Remote Creation of Quantum Coherence via Indefinite Causal Order

TL;DR

This paper demonstrates that indefinite causal order can enable remote creation of quantum coherence even when entanglement is lost, leveraging quantum discord as a resource in noisy quantum channels.

Contribution

It introduces a novel method using indefinite causal order to generate quantum coherence remotely, overcoming limitations of noisy channels that destroy entanglement.

Findings

Indefinite causal order preserves quantum discord despite losing entanglement.

Quantum coherence can be generated remotely without entanglement, using discord as a resource.

The method applies to various depolarizing channels and a unitary operator.

Abstract

Quantum coherence is a prime resource in quantum computing and quantum communication. Quantum coherence of an arbitrary qubit state can be created at a remote location using maximally entangled state, local operation and classical communication. However, if there is a noisy channel acting on one side of the shared resource, then, it is not possible to create perfect quantum coherence remotely. Here, we present a method for the creation of quantum coherence at a remote location via the use of entangled state and indefinite causal order. We show this specifically for the superposition of two completely depolarizing channels, two partially depolarizing channels and one completely depolarizing channel along with a unitary operator. We find that when the indefinite causal order of channels act on one-half of the entangled pair, then the shared state looses entanglement, but can retain non-zero quantum discord. This finding may have some interesting applications on its own where discord can be consumed as a resource. Our results suggest that the indefinite causal order along with a tiny amount of quantum discord can act as a resource in creating non-zero quantum coherence in the absence of entanglement.