Quantum nonlocality with arbitrary limited detection efficiency

Abstract

The demonstration and use of nonlocality, as defined by Bell's theorem, rely strongly on dealing with non-detection events due to losses and detectors' inefficiencies. Otherwise, the so-called detection loophole could be exploited. The only way to avoid this is to have detection efficiencies that are above a certain threshold. We introduce the intermediate assumption of limited detection efficiency, that is, in each run of the experiment, the overall detection efficiency is lower bounded by ${\eta }_{min}>0$. Hence, in an adversarial scenario, the adversaries have arbitrary large but not full control over the inefficiencies. We analyse the set of possible correlations that fulfill Limited Detection Locality (LDL) and show that they necessarily satisfy some linear Bell-like inequalities. We prove that quantum theory predicts the violation of one of these inequalities for all ${\eta }_{min}>0$. Hence, nonlocality can be demonstrated with arbitrarily small limited detection efficiencies. We validate this assumption experimentally via a twin-photon implementation in which two users are provided with one photon each out of a partially entangled pair. We exploit on each side a passive switch followed by two measurement devices with fixed settings. Assuming the switches are not fully controlled by an adversary, nor by hypothetical local variables, we reveal the nonlocality of the established correlations despite a low overall detection efficiency.

arXiv comment5+5 pages, 3 figures. Theory part previously put on arXiv at arXiv:1507.04937 Accepted in Physical Review Letters

References in corpus (17)

• Experimental loophole-free violation of a Bell inequality using entangled electron spins separated by 1.3 km
• Bell nonlocality
• Significant-loophole-free test of Bell's theorem with entangled photons
• Random Numbers Certified by Bell's Theorem
• A strong loophole-free test of local realism
• No Signalling and Quantum Key Distribution
• From Bell's Theorem to Secure Quantum Key Distribution
• Device-independent quantum key distribution secure against collective attacks
• Device-independent witnesses of genuine multipartite entanglement
• Experimentally faking the violation of Bell's inequalities
• Arbitrarily small amount of measurement independence is sufficient to manifest quantum nonlocality
• Device-independent demonstration of genuine multipartite entanglement
• Detection Loophole in Bell experiments: How post-selected local correlations can look non-local
• Experimental amplification of an entangled photon: what if the detection loophole is ignored?
• Bell inequality and the locality loophole: Active versus passive switches
• Demonstration of Quantum Nonlocality in presence of Measurement Dependence
• Tailored two-photon correlation and fair-sampling: a cautionary tale

Cited by in corpus (6)

• Quantum photonics at telecom wavelengths based on lithium niobate waveguides
• Device-independent point estimation from finite data and its application to device-independent property estimation
• Many-Body Localization : construction of the emergent local conserved operators via block real-space renormalization
• Measurement-dependent locality beyond i.i.d
• Measurement dependent locality
• Certifying long-range quantum correlations through routed Bell tests