Improving quantum state detection with adaptive sequential observations
Abstract
For many quantum systems intended for information processing, one detects the logical state of a qubit by integrating a continuously observed quantity over time. For example, ion and atom qubits are typically measured by driving a cycling transition and counting the number of photons observed from the resulting fluorescence. Instead of recording only the total observed count in a fixed time interval, one can observe the photon arrival times and get a state detection advantage by using the temporal structure in a model such as a hidden Markov model. We study what further advantage may be achieved by applying pulses to adaptively transform the state during the observation. We give a threestate example where adaptively chosen transformations yield a clear advantage, and we compare performances on an ion example, where we see improvements in some regimes. We provide a software package that can be used for exploration of temporally resolved strategies with and without adaptively chosen transformations.
 Publication:

Quantum Science and Technology
 Pub Date:
 July 2022
 DOI:
 10.1088/20589565/ac6972
 arXiv:
 arXiv:2204.00710
 Bibcode:
 2022QS&T....7c4004G
 Keywords:

 quantum;
 adaptive;
 sequential;
 detection;
 ion;
 Quantum Physics
 EPrint:
 Submitted for publication in Quantum Science and Technology. 26 pages, 8 figures. Corrected typos in appendix, updated acknowledgements