Distributed quantum computing

Abstract

A distributed quantum computing system 100, e.g. a quantum memory, comprises: quantum computing units 102 of qubits; quantum networking units 104, each coupled to qubits on the quantum computing units and being configured to selectively couple each qubit to a fixed number of outputs; entanglement units 106, each having inputs to receive signals from the quantum networking units 104 and configured to entangle the received signals; a fixed coupling network 110 comprising predefined network pathways between outputs of the quantum networking units and the inputs of the entanglement units; and a control system 108 configured to control the plurality of the quantum networking units 104 to entangle qubits of the quantum computing units according to a topology associated with an error correcting code. The networking units 104 comprise photonic integrated chips to selectively couple each qubit to the fixed number of outputs. Network pathways may comprise optical fibers. The topology may be divided into tiles with connections such that the number of connections between tiles is minimised. Entanglement units 106 comprise performing Bell state measurements. The error-correcting code may be: low-density parity-check, qLDPC; hyperbolic or semi-hyperbolic; Floquet. [figure 1]