Theoretical framework for thin film superfluid optomechanics: towards the quantum regime

Baker, Christopher G.; Harris, Glen I.; McAuslan, David L.; Sachkou, Yauhen; He, Xin; Bowen, Warwick P.

doi:10.1088/1367-2630/aa520d

Cited by 29 publications

(64 citation statements)

References 56 publications

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“…The complex surface displacement amplitude η of a travelling superfluid third-sound wave (or alternatively the sound-induced density fluctuations for a BEC) in a circular domain are given by [63]:…”

Section: A2 Vx Vymentioning

confidence: 99%

“…with '+' and '−' signs respectively corresponding to the CW and CCW travelling cases, as in equation (A.3). Note that while the motion of a solid circular membrane would also be given by equation (A.3), its velocity would be different to equation (A.4), leading to dramatically different effective mass scalings [63]. The surface displacement profile h ( ) R and instantaneous velocity field  ( ) R v 3 are plotted in figure 6(b), for a CW (m=1, n=2) Bessel mode with free boundary conditions.…”

Section: A2 Vx Vymentioning

confidence: 99%

“…with the kinetic energy E of the third-sound mode, for m>0, given by [63]: We note that, as expected, the splitting does not depend on the superfluid parameters (film thickness, density), and that it is linear in vortex flow field (see equation (A.6)), such that the splitting obeys the superposition principle, whereby the splitting due to an ensemble of vortices is equal to the sum of the splittings per vortex calculated individually. The result equation (A.14) holds for both superfluid helium thin films and Bose-Einstein condensates, with η being the film thickness perturbation/density perturbation, respectively.…”

Section: A3 Analytical Description Of Vortex-sound Couplingmentioning

confidence: 99%

“…In order to include vortices defined in the Electrostatics(es) module, a critical velocity is defined (v crit ≈60 m s −1 for superfluid helium [87]), and the acoustic background flow field  u 0 is set to: where T mode is the mode temperature. An analytical expression for the potential energy of a third sound mode E pot,3 is given in [63]. For the simple case of a uniform film thickness and free boundary conditions the conversion is given by…”

Section: D2 Notes On Implementation In Comsol ® Multiphysicsmentioning

confidence: 99%

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Modelling of vorticity, sound and their interaction in two-dimensional superfluids

et al. 2019

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Vorticity in two-dimensional superfluids is subject to intense research efforts due to its role in quantum turbulence, dissipation and the BKT phase transition. Interaction of sound and vortices is of broad importance in Bose-Einstein condensates and superfluid helium. However, both the modelling of the vortex flow field and of its interaction with sound are complicated hydrodynamic problems, with analytic solutions only available in special cases. In this work, we develop methods to compute both the vortex and sound flow fields in an arbitrary two-dimensional domain. Further, we analyse the dispersive interaction of vortices with sound modes in a two-dimensional superfluid and develop a model that quantifies this interaction for any vortex distribution on any two-dimensional bounded domain, possibly non-simply connected, exploiting analogies with fluid dynamics of an ideal gas and electrostatics. As an example application we use this technique to propose an experiment that should be able to unambiguously detect single circulation quanta in a helium thin film.

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Section: A2 Vx Vymentioning

confidence: 99%

Section: A2 Vx Vymentioning

confidence: 99%

Section: A3 Analytical Description Of Vortex-sound Couplingmentioning

confidence: 99%

Section: D2 Notes On Implementation In Comsol ® Multiphysicsmentioning

confidence: 99%

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Modelling of vorticity, sound and their interaction in two-dimensional superfluids

et al. 2019

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“…This may be encouraged by choosing the material carefully [176]. One intriguing application is to the photothermal control of third-sound (thin film) waves in He-3 superfluids coated on whispering gallery-mode resonators [177,178].…”

Section: Other Optomechanical Couplings and Techniquesmentioning

confidence: 99%

Quantum optomechanics in the unresolved sideband regime

Bennett¹

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A cavity optomechanical system is formed when the resonance frequency of an optical cavity is dependent upon the position of a mechanical oscillator. This is achieved in a plethora of physical systems, spanning the range from cold atom clouds trapped in miniaturised optical cavities through to the kilogram-scale test masses of the four kilometre long advanced Laser Interferometer Gravitationalwave Observatory. The dynamical coupling between light and vibration thus engendered modifies both the optical and mechanical behaviours, and is responsible for a number of intriguing phenomena.Indeed, with optomechanical tools it becomes possible to observe the fact that macroscopic mechanical oscillators are governed by the laws of quantum mechanics, rather than familiar classical equations of motion. The preparation of mechanical oscillators in truly quantum states, such as squeezed states and two-mode entangled states, has already been experimentally demonstrated. It is predicted that further advances along these lines will permit sensitive tests of fundamental physics, in addition to delivering significant improvements to sensor and information processing technologies.The majority of optomechanical protocols developed to date operate in the so-called resolved sideband limit, where the cavity bandwidth is small compared to the mechanical resonance frequency.This ensures that the optical cavity may be employed as a frequency-selective element for performing coherent control, but it also limits the quantity of circulating optical power and prevents one from reaching the standard quantum limit for position and force detection.In this thesis we report research that has expanded the optomechanical toolbox in the unresolved sideband regime, where the linewidth of the cavity is larger than the mechanical resonance frequency. This is a natural operating regime for large-mass and/or low-frequency mechanical oscillators; microcavity devices with small mode volumes and large optomechanical coupling rates; high-bandwidth, high-quantum-efficiency position and force detection; optical pulse manipulation; and hybrid devices couple to low-frequency quantum ancillae, such as the motional degrees of freedom of cold atoms.We begin this thesis by providing introductory material which covers advances in optomechanics and related fields; useful theoretical tools and their physical meanings; and some insights into technical details. These materials are included in the hope that they might be useful to other researchers in the field.Our first contribution to optomechanics in the unresolved sideband regime is a theoretical study of a remotely-coupled hybrid atom-optomechanical system. This uses a cloud of cold atoms as a 'quantum handle' with which to control the state of a mechanical oscillator. The two systems are coupled via light, which significantly relaxes experimental requirements on integration of vacuum and cryogenic apparatus. We derive the conditions under which laser cooling of the atomic ensemble permits one to sympathetica...

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Introduction and Overview

Sachkou¹

2020

Springer Theses

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Theoretical framework for thin film superfluid optomechanics: towards the quantum regime

Cited by 29 publications

References 56 publications

Modelling of vorticity, sound and their interaction in two-dimensional superfluids

Modelling of vorticity, sound and their interaction in two-dimensional superfluids

Quantum optomechanics in the unresolved sideband regime

Introduction and Overview

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