Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

npj Quantum Information

Observation of non-locality sharing among three observers with one entangled pair via optimal weak measurement

Mengjun Hu, Zhi‐Yuan Zhou, Xiao‐Min Hu, Chuan‐Feng Li, Guang‐Can Guo, Yong-Sheng Zhang

Published Nov 26, 2018• 94 citations
Publisher

Abstract

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.

DOI
10.1038/s41534-018-0115-x

Related papers

Observation of Nonlocality Sharing among Three Observers with One Entangled Pair via Optimal Weak Measurement

Mengjun Hu, Zhi‐Yuan Zhou, Xiao‐Min Hu +3 more

Bell nonlocality plays a fundamental role in quantum theory. Numerous tests of the Bell inequality have been reported since 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 nonlocality present in a single particle from an entangled pair using the method of weak measurements [Phys. Rev. Lett. {\bf 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 measurements in photonic system for the first time. Our results not only shed new light on the interplay between nonlocality and quantum measurements but may also be significant for important applications such as unbounded randomness certification and quantum steering.

arXiv:1609.01863•Sep 7, 2016•8 citations

Observation of nonlocality sharing via not-so-weak measurements

Tianfeng Feng, Changliang Ren, Yuling Tian +4 more

Nonlocality plays a fundamental role in quantum information science. Recently, it has been theoretically predicted and experimentally demonstrated that the nonlocality of an entangled pair may be shared among multiple observers using weak measurements with moderate strength. Here we devise an optimal protocol of nonlocality sharing among three observers and show experimentally that nonlocality sharing may be also achieved using weak measurements with near-maximum strength. Our result sheds light on the interplay between nonlocality and quantum measurements and may find applications in quantum steering, unbounded randomness certification, and quantum communication network.

arXiv:1912.02979•Physical Review A•Sep 28, 2020•43 citations

Einstein-Podolsky-Rosen steering in two-sided sequential measurements with one entangled pair

Jie Zhu, Mengjun Hu, Chuan‐Feng Li +2 more

Nonlocality and quantum measurement are two fundamental topics in quantum theory and their interplay attracts intensive focuses since the discovery of Bell theorem. Recently, nonlocality sharing among multiple observers with one entangled pair has been predicted and experimentally observed by generalized quantum measurement---weak measurement. However, only the one-sided sequential case, i.e., one Alice and multiple Bobs, is widely discussed and little is known about the two-sided case. Here, we theoretically and experimentally explore the nonlocality sharing in the two-sided sequential measurements case in which one entangled pair is distributed to multiple Alices and Bobs. We experimentally observed double Einstein-Podolsky-Rosen (EPR) steering among four observers in a photonic system. In the case that all observers adopt the same measurement strength of the weak measurement, it is observed that double EPR steering can be demonstrated simultaneously. The results not only deepen our understanding of relation between sequential measurements and nonlocality but also may find important applications in many quantum information tasks, such as randomness certification.

arXiv:2102.02550•Physical Review A•Mar 25, 2022•42 citations

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

Changliang Ren, Tianfeng Feng, Yao, Dan +2 more

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.

arXiv:2006.16462•Jun 30, 2020•1 citation

Violation of a tripartite Bell inequality by weak measurements

Mirko Pittaluga

Non-locality is one of the most characteristic trait of Quantum Mechanics, and it is linked to the conceptually counter-intuitive ability of some objects (when adequately prepared) to instantaneously know about each other’s state, no matter how much space-separated they are. At the development stage of Quantum Mechanics, non-locality had been an argument of intense debate among scientists due to its consequences that seemed to contradict physicists common sense. The scientific debate on the argument faced a turning point with the publication in 1964 of the landmark paper by J. S. Bell On the Einstein-Podolsky-Rosen Paradox, which ended the discussion whether or not non-locality was a true aspect of physical reality, raising it to one of the fundamental aspect of our comprehension of the physical world. The scientific interest for non-locality has recently substantially increased due to its striking applications in Quantum Information Theory. The major innovative traits of Quantum Information Theory, compared to Classical Information Theory, arise in fact from the usage of non-locality as a resource for information manipulation and transmission. The aim of this thesis is to investigate experimentally the non-local properties of a quantum system. This work is one of the first to prove that it is possible to share the non-local correlations of a two-photon entangled singlet state among three observers. The sharing of non-local correlations was possible through the employment of a weak measurement scheme, used to entangle the polarization degree of freedom of photons with a path degree of freedom used as ancilla for the weak measurement. In this thesis we briefly review all the theoretical tools necessary to understand the work (Quantum Mechanics, Optics, Quantum Optics) and we discuss in depth all the aspects of our work. We demonstrate theoretically how non-locality sharing is achievable, showing that it is possible to simultaneously violate two CHSH inequalities among three observers sharing a two-photon singlet state. We describe precisely our setup and its implementation. We finally present the obtained results, which confirm our theoretical model and expectations. The achievement of double violation and the realization of a simple weak measurement scheme may have important applications for Quantum Random Number Generation or for Quantum Key Distribution exploiting weak measurements.

•Dec 1, 2016•0 citations

Passive and active nonlocality sharing for a two-qubit system via weak measurements

Changliang Ren, Tianfeng Feng, Dan Yao +3 more

A well-known property of quantum nonlocality is monogamy. However, recent research by Silva et al. shows that multiple observers can share the nonlocality by using weak measurements [Phys. Rev. Lett. 114, 250401 (2015)]. In this paper, we deeply discuss nonlocality sharing for an arbitrary two-qubit state via weak measurements. Two types of nonlocality sharing, passive nonlocality sharing and active nonlocality sharing, which is another type of double violation of Clauser-Horne-Shimony-Holt (CHSH) inequality with many counterintuitive results existing, are fully analyzed. The two types are quite distinct. Active nonlocality sharing can be observed when Bob1 performs strong measurements only except for the ideal strong measurements. Also, a double violation still can be observed in the active nonlocality sharing even using a square pointer type for weak measurements of Bob1, which is impossible in the passive one. As a special example, for a Bell state, a double violation of Clauser-Horne-Shimony-Holt inequality can be always observed in a broad range whether the weak measurement of Bob1 is with an optimal pointer or a square pointer.

Physical Review A•Nov 26, 2019•27 citations
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.
Bell nonlocality plays a fundamental role in quantum theory. Numerous tests of the Bell inequality have been reported since 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 nonlocality present in a single particle from an entangled pair using the method of weak measurements [Phys. Rev. Lett. {\bf 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 measurements in photonic system for the first time. Our results not only shed new light on the interplay between nonlocality and quantum measurements but may also be significant for important applications such as unbounded randomness certification and quantum steering.
Nonlocality plays a fundamental role in quantum information science. Recently, it has been theoretically predicted and experimentally demonstrated that the nonlocality of an entangled pair may be shared among multiple observers using weak measurements with moderate strength. Here we devise an optimal protocol of nonlocality sharing among three observers and show experimentally that nonlocality sharing may be also achieved using weak measurements with near-maximum strength. Our result sheds light on the interplay between nonlocality and quantum measurements and may find applications in quantum steering, unbounded randomness certification, and quantum communication network.
Nonlocality and quantum measurement are two fundamental topics in quantum theory and their interplay attracts intensive focuses since the discovery of Bell theorem. Recently, nonlocality sharing among multiple observers with one entangled pair has been predicted and experimentally observed by generalized quantum measurement---weak measurement. However, only the one-sided sequential case, i.e., one Alice and multiple Bobs, is widely discussed and little is known about the two-sided case. Here, we theoretically and experimentally explore the nonlocality sharing in the two-sided sequential measurements case in which one entangled pair is distributed to multiple Alices and Bobs. We experimentally observed double Einstein-Podolsky-Rosen (EPR) steering among four observers in a photonic system. In the case that all observers adopt the same measurement strength of the weak measurement, it is observed that double EPR steering can be demonstrated simultaneously. The results not only deepen our understanding of relation between sequential measurements and nonlocality but also may find important applications in many quantum information tasks, such as randomness certification.
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.
Non-locality is one of the most characteristic trait of Quantum Mechanics, and it is linked to the conceptually counter-intuitive ability of some objects (when adequately prepared) to instantaneously know about each other’s state, no matter how much space-separated they are. At the development stage of Quantum Mechanics, non-locality had been an argument of intense debate among scientists due to its consequences that seemed to contradict physicists common sense. The scientific debate on the argument faced a turning point with the publication in 1964 of the landmark paper by J. S. Bell On the Einstein-Podolsky-Rosen Paradox, which ended the discussion whether or not non-locality was a true aspect of physical reality, raising it to one of the fundamental aspect of our comprehension of the physical world. The scientific interest for non-locality has recently substantially increased due to its striking applications in Quantum Information Theory. The major innovative traits of Quantum Information Theory, compared to Classical Information Theory, arise in fact from the usage of non-locality as a resource for information manipulation and transmission. The aim of this thesis is to investigate experimentally the non-local properties of a quantum system. This work is one of the first to prove that it is possible to share the non-local correlations of a two-photon entangled singlet state among three observers. The sharing of non-local correlations was possible through the employment of a weak measurement scheme, used to entangle the polarization degree of freedom of photons with a path degree of freedom used as ancilla for the weak measurement. In this thesis we briefly review all the theoretical tools necessary to understand the work (Quantum Mechanics, Optics, Quantum Optics) and we discuss in depth all the aspects of our work. We demonstrate theoretically how non-locality sharing is achievable, showing that it is possible to simultaneously violate two CHSH inequalities among three observers sharing a two-photon singlet state. We describe precisely our setup and its implementation. We finally present the obtained results, which confirm our theoretical model and expectations. The achievement of double violation and the realization of a simple weak measurement scheme may have important applications for Quantum Random Number Generation or for Quantum Key Distribution exploiting weak measurements.
A well-known property of quantum nonlocality is monogamy. However, recent research by Silva et al. shows that multiple observers can share the nonlocality by using weak measurements [Phys. Rev. Lett. 114, 250401 (2015)]. In this paper, we deeply discuss nonlocality sharing for an arbitrary two-qubit state via weak measurements. Two types of nonlocality sharing, passive nonlocality sharing and active nonlocality sharing, which is another type of double violation of Clauser-Horne-Shimony-Holt (CHSH) inequality with many counterintuitive results existing, are fully analyzed. The two types are quite distinct. Active nonlocality sharing can be observed when Bob1 performs strong measurements only except for the ideal strong measurements. Also, a double violation still can be observed in the active nonlocality sharing even using a square pointer type for weak measurements of Bob1, which is impossible in the passive one. As a special example, for a Bell state, a double violation of Clauser-Horne-Shimony-Holt inequality can be always observed in a broad range whether the weak measurement of Bob1 is with an optimal pointer or a square pointer.