The phenomenon of Anderson localization may occur in the presence of disorder in a variety of media. Disorder may in fact lead to distructive quantum interference of the multiple scattering paths of a particle or a wave, halting its diffusion in the media and localising the wave packet in a specific region.
Here we consider the effect of disorder on one-dimensional spin chains set up for ‘perfect state transfer’, where, due to a specific set of coupling between the spins, a quantum state can be transferred from one chain end to the other by simply letting the system evolve under the action of its natural Hamiltonian. This transfer dynamics has a well defined period.
These chains have been proposed as a powerful tool to transfer quantum information in solid state systems or to create and distribute entanglement. They could be embodied by very different physical systems, for example by linear chains of quantum dots with ground state excitons as pseudospins. In this case laser pulses could be used to inject the quantum state to be transferred across.
Our calculations show that a moderate amount of disorder could indeed induce Anderson localization in these one-dimensional systems. The level of localization depends on the chain length and on the injection site, becoming stronger for longer spin chains and for injection at the chain end [1].
These findings have practical implications for quantum devices based on spin chains, as disorder from e.g. fabrication defects might then lead to limiting the applicability of ‘perfect state transfer’ conditions.
[1]R. Ronke, M. Estarellas, I. D’Amico, T.P. Spiller, and T Miyadera, preprint
