Coherent control of the causal order of entanglement distillation

TL;DR

This paper introduces a quantum entanglement distillation protocol utilizing indefinite causal order, which improves fidelity and success probability over traditional methods, demonstrating practical advantages for quantum communication.

Contribution

It proposes a novel entanglement distillation protocol that employs indefinite causal order, showing enhanced performance compared to conventional fixed-order protocols.

Findings

Higher fidelity of distillation achieved

Increased probability of success for certain faulty pairs

Demonstrates practical advantage of indefinite causal order in quantum communication

Abstract

Indefinite causal order is an evolving field with potential involvement in quantum technologies. Here we propose and study one possible scenario of practical application in quantum communication: a compound entanglement distillation protocol that features two steps of a basic distillation protocol applied in a coherent superposition of two causal orders. This is achieved by using one faulty entangled pair to control-swap two others before a fourth pair is combined with the two swapped ones consecutively. As a result, the protocol distills the four faulty entangled states into one of a higher fidelity. Our protocol has a higher fidelity of distillation and probability of success for some input faulty pairs than conventional concatenations of the basic protocol that follow a definite distillation order. Our proposal shows the advantage of indefinite causal order in an application setting consistent with the requirements of quantum communication.