Projective measurements are sufficient for recycling nonlocality

Abstract

Unsharp measurements are widely seen as the key resource for recycling the nonlocality of an entangled state shared between several sequential observers. Contrasting this, we here show that nonlocality can be recycled using only standard projective measurements, without using quantum ancillas. Focusing on the CHSH inequality, we determine the optimal trade-off in the Bell parameters for a maximally entangled two-qubit state in the presence of shared classical randomness. We then find that non-maximally entangled states make possible larger sequential violations, which contrasts the standard CHSH scenario. Furthermore, we show that nonlocality can be recycled even when only using projective measurements and local randomness. We discuss the implications of our results for experimental implementations of sequential nonlocality.

Updated version. Typo corrected

References in corpus (4)

• Sharing non-locality and non-trivial preparation contextuality using same family of Bell expressions
• Sharing quantum nonlocality and genuine nonlocality with independent observables
• Limitations on sharing Bell nonlocality between sequential pairs of observers
• Recycling qubits for the generation of Bell nonlocality between independent sequential observers

Cited by in corpus (10)

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• Unbounded Sharing of Nonlocality Using Projective Measurements
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• Self-testing of multiple unsharpness parameters through sequential violations of non-contextual inequality
• Secure and robust randomness with sequential quantum measurements
• Simulating quantum instruments with projective measurements and quantum post-processing
• Semi-device-independent certification of quantum non-Markovianity using sequential Random Access Codes
• Optimal quantum violations of n-locality inequalities with conditional dependence on inputs
• Security of Device-independent Quantum Key Distribution under Sequential Attack
• Uncertainty-disturbance relations and applications