Quantum walks and wavepacket dynamics on a lattice with twisted photons

TL;DR

This paper demonstrates a novel photonic platform for quantum walks using the orbital angular momentum space of light, enabling scalable, interferometer-free quantum simulations with flexible control over states and exploration of topological features.

Contribution

It introduces a new method for implementing quantum walks in orbital angular momentum space without interferometers, enhancing scalability and control in photonic quantum simulations.

Findings

Successful experimental realization of quantum walks in orbital angular momentum space.

Ability to simulate band structure and topological features in momentum space.

Scalable implementation with resources growing linearly with steps.

Abstract

The "quantum walk" has emerged recently as a paradigmatic process for the dynamic simulation of complex quantum systems, entanglement production and quantum computation. Hitherto, photonic implementations of quantum walks have mainly been based on multi-path interferometric schemes in real space. Here, we report the experimental realization of a discrete quantum walk taking place in the orbital angular momentum space of light, both for a single photon and for two simultaneous photons. In contrast to previous implementations, the whole process develops in a single light beam, with no need of interferometers; it requires optical resources scaling linearly with the number of steps; and it allows flexible control of input and output superposition states. Exploiting the latter property, we explored the system band structure in momentum space and the associated spin-orbit topological features by simulating the quantum dynamics of Gaussian wavepackets. Our demonstration introduces a novel versatile photonic platform for quantum simulations.