Asymptotic adaptive bipartite entanglement-distillation protocol

Abstract

We present an asymptotic bipartite entanglement-distillation protocol that outperforms all existing asymptotic schemes. This protocol is based on the breeding protocol with the incorporation of two-way classical communication. Like breeding, the protocol starts with an infinite number of copies of a Bell-diagonal mixed state. Breeding can be carried out as successive stages of partial information extraction, yielding the same result: one bit of information is gained at the cost ͑measurement͒ of one pure Bell state pair ͑ebit͒. The basic principle of our protocol is at every stage to replace measurements on ebits by measurements on a finite number of copies, whenever there are two equiprobable outcomes. In that case, the entropy of the global state is reduced by more than one bit. Therefore, every such replacement results in an improvement of the protocol. We explain how our protocol is organized as to have as many replacements as possible. The yield is then calculated for Werner states.

Entanglement purification and quantum error correction

“…Protocols with improved yield (by optimizing the information gain of the measurements) have been developed in Ref. [102].…”

Stabilizer state breeding

“…[12] for CSS states. Again, we define a class of local Clifford operations that distribute the information content of multiple noisy copies of a stabilizer state without destroying the tensor product, i.e.…”

“…they transform multiple copies of a pure stabilizer state into multiple copies of the same stabilizer state. Breeding, contrary to hashing [12], starts from k noisy copies of an n-qubit stabilizer state and a pool of (1 − γ)k predistilled pure copies of the same state, where k is considered large (asymptotic protocol). After the local Clifford operations, we locally measure the (1 − γ)k initially pure copies, yielding information on the global state.…”

“…II A, we give a brief overview of the binary linear algebra framework in which we describe the stabilizer formalism. In the past, this "binary picture" has been proved useful in the context of distillation protocols [12,25,26,27]. In Sec.…”

Quantum entanglement capacity with classical feedback

“…This work is also closely related to entanglement purification protocols (EPP) [19,20,21,22,23], procedures by which two parties can extract pure-state entanglement out of some …”