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QI: Fachverband Quanteninformation

QI 4: Poster: Quantum Information

QI 4.19: Poster

Montag, 5. September 2022, 18:00–20:00, P2

Quantum Polyspectra - Grand Unified Theory of Continuous Quantum Measurements — •Markus Sifft and Daniel Hägele — Ruhr University Bochum, Faculty of Physics and Astronomy, Experimental Physics VI (AG), Germany

The evaluation of continuous quantum measurements is a challenge in research areas like circuit quantum electrodynamics, spin noise spectroscopy, and quantum sensing. Measurement records can exhibit as diverse results as quantum jumps, mainly Gaussian noise, or even stochastic peaks from detectors with single photon resolution. Until now, specialized theories were used to model and eventually evaluate such measurement records. The poster reports on our recent progress in unifying all continuous measurement schemes into one theory. The theory is based on the measurement record, its power spectrum, and its third and fourth order generalizations, so-called polyspectra. Expressions for quantum polyspectra can be derived without approximation from the stochastic master equation [1]. System parameters follow from fitting quantum polyspectra to measured spectra [2]. This approach allows for a systematic evaluation of quantum measurements including coherent quantum dynamics, environmental damping, and measurement backaction at arbitrary measurement strength (Zeno-physics). We present and interpret quantum polyspectra of conventional spin noise spectroscopy, quantum transport through quantum dots, and spin noise spectroscopy in the single-photon regime.

[1] Hägele et al., PRB 98, 205143 (2018), [2] Sifft et al., PRR 3, 033123 (2021)