Coherence evolution and transfer supplemented by state-restoring

TL;DR

This paper explores how quantum coherences evolve under certain conditions and introduces a method using unitary transformations at the receiver to partially restore the original coherence structure after transfer.

Contribution

It proposes a novel technique to untwist and restore quantum coherence structures at the receiver side using unitary transformations, enhancing quantum communication fidelity.

Findings

Coherences do not intertwist during evolution if Hamiltonian conserves spin-excitation number.

A unitary transformation can partially restore the sender's initial coherence structure at the receiver.

The method is demonstrated with a two-qubit sender-receiver communication line.

Abstract

The evolution of quantum coherences comes with a set of conservation laws provided that the Hamiltonian governing this evolution conserves the spin-excitation number. At that, coherences do not intertwist during the evolution. Using the transmission line and the receiver in the initial ground state we can transfer the coherences to the receiver without interaction between them, { although the matrix elements contributing to each particular coherence intertwist in the receiver's state. } Therefore we propose a tool based on the unitary transformation at the receiver side to { untwist these elements and thus} restore (at least partially) the structure of the sender's initial density matrix. A communication line with two-qubit sender and receiver is considered as an example of implementation of this technique.