Readout Error Mitigation for Mid-Circuit Measurements and Feedforward

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Abstract
Current quantum computing platforms suffer from readout errors, where faulty measurement outcomes are reported by the device. These errors are particularly harmful in quantum programs that rely on branch statements, where operations in later parts of the program are dynamically determined by mid-circuit measurements. We propose a general protocol for mitigating mid-circuit measurement errors. Our solution works for any number of mid-circuit measurement and feedforward layers without increasing circuit depth or two-qubit gate counts, is efficient under structural assumptions on error channels, and is suitable for immediate application on noisy intermediate-scale quantum devices. We experimentally demonstrate up to a ∼ 60 % reduction in error on superconducting quantum processors across several practically relevant feedforward circuits, including dynamic qubit resets, shallow-depth Greenberger–Horne–Zeilinger state preparation, and multistage quantum teleportation. This work paves the way for more error-resilient adaptive quantum circuits, crucial for current and future quantum computing applications.
Funding Information
  • National Research Foundation
  • Agency for Science, Technology and Research (NRF2021-QEP2-02-P03)
  • Agency for Science, Technology and Research (NRF2021-QEP2-02-P06)
  • Centre for Quantum Technologies Funding Initiative (S24Q2d0009)