Abstract: A quantum computer prepares system qubits into respective selected states by obtaining an initial steering circuit. The initial steering circuit is a quantum circuit comprising one or more quantum interactions between at least one detector qubit and the system qubits that is performable by the quantum computer. The quantum computer performs one or more iterations of causing the at least one detector qubit to be initialized into an initial detector state, causing performance of the steering circuit, and causing measurement of the at least one detector qubit. The quantum computer determines that the one or more system qubits are in the respective selected states. The quantum computer may then use the system qubits in performance of a quantum program. The initial steering circuit may be determined using a machine learning algorithm to determine parameters of a parameterized unitary operator enacted thereby. The steering circuit may be updated on each iteration.

Abstract: A system includes a plurality of qubits; a qubit manipulation system for controlling evolution of respective quantum states of the qubits; a measurement system for performing measurement of qubit quantum states; and a controller for controlling operation of the qubit manipulation system and receiving measurement results from the measurement system. The controller is configured to cause the qubit manipulation system to execute a first portion of a program circuit and an assertion circuit; and receive measurement results that indicate a quantum state of an ancilla qubit used in performing a comparison test between an assertion qubit on which an assertion channel of the assertion circuit was performed and system qubits on which the first portion of the program circuit was performed. The controller is further configured to process the measurement results to determine a noise status of the system; and provide an indication of the noise status.

Abstract: A quantum computer prepares a logical qubit in a selected state by obtaining a steering circuit. The steering circuit is a quantum circuit comprising one or more quantum interactions between at least one detector qubit and at least one system qubit that is performable by the quantum computer. The quantum computer comprises a plurality of physical qubits that includes the at least one detector qubit and the at least one system qubit. The quantum computer performs one or more iterations of causing one or more detector qubits of the plurality of physical qubits to be initialized into an initial state, causing performance of the steering circuit, and causing measurement of the one or more detector qubits. The quantum computer determines that the logical qubit is in the selected state. The quantum computer may then use the logical qubit in performance of a quantum program.

Abstract: A quantum computer prepares system qubits into respective selected states by obtaining an initial steering circuit. The initial steering circuit is a quantum circuit comprising one or more quantum interactions between at least one detector qubit and the system qubits that is performable by the quantum computer. The quantum computer performs one or more iterations of causing the at least one detector qubit to be initialized into an initial detector state, causing performance of the steering circuit, and causing measurement of the at least one detector qubit. The quantum computer determines that the one or more system qubits are in the respective selected states. The quantum computer may then use the system qubits in performance of a quantum program. The initial steering circuit may be determined using a machine learning algorithm to determine parameters of a parameterized unitary operator enacted thereby. The steering circuit may be updated on each iteration.