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- Gonzales-Ureta, Junior R., 1992-, et al.
(författare)
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Optimal and tight Bell inequalities for state-independent contextuality sets
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Two fundamental quantum resources, nonlocality and contextuality, can be connected through Bell inequalities that are violated by state-independent contextuality (SI-C) sets. These Bell inequalities allow for applications requiring simultaneous nonlocality and contextuality. For existing Bell inequalities, the nonlocality produced by SI-C sets is very sensitive to noise. This precludes actual experiments. Here, we identify the Bell inequalities for which the nonlocality produced by SI-C sets is optimal, i.e., maximally robust to either noise or detection inefficiency, for the simplest SI-C [S. Yu and C. H. Oh, Phys. Rev. Lett. 108, 030402 (2012)] and Kochen-Specker sets [A. Cabello et al., Phys. Lett. A 212, 183 (1996)] and show that, in both cases, nonlocality is sufficiently resistant for experiments.
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| 2. |
- Jogenfors, Jonathan, 1988-, et al.
(författare)
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Comment on "Franson Interference Generated by a Two-Level System"
- 2017
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In a recent Letter [Phys. Rev. Lett. 118, 030501 (2017)], Peiris, Konthasinghe, and Muller report a Franson interferometry experiment using pairs of photons generated from a two-level semiconductor quantum dot. The authors report a visibility of 66% and claim that this visibility “goes beyond the classical limit of 50% and approaches the limit of violation of Bell’s inequalities (70.7%).” We explain why we do not agree with this last statement and how to fix the problem.
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| 3. |
- Smania, Massimiliano, et al.
(författare)
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Avoiding apparent signalling in Bell tests for quantum information applications
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Bell tests have become a powerful tool for checking security, quantifying randomness, detecting entanglement, and many other applications, as well as for investigating fundamental physical limits. Most Bell experiments make the assumptions of fair sampling and equal detection efficiency, and some also the assumption of setting reproducibility. Here, we point out that there are typical experimental imperfections and practices that lead to the violation of these assumptions and can go unnoticed. This is a problem that can invalidate the conclusions of many past and future Bell experiments and allow for malicious attacks. Detecting, quantifying, and fixing this problem is therefore of fundamental importance, especially for modern applications where the experimental values are used to reach quantitative conclusions about security, randomness, or entanglement. To illustrate the issue and its causes, we present a set of Bell experiments using polarization-entangled photons, where we identify common imperfections and practices that cause the failure of the assumptions. These experiments tell us which methods we should avoid and to which aspects of the setup we should pay special attention. We show that the failure of these assumptions results in a violation of a fundamental requirement in any Bell experiment, namely, non-signalling. We present a test based on the deviation from the non-signalling conditions that quantify and help us to fix the problem. We emphasize that adopting the measures and conducting the tests suggested here is necessary in order to obtain reliable conclusions in modern quantum information applications based on Bell tests.
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