| 1. |
- Bergholm, Ville, et al.
(författare)
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Optimal control of hybrid optomechanical systems for generating non-classical states of mechanical motion
- 2019
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Ingår i: Quantum Science and Technology. - : IOP Publishing. - 2058-9565. ; 4:3
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Tidskriftsartikel (refereegranskat)abstract
- Cavity optomechanical systems are one of the leading experimental platforms for controlling mechanical motion in the quantum regime. We exemplify that the control over cavity optomechanical systems greatly increases by coupling the cavity also to a two-level system, thereby creating a hybrid optomechanical system. If the two-level system can be driven largely independently of the cavity, we show that the nonlinearity thus introduced enables us to steer the extended system to non-classical target states of the mechanical oscillator with Wigner functions exhibiting significant negative regions. We illustrate how to use optimal control techniques beyond the linear regime to drive the hybrid system from the near ground state into a Fock target state of the mechanical oscillator. We base our numerical optimization on realistic experimental parameters for exemplifying how optimal control enables the preparation of decidedly non-classical target states, where naive control schemes fail. Our results thus pave the way for applying the toolbox of optimal control in hybrid optomechanical systems for generating non-classical mechanical states.
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| 2. |
- Brunelli, M., et al.
(författare)
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Experimental Determination of Irreversible Entropy Production in out-of-Equilibrium Mesoscopic Quantum Systems
- 2018
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 121:16
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Tidskriftsartikel (refereegranskat)abstract
- By making use of a recently proposed framework for the inference of thermodynamic irreversibility in bosonic quantum systems, we experimentally measure and characterize the entropy production rates in the nonequilibrium steady state of two different physical systems a micromechanical resonator and a Bose-Einstein condensate each coupled to a high finesse cavity and hence also subject to optical loss. Key features of our setups, such as the cooling of the mechanical resonator and signatures of a structural quantum phase transition in the condensate, are reflected in the entropy production rates. Our work demonstrates the possibility to explore irreversibility in driven mesoscopic quantum systems and paves the way to a systematic experimental assessment of entropy production beyond the microscopic limit.
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| 3. |
- Ciers, Anastasiia, 1992, et al.
(författare)
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Integrated free-space optomechanics with AlGaAs heterostructures
- 2021
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Ingår i: 2021 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2021. - 9781557528209
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Konferensbidrag (refereegranskat)abstract
- We fabricated and characterized suspended bi-layered photonic crystal slabs in AlGaAs heterostructures. Our approach allows to create integrated, closely spaced membranes, which can exhibit photonic bound states in the continuum to increase light-matter interaction.
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| 4. |
- Fang, Hanlin, 1992, et al.
(författare)
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Localization and interaction of interlayer excitons in MoSe 2 /WSe 2 heterobilayers
- 2023
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Ingår i: Nature Communications. - 2041-1723 .- 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Transition metal dichalcogenide (TMD) heterobilayers provide a versatile platform to explore unique excitonic physics via the properties of the constituent TMDs and external stimuli. Interlayer excitons (IXs) can form in TMD heterobilayers as delocalized or localized states. However, the localization of IX in different types of potential traps, the emergence of biexcitons in the high-excitation regime, and the impact of potential traps on biexciton formation have remained elusive. In our work, we observe two types of potential traps in a MoSe2/WSe2 heterobilayer, which result in significantly different emission behavior of IXs at different temperatures. We identify the origin of these traps as localized defect states and the moiré potential of the TMD heterobilayer. Furthermore, with strong excitation intensity, a superlinear emission behavior indicates the emergence of interlayer biexcitons, whose formation peaks at a specific temperature. Our work elucidates the different excitation and temperature regimes required for the formation of both localized and delocalized IX and biexcitons and, thus, contributes to a better understanding and application of the rich exciton physics in TMD heterostructures.
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| 5. |
- Fitzgerald, Jamie, 1992, et al.
(författare)
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Cavity optomechanics with photonic bound states in the continuum
- 2021
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Ingår i: Physical Review Research. - 2643-1564. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- We propose a versatile, free-space cavity optomechanics platform built from two photonic crystal membranes, one of which is freely suspended, and designed to form a microcavity less than one wavelength long. This cavity features a series of photonic bound states in the continuum that, in principle, trap light forever and can be favorably used together with evanescent coupling for realizing various types of optomechanical couplings, such as linear or quadratic coupling of either dispersive or dissipative type, by tuning the photonic crystal patterning and cavity length. Crucially, this platform allows for a quantum cooperativity exceeding unity in the ultrastrong single-photon coupling regime, surpassing the performance of conventional Fabry-Perot-based cavity optomechanical devices in the nonresolved sideband regime. This platform allows for exploring new regimes of the optomechanical interaction, in particular in the framework of pulsed and single-photon optomechanics.
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| 6. |
- Fitzgerald, Jamie, 1992, et al.
(författare)
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Nanophotonic Structures for Cavity Optomechanics
- 2021
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Ingår i: 2021 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2021. ; June 2021
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Konferensbidrag (refereegranskat)abstract
- In this contribution, we will show how nanophotonic structures can be used to gain access to previously inaccessible regimes in cavity optomechanics [1]. We introduce a novel optomechanics platform, built from two photonic crystal membranes [2] , one of which is freely suspended (see Fig. 1 ). This cavity supports a series of photonic bound states in the continuum (BICs) that, in principle, trap light forever [3] and can be favourably used together with evanescent coupling for realizing various types of optomechanical couplings, such as linear or quadratic coupling of either dispersive or dissipative type, by tuning the photonic crystal patterning and cavity length. By combining light propagation in both free-space (between the photonic-crystal membranes) and guided-mode (over the photonic-crystal membranes) form, our platform merges the strengths offered by in-plane and out-of-plane optomechanical systems.
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| 7. |
- Fitzgerald, Jamie, 1992, et al.
(författare)
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Towards New Regimes in Cavity Optomechanics with Photonic Bound States in the Continuum in Photonic Crystal Membranes
- 2022
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Ingår i: International Conference on Metamaterials, Photonic Crystals and Plasmonics. - 2429-1390. ; , s. 633-634
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Konferensbidrag (refereegranskat)abstract
- We will present an optomechanics platform based on photonic bound states in the continuum and show that this platform is very flexible and makes it possible to reach different regimes of cavity optomechanics, e.g., with linear or quadratic coupling of either dispersive or dissipative type. Bound states in the continuum enable to build compact optomechanical devices, resulting in linear optomechanical coupling strengths that are orders of magnitude larger than conventional out-of-plane systems and comparable to values observed for in-plane geometries.
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| 8. |
- Gut, C., et al.
(författare)
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Stationary optomechanical entanglement between a mechanical oscillator and its measurement apparatus
- 2020
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Ingår i: PHYSICAL REVIEW RESEARCH. - 2643-1564. ; 2:3
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Tidskriftsartikel (refereegranskat)abstract
- We provide an argument to infer stationary entanglement between light and a mechanical oscillator based on continuous measurement of light only. We propose an experimentally realizable scheme involving an optomechanical cavity driven by a resonant, continuous-wave field operating in the non-sideband-resolved regime. This corresponds to the conventional configuration of an optomechanical position or force sensor. We show analytically that entanglement between the mechanical oscillator and the output field of the optomechanical cavity can be inferred from the measurement of squeezing in (generalized) Einstein-Podolski-Rosen quadratures of suitable temporal modes of the stationary light field. Squeezing can reach levels of up to 50% of noise reduction below shot noise in the limit of large quantum cooperativity. Remarkably, entanglement persists even in the opposite limit of small cooperativity. Viewing the optomechanical device as a position sensor, entanglement between mechanics and light is an instance of object-apparatus entanglement predicted by quantum measurement theory.
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| 9. |
- Gutierrez Latorre, Martí, 1993, et al.
(författare)
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Chip-based superconducting traps for levitation of micrometer-sized particles in the Meissner state
- 2020
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Ingår i: Superconductor Science and Technology. - : IOP Publishing. - 0953-2048 .- 1361-6668. ; 33:10
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Tidskriftsartikel (refereegranskat)abstract
- We present a detailed analysis of two chip-based superconducting trap architectures capable of levitating micrometer-sized superconducting particles in the Meissner state. These architectures are suitable for performing novel quantum experiments with more massive particles or for force and acceleration sensors of unprecedented sensitivity. We focus in our work on a chip-based anti-Helmholtz coil-type trap (AHC) and a planar double-loop (DL) trap. We demonstrate their fabrication from superconducting Nb films and the fabrication of superconducting particles from Nb or Pb. We apply finite element modeling (FEM) to analyze these two trap architectures in detail with respect to trap stability and frequency. Crucially, in FEM we account for the complete three-dimensional geometry of the traps, finite magnetic field penetration into the levitated superconducting particle, demagnetizing effects, and flux quantization. We can, thus, analyze trap properties beyond assumptions made in analytical models. We find that realistic AHC traps yield trap frequencies well above 10 kHz for levitation of micrometer-sized particles and can be fabricated with a three-layer process, while DL traps enable trap frequencies below 1 kHz and are simpler to fabricate in a single-layer process. Our numerical results guide future experiments aiming at levitating micrometer-sized particles in the Meissner state with chip-based superconducting traps. The modeling we use is also applicable in other scenarios using superconductors in the Meissner state, such as for designing superconducting magnetic shields or for calculating filling factors in superconducting resonators.
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| 10. |
- Gutierrez Latorre, Martí, 1993, et al.
(författare)
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Superconducting Microsphere Magnetically Levitated in an Anharmonic Potential with Integrated Magnetic Readout
- 2023
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Ingår i: Physical Review Applied. - 2331-7019. ; 19:5
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Tidskriftsartikel (refereegranskat)abstract
- Magnetically levitated superconducting microparticles offer a promising path to quantum experiments with picogram to microgram objects. In this work, we levitate a 700 ng∼1017amu superconducting microsphere in a magnetic chip trap in which detection is integrated. We measure the center-of-mass motion of the particle using a dc superconducting quantum interference device magnetometer. The trap frequencies are continuously tunable between 30 and 160 Hz and the particle remains stably trapped over days in a dilution-refrigerator environment. We characterize the motional-amplitude-dependent frequency shifts, which arise from trap anharmonicities, namely, Duffing nonlinearities and mode couplings. We explain this nonlinear behavior using finite-element modeling of the chip-based trap potential. This work may constitute a first step toward quantum experiments and ultrasensitive inertial sensors with magnetically levitated superconducting microparticles.
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