Interrelation of Elasticity and Thermal Bath in Nanotube Cantilevers.

We report the first study on the thermal behavior of the stiffness of individual carbon nanotubes, which is achieved by measuring the resonance frequency of their fundamental mechanical bending modes. We observe a reduction of the Young's modulus over a large temperature range with a slope -(173±65) ppm/K in its relative shift. These findings are reproduced by two different theoretical models based on the thermal dynamics of the lattice. These results reveal how the measured fundamental bending modes depend on the phonons in the nanotube via the Young's modulus. An alternative description based on the coupling between the measured mechanical modes and the phonon thermal bath in the Akhiezer limit is discussed.

Mass Sensing for the Advanced Fabrication of Nanomechanical Resonators.

We report on a nanomechanical engineering method to monitor matter growth in real time via e-beam electromechanical coupling. This method relies on the exceptional mass sensing capabilities of nanomechanical resonators. Focused electron beam-induced deposition (FEBID) is employed to selectively grow platinum particles at the free end of singly clamped nanotube cantilevers. The electron beam has two functions: it allows both to grow material on the nanotube and to track in real time the deposited mass by probing the noise-driven mechanical resonance of the nanotube. On the one hand, this detection method is highly effective as it can resolve mass deposition with a resolution in the zeptogram range; on the other hand, this method is simple to use and readily available to a wide range of potential users because it can be operated in existing commercial FEBID systems without making any modification. The presented method allows one to engineer hybrid nanomechanical resonators with precisely tailored functionalities. It also appears as a new tool for studying the growth dynamics of ultrathin nanostructures, opening new opportunities for investigating so far out-of-reach physics of FEBID and related methods.

Shot-Noise-Limited Nanomechanical Detection and Radiation Pressure Backaction from an Electron Beam.

Detecting nanomechanical motion has become an important challenge in science and technology. Recently, electromechanical coupling to focused electron beams has emerged as a promising method adapted to ultralow scale systems. However the fundamental measurement processes associated with such complex interaction remain to be explored. Here we report a highly sensitive detection of the Brownian motion of µm-long semiconductor nanowires (InAs). The measurement imprecision is found to be set by the shot noise of the secondary electrons generated along the electromechanical interaction. By carefully analyzing the nanoelectromechanical dynamics, we demonstrate the existence of a radial backaction process that we identify as originating from the momentum exchange between the electron beam and the nanomechanical device, which is also known as radiation pressure.

Real-Time Measurement of Nanotube Resonator Fluctuations in an Electron Microscope.

Mechanical resonators based on low-dimensional materials provide a unique platform for exploring a broad range of physical phenomena. The mechanical vibrational states are indeed extremely sensitive to charges, spins, photons, and adsorbed masses. However, the roadblock is often the readout of the resonator, because the detection of the vibrational states becomes increasingly difficult for smaller resonators. Here, we report an unprecedentedly sensitive method to detect nanotube resonators with effective masses in the 10-20 kg range. We use the beam of an electron microscope to resolve the mechanical fluctuations of a nanotube in real-time for the first time. We obtain full access to the thermally driven Brownian motion of the resonator, both in space and time domains. Our results establish the viability of carbon nanotube resonator technology at room temperature and pave the way toward the observation of novel thermodynamics regimes and quantum effects in nanomechanics.

Synchronizing the dynamics of a single nitrogen vacancy spin qubit on a parametrically coupled radio-frequency field through microwave dressing.

A hybrid spin-oscillator system in parametric interaction is experimentally emulated using a single nitrogen vacancy (NV) spin qubit immersed in a radio frequency (rf) field and probed with a quasiresonant microwave (MW) field. We report on the MW-mediated locking of the NV spin dynamics onto the rf field, appearing when the MW-driven Rabi precession frequency approaches the rf frequency and for sufficiently large rf amplitudes. These signatures are analogous to a phononic Mollow triplet in the MW rotating frame for the parametric interaction and promise to have impact in spin-dependent force detection strategies.

Backaction amplification and quantum limits in optomechanical measurements.

Optical interferometry is by far the most sensitive displacement measurement technique available, with sensitivities at the 10(-20) m/square root(Hz) level in the large-scale gravitational-wave interferometers currently in operation. Second-generation interferometers will experience a tenfold improvement in sensitivity and be mainly limited by quantum noise, close to the standard quantum limit (SQL), once considered as the ultimate displacement sensitivity achievable by interferometry. In this Letter, we experimentally demonstrate one of the techniques envisioned to go beyond the SQL: amplification of a signal by radiation-pressure backaction in a detuned cavity.

Optomechanics with a hybrid carbon nanotube resonator.

In just 20 years of history, the field of optomechanics has achieved impressive progress, stepping into the quantum regime just 5 years ago. Such remarkable advance relies on the technological revolution of nano-optomechanical systems, whose sensitivity towards thermal decoherence is strongly limited due to their ultra-low mass. Here we report a hybrid approach pushing nano-optomechanics to even lower scales. The concept relies on synthesising an efficient optical scatterer at the tip of singly clamped carbon nanotube resonators. We demonstrate high signal-to-noise motion readout and record force sensitivity, two orders of magnitude below the state of the art. Our work opens the perspective to extend quantum experiments and applications at room temperature.

Dynamical backaction cooling with free electrons.

The ability to cool single ions, atomic ensembles, and more recently macroscopic degrees of freedom down to the quantum ground state has generated considerable progress and perspectives in fundamental and technological science. These major advances have been essentially obtained by coupling mechanical motion to a resonant electromagnetic degree of freedom in what is generally known as laser cooling. Here, we experimentally demonstrate the first self-induced coherent cooling mechanism that is not mediated by an electromagnetic resonance. Using a focused electron beam, we report a 50-fold reduction of the motional temperature of a nanowire. Our result primarily relies on the sub-nanometre confinement of the electron beam and generalizes to any delayed and spatially confined interaction, with important consequences for near-field microscopy and fundamental nanoscale dissipation mechanisms.

Bidimensional nano-optomechanics and topological backaction in a non-conservative radiation force field.

Optomechanics, which explores the fundamental coupling between light and mechanical motion, has made important advances in manipulating macroscopic mechanical oscillators down to the quantum level. However, dynamical effects related to the vectorial nature of the optomechanical interaction remain to be investigated. Here we study a nanowire with subwavelength dimensions coupled strongly to a tightly focused beam of light, enabling an ultrasensitive readout of the nanoresonator dynamics. We determine experimentally the vectorial structure of the optomechanical interaction and demonstrate that a bidimensional dynamical backaction governs the nanowire dynamics. Moreover, the spatial topology of the optomechanical interaction is responsible for novel canonical signatures of strong coupling between mechanical modes, which leads to a topological instability that underlies the non-conservative nature of the optomechanical interaction. These results have a universal character and illustrate the increased sensitivity of nanomechanical devices towards spatially varying interactions, opening fundamental perspectives in nanomechanics, optomechanics, ultrasensitive scanning force microscopy and nano-optics.

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.

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.

Scheme to probe optomechanical correlations between two optical beams down to the quantum level.

The quantum effects of radiation pressure are expected to limit the sensitivity of second-generation gravitational-wave interferometers. Though ubiquitous, such effects are so weak that they have not been experimentally demonstrated yet. Using a high-finesse optical cavity and a classical intensity noise, we have demonstrated radiation-pressure induced correlations between two optical beams sent into the same moving mirror cavity. Our scheme can be used to retrieve weak correlations at the quantum level and has applications both in high-sensitivity measurements and in quantum optics.

Observation of back-action noise cancellation in interferometric and weak force measurements.

We experimentally demonstrate a cancellation of back-action noise in optical measurements. Back-action cancellation was first proposed within the framework of gravitational-wave detection by dual resonators as a way to drastically improve their sensitivity. We have developed an experiment based on a high-finesse Fabry-Perot cavity to study radiation-pressure effects in ultrasensitive displacement measurements. Using an intensity-modulated intracavity field to mimic the quantum radiation-pressure noise, we report the first observation of back-action cancellation due to a coherent mechanical response of the mirrors in the cavity to the radiation-pressure noise. We have observed a sensitivity improvement by a factor larger than 20 both in displacement and weak-force measurements.