Pierre Verlot

A hybrid on-chip optomechanical transducer for ultrasensitive force measurements

Nanoscale mechanical oscillators are used as ultrasensitive detectors of force, mass and charge. Nanomechanical oscillators have also been coupled with optical and electronic resonators to explore the quantum properties of mechanical systems. Here, we report an optomechanical transducer in which a Si(3)N(4) nanomechanical beam is coupled to a disk-shaped optical resonator made of silica on a single chip. We demonstrate a force sensitivity of 74 aN Hz(-1/2) at room temperature with a readout stability better than 1% at the minute scale. Our system is particularly suited for the detection of very weak incoherent forces, which is difficult with existing approaches because the force resolution scales with the fourth root of the averaging time. By applying dissipative feedback based on radiation pressure, we significantly relax this constraint and are able to detect an incoherent force with a force spectral density of just 15 aN Hz(-1/2) (which is 25 times less than the thermal noise) within 35 s of averaging time (which is 30 times less than the averaging time that would be needed in the absence of feedback). It is envisaged that our hybrid on-chip transducer could improve the performance of various forms of force microscopy.

Strain-mediated coupling in a quantum dot–mechanical oscillator hybrid system

Recent progress in nanotechnology has allowed the fabrication of new hybrid systems in which a single two-level system is coupled to a mechanical nanoresonator. In such systems the quantum nature of a macroscopic degree of freedom can be revealed and manipulated. This opens up appealing perspectives for quantum information technologies, and for the exploration of the quantum-classical boundary. Here we present the experimental realization of a monolithic solid-state hybrid system governed by material strain: a quantum dot is embedded within a nanowire that features discrete mechanical resonances corresponding to flexural vibration modes. Mechanical vibrations result in a time-varying strain field that modulates the quantum dot transition energy. This approach simultaneously offers a large light-extraction efficiency and a large exciton-phonon coupling strength g0. By means of optical and mechanical spectroscopy, we find that g0/2 π is nearly as large as the mechanical frequency, a criterion that defines the ultrastrong coupling regime.

Stabilization of a linear nanomechanical oscillator to its thermodynamic limit

The rapid development of micro- and nanomechanical oscillators in the past decade has led to the emergence of novel devices and sensors that are opening new frontiers in both applied and fundamental science. The potential of these devices is however affected by their increased sensitivity to external perturbations. Here we report a non-perturbative optomechanical stabilization technique and apply the method to stabilize a linear nanomechanical beam at its thermodynamic limit at room temperature. The reported ability to stabilize a nanomechanical oscillator to the thermodynamic limit can be extended to a variety of systems and increases the sensitivity range of nanomechanical sensors in both fundamental and applied studies.

A hybrid on-chip optonanomechanical transducer for ultra-sensitive force measurements

We realize an integrated hybrid optonanomechanical transducer for the detection of weak forces. We propose and demonstrate with our system that dissipative feedback dramatically decreases the averaging time necessary to detect an incoherent force.

Brownian fluctuations of carbon nanotube resonators

Carbon nanotube mechanical resonators hold an exceptional sensing potential, relying on their extremely low mass. As a consequence, the fundamental thermal forces are transduced into very large motion fluctuations. However, the most basic properties of these fluctuations remain poorly understood. Here we couple the motion of nanotube-based resonators to a free propagating electron beam to demonstrate that singly-clamped nanotube resonators undergo thermally-driven Brownian motion.

Self-synchronization of a NV spin qu-bit on a radio-frequency field enabled by microwave dressing

Summary form only given. Probing the quantum world with macroscopic objects has been a core challenge for research during the past decades. Proposed systems to reach this goal include hybrid devices that couple a nanomechanical resonator to a single spin two level system [1]. In particular, the coherent actuation of a macroscopic mechanical oscillator by a single electronic spin would open perspectives in the creation of arbitrary quantum states of motion. In order to anticipate this regime and to explore advanced spin manipulation protocols, we have set up an experiment emulating hybrid spin-mechanical systems of infinite mass by parametrically coupling a radio frequency (RF) field to the spin. A wave-guide allows us to magnetically address the and components of single NV electron spin in nano-diamonds, which represents a tool for investigating the mechanical resonator - spin coupling at ambient conditions. The oscillatory motion of the resonator through a magnetic field gradient is simulated with a magnetic field oscillating at RF frequencies MHz along the axis while the spin population is probed with a microwave field along the direction. We investigate both the steady state regime (with ESR techniques) and the dynamical evolution of the system through Rabi oscillations, which allows investigating the motional sideband generation in the spin energy spectra, revealing how the oscillator motion is imprinted on the spin dynamics, see Fig. 1. Furthermore we demonstrate how the spin dynamics self-synchronizes on the oscillation frequency when the microwave-driven Rabi frequency approaches the oscillation frequency, which is concomitant with an increase in coherence time, as observed in Fig. 2. This mechanism, which appears when the emulated oscillatory motion is driven at large amplitudes, simulating a hybrid spin-mechanical system in the strong coupling regime, can be elegantly described in terms of doubly dressing the spin states. Potential applications for mechanical QND detection of spin states of this phenomenon are discussed.

Stabilization of a linear optonanomechanical oscillator to its ultimate thermodynamic limit

We realize a non-invasive optomechanical stabilization scheme and apply it to the fundamental mechanical mode of a nanobeam. We are able to significantly decrease its frequency noise to its ultimate thermodynamic limit at room temperature.

A versatile scheme for read-out and actuation of nanomechanical motion using silica microspheres

We employ silica microspheres to detect and actuate nanomechanical motion. With Si3N4-nanostrings, we achieve significant passive cooling by radiation pressure. Feedback-cooling enables stable operation at optical powers beyond the parametric-instability threshold, paving the way to detect quantum backation.

Experimental Optomechanics with Single and Twin Moving Mirrors

We present experiments where the motion of micro-mirrors is optically monitored with a quantum-limited sensitivity. Direct effects of radiation pressure on single and twin-mirror cavities are experimentally demonstrated. Applications to quantum optics are discussed.

Observation of radiation-pressure effects and back-action cancellation in interferometric measurements

In the case of gravitational-wave resonant detectors such as dual spheres with optical readout, the sensitivity can be strongly improved by a back-action cancellation effect related to the specific geometry of this kind of detectors. We report the observation of such a back-action cancellation. Our experiment is based on a high-finesse Fabry-Perot cavity where the displacements of both mirrors are monitored by sending a very stable laser beam in the cavity and measuring the phase of the reflected beam with an homodyne detection. Between 100 kHz and 4 MHz, the sensitivity is only limited by the shot noise. We have performed an exhaustive study of the internal thermal noise of mirrors and optomechanical properties of internal acoustic modes: resonance frequency, quality factor, effective mass, and spatial structure.