Edge-state-enhanced transport in a two-dimensional quantum walk
2015 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 91, no 2, 022324Article in journal (Refereed) Published
Quantum walks on translation-invariant regular graphs spread quadratically faster than their classical counterparts. The same coherence that gives them this quantum speedup inhibits or even stops their spread in the presence of disorder. We ask how to create an efficient transport channel from a fixed source site (A) to fixed target site (B) in a disordered two-dimensional discrete-time quantum walk by cutting some of the links. We show that the somewhat counterintuitive strategy of cutting links along a single line connecting A to B creates such a channel. The efficient transport along the cut is due to topologically protected chiral edge states, which exist even though the bulk Chern number in this system vanishes. We give a realization of the walk as a periodically driven lattice Hamiltonian and identify the bulk topological invariant responsible for the edge states as the quasienergy winding of this Hamiltonian.
Place, publisher, year, edition, pages
2015. Vol. 91, no 2, 022324
IdentifiersURN: urn:nbn:se:su:diva-115920DOI: 10.1103/PhysRevA.91.022324ISI: 000350064200005OAI: oai:DiVA.org:su-115920DiVA: diva2:806069