Improved entanglement–purification protocol using three Werner states and LOCC

Fast multi-copy entanglement purification with linear optics

“…The recent EPP also exploited the CNOT gate. [69] It is known that the CNOT gate is hard to realize in the current experiment conditions. The deterministic Bell-state measurement is also a big challenge in linear optics, which greatly limits the application of these EPPs.…”

“…There are several protocols using three copies of the low quality mixed state. [66][67][68][69] For example, in 2000, Feng et al described an EPP with controlled-controlled-not (CCNOT) operations. Their EPP was improved by Metwally and Obada.…”

“…[68] In 2015, an efficient EPP with three Werner states were proposed. [69] In this paper, we will describe a different EPP, which uses multi-copy low quality mixed states to realize the entanglement purification. Different from the previous multi-copy EPPs, what is most advantageous is that this protocol does not require the CCNOT gate or CNOT gate.…”

Multi-copy entanglement purification with practical spontaneous parametric down conversion sources

“…[19,[28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] The third group is to use the multi-copy degraded mixed states. [45][46][47][48][49][50] In the third group, they usually exploit the controlled-not (CNOT) gates and controlled-controlled-not (CCNOT) gates to complete the purification. However, CNOT and CCNOT are not feasible in current experimental condition, which makes this kind of protocols be far away from current application.…”