Quantum Communication through Spin Chain Dynamics: an Introductory Overview

TL;DR

This paper provides an overview of using spin chains as quantum wires for transmitting quantum information, highlighting methods to improve transfer fidelity without external modulation.

Contribution

It introduces various strategies to achieve perfect quantum state transfer in uniformly coupled spin chains, expanding on existing approaches.

Findings

Uniform chains suffer from dispersion reducing transfer quality.

Multiple proposed methods can achieve perfect state transfer.

The field is actively developing with diverse techniques.

Abstract

We present an introductory overview of the use of spin chains as quantum wires, which has recently developed into a topic of lively interest. The principal motivation is in connecting quantum registers without resorting to optics. A spin chain is a permanently coupled 1D system of spins. When one places a quantum state on one end of it, the state will be dynamically transmitted to the other end with some efficiency if the spins are coupled by an exchange interaction. No external modulations or measurements on the body of the chain, except perhaps at the very ends, is required for this purpose. For the simplest (uniformly coupled) chain and the simplest encoding (single qubit encoding), however, dispersion reduces the quality of transfer. We present a variety of alternatives proposed by various groups to achieve perfect quantum state transfer through spin chains. We conclude with a brief discussion of the various directions in which the topic is developing.