Recycled entanglement detection by arbitrarily many sequential and independent pairs of observers

Abstract

We investigate the witnessing of two-qubit entangled states by sequential and independent pairs of observers, with both observers of each pair acting independently on their part of the shared state from spatially separated laboratories, and subsequently passing their qubits to the next pair in the sequence. It has previously been conjectured that not more than one pair of observers can detect Clauser-Horne-Shimony-Holt "Bell-nonlocal" correlations in a similar set-up. This is intriguing since it is possible to have an arbitrarily long sequence of Bell-nonlocal correlations when only a single observer is allowed to share a bipartite state with multiple observers at the other end. It is therefore interesting to ask whether such restrictions are also present when entangled correlations are considered in the scenario of multiple pairs of observers. We find that a two-qubit entangled state can be used to witness entanglement arbitrarily many times, by pairs of observers, acting sequentially and independently. We prove the statement to be true when the initial pair of observers in the sequence share any pure entangled state or when they share a state from a class of mixed entangled states. We demonstrate that the phenomenon can also be observed for a certain class of entangled states in which an arbitrarily long sequence of observer pairs witnessing entanglement is reached in the limit of the initial entanglement content tending to a vanishing amount.

arXiv comment6 pages, 1 figure

References in corpus (36)

• Quantum entanglement
• Separability of Mixed States: Necessary and Sufficient Conditions
• Bell nonlocality
• Entanglement detection
• Device-independent security of quantum cryptography against collective attacks
• Random Numbers Certified by Bell's Theorem
• No Signalling and Quantum Key Distribution
• Bell Inequalities and the Separability Criterion
• A Multiparticle Generalization of Entanglement Swapping
• A simple formula for the average gate fidelity of a quantum dynamical operation
• Free randomness can be amplified
• Private Randomness Expansion With Untrusted Devices
• Entanglement witnesses: construction, analysis and classification
• Multiple Observers Can Share the Nonlocality of Half of an Entangled Pair by Using Optimal Weak Measurements
• Reflections upon separability and distillability
• Experimental detection of entanglement via witness operators and local measurements
• Arbitrarily many independent observers can share the nonlocality of a single maximally entangled qubit pair
• Witnessing entanglement sequentially: Maximally entangled states are not special
• Three-observer Bell inequality violation on a two-qubit entangled state
• Quantum Cryptography with Imperfect Apparatus
• Facets of bipartite nonlocality sharing by multiple observers via sequential measurements
• Sharing quantum nonlocality and genuine nonlocality with independent observables
• Experimental Certification of Sustained Entanglement and Nonlocality after Sequential Measurements
• Limitations on sharing Bell nonlocality between sequential pairs of observers
• Detection of genuine tripartite entanglement by multiple sequential observers
• Observation of nonlocality sharing via not-so-weak measurements
• Sharing of tripartite nonlocality by multiple observers measuring sequentially at one side
• Einstein-Podolsky-Rosen Steering in Two-sided Sequential Measurements with One Entangled Pair
• Sequential measurement-device-independent entanglement detection by multiple observers
• Recycling qubits for the generation of Bell nonlocality between independent sequential observers
• Non-locality sharing for a three-qubit system via multilateral sequential measurements
• Entanglement witnessing by arbitrarily many independent observers recycling a local quantum shared state
• Strengthened Bell inequalities for orthogonal spin directions
• Resource theoretic efficacy of the single copy of a two-qubit entangled state in a sequential network
• Strengthened Bell Inequalities for Entanglement Verification
• Bell nonlocality between sequential pairs of observers

Cited by in corpus (9)

• Quantum Correlation Sharing: A Review On Recent Progress From Nonlocality To Other Non-Classical Correlations
• Quantifying the intrinsic randomness in sequential measurements
• Sharing EPR steering between sequential pairs of observers
• Sequentially witnessing entanglement by independent observer pairs
• Recycled detection of genuine multiparty entanglement of unlimitedly stretched array of parties and arbitrarily long series of sequential observers
• Security of Device-independent Quantum Key Distribution under Sequential Attack
• Local entanglement transfer to multiple pairs of spatially separated observers
• Sequential information theoretic protocols in continuous variable systems
• Unbounded entanglement-sustaining sequential local quantum state discrimination