Abstract
Bell non-locality plays a fundamental role in quantum theory. Numerous tests of the Bell inequality have been reported as the ground-breaking discovery of the Bell theorem. Up to now, however, most discussions of the Bell scenario have focused on a single pair of entangled particles distributed to only two separated observers. Recently, it has been shown surprisingly that multiple observers can share the non-locality from an entangled pair using the method of weak measurement without post-selection [Phys. Rev. Lett. 114, 250401 (2015)]. Here we report an observation of double CHSH-Bell inequality violations for a single pair of entangled photons with strength continuous-tunable optimal weak measurement in a photonic system. Our results shed new light on the interplay between non-locality and quantum measurements and our design of weak measurement protocol may also be significant for important applications such as unbounded randomness certification and quantum steering.
Highlights
IntroductionNon-locality, which was pointed out by Einstein, Podolsky and Rosen (EPR),[1] plays a fundamental role in quantum theory
Non-locality, which was pointed out by Einstein, Podolsky and Rosen (EPR),[1] plays a fundamental role in quantum theory. It has been intensively investigated as the ground-breaking discovery of Bell theorem by John Bell in 1964.2 Bell theorem states that any local-realistic theory cannot reproduce all the predictions of quantum theory and gives an experimental testable inequality[3] that later improved by Clauser, Horne, Shimony and Holt (CHSH).[4]
Using the concept of weak measurement without post-selection, Silva et al give a surprising-positive answer to above question and show a marvellous physical fact that measurement disturbance and information gain of a single system are closely related to nonlocality distribution among multiple observers in one entangled pair.[18]
Summary
Non-locality, which was pointed out by Einstein, Podolsky and Rosen (EPR),[1] plays a fundamental role in quantum theory. It has been intensively investigated as the ground-breaking discovery of Bell theorem by John Bell in 1964.2 Bell theorem states that any local-realistic theory cannot reproduce all the predictions of quantum theory and gives an experimental testable inequality[3] that later improved by Clauser, Horne, Shimony and Holt (CHSH).[4] Numerous tests of CHSH-Bell inequality have been realized in various quantum systems[5,6,7,8,9,10,11,12,13] and strong loophole-free Bell tests have been reported recently.[14,15,16]. Using the concept of weak measurement without post-selection, Silva et al give a surprising-positive answer to above question and show a marvellous physical fact that measurement disturbance and information gain of a single system are closely related to nonlocality distribution among multiple observers in one entangled pair.[18]
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