a plurality of qubits;

one or more quantum circuit refrigerators, each of the one or more quantum circuit refrigerators including a tunneling junction and a control input for receiving a control signal, and each of the one or more quantum circuit refrigerators configured to enable photon-assisted single-electron tunneling across the respective tunneling junction in response to a control signal received through the respective control input;

coupling elements located between the plurality of qubits and the one or more quantum circuit refrigerators, the coupling elements configured to couple each of the plurality of qubits to one of the one or more quantum circuit refrigerators; and

a common control signal line to the control inputs of the one or more quantum circuit refrigerators,

wherein the plurality of qubits, the one or more quantum circuit refrigerators, and the coupling elements are configured for operation in a cryogenically cooled environment, and

wherein the common control signal line is configured for crossing into the cryogenically cooled environment from a room temperature environment.