Experimentally finding dense subgraphs using a time-bin encoded Gaussian boson sampling device

TL;DR

This paper demonstrates the first experimental use of a time-bin encoded Gaussian boson sampling device to find dense subgraphs, showing improved results over classical methods for small graph sizes.

Contribution

It introduces a novel experimental implementation of GBS using time-bin encoding and applies it to dense subgraph search, highlighting practical quantum advantages.

Findings

Improved dense subgraph detection for 3-4 node subgraphs.

First experimental implementation of time-bin encoded GBS.

Analysis of imperfections affecting GBS performance.

Abstract

Gaussian Boson Sampling (GBS) is a quantum computing concept based on drawing samples from a multimode nonclassical Gaussian state using photon-number resolving detectors. It was initially posed as a near-term approach aiming to achieve quantum advantage, but several applications have been proposed ever since, such as the calculation of graph features or molecular vibronic spectra, among others. For the first time, we use a time-bin encoded interferometer to implement GBS experimentally and extract samples to enhance the search for dense subgraphs in a graph. Our results indicate an improvement over classical methods for subgraphs of sizes three and four in a graph containing ten nodes. In addition, we numerically explore the role of imperfections in the optical circuit and on the performance of the algorithm.