Assess alternative measurement observables for hardware torsion decoding

Investigate whether classical-shadow measurements or expectation-value-based measurements provide useful, hardware-compatible alternatives to computational-basis probability-CDF decoding for torsion decoding or optimization in the Quantum Torsion Folder framework.

Background

The Quantum Torsion Folder encodes molecular torsions in quantum-state information but uses different decoding procedures in simulation and on hardware. Statevector simulations directly access relative phases, whereas physical quantum processors use computational-basis probabilities and an empirical cumulative-distribution-function decoder because standard measurements do not expose complex phases.

The paper notes that this probability-based approach incurs substantial shot and measurement overhead, particularly as the number of populated basis states grows. Alternative observables, including classical shadows and expectation values, could potentially provide more efficient hardware-compatible information for torsion decoding or optimization, but their usefulness is not established.

References

Furthermore, future work could investigate whether classical-shadow or expectation-value-based measurements provide useful alternative hardware-compatible observables for torsion decoding or optimization.

— Logarithmic-scale variational quantum eigensolver for off-lattice protein structure prediction in continuous torsional angle space  (2609.02113 - Cumbo et al., 2 Sep 2026) in Materials and Methods, section “Overflow of the Quantum process,” paragraph on hardware-compatible mapping

Direct recovery of the relative computational-basis amplitude phases used by the simulator decoder would require additional phase-sensitive measurements, such as interference measurements or an appropriate tomographic protocol. These approaches would introduce substantial circuit and measurement overhead, and determining whether they can recover the required relative-phase vector efficiently remains an important direction for future investigation.

— Logarithmic-scale variational quantum eigensolver for off-lattice protein structure prediction in continuous torsional angle space  (2609.02113 - Cumbo et al., 2 Sep 2026) in Discussion and Conclusions, subsection “Hardware Feasibility,” paragraph on phase-sensitive measurements