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This paper is a theory and simulation study of a two-qubit quantum sensing protocol, not a demonstration on hardware. Its main finding is a trade-off: avoiding direct readout of the sensor can work, but only if the disturbance model matches the device, since a directly read sensor with ideal controls gives higher information rates. For quantum hardware groups, the practical question is how well the noise and coupling assumptions transfer to real qubits.
Helper-assisted quantum sensing with low dressed-state leakage
arXiv:2610.41404v1 Announce Type: new Abstract: We study a two-qubit sensing protocol in which only a helper qubit is read out. Calibrated loading and unloading encode a transverse signal in the helper's phase, keep leakage out of a selected dressed-state band small, and return the sensor close to its idle ground state. We derive an information bound for a single sensor whose excitation stays below a prescribed budget, and simulate repeated operation with an uncertain coupling and finite-duration resets in a driven open-system model. At the tested settings, finite measurement records support estimation with infrequent resets. A helper flip at zero coupling, combined with a reversal of the coupling sign, suppresses a static helper offset shared across a record while retaining the signal, at a cost of about 27% of the no-offset information of a plain sequence of equal duration. Under slowly varying noise, averaging each cycle's likelihood over the correct noise law removes most of the added bias, and a wrong noise law can worsen the estimate. A selected directly read sensor with ideal controls and repeated nondemolition verification has the higher information rate. Any practical benefit of avoiding direct readout therefore requires a device-specific disturbance model.
Abstract:We study a two-qubit sensing protocol in which only a helper qubit is read out. Calibrated loading and unloading encode a transverse signal in the helper's phase, keep leakage out of a selected dressed-state band small, and return the sensor close to its idle ground state. We derive an information bound for a single sensor whose excitation stays below a prescribed budget, and simulate repeated operation with an uncertain coupling and finite-duration resets in a driven open-system model. At the tested settings, finite measurement records support estimation with infrequent resets. A helper flip at zero coupling, combined with a reversal of the coupling sign, suppresses a static helper offset shared across a record while retaining the signal, at a cost of about 27% of the no-offset information of a plain sequence of equal duration. Under slowly varying noise, averaging each cycle's likelihood over the correct noise law removes most of the added bias, and a wrong noise law can worsen the estimate. A selected directly read sensor with ideal controls and repeated nondemolition verification has the higher information rate. Any practical benefit of avoiding direct readout therefore requires a device-specific disturbance model.
31 pages, 7 figures, 4 tables. Code and data: this https URL
Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
arXiv:2610.41404 [quant-ph]
(or arXiv:2610.41404v1 [quant-ph] for this version)
https://doi.org/10.48550/arXiv.2610.41404 Focus to learn more arXiv-issued DOI via DataCite (pending registration)
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