Abstract: A method is provided for determining a control sequence for performing a multiqudit algorithm on a quantum computer, the multi-qudit algorithm expressible as a series of one or more k-qudit interactions. The method comprises, for each of the k-qudit interactions, decomposing the k-qudit interaction into a sequence of single-qudit unitary rotations and/or two-qudit unitary rotations from the continuous family of controllable unitary rotations generated by underlying physical interactions in the hardware of the quantum computer subject to a specified minimum interaction time, said sequence being physically implementable on the quantum computer. The method further comprises combining the sequences to form a combined interaction sequence. The method further comprises determining, based on the combined interaction sequence, the control sequence for performing the multiqudit algorithm on the quantum computer.

Abstract: A method comprises, for each of a plurality of FLO circuits, (i) executing, one or more times using the quantum information processor, that FLO circuit to determine a first value of an observable; and (ii) classically simulating that FLO circuit to determine a second value of the observable. A training set comprises tuples, each tuple comprising parameter(s) for defining a FLO circuit, the corresponding first value of the observable determined for that FLO circuit, and the corresponding second value of the observable determined for that FLO circuit. The training set is used to determine a noise inversion function. The quantum information processor executes one or more times a quantum circuit for implementing at least a part of the algorithm to determine a noisy value of an observable. The noise inversion function is applied to the noisy value and a corrected value of the observable is determined.

Abstract: The invention relates to methods and apparatuses for reconstructing phase information in a time series, the time series being derived from a time evolution of an input state acted on by a Hamiltonian, H. First, an input state, |?, a total time evolution time, T, and the Hamiltonian, H are received. Next a time evolution of the input state is enacted, using H to generate an absolute value of a first time series, |f1|. In addition at least one additional family of absolute values of time series is generated, each time series being a discrete or continuous function of time t, for t?[0,T]. Finally, phase information is extracted for the time series of the input state from the absolute values of the first time series and the at least one additional family of absolute values of time series.

Abstract: A computer-implemented method of determining a control sequence for performing a quantum operation on a quantum information processor comprising a plurality of qubits is described herein. The quantum operation is characterised by a fermionic quantum operator for acting on local fermionic modes. The method comprises translating, using a fermion-to-qubit encoding, the fermionic quantum operator to a qubit operator for operating on the plurality of qubits, and determining from the qubit operator a control sequence for performing the quantum operation on the quantum information processor. Apparatuses and computer-readable media are also described.

Abstract: A computer-implemented method of determining a control sequence for performing a quantum operation on a quantum information processor comprising a plurality of qubits is described herein. The quantum operation is characterised by a fermionic quantum operator for acting on local fermionic modes. The method comprises translating, using a fermion-to -qubit encoding, the fermionic quantum operator to a qubit operator for operating on the plurality of qubits, and determining from the qubit operator a control sequence for performing the quantum operation on the quantum information processor. Apparatuses and computer-readable media are also described.

Abstract: A method is provided for determining a control sequence for performing a multiqudit algorithm on a quantum computer, the multiqudit algorithm expressible as a series of one or more k-qudit interactions. The method comprises, for each of the k-qudit interactions, decomposing the k-qudit interaction into a sequence of single-qudit unitary rotations and/or two-qudit unitary rotations from the continuous family of controllable unitary rotations generated by underlying physical interactions in the hardware of the quantum computer subject to a specified minimum interaction time, said sequence being physically implementable on the quantum computer. The method further comprises combining the sequences to form a combined interaction sequence. The method further comprises determining, based on the combined interaction sequence, the control sequence for performing the multiqudit algorithm on the quantum computer.

Abstract: A method comprises, for each of a plurality of FLO circuits, (i) executing, one or more times using the quantum information processor, that FLO circuit to determine a first value of an observable; and (ii) classically simulating that FLO circuit to determine a second value of the observable. A training set comprises tuples, each tuple comprising parameter(s) for defining a FLO circuit, the corresponding first value of the observable determined for that FLO circuit, and the corresponding second value of the observable determined for that FLO circuit. The training set is used to determine a noise inversion function. The quantum information processor executes one or more times a quantum circuit for implementing at least a part of the algorithm to determine a noisy value of an observable. The noise inversion function is applied to the noisy value and a corrected value of the observable is determined.