Photons Walking the Line: A quantum walk with adjustable coin operations

TL;DR

This paper demonstrates a robust implementation of a five-step coined quantum walk using passive optical elements, showing faster photon spread than classical walks and enabling future quantum search algorithms.

Contribution

It introduces a fiber network loop setup for quantum walks with adjustable coin operations, maintaining resource efficiency as the walker's position space expands.

Findings

Non-Gaussian distribution of final position observed

Faster spread of photon wave-packet compared to classical walk

Implementation across various coin settings and initial states

Abstract

We present the first robust implementation of a coined quantum walk over five steps using only passive optical elements. By employing a fiber network loop we keep the amount of required resources constant as the walker's position Hilbert space is increased. We observed a non-Gaussian distribution of the walker's final position, thus characterizing a faster spread of the photon wave-packet in comparison to the classical random walk. The walk is realized for many different coin settings and initial states, which opens the way for the implementation of a quantum walk-based search algorithm.