Extended flag gadgets for low-overhead circuit verification

Abstract

Flag verification techniques are useful in quantum error correction for detecting critical faults. Here we present an application of flag verification techniques to improving post-selected performance of near-term algorithms. We extend the definition of what constitutes a flag by creating error-detection gadgets based on known transformations of unitary operators. In the case of Clifford or near-Clifford circuits, these unitary operators can be chosen to be controlled Pauli gates, leading to gadgets which require only a small number of additional Clifford gates. We show that such flags can improve circuit fidelities by up to a factor of 2 after post selection, and demonstrate their effectiveness over error models featuring single-qubit depolarizing noise, crosstalk, and two-qubit coherent overrotation.

7 pages, 7 figures

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• Fault-tolerant quantum error correction using error weight parities
• Error Suppression for Arbitrary-Size Black Box Quantum Operations
• Low-Depth Flag-Style Syndrome Extraction for Small Quantum Error-Correction Codes
• QuTracer: Mitigating Quantum Gate and Measurement Errors by Tracing Subsets of Qubits
• Detecting Errors in a Quantum Network with Pauli Checks
• Pathfinding Quantum Simulations of Neutrinoless Double-Beta Decay
• Error Crafting in Mixed Quantum Gate Synthesis
• Real-time adaptation of quantum noise channel estimates
• Symmetric channel verification for purifying noisy quantum channels
• Optimized Clifford Noise Reduction: Theory, Simulations and Experiments