Experimental loopback boson sampling

TL;DR

This paper demonstrates an enhanced boson sampling experiment using optical feedback lines to introduce temporal correlations, thereby increasing the system's computational complexity and advancing photonic quantum computing.

Contribution

It introduces a novel feedback-based approach to boson sampling, creating temporal correlations that boost complexity and provide a resource-efficient path toward quantum advantage.

Findings

Successfully reconstructed the unitary matrix of the interferometer

Validated the system behavior as distinct from standard boson sampling

Quantified the increased complexity of the sampler

Abstract

We present an experimental demonstration of boson sampling enhanced by optical feedback lines, a novel approach that introduces temporal correlations among photons to amplify computational complexity. We utilize a 25-mode femtosecond laser-written interferometer with five output channels connected to five input channels to create correlations between consecutive photon arrival events. We have reconstructed the unitary matrix of the chip and have conducted Bayesian analysis to validate the sampler and confirm that the system exhibits behavior distinct from standard boson sampling. We also built a theoretical description of the system based on the transformation of annihilation operators and, using it, delivered the structure of the transmission matrix and the complexity of our boson sampler in terms of a conventional boson sampler. This work advances photonic quantum computing by demonstrating a resource-efficient method to increase sampling complexity, paving the way for scalable demonstration of quantum advantage with single photons.