence of the choice of postprocessing method on Bell inequalities

Czechlewski, Mikołaj; Pawłowski, Marcin

doi:10.1103/physreva.97.062123

Cited by 5 publications

(9 citation statements)

References 31 publications

(42 reference statements)

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“…In Bell tests, the assignment strategy leads to lowering the maximally achievable quantum value of the Bell inequality, but does not increase the local bound [24]. As we show in the next section, this is not true in general for entanglement witnessing, and some local assignments can lead to negative values.…”

Section: Preliminariesmentioning

confidence: 91%

“…The literature that addresses the detection inefficiency problem, primarily in the context of the Bell test, describes two primary methods for handling no-click events [24]. In the first approach, referred to as the discard strategy, one simply ignores all the events where at least one of the detectors did not click (for estimation of joint probabilities).…”

Section: Preliminariesmentioning

confidence: 99%

“…The same mapping of probabilities is performed when one assumes the fair sampling. However, in case of the discard strategy (in Bell tests) one takes into account the effect of losses by increasing the local bound of a Bell inequality [25,24]. As we show in the next section, this also applies to entanglement witnessing: for imperfect detectors, the expectation value of a witness with respect to separable states can take negative values.…”

Section: Preliminariesmentioning

confidence: 99%

“…In Appendix C we give an explicit solution to the SDP in Eq. (24) for the Bell witness. The value of W π 4 ρ π 4 with respect to the Bell state can be calculated from Eq.…”

Section: Assignment Strategymentioning

confidence: 99%

See 3 more Smart Citations

Entanglement witnessing with untrusted detectors

Viola¹,

Miklin²,

Gachechiladze³

et al. 2023

Preprint

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We consider the problem of entanglement detection in the presence of faulty, potentially malicious detectors. A common-and, as of yet, the only-approach to this problem is to perform a Bell test in order to identify nonlocality of the measured entangled state. However, there are two significant drawbacks in this approach: the requirement to exceed a critical, and often high, detection efficiency, and much lower noise tolerance. In this paper, we propose an alternative approach to this problem, which is resilient to the detection loophole and is based on the standard tool of entanglement witness. We discuss how the two main techniques to detection losses, namely the discard and assignment strategies, apply to entanglement witnessing. We demonstrate using the example of a two-qubit Bell state that the critical detection efficiency can be significantly reduced compared to the Bell test approach.

show abstract

Section: Preliminariesmentioning

confidence: 91%

Section: Preliminariesmentioning

confidence: 99%

Section: Preliminariesmentioning

confidence: 99%

“…In Appendix C we give an explicit solution to the SDP in Eq. (24) for the Bell witness. The value of W π 4 ρ π 4 with respect to the Bell state can be calculated from Eq.…”

Section: Assignment Strategymentioning

confidence: 99%

See 2 more Smart Citations

Entanglement witnessing with untrusted detectors

Viola¹,

Miklin²,

Gachechiladze³

et al. 2023

Preprint

View full text Add to dashboard Cite

show abstract

“…The key problem that we investigate in this work is how the no-click events affect the expectation value of W and, consequently, entanglement detection. The literature that addresses the detection inefficiency problem, primarily in the context of the Bell test, describes two primary methods for handling no-click events [25]. In the first approach, referred to as the discard strategy, one simply ignores all the events where at least one of the detectors did not click (for estimation of joint probabilities).…”

Section: Preliminariesmentioning

confidence: 99%

Entanglement witnessing with untrusted detectors

Viola,

Miklin,

Gachechiladze

et al. 2023

J. Phys. A: Math. Theor.

Self Cite

View full text Add to dashboard Cite

We consider the problem of entanglement detection in the presence of faulty, potentially malicious detectors. A common—and, as of yet, the only—approach to this problem is to perform a Bell test in order to identify nonlocality of the measured entangled state. However, there are two significant drawbacks in this approach: the requirement to exceed a critical, and often high, detection efficiency, and much lower noise tolerance. In this paper, we propose an alternative approach to this problem, which is resilient to the detection loophole and is based on the standard tool of entanglement witness. We discuss how the two main techniques to detection losses, namely the discard and assignment strategies, apply to entanglement witnessing. We demonstrate using the example of a two-qubit Bell state that the critical detection efficiency can be significantly reduced compared to the Bell test approach.

show abstract

Extending loophole-free nonlocal correlations to arbitrarily large distances

Chaturvedi,

Viola,

Pawłowski

2024

npj Quantum Inf

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Quantum theory allows spatially separated observers to share nonlocal correlations, which enable them to accomplish classically inconceivable information processing and cryptographic feats. However, the distances over which nonlocal correlations can be realized remain severely limited due to their high fragility to noise and high threshold detection efficiencies. To enable loophole-free nonlocality across large distances, we introduce Bell experiments wherein the spatially separated parties randomly choose the location of their measurement devices. We demonstrate that when devices close to the source are perfect and witness extremal nonlocal correlations, such correlations can be extended to devices placed arbitrarily far from the source. To accommodate imperfections close to the source, we demonstrate an analytic trade-off: the higher the loophole-free nonlocality close to the source, the lower the threshold requirements away from the source. We utilize this trade-off and formulate numerical methods to estimate the critical requirements of individual measurement devices in such experiments.

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Influence of the choice of postprocessing method on Bell inequalities

Cited by 5 publications

References 31 publications

Entanglement witnessing with untrusted detectors

Entanglement witnessing with untrusted detectors

Entanglement witnessing with untrusted detectors

Extending loophole-free nonlocal correlations to arbitrarily large distances

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