Rostock 2019 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 56: Quantum Optics III
Q 56.2: Vortrag
Donnerstag, 14. März 2019, 14:30–14:45, S Ex 04 E-Tech
Quantum witness of a damped qubit with generalized measurements — •Manuel Bojer1, Alexander Friedenberger1, and Eric Lutz1,2 — 1Department of Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg, D-91058 Erlangen, Germany — 2Institute for Theoretical Physics I, University of Stuttgart, D-70550 Stuttgart, Germany
We evaluate the quantum witness based on the no-signaling-in-time condition of a damped two-level system for nonselective generalized measurements of varying strength. We explicitly compute its dependence on the measurement strength for a generic example. We find a vanishing derivative for weak measurements and an infinite derivative in the limit of projective measurements. The quantum witness is hence mostly insensitive to the strength of the measurement in the weak measurement regime and displays a singular, extremely sensitive dependence for strong measurements. We finally relate this behavior to that of the measurement disturbance defined in terms of the fidelity between pre-measurement and post-measurement states.