Mechanical systems can be influenced by a wide variety of small forces, ranging from gravitational to optical, electrical, and magnetic. When mechanical resonators are scaled down to nanometer-scale dimensions, these forces can be harnessed to enable coupling to individual quantum systems. We demonstrate that the coherent evolution of a single electronic spin associated with a nitrogen vacancy center in diamond can be coupled to the motion of a magnetized mechanical resonator. Coherent manipulation of the spin is used to sense driven and Brownian motion of the resonator under ambient conditions with a precision below 6 picometers. With future improvements, this technique could be used to detect mechanical zero-point fluctuations, realize strong spin-phonon coupling at a single quantum level, and implement quantum spin transducers.

Cavity-enhanced radiation pressure coupling between optical and mechanical degrees of freedom allows quantum-limited position measurements and gives rise to dynamical backaction enabling amplification and cooling of mechanical motion. Here we demonstrate purely dispersive coupling of high Q nanomechanical oscillators to an ultra-high finesse optical microresonator via its evanescent field, extending cavity optomechanics to nanomechanical oscillators. Dynamical backaction mediated by the optical dipole force is observed, leading to laser-like coherent nanomechanical oscillations solely due to radiation pressure. Moreover, sub-fm/Hz 1/2 displacement sensitivity is achieved, with a measurement imprecision equal to the standard quantum limit (SQL), which coincides with the nanomechanical oscillator's zero-point fluctuations. The achievement of an imprecision at the SQL and radiation-pressure dynamical backaction for nanomechanical oscillators may have implications not only for detecting quantum phenomena in mechanical systems, but also for a variety of other precision experiments. Owing to the flexibility of the near-field coupling approach, it can be readily extended to a diverse set of nanomechanical oscillators and particularly provides a route to experiments where radiation pressure quantum backaction dominates at room temperature, enabling ponderomotive squeezing or QND measurements.Nanomechanical oscillators [1, 2] possess wide-ranging applications in both fundamental and applied sciences. Due to their small mass they are ideal candidates for probing quantum limits of mechanical motion in an experimental setting. Moreover, they are the basis of various precision measurements [3, 4] and integral part of atomic and magnetic force microscopy [5] that are pivotal tools for solid state physics and material science. Significant attention has been devoted to developing sensitive readout techniques for nanomechanical motion over the past decade. A natural scale for comparing the performance achieved with systems of different size and mass is given by the variance of the mechanical oscillators' zero-point motion x (t) 2 zp = /(2mΩm) ( : reduced Planck constant; m, Ωm/2π, Q: mass, resonance frequency, quality factor of the oscillator). In Fourier space the zero-point motion can be described by the single-sided (double-sided) spectral density Sxx [Ω], which at the mechanical oscillator's resonance evaluates to Sxx [Ωm] = 2 Q/mΩ 2 m (Sxx [Ωm] = Q/mΩ 2 m ) and coincides with the standard quantum limit [6, 7, 8, 9] (SQL) of continuous position measurement. So far, the most sensitive transducers for nanomechanical motion have been based on electron flow using a single electron transistor [10] (SET) or atomic point contact [11] (APC) coupled to a nanomechanical string in cryogenic environment and have achieved a position imprecision of order 10 −15 m/Hz 1/2 . An imprecision at the level of the SQL, however, has not been achieved yet. In contrast, parametric motion transducers based on photons in a cavity-which are the b...

We experimentally demonstrate the use of a single electronic spin to measure the quantum dynamics of distant individual nuclear spins from within a surrounding spin bath. Our technique exploits coherent control of the electron spin, allowing us to isolate and monitor nuclear spins weakly coupled to the electron spin. Specifically, we detect the evolution of distant individual 13C nuclear spins coupled to single nitrogen vacancy centers in a diamond lattice with hyperfine couplings down to a factor of 8 below the electronic spin bare dephasing rate. Potential applications to nanoscale magnetic resonance imaging and quantum information processing are discussed.

We study the transverse oscillatory modes of nanomechanical silicon nitride strings under high tensile stress as a function of geometry and mode index m ≤ 9. Reproducing all observed resonance frequencies with classical elastic theory we extract the relevant elastic constants. Based on the oscillatory local strain we successfully predict the observed mode-dependent damping with a single frequency independent fit parameter. Our model clarifies the role of tensile stress on damping and hints at the underlying microscopic mechanisms.The resonant motion of nanoelectromechanical systems receives a lot of recent attention. Their large frequencies, low damping i.e. high mechanical quality factors, and small masses make them equally important as sensors [1][2][3][4] and for fundamental studies [3][4][5][6][7][8][9]. In either case, low damping of the resonant motion is very desirable. Despite significant experimental progress [10,11], a satisfactory understanding of the microscopic causes of damping is not yet achieved. Here we present a systematic study of the damping of doubly-clamped resonators fabricated out of prestressed silicon nitride leading to high mechanical quality factors [10]. Reproducing the observed mode frequencies applying continuum mechanics, we are able to quantitatively model their quality factors by assuming that damping is caused by the local strain induced by the resonator's displacement. Considering various microscopic mechanisms, we conclude that the observed damping is most likely dominated by dissipation via localized defects uniformly distributed throughout the resonator.

Any polarizable body placed in an inhomogeneous electric field experiences a dielectric force. This phenomenon is well known from the macroscopic world: a water jet is deflected when approached by a charged object. This fundamental mechanism is exploited in a variety of contexts-for example, trapping microscopic particles in an optical tweezer, where the trapping force is controlled via the intensity of a laser beam, or dielectrophoresis, where electric fields are used to manipulate particles in liquids. Here we extend the underlying concept to the rapidly evolving field of nanoelectromechanical systems (NEMS). A broad range of possible applications are anticipated for these systems, but drive and detection schemes for nanomechanical motion still need to be optimized. Our approach is based on the application of dielectric gradient forces for the controlled and local transduction of NEMS. Using a set of on-chip electrodes to create an electric field gradient, we polarize a dielectric resonator and subject it to an attractive force that can be modulated at high frequencies. This universal actuation scheme is efficient, broadband and scalable. It also separates the driving scheme from the driven mechanical element, allowing for arbitrary polarizable materials and thus potentially ultralow dissipation NEMS. In addition, it enables simple voltage tuning of the mechanical resonance over a wide frequency range, because the dielectric force depends strongly on the resonator-electrode separation. We use the modulation of the resonance frequency to demonstrate parametric actuation. Moreover, we reverse the actuation principle to realize dielectric detection, thus allowing universal transduction of NEMS. We expect this combination to be useful both in the study of fundamental principles and in applications such as signal processing and sensing.