title: Perfect state transfer in quantum spin networks.
abstract: We propose a class of qubit networks that admit the perfect state transfer of any quantum state in a fixed period of time. Unlike many other schemes for quantum computation and communication, these networks do not require qubit couplings to be switched on and off. When restricted to N-qubit spin networks of identical qubit couplings, we show that 2log3N is the maximal perfect communication distance for hypercube geometries. Moreover, if one allows fixed but different couplings between the qubits, then perfect state transfer can be achieved over arbitrarily long distances in a linear chain.
authors.affiliation: Centre for Quantum Computation, Centre for Mathematical Sciences, DAMTP, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, United Kingdom. matthias.christandl@qubit.org
authors.forename: Matthias
authors.initials: M
authors.lastname: Christandl
authors.forename: Nilanjana
authors.initials: N
authors.lastname: Datta
authors.forename: Artur
authors.initials: A
authors.lastname: Ekert
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Landahl