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Quantum

The limits of erasure-based postselection for quantum error mitigation

Sam J. Griffiths, Jamie Friel, Brian Vlastakis

Featured July 2, 2026

Original Paper

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Simply

By using special 'dual-rail' qubits that turn common errors into detectable 'erasures,' the paper shows that simply throwing away bad results (postselection) can make quantum computers work much better, even with imperfect error checks.

In depth
This paper explores using postselection with erasure-dominant qubits to mitigate errors in near-term quantum computers. The authors demonstrate that by encoding logical qubits into two physical modes (dual-rail), energy relaxation events become detectable erasures. Discarding circuit runs where erasures are detected significantly improves circuit fidelity, even with imperfect erasure checks, allowing dual-rail systems to surpass noise floors where conventional single-rail systems fail.

Key Takeaways

  • 1
    The study introduces a numerical framework and an open-source library, erado, for simulating circuit-level erasure noise and postselection in quantum circuits.
  • 2
    The authors demonstrate that postselection effectively mitigates erasure noise, improving quantum Fourier transform (QFT) fidelity, even when accounting for imperfect erasure detection and gate depolarizing noise.
  • 3
    The paper shows that postselected dual-rail systems can outperform single-rail systems, enabling operation beyond fundamental noise floors at the kiloquop scale, justifying this approach for the NISQ era.

Conceptual Flow

HIGH LEVEL
1
Methodology: Turning Errors into Detectable Erasures

Instead of hidden errors, special qubits make errors obvious, so bad results can be thrown away.

Normal Qubit
Hidden Error
Causes Bad Result
Unreliable Answer
2
Results: Better Answers by Discarding Bad Runs

By only keeping the good results, the new method gives much more accurate answers than the old way.

Special Qubit
Obvious Error
Discard Bad Run
Reliable Answer