Berlin 2018 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 50: HL Poster IV

HL 50.18: Poster

Thursday, March 15, 2018, 19:00–21:00, Poster B

Higher order noise spectra of continuous quantum measurements — •Daniel Hägele and Fabian Schefczik — Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, Bochum, Germany

Quantum physics does not allow for a perturbation free measurement. Nevertheless, experimental methods like spin noise spectroscopy gain important information about a quantum system by weakly probing the system with a laser beam yielding a detector output z(t). The noise spectrum S_z(ω) of z consists of a constant laser shot noise background and an additional contribution that reveals some dynamical properties of the quantum system. We show that additional information can be obtained from z(t) if also higher order spectra are evaluated. Treating continuous quantum measurements within a stochastic master equation approach, we recently derived the all-order continuous quantum noise formula (CQNF) which expresses z(t) without approximations in terms of multiple convolutions of white Gaussian noise, the system propagator G(t), and the observable A in dependence on the measurement strength β [1]. Quantum mechanical expressions for the third order bispectrum and the fourth order trispectum follow. The power of higher order noise spectroscopy is demonstrated by calculating fourth order spectra for the indium electron donor in the semiconductor ZnO. The strong coupling of the electron spin to the 9/2 indium nuclear spin leads to a rich dynamics that leaves characteristic fingerprints in higher order quantum noise spectra.

[1] D. Hägele, https://arxiv.org/abs/1611.02077