Quantum dynamics of a repeatedly measured oscillator-spin system

We study theoretically the dynamics of a hybrid optomechanical system consisting of a macroscopic mechanical membrane magnetically coupled to a spinor Bose-Einstein condensate via a nanomagnet attached at the membrane center. We demonstrate that this coupling permits us to monitor indirectly the center-of-mass position of the membrane via measurements of the spin of the condensed atoms. These measurements normally induce a significant backaction on the membrane motion, which we quantify for the cases of thermal and coherent initial states of the membrane. We discuss the possibility of measuring this quantum backaction via repeated measurements. We also investigate the potential to generate nonclassical states of the membrane, in particular Schr\"odinger-cat states, via such repeated measurements.We study theoretically the dynamics of a hybrid optomechanical system consisting of a macroscopic mechanical membrane magnetically coupled to a spinor Bose-Einstein condensate via a nanomagnet attached at the membrane center. We demonstrate that this coupling permits us to monitor indirectly the center-of-mass position of the membrane via measurements of the spin of the condensed atoms. These measurements normally induce a significant backaction on the membrane motion, which we quantify for the cases of thermal and coherent initial states of the membrane. We discuss the possibility of measuring this quantum backaction via repeated measurements. We also investigate the potential to generate nonclassical states of the membrane, in particular Schr\"odinger-cat states, via such repeated measurements.

arXiv:1105.1856Physical Review AAug 25, 201123 citations

Quantum Dynamics Effected by Repeated Measurements

J. Clausen, V. M. Akulin, J. Salo +1 more

Springer eBooksDec 13, 20050 citations

Quantum Zeno effect in self-sustaining systems: Suppressing phase diffusion via repeated measurements

Wenlin Li, Najmeh Eshaqi-Sani, Wen-Zhao Zhang +1 more

We study the effect of frequent projective measurements on the dynamics of quantum self-sustaining systems by considering the prototypical example of the quantum van der Pol oscillator. Quantum fluctuations are responsible for phase diffusion which progressively blurs the semiclassical limit-cycle dynamics and synchronization, either to an external driving or between two coupled self-sustained oscillators. We show that by subjecting the system to repeated measurements of heterodyne type at an appropriate repetition frequency one can significantly suppress phase diffusion without spoiling the semiclassical dynamics. This quantum Zeno-like effect may be effective in the case of either one or two coupled van der Pol oscillators, and we discuss its possible implementation in the case of trapped ions.We study the effect of frequent projective measurements on the dynamics of quantum self-sustaining systems by considering the prototypical example of the quantum van der Pol oscillator. Quantum fluctuations are responsible for phase diffusion which progressively blurs the semiclassical limit-cycle dynamics and synchronization, either to an external driving or between two coupled self-sustained oscillators. We show that by subjecting the system to repeated measurements of heterodyne type at an appropriate repetition frequency one can significantly suppress phase diffusion without spoiling the semiclassical dynamics. This quantum Zeno-like effect may be effective in the case of either one or two coupled van der Pol oscillators, and we discuss its possible implementation in the case of trapped ions.

arXiv:2107.06046Physical Review AApr 19, 202112 citations

Quantum Control of Hybrid Spin-Oscillator Systems

Sebastian Saner

Springer thesesJan 1, 20261 citation

Nonclassical dynamics induced by a quantum meter

J. Clausen, J. Salo, V. M. Akulin +1 more

Conventionally, the effect of measurements on a quantum system is assumed to introduce decoherence, which renders the system classical-like. We consider here a microscopic meter, that is, an auxiliary essentially quantum system whose state is measured repeatedly, and show that it can be employed to induce transitions from classical states into inherently quantumlike states. The meter state is assumed to be lost in the environment and we derive a non-Markovian master equation for the dynamic system in the case of nondemolition coupling to the meter; this equation can be cast in the form of an $({N}_{a})$ th-order differential equation in time, where ${N}_{a}$ is the dimension of the meter basis. We apply the approach to a harmonic oscillator coupled to a spin- $\frac{1}{2}$ meter and demonstrate how it can be used to engineer effective Hamiltonian evolution, subject to decoherence induced by the projective meter measurements.Conventionally, the effect of measurements on a quantum system is assumed to introduce decoherence, which renders the system classical-like. We consider here a microscopic meter, that is, an auxiliary essentially quantum system whose state is measured repeatedly, and show that it can be employed to induce transitions from classical states into inherently quantumlike states. The meter state is assumed to be lost in the environment and we derive a non-Markovian master equation for the dynamic system in the case of nondemolition coupling to the meter; this equation can be cast in the form of an $({N}_{a})$th-order differential equation in time, where ${N}_{a}$ is the dimension of the meter basis. We apply the approach to a harmonic oscillator coupled to a spin-$\frac{1}{2}$ meter and demonstrate how it can be used to engineer effective Hamiltonian evolution, subject to decoherence induced by the projective meter measurements.

Physical Review ADec 5, 20053 citations

({N}_{a})

th-order differential equation in time, where

{N}_{a}

is the dimension of the meter basis. We apply the approach to a harmonic oscillator coupled to a spin-

\frac{1}{2}

meter and demonstrate how it can be used to engineer effective Hamiltonian evolution, subject to decoherence induced by the projective meter measurements.