Continuous-Time Quantum Walks on the Symmetric Group

Luke C. Brown, William J. Martin, Duncan Wright

Zlatko Dimcovic, Yevgeniy Kovchegov

Avah Banerjee

Heath Gerhardt, John Watrous

In this paper we study continuous-time quantum walks on Cayley graphs of the symmetric group, and prove various facts concerning such walks that demonstrate significant differences from their classical analogues. In particular, we show that for several natural choices for generating sets, these quantum walks do not have uniform limiting distributions, and are effectively blind to large areas of the graphs due to destructive interference.

Shyam Dhamapurkar, Yu–Hang Dang, Saniya Wagh +1 more

Random walk algorithms, including sampling and approximations, have played a significant role in statistical physics and theoretical computer science. Mixing through walks is the process for a Markov chain to approximate a stationary distribution for a group. Quantum walks have shown potential advantages in mixing time over the classical case but lack general proof in the finite group case. Here, we investigate the continuous-time quantum walks on Cayley graphs of the dihedral group D2n for odd n, generated by the smallest inverse closed symmetric subset. We present a significant finding that, in contrast to the classical mixing time on these Cayley graphs, which typically takes at least order Ω(n2log(1/2ε)), the continuous-time quantum walk mixing time on D2n is of order Ω($n(log n)$5log(1/ε)), achieving a quadratic improvement over the classical case. Our paper advances the general understanding of quantum walk mixing on Cayley graphs, highlighting the improved mixing time achieved by continuous-time quantum walks on D2n. This work has potential applications in algorithms for a class of sampling problems based on non-abelian groups.

Daniel ben‐Avraham, Eric M. Bollt, Christino Tamon