Non-locality can be Shared between Alice and three Bobs in unbiased settings case

TL;DR

This paper demonstrates that quantum nonlocality can be shared among four observers, including three sequential Bobs, by unbiased measurements, challenging previous beliefs about the monogamy of nonlocality.

Contribution

It provides the first analytical and numerical evidence that nonlocality can be shared among more than two observers with unbiased measurements, overturning prior assumptions.

Findings

Triple violation of CHSH inequality observed among Alice and three Bobs

Sharing of nonlocality with more than two observers demonstrated

Unbiased measurements enable multiple sequential observers to share nonlocality

Abstract

A well-known property of quantum nonlocality is monogamy. However, recent research by Silva \emph{et al.} shows that multiple observers can share the nonlocality by using weak measurements [Phys. Rev. Lett. 114, 250401 (2015)]. There is an open question left in their result: whether the nonlocality of a single particle from an entangled pair can be shared among more than two observers that act sequentially and independently of each other? In this work, we analytical and numerical shows that it is possible to observe a triple violation of CHSH inequality between Alice and three Bobs when the measurements of each of the several observers at one side are unbiased with respect to the previous observers. This result overturns the conclusions and proofs of previous related work on this issue which has been widely shared in the scientific community before.