29 research outputs found
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
Progress toward detection of individual TLS in nanomechanical resonators
The low temperature properties of amorphous solids are usually explained in
terms of atomic-scale tunneling two level systems (TLS). For almost 20 years,
individual TLS have been probed in insulating layers of superconducting quantum
circuits. Detecting individual TLS in mechanical systems has been proposed but
not definitively demonstrated. We describe an optomechanical system that is
appropriate for this goal and describe our progress toward achieving it. In
particular, we show that the expected coupling between the mechanical mode and
a resonant TLS is strong enough for high visibility of a TLS given the
linewidth of the mechanical mode. Furthermore, the electronic noise level of
our measurement system is low enough and the anomalous force noise observed in
other nanomechanical devices is absent
Quantum-mechanics free subsystem with mechanical oscillators
Quantum mechanics sets a limit for the precision of measurement of the
position of an oscillator. The quantum noise associated with the measurement of
a quadrature of the motion imprints a backaction on the orthogonal quadrature,
which feeds back to the measured observable in the case of a continuous
measurement. In a quantum backaction evading measurement, the added noise can
be confined in the orthogonal quadrature. Here we show how it is possible to
evade this limitation and measure an oscillator without backaction by
constructing one effective oscillator from two physical oscillators. This
facilitates detection of weak forces and the creation and measurement of
nonclassical motional states of the oscillators. We realize the proposal using
two micromechanical oscillators, and show the measurements of two collective
quadratures while evading the quantum backaction by decibels on both of
them, obtaining a total noise within a factor two from the full quantum limit.
Moreover, by modifying the measurement we directly verify the quantum
entanglement of the two oscillators by measuring the Duan quantity
decibels below the separability bound
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
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
Ground-state cooling of a mechanical oscillator by heating
Dissipation and the accompanying fluctuations are often seen as detrimental
for quantum systems, since they are associated with fast relaxation and loss of
phase coherence. However, it has been proposed that a pure state can be
prepared if external noise induces suitable downwards transitions, while
exciting transitions are blocked. We demonstrate such a refrigeration mechanism
in a cavity optomechanical system, where we prepare a mechanical oscillator in
its ground state by injecting strong electromagnetic noise at frequencies
around the red mechanical sideband of the cavity. The optimum cooling is
reached with a noise bandwidth smaller than, but on the order of the cavity
decay rate. At higher bandwidths, cooling is less efficient. In the opposite
regime where the noise bandwidth becomes comparable to the mechanical damping
rate, damping follows the noise amplitude adiabatically, and the cooling is
also suppressed
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