Abstract: Systems and techniques for active quantum memory (AQM) and quantum circuits with feedback are described. For instance, one or more aspects of the present disclosure may enable the indefinite storage of one or more qubits via a sequence of quantum teleportations or quantum swaps involving the rapid periodic executions of a standard teleportation or swap protocols with feedback (e.g., provided the total feedback cycle time is less than the decoherence time for a qubit). The stored quantum state may be passed repeatedly back-and-forth between two of the qubits, and the stored quantum state may be maintained by the input energy on each cycle required to initialize the entangled qubit pair (e.g., where the cycle period is chosen to be less than the decoherence time of the qubits to maintain state information over many cycles).

Abstract: Systems and techniques for active quantum memory (AQM) and quantum teleportation circuits with feedback are described. For instance, one or more aspects of the present disclosure may enable the indefinite storage of one or more qubits via a sequence of quantum teleportations involving the rapid periodic executions of a standard teleportation protocol with feedback (e.g., provided the total feedback cycle time is less than the decoherence time for a qubit). For each qubit stored, a pair of entangled qubits are injected on each feedback cycle and two qubits are measured. The stored quantum state may be passed repeatedly back-and-forth between two of the qubits, and the stored quantum state may be maintained by the input energy on each cycle required to initialize the entangled qubit pair (e.g., where the cycle period is chosen to be less than the decoherence time of the qubits to maintain state information over many cycles).