Implementing large instances of quantum algorithms requires the processing of many quantum information carriers in a hardware platform that supports the integration of different components. Although established semiconductor fabrication processes can integrate many photonic components, the generation and algorithmic processing of many photons has been a bottleneck in integrated photonics. Here, we report the on-chip generation and algorithmic processing of quantum states of light with up to eight photons. Switching between different optical pumping regimes, we implement the scattershot Gaussian and standard boson sampling protocols in the same silicon chip, which integrates linear and nonlinear photonic circuitry. We use these results to benchmark a quantum algorithm for calculating molecular vibronic spectra. Our techniques can be readily scaled for the on-chip implementation of specialized quantum algorithms with tens of photons, pointing the way to efficiency advantages over conventional computers.
The authors thank N. Maraviglia, R. Chadwick, C. Sparrow, L. Banchi, G. Sinclair and D. Bacco for useful discussions and W.A. Murray, M. Loutit, E. Johnston, H. Fedder, M. Schlagmüller, M. Borghi and J. Lennon for technical assistance. The authors acknowledge support from the Engineering and Physical Sciences Research Council (EPSRC), the European Research Council (ERC) and European Commission (EC) funded grants PICQUE, BBOI, QuChip, QuPIC, QITBOX, Quantera-eranet Square, VILLUM FONDEN, QUANPIC (ref. 00025298) and the Center of Excellence, Denmark SPOC (ref. DNRF123). J.W. acknowledges support from the Beijing Academy of Quantum Information Sciences (Y18G21) and from The Key R&D Program of Guangdong province (2018B030329001). A.L. acknowledges fellowship support from EPSRC (EP/N003470/1).