Universal control for implementing quantum gates

An apparatus for implementing a single qubit unitary quantum gate, the apparatus comprising:

• one or more classical processors;
• a quantum device in data communication with the one or more classical processors, wherein the quantum device comprises:
• one or more qubits;
• one or more control pulse drivelines;
• one or more couplers, each coupler coupling a corresponding qubit to a control pulse driveline;
• a control pulse generator configured to generate control pulses on the one or more drivelines;
• wherein the apparatus is configured to perform operations comprising:
• defining a universal quantum control cost function, wherein the control cost function comprises a total runtime penalty term and a qubit leakage penalty term representing qubit leakage during a time dependent Hamiltonian evolution that realizes the unitary quantum gate;
• adjusting parameters of the time dependent Hamiltonian evolution to vary a control cost according to the control cost function such that total quantum gate runtime and qubit leakage errors are reduced;
• generating a control pulse for the unitary quantum gate using the adjusted parameters;
• and
• applying the control pulse to the one or more qubits to implement the unitary quantum gate.