Entanglement Swapping and Quantum Correlation Transferring

Xinglan Zhang, Fei Chen, Yankun Guo +2 more

Pratapaditya Bej, Arkaprabha Ghosal, Arup Roy +2 more

We study how different types of quantum correlations can be established as the consequence of a generalized entanglement swapping protocol where, starting from two Bell pairs (1,2) and (3,4), a general quantum measurement [denoted by a positive operator-valued measure (POVM)] is performed on the pair (2,3), which results in creating quantum correlation in (1,4) shared between two spatially separated observers. Contingent upon using different kinds of POVMs, we show generation or destruction of different quantum correlations in the pairs (1,4), (1,2), and (3,4). This thus reflects nontrivial transfer of quantum correlations from the pairs (1,2) and (3,4) to the pair (1,4). As an offshoot, this paper provides an operational tool to generate different types of single parameter families of quantum correlated states [for example, entangled but not Einstein-Podolsky-Rosen (EPR) steerable, or EPR steerable but not Bell nonlocal, or Bell nonlocal] by choosing different quantum measurements in the basic entanglement swapping setup. We further extend our paper by taking mixed initial states shared by the pairs (1,2) and (3,4). Finally, we study network nonlocality in our scenario. Here, we find the appropriate POVM measurement for which the generated correlation demonstrates or does not demonstrate network nonlocality for the whole range of the measurement parameter.

Simon J. D. Phoenix

Using the information content of correlations between multipartite systems, together with the notion of partitioning, we show that some general results about the evolution of correlations in quantum systems can be derived with only elementary methods. In particular, we show that for 2 quantum systems A and B, each comprised of a number of sub-systems, in which a partition of A interacts unitarily with a partition of B, then the total correlation can only increase (or remain unchanged) and is given simply by the sum of the initial correlation and the correlation that develops as a result of the interaction. We then show that in a 4 qubit entanglement swapping process the transferred degree of entanglement is bounded by the lower of the initial degrees of entanglements of the qubits.

Chun Miao, Ming Yang, Zhuo‐Liang Cao

홍정식

Matthew Daniell, Jian-Wei Pan, Gregor Weihs +1 more

Summary form only given. Entanglement is the resource that makes quantum communication and quantum computation work. The most basic quantum communication protocols are quantum cryptography, quantum teleportation and entanglement swapping. In quantum teleportation one of two parties wants to send the other one a quantum state using some independent carrier. Entanglement swapping in its simplest form is the use of quantum teleportation to transmit a quantum state that is already entangled with some other state. Thereby the entanglement that existed between the original particle and its partner is transferred to the output particle. Both teleportation and entanglement swapping have successfully been demonstrated. However, in none of the experiments the quality of teleportation was high enough to produce output correlations that could have violated a Bell-type inequality. In this work we will show that qubit teleportation using polarization-entangled photon pairs can produce the desired correlations.