Characterizing noisy non-clifford gates through partial pauli twirling or through alternating pauli twirling

A computer-implemented method, comprising:

• generating, by a system operatively coupled to a processor, a quantum circuit comprising a series of one or more instances of a quantum gate of interest, and further having each instance of the quantum gate of interest being bounded by a pair of Pauli gates, wherein each pair of Pauli gates comprises two of the same bounding Pauli gate;
• selecting, by the system, separately for each instance of the quantum gate of interest, and employing a partial randomness, the bounding Pauli gate to employ for each instance of the quantum gate of interest;
• selecting, by the system, an initial Pauli gate as Pi from a state-based set of Pauli gates where Pi and Pj∝(A⊗B)Pi both anti-commute with a rotation axis A⊗B of the quantum gate of interest, wherein A, B∈{X, Y, Z};
• and
• based on one or more parameters of a curve, to which an expectation value, resulting from (i) a measurement outcome of execution of the quantum circuit at a quantum system and (ii) subsequent readout twirling of the initial Pauli gate, is fitted, generating, by the system, an element characterizing noise of the quantum gate of interest.

A computer program product facilitating a process to characterize a noisy quantum gate, the computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions executable by a processor to cause the processor to:

• generate, by the processor, a quantum circuit comprising a series of one or more instances of a quantum gate of interest, and further having each instance of the quantum gate of interest being bounded by a pair of Pauli gates, wherein each pair of Pauli gates comprises two of the same bounding Pauli gate;
• select, by the processor, separately for each instance of the quantum gate of interest, and employing a partial randomness, the bounding Pauli gate to employ for each instance of the quantum gate of interest;
• select, by the processor, an initial Pauli gate as Pi from a state-based set of Pauli gates where Pi and Pj∝(A⊗B)Pi both anti-commute with a rotation axis A⊗B of the quantum gate of interest, wherein A, B∈{X, Y, Z};
• and
• based on one or more parameters of a curve, to which an expectation value, resulting from (i) a measurement outcome of execution of the quantum circuit at a quantum system and (ii) subsequent readout twirling of the initial Pauli gate, is fitted, generate, by the processor, an element characterizing noise of the quantum gate of interest.