Extensible universal photonic quantum computing with nonlinearity

Abstract Universal quantum computing requires an architecture that supports both linear circuits and, crucially, strong nonlinear resources. For quantum photonic systems, integrating such nonlinearities with scalable linear circuitry has been a main bottleneck, leaving most optical experiments without nonlinear operations and, consequently, incapable of achieving universality. Here we report on an extensible photonic computer that supports a universal physical gate set by seamlessly combining fully programmable, scalable linear-optical networks with integrated nonlinear modules. This platform enables a broad range of quantum computing and simulation tasks. We demonstrate the quasi-deterministic generation of optical Gottesman–Kitaev–Preskill states, which are essential resources for bosonic error correction yet had previously been realized only probabilistically. Furthermore, we simulate complex many-body quantum dynamics, exemplified by the Bose–Hubbard model. Such quantum simulation tasks have long been considered beyond the reach of photonic hardware limited to linear operations. These capabilities, enabled by our extensible architecture, establish a viable route towards photonic quantum simulation and fault-tolerant quantum computing.