Remote creation of quantum coherence via indefinite causal order
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Abstract
Quantum coherence is a prime resource in quantum computing and quantum communication. Quantum coherence of an arbitrary qubit 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 acts on one half of the entangled pair, then the shared state loses entanglement, but can retain nonzero 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 nonzero quantum coherence in the absence of entanglement.