21 research outputs found
Synchronizing the dynamics of a single NV 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 NV spin qubit immersed in a radio frequency (RF) field
and probed with a quasi resonant 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 analog 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
Observation of a phononic Mollow triplet in a hybrid spin-nanomechanical system
Reminiscent of the bound character of a qubit's dynamics confined on the
Bloch sphere, the observation of a Mollow triplet in the resonantly driven
qubit fluorescence spectrum represents one of the founding signatures of
Quantum Electrodynamics. Here we report on its observation in a hybrid
spin-nanomechanical system, where a Nitro-gen Vacancy spin qubit is
magnetically coupled to the vibrations of a Silicon Carbide nanowire. A
resonant microwave field turns the originally parametric hybrid interac-tion
into a resonant process, where acoustic phonons are now able to induce
transitions between the dressed qubit states, leading to synchronized
spin-oscillator dynamics. We further explore the vectorial character of the
hybrid coupling to the bidimensional de-formations of the nanowire. The
demonstrated microwave assisted synchronization of the spin-oscillator dynamics
opens novel perspectives for the exploration of spin-dependent forces, the
key-ingredient for quantum state transfer
Nano-optomechanical measurement in the photon counting regime
Optically measuring in the photon counting regime is a recurrent challenge in
modern physics and a guarantee to develop weakly invasive probes. Here we
investigate this idea on a hybrid nano-optomechanical system composed of a
nanowire hybridized to a single Nitrogen-Vacancy (NV) defect. The vibrations of
the nanoresonator grant a spatial degree of freedom to the quantum emitter and
the photon emission event can now vary in space and time. We investigate how
the nanomotion is encoded on the detected photon statistics and explore their
spatio-temporal correlation properties. This allows a quantitative measurement
of the vibrations of the nanomechanical oscillator at unprecedentedly low light
intensities in the photon counting regime when less than one photon is detected
per oscillation period, where standard detectors are dark-noise-limited. These
results have implications for probing weakly interacting nanoresonators, for
low temperature experiments and for investigating single moving markers
Deviation from the normal mode expansion in a coupled graphene-nanomechanical system
We optomechanically measure the vibrations of a nanomechanical system made of
a graphene membrane suspended on a silicon nitride nanoresonator. When probing
the thermal noise of the coupled nanomechanical device, we observe a
significant deviation from the normal mode expansion. It originates from the
heterogeneous character of mechanical dissipation over the spatial extension of
coupled eigenmodes, which violates one of the fundamental prerequisite for
employing this commonly used description of the nanoresonators' thermal noise.
We subsequently measure the local mechanical susceptibility and demonstrate
that the fluctuation-dissipation theorem still holds and permits a proper
evaluation of the thermal noise of the nanomechanical system. Since it
naturally becomes delicate to ensure a good spatial homogeneity at the
nanoscale, this approach is fundamental to correctly describe the thermal noise
of nanomechanical systems which ultimately impact their sensing capacity
Cavity nano-optomechanics in the ultrastrong coupling regime with ultrasensitive force sensors
In a canonical optomechanical system, mechanical vibrations are dynamically encoded on an optical probe field which reciprocally exerts a backaction force. Due to the weak single photon coupling strength achieved with macroscopic oscillators, most of existing experiments were conducted with large photon numbers to achieve sizeable effects, thereby causing a dilution of the original optomechanical non-linearity. Here, we investigate the optomechanical interaction of an ultrasensi-tive suspended nanowire inserted in a fiber-based microcavity mode. This implementation allows to enter far into the hitherto unexplored ultrastrong optomechanical coupling regime, where one single intracavity photon can displace the oscillator by more than its zero point fluctuations. To fully characterize our system, we implement nanowire-based scanning probe measurements to map the vectorial optomechanical coupling strength, but also to reveal the intracavity optomechanical force field experienced by the nanowire. This work establishes that the single photon cavity optomechanics regime is within experimental reach. Introduction-The field of optomechanics has gone through many impressive developments over the last decades [1]. The coupling between a probe light field and a mechanical degree of freedom, an oscillator, possibly assisted by a high finesse cavity was early proposed as an ideal platform to explore the quantum limits of ultrasen-sitive measurements, where the quantum fluctuations of the light are the dominant source of measurement noise [2-5]. The measurement backaction was also employed to manipulate the oscillator state through optical forces and dynamical backaction, leading to optomechanical correlations between both components of the system. In this framework, ground state cooling, mechanical detection of radiation pressure quantum noise, advanced correlation between light and mechanical states or optomechanical squeezing were reported [6-19]. All those impressive results were obtained in the linear regime of cavity optomechanics, making use of large photon numbers, where the interaction Hamiltonian is linearized around an operating setpoint. However, the optomechanical interaction possesses an intrinsic non-linearity at the single excitation level, which has for the moment remained far from experimental reach due to the weak single photon coupling strength achieved with macroscopic oscillators. This regime is achieved when a single photon in the cavity shifts the static rest position of the mechanical resonator by a quantity δx (1) which is larger than its zero point fluctuations δx zpf. A very strong optomechanical interaction is indeed needed to fulfil this condition since it requires g 0 /Ω m > 1 where g 0 is the single photon optomechanical coupling and Ω m the resonant pulsation of the mechanical oscillator. Operating in the ultra-strong coupling regime is thus an experimenta
Ultrasensitive nano-optomechanical force sensor at dilution temperatures
Cooling down nanomechanical force probes is a generic strategy to enhance
their sensitivities through the concomitant reduction of their thermal noise
and mechanical damping rates. However, heat conduction mechanisms become less
efficient at low temperatures, which renders difficult to ensure and verify
their proper thermalization. To operate with minimally perturbing measurements,
we implement optomechanical readout techniques operating in the photon counting
regime to probe the dynamics of suspended silicon carbide nanowires in a
dilution refrigerator. Readout of their vibrations is realized with
sub-picowatt optical powers, in a regime where less than one photon is
collected per oscillation period. We demonstrate their thermalization down to
mK and report on record sensitivities for scanning probe force
sensors, at the level, with a sensitivity to lateral
force field gradients in the fN/m range. This work opens the road toward
nanomechanical vectorial imaging of faint forces at dilution temperatures, at
minimal excitation levels
Ferromagnetic resonance and magnetic damping in C-doped Mn5Ge3
International audience2 X-band ferromagnetic resonance (FMR) was used to investigate static and dynamic magnetic properties of Mn5Ge3 and Carbon-doped Mn5Ge3 (C0.1 and C0.2) thin films grown on Ge(111). The temperature dependence of magnetic anisotropy shows an increased perpendicular magneto-crystalline contribution at low temperature with an in-plane easy axis due to the large shape contribution. We find that our samples show as small as 40Oe FMR linewidth (corresponding Gilbert damping α=0.005), for the out-of-plane direction, certifying of their very good structural quality. The perpendicular linewidth shows a minimum around 200K for all samples, which seems not correlated to the C-doping. The magnetic relaxation parameters have been determined and indicate as main extrinsic contribution the two-magnon scattering. A transition from six-fold to twofold plus fourth-fold in-plane anisotropy is observed in the FMR linewidth of Mn5Ge3C0.2 around 200K
Measurement of the dynamical dipolar coupling in a pair of magnetic nano-disks using a Ferromagnetic Resonance Force Microscope
International audienceWe perform an extensive experimental spectroscopic study of the collective spin-wave dynamics occurring in a pair of magnetic nano-disks coupled by the magneto-dipolar interaction. For this, we take advantage of the stray field gradient produced by the magnetic tip of a ferromagnetic resonance force microscope (f-MRFM) to continuously tune and detune the relative resonance frequencies between two adjacent nano-objects. This reveals the anti-crossing and hybridization of the spin-wave modes in the pair of disks. At the exact tuning, the measured frequency splitting between the binding and anti-binding modes precisely corresponds to the strength of the dynamical dipolar coupling . This accurate f-MRFM determination of is measured as a function of the separation between the nano-disks. It agrees quantitatively with calculations of the expected dynamical magneto-dipolar interaction in our sample
Universal Vectorial and Ultrasensitive Nanomechanical Force Field Sensor
Miniaturization of force probes into nanomechanical oscillators enables
ultrasensitive investigations of forces on dimensions smaller than their
characteristic length scale. Meanwhile it also unravels the force field
vectorial character and how its topology impacts the measurement. Here we
expose an ultrasensitive method to image 2D vectorial force fields by
optomechanically following the bidimensional Brownian motion of a singly
clamped nanowire. This novel approach relies on angular and spectral tomography
of its quasi frequency-degenerated transverse mechanical polarizations:
immersing the nanoresonator in a vectorial force field does not only shift its
eigenfrequencies but also rotate eigenmodes orientation as a nano-compass. This
universal method is employed to map a tunable electrostatic force field whose
spatial gradients can even take precedence over the intrinsic nanowire
properties. Enabling vectorial force fields imaging with demonstrated
sensitivities of attonewton variations over the nanoprobe Brownian trajectory
will have strong impact on scientific exploration at the nanoscale