Phase-Sensitive Benchmarking of Composite Quantum Gates with Chiral-Interference Circuits on Quantum Hardware

We construct and experimentally implement compact gate-native circuits that simulate the state-transfer interference underlying three- and four-level chiral-resolution protocols. Both models are encoded in a two-qubit register, with the enantiomer-dependent sign of one of the couplings simulated by a conditional-phase operation in the four-level circuit and by the sign of a final rotation in the three-level circuit. On an IBM quantum processor, the two circuits produce the expected enantiomer-dependent output states with probabilities of nearly $98\%$. We then use these circuits as physically motivated, phase-sensitive benchmarks for composite quantum gates. We introduce rotation-angle error to the single-qubit operations and replace them by several composite gates, including B5, SK1, BB1, H5s, and X5. The comparison demonstrates that single-gate robustness does not translate to equivalent whole-circuit robustness. In particular, variable-rotation sequences do not preserve the required relative phases, making them unsuitable for error correction in circuits. By contrast, the H5s/X5 sequences maintain high target-state populations for relative errors as large as $50\%$, whereas elementary rotations reach the same threshold only for approximately $8\%$. The three-level circuit exhibits a similar enhancement and additionally reveals an error-cancellation symmetry whose protection under composite replacement is exact only when the relevant full propagators satisfy an inverse relation.

Source: arXiv:2607.18137v1 - http://arxiv.org/abs/2607.18137v1 PDF: https://arxiv.org/pdf/2607.18137v1 Original Link: http://arxiv.org/abs/2607.18137v1