The disclosure describes various aspects of a software-defined quantum computer. For example, a software-defined quantum computing architecture for allocating qubits is described that includes an application programming interface (API); a quantum operating system (OS) on which the API executes, with the quantum OS including a resource manager and a switch; and a plurality of quantum cores connected by the switch of the quantum resource OS. Moreover, the resource manager of the quantum resource OS determines an allocation of a plurality of qubits in the plurality of quantum cores.