3,878 research outputs found
Optomechanical position detection enhanced by de-amplification using intracavity squeezing
It has been predicted and experimentally demonstrated that by injecting
squeezed light into an optomechanical device it is possible to enhance the
precision of a position measurement. Here, we present a fundamentally different
approach where the squeezing is created directly inside the cavity by a
nonlinear medium. Counterintuitively, the enhancement of the signal to noise
ratio works by de-amplifying precisely the quadrature that is sensitive to the
mechanical motion without losing quantum information. This enhancement works
for systems with a weak optomechanical coupling and/or strong mechanical
damping. This could allow for larger mechanical bandwidth of quantum limited
detectors based on optomechanical devices. Our approach can be
straightforwardly extended to Quantum Non Demolition (QND) qubit detection.Comment: references added, slight change
Fermionic Mach-Zehnder interferometer subject to a quantum bath
We study fermions in a Mach-Zehnder interferometer, subject to a
quantum-mechanical environment leading to inelastic scattering, decoherence,
renormalization effects, and time-dependent conductance fluctuations. Both the
loss of interference contrast as well as the shot noise are calculated, using
equations of motion and leading order perturbation theory. The full dependence
of the shot-noise correction on setup parameters, voltage, temperature and the
bath spectrum is presented. We find an interesting contribution due to
correlations between the fluctuating renormalized phase shift and the output
current, discuss the limiting behaviours at low and high voltages, and compare
with simpler models of dephasing.Comment: 5 pages, 3 figure
Quantum techniques using continuous variables of light
We present schemes for the generation and evaluation of continuous variable
entanglement of bright optical beams and give a brief overview of the variety
of optical techniques and quantum communication applications on this basis. A
new entanglement-based quantum interferometry scheme with bright beams is
suggested. The performance of the presented schemes is independent of the
relative interference phase which is advantageous for quantum communication
applications.Comment: 11 pages, 5 figures; minor correction, accepted versio
The Standard Quantum Limit of Coherent Beam Combining
Coherent beam combining refers to the process of generating a bright output
beam by merging independent input beams with locked relative phases. We report
the first quantum mechanical noise limit calculations for coherent beam
combining and compare our results to quantum-limited amplification. Our
coherent beam combining scheme is based on an optical Fourier transformation
which renders the scheme compatible with integrated optics. The scheme can be
layed out for an arbitrary number of input beams and approaches the shot noise
limit for a large number of inputs
Nonlinear and Quantum Optics with Whispering Gallery Resonators
Optical Whispering Gallery Modes (WGMs) derive their name from a famous
acoustic phenomenon of guiding a wave by a curved boundary observed nearly a
century ago. This phenomenon has a rather general nature, equally applicable to
sound and all other waves. It enables resonators of unique properties
attractive both in science and engineering. Very high quality factors of
optical WGM resonators persisting in a wide wavelength range spanning from
radio frequencies to ultraviolet light, their small mode volume, and tunable
in- and out- coupling make them exceptionally efficient for nonlinear optical
applications. Nonlinear optics facilitates interaction of photons with each
other and with other physical systems, and is of prime importance in quantum
optics. In this paper we review numerous applications of WGM resonators in
nonlinear and quantum optics. We outline the current areas of interest,
summarize progress, highlight difficulties, and discuss possible future
development trends in these areas.Comment: This is a review paper with 615 references, submitted to J. Op
Reduction of Guided Acoustic Wave Brillouin Scattering in Photonic Crystal Fibers
Guided Acoustic Wave Brillouin Scattering (GAWBS) generates phase and
polarization noise of light propagating in glass fibers. This excess noise
affects the performance of various experiments operating at the quantum noise
limit. We experimentally demonstrate the reduction of GAWBS noise in a photonic
crystal fiber in a broad frequency range using cavity sound dynamics. We
compare the noise spectrum to the one of a standard fiber and observe a 10-fold
noise reduction in the frequency range up to 200 MHz. Based on our measurement
results as well as on numerical simulations we establish a model for the
reduction of GAWBS noise in photonic crystal fibers.Comment: 4 pages, 7 figures; added numerical simulations, added reference
Photon shuttle: Landau-Zener-Stuckelberg dynamics in an optomechanical system
The motion of micro- and nanomechanical resonators can be coupled to electromagnetic fields. Such optomechanical setups allow one to explore the interaction of light and matter in a new regime at the boundary between quantum and classical physics. We propose an approach to investigate nonequilibrium photon dynamics driven by mechanical motion in a recently developed setup with a membrane between two mirrors, where photons can be shuttled between the two halves of the cavity. For modest driving strength we predict the possibility of observing an Autler-Townes splitting indicative of Rabi dynamics. For large drive, we show that this system displays Landau-Zener-Stueckelberg dynamics originally known from atomic two-state systems
Quantum nature of Gaussian discord : experimental evidence and role of system-environment correlations
L.M. acknowledges Project No. P205/12/0694 of Czech Science Foundation (GACR). N.K. is grateful for the support provided by the A. von Humboldt Foundation. N.Q. and N.K. acknowledge the support from the Scottish Universities Physics Alliance (SUPA) and the Engineering and Physical Sciences Research Council (EPSRC). The project was supported within the framework of the BMBF grant âQuORepâ and in the framework of the International Max Planck Partnership (IMPP) with Scottish Universities.We provide experimental evidence of quantum features in bipartite states classified as entirely classical according to a conventional criterion based on the Glauber P function but possessing nonzero Gaussian quantum discord. Their quantum nature is experimentally revealed by acting locally on one part of the discordant state. We experimentally verify and investigate the effect of discord increase under the action of local loss and link it to the entanglement with the environment. Adding an environmental system purifying the state, we unveil the flow of quantum correlations within a global pure system using the Koashi-Winter inequality. For a discordant state generated by splitting a state in which the initial squeezing is destroyed by random displacements, we demonstrate the recovery of entanglement highlighting the role of system-environment correlations.Publisher PDFPeer reviewe
- âŠ