Quantum computing experiments are moving into a new realm of increasing size and complexity, with the short-term goal of demonstrating an advantage over classical computers. Boson sampling is a promising platform for such a goal; however, the number of detected single photons is up to five so far, limiting these small-scale implementations to a proof-of-principle stage. Here, we develop solid-state sources of highly efficient, pure, and indistinguishable single photons and 3D integration of ultralow-loss optical circuits. We perform experiments with 20 pure single photons fed into a 60-mode interferometer. In the output, we detect up to 14 photons and sample over Hilbert spaces with a size up to 3.7×10^14, over 10 orders of magnitude larger than all previous experiments, which for the first time enters into a genuine sampling regime where it becomes impossible to exhaust all possible output combinations. The results are validated against distinguishable samplers and uniform samplers with a confidence level of 99.9%.
Wang, H., Qin, J., Ding, X., Chen, M-C., Chen, S., You, X., ... Pan, J-W. (2019). Boson Sampling with 20 Input Photons and a 60-Mode Interferometer in a 10^14-Dimensional Hilbert Space. Physical review letters, 123(25), . https://doi.org/10.1103/PhysRevLett.123.250503