19 research outputs found
Cavity cooling of a levitated nanosphere by coherent scattering
We report three-dimensional cooling of a levitated nanoparticle inside an
optical cavity. The cooling mechanism is provided by cavity-enhanced coherent
scattering off an optical tweezer. The observed 3D dynamics and cooling rates
are as theoretically expected from the presence of both linear and quadratic
terms in the interaction between the particle motion and the cavity field. By
achieving nanometer-level control over the particle location we optimize the
position-dependent coupling and demonstrate axial cooling by two orders of
magnitude at background pressures as high as mbar. We also
estimate a significant ( dB) suppression of laser phase noise, and hence
of residual heating, which is a specific feature of the coherent scattering
scheme. The observed performance implies that quantum ground state cavity
cooling of levitated nanoparticles can be achieved for background pressures
below mbar
Fluctuation-induced Forces on Nanospheres in External Fields
We analyze the radiative forces between two dielectric nanospheres mediated
via the quantum and thermal fluctuations of the electromagnetic field in the
presence of an external drive. We generalize the scattering theory description
of fluctuation forces to include external quantum fields, allowing them to be
in an arbitrary quantum state. The known trapping and optical binding
potentials are recovered for an external coherent state. We demonstrate that an
external squeezed vacuum state creates similar potentials to a laser, despite
its zero average intensity. Moreover, Schr\"odinger cat states of the field can
enhance or suppress the optical potential depending on whether they are odd or
even. Considering the nanospheres trapped by optical tweezers, we examine the
total interparticle potential as a function of various experimentally relevant
parameters, such as the field intensity, polarization, and phase of the
trapping lasers. We demonstrate that an appropriate set of parameters could
produce mutual bound states of the two nanospheres with potential depth as
large as K. Our results are pertinent to ongoing experiments with
trapped nanospheres in the macroscopic quantum regime, paving the way for
engineering interactions among macroscopic quantum systems
Force-Gradient Sensing and Entanglement via Feedback Cooling of Interacting Nanoparticles
We show theoretically that feedback-cooling of two levitated, interacting
nanoparticles enables differential sensing of forces and the observation of
stationary entanglement. The feedback drives the two particles into a
stationary, non-thermal state which is susceptible to inhomogeneous force
fields and which exhibits entanglement for sufficiently strong inter-particle
couplings. We predict that force-gradient sensing at the zepto-Newton per
micron range is feasible and that entanglement due to the Coulomb interaction
between charged particles can be realistically observed in state-of-the-art
setups.Comment: 14 pages, 4 figure
Exponentially Enhanced non-Hermitian Cooling
Certain non-Hermitian systems exhibit the skin effect, whereby the
wavefunctions become exponentially localized at one edge of the system. Such
exponential amplification of wavefunction has received significant attention
due to its potential applications in e.g., classical and quantum sensing.
However, the opposite edge of the system, featured by the exponentially
suppressed wavefunctions, remains largely unexplored. Leveraging this
phenomenon, we introduce a non-Hermitian cooling mechanism, which is
fundamentally distinct from traditional refrigeration or laser cooling
techniques. Notably, non-Hermiticity will not amplify thermal excitations, but
rather redistribute them. Hence, thermal excitations can be cooled down at one
edge of the system, and the cooling effect can be exponentially enhanced by the
number of auxiliary modes, albeit with a lower bound that depends on the
dissipative interaction with the environment. Non-Hermitian cooling does not
rely on intricate properties such as exceptional points or non-trivial
topology, and it can apply to a wide range of Bosonic modes such as photons,
phonons, magnons, etc.Comment: 12 pages, 4 figure
Non-Hermitian dynamics and nonreciprocity of optically coupled nanoparticles
Non-Hermitian dynamics, as observed in photonic, atomic, electrical, and
optomechanical platforms, holds great potential for sensing applications and
signal processing. Recently, fully tunable nonreciprocal optical interaction
has been demonstrated between levitated nanoparticles. Here, we use this
tunability to investigate the collective non-Hermitian dynamics of two
nonreciprocally and nonlinearly interacting nanoparticles. We observe
parity-time symmetry breaking and, for sufficiently strong coupling, a
collective mechanical lasing transition, where the particles move along stable
limit cycles. This work opens up a research avenue of nonequilibrium
multi-particle collective effects, tailored by the dynamic control of
individual sites in a tweezer array
Cavity cooling of an optically levitated submicron particle
The coupling of a levitated submicron particle and an optical cavity
field promises access to a unique parameter regime both for
macroscopic quantum experiments and for high-precision force
sensing. We report a demonstration of such controlled interactions
by cavity cooling the center-of-mass motion of an optically trapped
submicron particle. This paves the way for a light–matter
interface that can enable room-temperature quantum experiments
with mesoscopic mechanical systems
Research campaign : macroscopic quantum resonators (MAQRO)
The objective of the proposed macroscopic quantum resonators (MAQRO) mission is to harness space for achieving long free-fall times, extreme vacuum, nano-gravity, and cryogenic temperatures to test the foundations of physics in macroscopic quantum experiments at the interface with gravity. Developing the necessary technologies, achieving the required sensitivities and providing the necessary isolation of macroscopic quantum systems from their environment will lay the path for developing novel quantum sensors. Earlier studies showed that the proposal is feasible but that several critical challenges remain, and key technologies need to be developed. Recent scientific and technological developments since the original proposal of MAQRO promise the potential for achieving additional science objectives. The proposed research campaign aims to advance the state of the art and to perform the first macroscopic quantum experiments in space. Experiments on the ground, in micro-gravity, and in space will drive the proposed research campaign during the current decade to enable the implementation of MAQRO within the subsequent decade