Independent State and Measurement Characterization for Quantum Computers

Abstract

Correctly characterizing state preparation and measurement (SPAM) processes is a necessary step towards building reliable quantum processing units (QPUs). In this work, we discuss the subtleties behind separately measuring SPAM errors. We propose a protocol that can separately estimate SPAM errors, in the case where quantum gates are ideal. In the case where the quantum gates are imperfect, we derive bounds on the estimated SPAM error rates, based on gate error measures which can be estimated independently of SPAM processes. Our method shows that the gauge ambiguity in characterizing SPAM operations can be resolved, by assuming that there exists one qubit whose initial state is uncorrelated with other qubits in a QPU. We test the protocol on a publicly available five-qubit QPU and demonstrate its validity by comparing our results with simulations.

12 pages, 4 figures. Accepted journal version. Expanded with clearer formatting, more detailed calculations in the appendix, new data with a different presentation, and computer simulations

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• The Role of Quantum Computing in Advancing Scientific High-Performance Computing: A perspective from the ADAC Institute
• Universal framework for simultaneous tomography of quantum states and SPAM noise
• Readout Error Mitigation for Mid-Circuit Measurements and Feedforward
• Measuring NISQ Gate-Based Qubit Stability Using a 1+1 Field Theory and Cycle Benchmarking
• Operation fidelity explored by numerical range of Kraus operators
• Deep Neural Network-assisted improvement of quantum compressed sensing tomography
• Precision Bounds for Characterising Quantum Measurements
• Algorithmic cooling for resolving state preparation and measurement errors in quantum computing
• Dual Map Framework for Noise Characterization of Quantum Computers
• Corrupted sensing quantum state tomography
• Quantum Process Tomography with Digital Twins of Error Matrices