In cavity optomechanics, light is used to control mechanical motion. A central goal of the field is achieving single-photon strong coupling, which would enable the creation of quantum superposition states of motion. Reaching this limit requires significant improvements in optomechanical coupling and cavity coherence. Here we introduce an optomechanical architecture consisting of a silicon nitride membrane coupled to a three-dimensional superconducting microwave cavity. Exploiting their large quality factors, we achieve an optomechanical cooperativity of 146,000 and perform sideband cooling of the kilohertz-frequency membrane motion to 34±5 μK, the lowest mechanical mode temperature reported to date. The achieved cooling is limited only by classical noise of the signal generator, and should extend deep into the ground state with superconducting filters. Our results suggest that this realization of optomechanics has the potential to reach the regimes of ultra-large cooperativity and single-photon strong coupling, opening up a new generation of experiments.
Surface acoustic waves (SAWs) strongly modulate the shallow electric potential in piezoelectric materials. In semiconductor heterostructures such as GaAs/AlGaAs, SAWs can thus be employed to transfer individual electrons between distant quantum dots. This transfer mechanism makes SAW technologies a promising candidate to convey quantum information through a circuit of quantum logic gates. Here we present two essential building blocks of such a SAW-driven quantum circuit. First, we implement a directional coupler allowing to partition a flying electron arbitrarily into two paths of transportation. Second, we demonstrate a triggered single-electron source enabling synchronisation of the SAW-driven sending process. Exceeding a single-shot transfer efficiency of 99%, we show that a SAW-driven integrated circuit is feasible with single electrons on a large scale. Our results pave the way to perform quantum logic operations with flying electron qubits.
We study mechanical dissipation of the fundamental mode of millimeter-sized, high quality-factor (Q) metalized silicon nitride membranes at temperatures down to 14 mK using a three-dimensional optomechanical cavity. Below 200 mK, high-Q modes of the membranes show a diverging increase of Q with decreasing temperature, reaching Q = 1.27 × 10 8 at 14 mK, an order of magnitude higher than reported before. The ultra-low dissipation makes the membranes highly attractive for the study of optomechanics in the quantum regime, as well as for other applications of optomechanics such as microwave to optical photon conversion.
Microwave optomechanical circuits have been demonstrated in the past years to be extremely powerfool tools for both, exploring fundamental physics of macroscopic mechanical oscillators as well as being promising candidates for novel on-chip quantum limited microwave devices. In most experiments so far, the mechanical oscillator is either used as a passive device element and its displacement is detected using the superconducting cavity or manipulated by intracavity fields. Here, we explore the possibility to directly and parametrically manipulate the mechanical nanobeam resonator of a cavity electromechanical system, which provides additional functionality to the toolbox of microwave optomechanical devices. In addition to using the cavity as an interferometer to detect parametrically modulated mechanical displacement and squeezed thermomechanical motion, we demonstrate that parametric modulation of the nanobeam resonance frequency can realize a phase-sensitive parametric amplifier for intracavity microwave photons. In contrast to many other microwave amplification schemes using electromechanical circuits, the presented technique allows for simultaneous cooling of the mechanical element, which potentially enables this type of optomechanical microwave amplifier to be quantum-limited. INTRODUCTIONSuperconducting microwave circuits have been demonstrated to be extremely powerful tools for the fields of quantum information processing 1-3 , circuit quantum electrodynamics 4-8 , astrophysical detector technologies 9 and microwave optomechanics 10-12 . In the latter, microwave fields in superconducting cavities are parametrically coupled to mechanical elements such as suspended capacitor drumheads or metallized nanobeams, enabling high-precision detection and manipulation of mechanical motion. Milestones achieved in the field include sideband-cooling of mechanical oscillators to the quantum ground state 11 , strong coupling between photons and phonons 13 , the generation of non-Gaussian states of motion [14][15][16] or the entanglement between two mechanial oscillators 17 .Recently, there are increasing efforts taken towards building passive and active quantum limited microwave elements for quantum technologies based on microwave optomechanical circuits, connecting the fields of microwave optomechanics, circuit quantum electrodynamics and quantum information science 18-20 . Among the most important developments into this direction are the demonstration of microwave amplification by blue sideband driving in simple optomechanical circuits 21 , and the realization of directional microwave amplifiers 22 as well as microwave circulators 23,24 in more complex multimode systems 25 .Recent theoretical work 26-28 on optomechanical systems with a parametrically driven mechanical oscillator proposed the use of mechanical parametric driving to enable parametric amplification with enhanced bandwidth and reduced added noise, compared to the case of a optomechanical amplifier using a blue-sideband drive 26 . Furthermore, the authors pre...
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