  We propose a class of qubit networks that admit perfect 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 2 log_3 N 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.
