Determine the source of the GHZ asymmetry

Determine whether the observed asymmetry in the four-qubit GHZ experiment originates from coherent gate error, basis-change compilation, readout, or epoch-specific hardware drift.

Background

The four-qubit GHZ experiment was designed to test computational-basis phase invariance, even X-parity response, and odd Y-parity response. Although the Y-parity record was approved for the measured phase response, the preregistered X-even conjunction failed because nonzero odd contrasts were observed. The experiment rejected the planned symmetry statement but did not isolate the physical mechanism responsible for the asymmetry. Resolving whether the effect is caused by coherent circuit errors, basis-change compilation, readout, or temporal drift would require additional calibrated or comparative experiments.

References

The experiment does not identify whether the asymmetry originates in coherent gate error, basis-change compilation, readout, or epoch-specific drift.

— Completing or Refusing Low-Dimensional Records of Structured Quantum Circuits: Measurement Loss, Compression Loss, and Hardware Drift  (2609.01303 - Cho et al., 1 Sep 2026) in Section 4.4, “Predeclared completion test across circuit classes”

The replication certifies practical equivalence only for its four new blocks; it neither retroactively converts the first protocol into a success nor identifies whether the original deviation was shot noise, slow drift, or another transient hardware effect.

— Completing or Refusing Low-Dimensional Records of Structured Quantum Circuits: Measurement Loss, Compression Loss, and Hardware Drift  (2609.01303 - Cho et al., 1 Sep 2026) in Section 5, “Engineering interpretation and limitations”