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TT: Fachverband Tiefe Temperaturen
TT 33: Focus Session: Nanomechanical Systems for Classical and Quantum Sensing I (joint session TT/DY/HL/QI)
TT 33.2: Talk
Tuesday, March 19, 2024, 12:00–12:15, H 3007
Logarithmic susceptibility of a quantum parametrically modulated oscillator — •Daniel Boneß1, Wolfgang Belzig1, and Mark Dykman2 — 1Department of Physics, University of Konstanz, 78457 Konstanz, Germany — 2Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
A weakly damped nonlinear oscillator modulated close to twice its eigenfrequency has two stable states, which have the same vibration amplitudes but opposite phases. The states are equally populated due to classical or quantum fluctuations.
An extra force at half the modulation frequency lifts the symmetry of the states. Even a weak force can result in a significant change of the populations, as it beats against the intensity of quantum and classical fluctuations. We develop an approach that allows us to find this population change.
We also study the effect of the extra force with frequency slightly detuned away from half the modulation frequency. For a detuning that is small compared to the switching rate the force leads to the imbalance of populations that is modulated at the frequency of the detuning. For larger detuning, the adiabatic picture breaks down and the wells are again equally populated. However, the rates of switching between the wells is exponentially increased. We calculate the change of the logarithm of the switching rate, termed logarithmic susceptibility, using the real-time instanton method. The results are relevant for controlling parametric oscillators and their application in quantum information systems.
Keywords: Symmetry breaking; Nanomechanics; Nonlinear dynamics; Fluctuations; Quantum Activation