Quantum communication through spin chain dynamics: an introductory overview

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.

Acknowledgements

I would like to particularly thank Daniel Burgarth, the chief architect of the dual rail protocol, and my collaborator in many of the papers covered here. I would also like to thank my other collaborators in various papers mentioned in this review, namely, Vittorio Giovannetti, Vladimir Korepin, Vlatko Vedral, Man-Hong Yung, Simon Benjamin, Debbie Leung, Christopher Hadley, Alessio Serafini, Dimitris Angelakis, Kurt Jacobs, Kosuke Shizume, Bai-Qi Jin, Yasser Omar, Antonio Costa, Jens Eisert, Martin Plenio, Benoit Vaucher, Tania Montiero, Tom Boness, Andrew Fisher and Martina Avellino. I thank EPSRC for an Advanced Research Fellowship and for support through the grant GR/S62796/01 and the QIPIRC (GR/S82176/01).