Processing quantum information

A quantum information processing method comprising:

• encoding information in a first processor node and a second processor node, the first processor node includes a first plurality of qubits and a first actuator, the first plurality of qubits being coupled to the first actuator by respective intra-node quantum couplings in the first processor node, the second processor node includes a second plurality of qubits and a second actuator, the second qubit being coupled to the second actuator by respective intra-node quantum couplings in the second processor node, the second actuator being coupled to the first actuator by an inter-node quantum coupling;
• and
• processing the information using cross-node quantum interactions between the first plurality of qubits and the second plurality of qubits, the cross-node quantum interactions being produced by non-commutivity of the inter-node quantum coupling and each intra-node quantum coupling in the first and second processor nodes, wherein processing the information includes performing a multi-qubit quantum gate on a first qubit in the first processor node and a second qubit in the second processor node.;
• wherein processing the information includes applying control operations to the first and second processor nodes, and the control operations define an interaction frame in which the cross-node quantum interaction between the first qubit and the second qubit dominates the dynamics of the respective first and second qubits;
• wherein the intra-node quantum coupling H1 between the first qubit and the first actuator commutes with the intra-node quantum coupling H2 between the second qubit and the second actuator, and the cross-node quantum interaction is induced from an effective coupling term [[H3, (H1+H2)], (H1+H2)], where H3 represents the inter-node quantum coupling.

A quantum information processor comprising:

• a node system comprising a plurality of processor nodes, each of the processor nodes includes a plurality of qubits and an actuator;
• and
• a control system operable to perform a multi-qubit quantum gate based on a cross-node quantum interaction between the qubits of different processor nodes, wherein the cross-node quantum interaction between the qubits of different processor nodes are produced by non-commutivity of:
• intra-node quantum couplings between the plurality of qubits and the respective actuator of each processor node;
• and
• inter-node quantum couplings between the actuators of the different nodess;
• wherein the control system is operable to manipulate a first qubit in the first processor node and a second qubit in the second processor node by applying control operations to the actuators, and the control operations define an interaction frame in which the cross-node quantum interaction between the first qubit and the second qubit dominates the dynamics of the respective first and second qubits;
• wherein the intra-node quantum coupling H1 between the first qubit and the first actuator commutes with the intra-node quantum coupling H2 between the second qubit and the second actuator, and the control system is operable to induce the cross-node quantum interaction from an effective coupling term [[H3, (H1+H2)], (H1+H2)], where H3 represents the inter-node quantum coupling.