# Programmable linear quantum networks with a multimode fibre

## TL;DR

This paper presents a scalable, reconfigurable quantum optical network using multimode fibre and wavefront shaping, capable of implementing complex linear transformations for quantum information processing.

## Contribution

It introduces a novel approach to scalable reconfigurable quantum circuits using multimode fibre and wavefront shaping techniques, validated with two-photon quantum states.

## Key findings

- Successfully programmed and validated optical networks with spatial and polarisation modes.
- Demonstrated reconfigurability through a tunable coherent absorption experiment.
- Showed potential for scaling up quantum information processing applications.

## Abstract

Reconfigurable quantum circuits are fundamental building blocks for the implementation of scalable quantum technologies. Their implementation has been pursued in linear optics through the engineering of sophisticated interferometers. While such optical networks have been successful in demonstrating the control of small-scale quantum circuits, scaling up to larger dimensions poses significant challenges. Here, we demonstrate a potentially scalable route towards reconfigurable optical networks based on the use of a multimode fibre and advanced wavefront-shaping techniques. We program networks involving spatial and polarisation modes of the fibre and experimentally validate the accuracy and robustness of our approach using two-photon quantum states. In particular, we illustrate the reconfigurability of our platform by emulating a tunable coherent absorption experiment. By demonstrating reliable reprogrammable linear transformations, with the prospect to scale, our results highlight the potential of complex media driven by wavefront shaping for quantum information processing.