Abstract: One example aspect of the present disclosure is directed to a method for characterizing a multi-qubit logic gate operating on a pair of qubits. The method includes iteratively performing, via a multi-qubit quantum circuit, a set of serial operations on the pair of qubits. The multi-qubit quantum circuit includes the multi-qubit logic gate, a first single-qubit logic gate operating on the first qubit, and a second single-qubit logic gate operating on the second qubit. After iteratively performing the set of serial operations on the pair of qubits, a first quantum state of the first qubit and a second quantum state of the second qubit are measured. A first set of expectation values for the first qubit and a second set of expectation values for the second qubit are determined. A value for a first parameter of a set of parameters of the multi-qubit logic gate is determined.

Abstract: The disclosure is directed to characterizing a quantum logic circuit (QLC), via a set of intrinsic parameters. One method includes selecting control vectors that are associated with phase shifts for the intrinsic parameters such that experimental unitary operators for the QLC are defined. Each experimental unitary operator is based on the intrinsic parameters and phase shifts associated with a corresponding control vector. For each control vector, eigenvalues for the corresponding unitary operator are estimated based on qubit measurements performed subsequent to tuning the QLC in accordance with the control vector. The eigenvalues correspond to quasienergy levels of the qubits. Values for the set of intrinsic parameters may be determined based on the eigenvalues.

Abstract: Methods, systems and apparatus for dynamically decoupling and performing a target unitary operation to a qubit. In one aspect, a method includes generating a control signal that implements a dynamical decoupling control sequence and applying the control signal to the qubit to dynamically decouple the qubit and perform the target unitary operation on the qubit. The target unitary operation includes a product of multiple sub-unitary operations. The dynamical decoupling control sequence includes a plurality of single qubit gates, where one or more of the single qubit gates comprise a single qubit gate that implements one or more of sub-unitary operations of the multiple sub-unitary operations.

Abstract: The disclosure is directed to characterizing a quantum logic circuit (QLC), via a set of intrinsic parameters. One method includes selecting control vectors that are associated with phase shifts for the intrinsic parameters such that experimental unitary operators for the QLC are defined. Each experimental unitary operator is based on the intrinsic parameters and phase shifts associated with a corresponding control vector. For each control vector, eigenvalues for the corresponding unitary operator are estimated based on qubit measurements performed subsequent to tuning the QLC in accordance with the control vector. The eigenvalues correspond to quasienergy levels of the qubits. Values for the set of intrinsic parameters may be determined based on the eigenvalues.

Abstract: Systems and methods for quantum computing devices are provided. In one example, a method may include preparing one or more qubits in a selected initial state of a set of initial states. The method may include implementing a first quantum circuit for n repetitions on the one or more qubits, the first quantum circuit comprising one or more quantum gates. The method may include implementing a second quantum circuit to map a state of the one or more qubits towards a target state, the second quantum circuit based on a unitary associated with the first quantum circuit. The method may include performing a measurement of the one or more qubits. The method may include determining a fidelity between the first quantum circuit and the unitary based at least in part on the measurement of the one or more qubits.