# The trapping problem of quantum walks

## Bálint Kollár

### (Wigner RCP SZFKI)

Time: Tue Mar 3 13:00:00 2015

Location: Building 1, Auditorium

The expected behaviour of homogeneous discrete time quantum walks is the fast (ballistic) spreading of the wavefunction over the underlying lattice. In some cases, however, they can remain localized at their initial position. This phenomenon is called "trapping". Trapping is caused by the destructive interference of outgoing waves, and is a purely quantum effect: similar phenomenon does not exist in classical walks. Up to now, the classification of such trapping quantum walks were not given. We tackle this problem by using a systematic, constructive approach. We explicitly give several classes of trapping two-dimensional quantum walks and show some applications, e.g. the possible optimization of quantum walk based searches.