  Photonics offers unique advantages as a substrate for quantum information
processing, but imposes fundamental scalability challenges. Nondeterministic
schemes impose massive resource overheads, while deterministic schemes require
prohibitively many identical quantum emitters to realize sizeable quantum
circuits. Here we propose a scalable architecture for a photonic quantum
computer which needs minimal quantum resources to implement any quantum
circuit: a single coherently controlled atom. Optical switches endow a photonic
quantum state with a synthetic time dimension by modulating photon-atom
couplings. Quantum operations applied to the atomic qubit can be teleported
onto the photonic qubits via projective measurement, and arbitrary quantum
circuits can be compiled into a sequence of these teleported operators. This
design negates the need for many identical quantum emitters to be integrated
into a photonic circuit and allows effective all-to-all connectivity between
photonic qubits. The proposed device has a machine size which is independent of
quantum circuit depth, does not require single-photon detectors, operates
deterministically, and is robust to experimental imperfections.
