Quantum walks and gravitational waves

Abstract

A new family of discrete-time quantum walks (DTQWs) propagating on a regular $(1+2)$D spacetime lattice is introduced. The continuous limit of these DTQWs is shown to coincide with the dynamics of a Dirac fermion interacting with an arbitrary relativistic gravitational field. This family is used to model the influence of arbitrary linear gravitational waves (GWs) on DTQWs. Pure shear GWs are studied in detail. On large spatial scales, pure shear GWs do not modify the polarizations of the fermion eigen-modes, but rescale all energies by a common factor. On smaller scales typically comparable to two or three lattice steps, both polarizations and energies are modified in a non-trivial way. This effect is particularly salient on interference patterns between the fermion eigen-modes.