Experimental Certification of Sustained Entanglement and Nonlocality after Sequential Measurements

Abstract

Entanglement is a fundamental resource for quantum information science. However, bipartite entanglement is destroyed when one particle is observed via projective (sharp) measurements, as it is typically the case in most experiments. Here we experimentally show that, if instead of sharp measurements, one performs many sequential unsharp measurements on one particle which are suitably chosen depending on the previous outcomes, then entanglement is preserved and it is possible to reveal quantum correlations through measurements on the second particle at any step of the sequence. Specifically, we observe that pairs of photons entangled in polarization maintain their entanglement when one particle undergoes three sequential measurements, and each of these can be used to violate a CHSH inequality. This proof-of-principle experiment demonstrates the possibility of repeatedly harnessing two crucial resources, entanglement and Bell nonlocality, that, in most quantum protocols, are destroyed after a single measurement. The protocol we use, which in principle works for an unbounded sequence of measurements, can be useful for randomness extraction.

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Cited by in corpus (33)

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• Detection of genuine tripartite entanglement by multiple sequential observers
• Genuine Einstein-Podolsky-Rosen steering of three-qubit states by multiple sequential observers
• Experimental Demonstration of Sequential Quantum Random Access Codes
• Experimental Test of Sequential Weak Measurements for Certified Quantum Randomness Extraction
• Einstein-Podolsky-Rosen Steering in Two-sided Sequential Measurements with One Entangled Pair
• Noise-robust preparation contextuality shared between any number of observers via unsharp measurements
• Sequential measurement-device-independent entanglement detection by multiple observers
• Recycling qubits for the generation of Bell nonlocality between independent sequential observers
• Projective measurements are sufficient for recycling nonlocality
• Recycled entanglement detection by arbitrarily many sequential and independent pairs of observers
• Entanglement witnessing by arbitrarily many independent observers recycling a local quantum shared state
• Quantum Correlation Sharing: A Review On Recent Progress From Nonlocality To Other Non-Classical Correlations
• Single-pair measurement of the Bell parameter
• Network nonlocality sharing via weak measurements in the generalized star network configuration
• Widening the sharpness modulation region of an entanglement-assisted sequential quantum random access code: Theory, experiment, and application
• Ability of unbounded pairs of observers to achieve quantum advantage in random access codes with a single pair of qubits
• Resource theoretic efficacy of the single copy of a two-qubit entangled state in a sequential network
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• Recovering quantum entanglement after its certification
• Protecting three-dimensional entanglement from correlated amplitude damping channel
• Quantum formalism on the plane: POVM-Toeplitz quantization, Naimark theorem and linear polarisation of the light
• Security of Device-independent Quantum Key Distribution under Sequential Attack
• Sequential information theoretic protocols in continuous variable systems
• Device-independent secure correlations in sequential quantum scenarios