Coherent state transfer via highly mixed quantum spin chains

TL;DR

This paper demonstrates that highly mixed quantum spin chains can effectively transfer quantum information, offering practical advantages over pure-state chains and enabling new experimental implementations.

Contribution

It introduces protocols for perfect quantum state transfer in mixed-state spin chains, expanding the feasible Hamiltonians for quantum communication.

Findings

Mixed-state chains exhibit similar transport properties to pure-state chains.

Protocols enable perfect quantum information transfer in mixed-state chains.

Hamiltonians without excitation number conservation are usable, compatible with natural interactions.

Abstract

Spin chains have been proposed as quantum wires in many quantum information processing architectures. Coherent transmission of quantum information over short distances is enabled by their internal dynamics, which drives the transport of single-spin excitations in perfectly polarized chains. Given the practical challenge of preparing the chain in a pure state, we propose to use a chain that is initially in the maximally mixed state. We compare the transport properties of pure and mixed-state chains, finding similarities that enable the experimental study of pure-state transfer by its simulation via mixed-state chains, and demonstrate protocols for the perfect transfer of quantum information in these chains. Remarkably, mixed-state chains allow the use of Hamiltonians which do not preserve the total number of excitations, and which are more readily obtainable from the naturally occurring magnetic dipolar interaction. We propose experimental implementations using solid-state nuclear magnetic resonance and defect centers in diamond.