Quantum ratchet in disordered quantum walk

TL;DR

This paper demonstrates how a quantum ratchet effect can be achieved in disordered quantum walks by using fixed coin operations at specific positions, enabling directed transport and optimized displacement.

Contribution

It introduces a novel method to induce directed transport in disordered quantum walks through fixed coin operations, combining standard and disordered evolutions for enhanced displacement.

Findings

Quantum ratchet effect achieved with fixed coin operations.

Directed transport can be optimized to linear displacement over time.

Coherent quantum transport realized using entangling unitary operators.

Abstract

Symmetrically evolving discrete quantum walk results in dynamic localization with zero mean displacement when the standard evolution operations are replaced by a temporal disorder evolution operation. In this work we show that the quantum ratchet action, that is, a directed transport in standard or disordered discrete-time quantum walk can be realized by introducing a pawl like effect realized by using a fixed coin operation at marked positions that is, different from the ones used for evolution at other positions. We also show that the combination of standard and disordered evolution operations can be optimized to get the mean displacement of order $\propto$ t (number of walk steps). This model of quantum ratchet in quantum walk is defined using only a set of entangling unitary operators resulting in the coherent quantum transport.