60 research outputs found
Noise thermometry and electron thermometry of a sample-on-cantilever system below 1 Kelvin
We have used two types of thermometry to study thermal fluctuations in a
microcantilever-based system below 1 K. We measured the temperature of a
cantilever's macroscopic degree-of-freedom (via the Brownian motion of its
lowest flexural mode) and its microscopic degrees-of-freedom (via the electron
temperature of a metal sample mounted on the cantilever). We also measured both
temperatures' response to a localized heat source. We find it possible to
maintain thermal equilibrium between these two temperatures and a refrigerator
down to at least 300 mK. These results are promising for ongoing experiments to
probe quantum effects using micromechanical devices
EPR-based ghost imaging using a single-photon-sensitive camera
Correlated photon imaging, popularly known as ghost imaging, is a technique whereby an image is formed from light that has never interacted with the object. In ghost imaging experiments, two correlated light fields are produced. One of these fields illuminates the object, and the other field is measured by a spatially resolving detector. In the quantum regime, these correlated light fields are produced by entangled photons created by spontaneous parametric down-conversion. To date, all correlated photon ghost imaging experiments have scanned a single-pixel detector through the field of view to obtain spatial information. However, scanning leads to poor sampling efficiency, which scales inversely with the number of pixels, N, in the image. In this work, we overcome this limitation by using a time-gated camera to record the single-photon events across the full scene. We obtain high-contrast images, 90%, in either the image plane or the far field of the photon pair source, taking advantage of the EinsteinâPodolskyâRosen-like correlations in position and momentum of the photon pairs. Our images contain a large number of modes, >500, creating opportunities in low-light-level imaging and in quantum information processing
Distribution and dynamics of entanglement in high-dimensional quantum systems using convex-roof extended negativity
We develop theories of entanglement distribution and of entanglement dynamics
for qudit systems, which incorporate previous qubit formulations. Using
convex-roof extended negativity, we generalize previous qubit results for
entanglement distribution with isotropic states and for entanglement dynamics
with the depolarizing channel, and we establish a relation between these two
types of entanglement networks.Comment: 4 page
Optomechanics for quantum technologies
The ability to control the motion of mechanical systems through interaction with light has opened the door to a plethora of applications in fundamental and applied physics. With experiments routinely reaching the quantum regime, the focus has now turned towards creating and exploiting interesting non-classical states of motion and entanglement in optomechanical systems. Quantumness has also shifted from being the very reason why experiments are constructed to becoming a resource for the investigation of fundamental physics and the creation of quantum technologies. Here, by focusing on opto- and electromechanical platforms we review recent progress in quantum state preparation and entanglement of mechanical systems, together with applications to signal processing and transduction, quantum sensing and topological physics, as well as small-scale thermodynamics
Strong and Tunable Nonlinear Optomechanical Coupling in a Low-Loss System
A major goal in optomechanics is to observe and control quantum behavior in a
system consisting of a mechanical resonator coupled to an optical cavity. Work
towards this goal has focused on increasing the strength of the coupling
between the mechanical and optical degrees of freedom; however, the form of
this coupling is crucial in determining which phenomena can be observed in such
a system. Here we demonstrate that avoided crossings in the spectrum of an
optical cavity containing a flexible dielectric membrane allow us to realize
several different forms of the optomechanical coupling. These include cavity
detunings that are (to lowest order) linear, quadratic, or quartic in the
membrane's displacement, and a cavity finesse that is linear in (or independent
of) the membrane's displacement. All these couplings are realized in a single
device with extremely low optical loss and can be tuned over a wide range in
situ; in particular, we find that the quadratic coupling can be increased three
orders of magnitude beyond previous devices. As a result of these advances, the
device presented here should be capable of demonstrating the quantization of
the membrane's mechanical energy.Comment: 12 pages, 4 figures, 1 tabl
Winterberg's conjectured breaking of the superluminal quantum correlations over large distances
We elaborate further on a hypothesis by Winterberg that turbulent
fluctuations of the zero point field may lead to a breakdown of the
superluminal quantum correlations over very large distances. A phenomenological
model that was proposed by Winterberg to estimate the transition scale of the
conjectured breakdown, does not lead to a distance that is large enough to be
agreeable with recent experiments. We consider, but rule out, the possibility
of a steeper slope in the energy spectrum of the turbulent fluctuations, due to
compressibility, as a possible mechanism that may lead to an increased
lower-bound for the transition scale. Instead, we argue that Winterberg
overestimated the intensity of the ZPF turbulent fluctuations. We calculate a
very generous corrected lower bound for the transition distance which is
consistent with current experiments.Comment: 7 pages, submitted to Int. J. Theor. Phy
Optical Nanofibers: a new platform for quantum optics
The development of optical nanofibers (ONF) and the study and control of
their optical properties when coupling atoms to their electromagnetic modes has
opened new possibilities for their use in quantum optics and quantum
information science. These ONFs offer tight optical mode confinement (less than
the wavelength of light) and diffraction-free propagation. The small cross
section of the transverse field allows probing of linear and non-linear
spectroscopic features of atoms with exquisitely low power. The cooperativity
-- the figure of merit in many quantum optics and quantum information systems
-- tends to be large even for a single atom in the mode of an ONF, as it is
proportional to the ratio of the atomic cross section to the electromagnetic
mode cross section. ONFs offer a natural bus for information and for
inter-atomic coupling through the tightly-confined modes, which opens the
possibility of one-dimensional many-body physics and interesting quantum
interconnection applications. The presence of the ONF modifies the vacuum
field, affecting the spontaneous emission rates of atoms in its vicinity. The
high gradients in the radial intensity naturally provide the potential for
trapping atoms around the ONF, allowing the creation of one-dimensional arrays
of atoms. The same radial gradient in the transverse direction of the field is
responsible for the existence of a large longitudinal component that introduces
the possibility of spin-orbit coupling of the light and the atom, enabling the
exploration of chiral quantum optics.Comment: 65 pages, to appear in Advances in Atomic, Molecular and Optical
Physic
Laser-induced rotation and cooling of a trapped microgyroscope in vacuum
This work was supported by the UK Engineering and Physical Sciences Research Council (EPSRC grant numbers: EP/J01771X/1 and EP/G061688/1)Quantum state preparation of mesoscopic objects is a powerful playground for the elucidation of many physical principles. The field of cavity optomechanics aims to create these states through laser cooling and by minimizing state decoherence. Here we demonstrate simultaneous optical trapping and rotation of a birefringent microparticle in vacuum using a circularly polarized trapping laser beamâa microgyroscope. We show stable rotation rates up to 5âMHz. Coupling between the rotational and translational degrees of freedom of the trapped microgyroscope leads to the observation of positional stabilization in effect cooling the particle to 40âK. We attribute this cooling to the interaction between the gyroscopic directional stabilization and the optical trapping field.Publisher PDFPeer reviewe
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