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arXiv · 2308.12760

Network-Device-Independent Certification of Causal Nonseparability

Hippolyte Dourdent·Alastair A. Abbott·Ivan Šupić·Cyril Branciard
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Abstract

Causal nonseparability is the property underlying quantum processes incompatible with a definite causal order. So far it has remained a central open question as to whether any process with a clear physical realisation can violate a causal inequality, so that its causal nonseparability can be certified in a device-independent way, as originally conceived. Here we present a method solely based on the observed correlations, which certifies the causal nonseparability of all the processes that can induce a causally nonseparable distributed measurement in a scenario with trusted quantum input states, as defined in [Dourdent et al., Phys. Rev. Lett. 129, 090402 (2022)]. This notably includes the celebrated quantum switch. This device-independent certification is achieved by introducing a network of untrusted operations, allowing one to self-test the quantum inputs on which the effective distributed measurement induced by the process is performed.

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Hippolyte Dourdent, Alastair A. Abbott, Ivan Šupić, Cyril Branciard. 2023-08-24. Network-Device-Independent Certification of Causal Nonseparability. https://doi.org/10.22331/q-2024-10-30-1514

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