Microsoft Technology Licensing, LLC

Adam Edward Paetznick

Nicolas Guillaume Delfosse

Vadym Kliuchnikov

Kristin E Lauter

Alexander Vaschillo

Michael Edward Beverland

Marcus Palmer Da Silva

Mohamed Ayman El Mandouh

A method of probabilistically canceling noise in a measurement-based quantum device includes obtaining a sequence of ideal measurements included within a quantum algorithm and selecting a sequence of noisy measurements for emulating the sequence of ideal measurements. Each of the noisy measurements in the selected sequence approximates a corresponding one of the ideal measurements and is adjusted by a quantum correction, where the noisy measurements are selected according to a carefully chosen distribution to cancel known features of noise in those same noisy measurements in the sequence.

Probabilistic error cancellation for measurement-based quantum computation

A computing system including a processor configured to receive a stabilizer circuit specification of a stabilizer circuit that includes one or more elementary operations. The elementary operations are each selected from the group consisting of an allocation of one or more qubits in a stabilizer state, an allocation of one or more random classical bits, a Clifford unitary, a Pauli unitary conditional on respective parities of measurement outcomes and/or respective parities of the random classical bits, a joint multi-qubit Pauli measurement, and a destructive one-qubit Pauli measurement. The processor is further configured to compute a standardized stabilizer instrument specification of a stabilizer instrument based at least in part on the stabilizer circuit specification. The standardized stabilizer instrument specification includes an input Clifford unitary, an output Clifford unitary, and a plurality of bit matrices. The processor is further configured to store the standardized stabilizer instrument specification in memory.

Stabilizer instrument specification for stabilizer circuit

A method to correct a fault in application of a Clifford circuit to a qubit register of a quantum computer comprises: (A) receiving circuit data defining the Clifford circuit; (B) emitting outcome code based on the circuit data, the outcome code including a series of outcome checks each corresponding to an anticipated error syndrome of the application of the Clifford circuit to the qubit register; and (C) emitting space-time quantum code corresponding to the Clifford circuit based on the circuit data and on the outcome code, the space-time quantum code including a series of check operators that support quantum-error correction, thereby enabling fault correction in the application of the Clifford circuit to the qubit register.

Fault correction for Clifford circuits

A method to build a lookup decoder for mapping error syndromes based on quantum-stabilizer code to corresponding error corrections comprises (A) enumerating a subset of error syndromes up to a maximum error weight based on the quantum-stabilizer code; (B) iterating through the subset of error syndromes to compute an error state of highest probability for each error syndrome of the subset, where the error state defines error in a qubit register of a quantum computer; and (C) for each error syndrome of the subset of error syndromes, storing in classical computer memory an error correction based on the error state of highest probability and mapped to that error syndrome.

Construction of lookup decoders for stabilizer codes

A low-cost solution for performing a quantum operation provides for defining a target unitary that rotates a single qubit by a target rotation to place the qubit in a target state. The method further provides for identifying multiple projective rotation circuits that each implement an approximation of the target rotation upon successful measurement and assigning a selection probability to each of the multiple identified projective rotation circuits, the selection probability being defined by a metric that increases in value in proportion to a proximity between a qubit state resulting from the approximation and the target qubit state. The method further provides for probabilistically selecting one of the multiple projective rotation circuits according to the assigned selection probabilities and outputting a circuit definition that includes the selected projective rotation circuit.

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Bellevue, WA, United States of America

Adam Edward Paetznick