1,737 research outputs found
Cross-Phase Modulation Enhancement Via a Resonating Cavity: Semiclassical Description
We evaluate the advantages of performing cross-phase modulation (XPM) on a
very-far-off-resonance atomic system. We consider a ladder system with a weak
(few-photon level) control coherent field imparting a conditional nonlinear
phase shift on a probe beam. We find that by coupling to an optical resonator
the optimal XPM is enhanced proportional to the finesse of the resonator by a
factor of . We present a semi-classical description of the system and
show that the phenomenon is optimal in the self-defined condition of
off-resonance-effective-cooperativity equal to one
Efficient high-dimensional entanglement imaging with a compressive sensing, double-pixel camera
We implement a double-pixel, compressive sensing camera to efficiently
characterize, at high resolution, the spatially entangled fields produced by
spontaneous parametric downconversion. This technique leverages sparsity in
spatial correlations between entangled photons to improve acquisition times
over raster-scanning by a scaling factor up to n^2/log(n) for n-dimensional
images. We image at resolutions up to 1024 dimensions per detector and
demonstrate a channel capacity of 8.4 bits per photon. By comparing the
classical mutual information in conjugate bases, we violate an entropic
Einstein-Podolsky-Rosen separability criterion for all measured resolutions.
More broadly, our result indicates compressive sensing can be especially
effective for higher-order measurements on correlated systems.Comment: 10 pages, 7 figure
Paraxial ray optics cloaking
Despite much interest and progress in optical spatial cloaking, a
three-dimensional (3D), transmitting, continuously multidirectional cloak in
the visible regime has not yet been demonstrated. Here we experimentally
demonstrate such a cloak using ray optics, albeit with some edge effects. Our
device requires no new materials, uses isotropic off-the-shelf optics, scales
easily to cloak arbitrarily large objects, and is as broadband as the choice of
optical material, all of which have been challenges for current cloaking
schemes. In addition, we provide a concise formalism that quantifies and
produces perfect optical cloaks in the small-angle (`paraxial') limit
Paraxial full-field cloaking
We complete the `paraxial' (small-angle) ray optics cloaking formalism
presented previously [Choi and Howell, Opt. Express 22, 29465 (2014)], by
extending it to the full-field of light. Omnidirectionality is then the only
relaxed parameter of what may be considered an ideal, broadband, field cloak.
We show that an isotropic plate of uniform thickness, with appropriately
designed refractive index and dispersion, can match the phase over the whole
visible spectrum. Our results support the fundamental limits on cloaking for
broadband vs. omnidirectionality, and provide insights into when anisotropy may
be required
Practical Advantages of Almost-Balanced-Weak-Values Metrological Techniques
Precision measurements of ultra-small linear velocities of one of the mirrors
in a Michelson interferometer are performed using two different weak-values
techniques. We show that the technique of Almost-Balanced Weak Values (ABWV)
offers practical advantages over the technique of Weak-Value Amplification
(WVA), resulting in larger signal-to-noise ratios and the possibility of longer
integration times due to robustness to slow drifts. As an example of the
performance of the ABWV protocol we report a velocity sensitivity of 60 fm/s
after 40 hours of integration time. The sensitivity of the Doppler shift due to
the moving mirror is of 150 nHz
Improving Einstein-Podolsky-Rosen Steering Inequalities with State Information
We discuss the relationship between entropic Einstein-Podolsky-Rosen
(EPR)-steering inequalities and their underlying uncertainty relations, along
with the hypothesis that improved uncertainty relations lead to tighter
EPR-steering inequalities. In particular, we discuss how the intrinsic
uncertainty in a mixed quantum state is used to improve existing uncertainty
relations and how this information affects one's ability to witness
EPR-steering. As an example, we consider the recent improvement (using a
quantum memory) to the entropic uncertainty relation between pairs of discrete
observables (Nat. Phys. 6, 659 (2010)) and show that a trivial substitution of
the tighter bound in the steering inequality leads to contradictions, due in
part to the fact that the improved bound depends explicitly on the state being
measured. By considering the assumptions that enter into the development of a
steering inequality, we derive correct steering inequalities from these
improved uncertainty relations and find that they are identical to ones already
developed (Phys. Rev. A, 87, 062103 (2013)). In addition, we consider how one
can use the information about the quantum state to improve our ability to
witness EPR-steering, and develop a new symmetric EPR-steering inequality as a
result.Comment: 6 page
Uncertainty Relation for Mutual Information
We postulate the existence of a universal uncertainty relation between the
quantum and classical mutual informations between pairs of quantum systems.
Specifically, we propose that the sum of the classical mutual information,
determined by two mutually unbiased pairs of observables, never exceeds the
quantum mutual information. We call this the complementary-quantum correlation
(CQC) relation and prove its validity for pure states, for states with one
maximally mixed subsystem, and for all states when one measurement is minimally
disturbing. We provide results of a Monte Carlo simulation suggesting the CQC
relation is generally valid. Importantly, we also show that the CQC relation
represents an improvement to an entropic uncertainty principle in the presence
of a quantum memory, and that it can be used to verify an achievable secret key
rate in the quantum one-time pad cryptographic protocol.Comment: 6 pages, 2 figure
Noise suppression in inverse weak value based phase detection
We examine the effect of different sources of technical noise on inverse weak
value-based precision phase measurements. We find that this type of measurement
is similarly robust to technical noise as related experiments in the weak value
regime. In particular, the measurements considered here are robust to additive
Gaussian white noise and angular jitter noise commonly encountered in optical
experiments. Additionally, we show the same techniques used for precision phase
measurement can be used with the same technical advantages for optical
frequency measurements.Comment: 6 pages, 4 figure
Frequency-modulated continuous-wave LiDAR compressive depth-mapping
We present an inexpensive architecture for converting a frequency-modulated
continuous-wave LiDAR system into a compressive-sensing based depth-mapping
camera. Instead of raster scanning to obtain depth-maps, compressive sensing is
used to significantly reduce the number of measurements. Ideally, our approach
requires two difference detectors. % but can operate with only one at the cost
of doubling the number of measurments. Due to the large flux entering the
detectors, the signal amplification from heterodyne detection, and the effects
of background subtraction from compressive sensing, the system can obtain
higher signal-to-noise ratios over detector-array based schemes while scanning
a scene faster than is possible through raster-scanning. %Moreover, we show how
a single total-variation minimization and two fast least-squares minimizations,
instead of a single complex nonlinear minimization, can efficiently recover
high-resolution depth-maps with minimal computational overhead. Moreover, by
efficiently storing only data points from measurements of an
pixel scene, we can easily extract depths by solving only two linear equations
with efficient convex-optimization methods
Technical advantages for weak value amplification: When less is more
The technical merits of weak value amplification techniques are analyzed. We
consider models of several different types of technical noise in an optical
context and show that weak value amplification techniques (which only use a
small fraction of the photons) compare favorably with standard techniques
(which uses all of them). Using the Fisher information metric, we demonstrate
that weak value techniques can put all of the Fisher information about the
detected parameter into a small portion of the events and show how this fact
alone gives technical advantages. We go on to consider a time correlated noise
model, and find that a Fisher information analysis indicates that while the
standard method can have much larger information about the detected parameter
than the postselected technique. However, the estimator needed to gather the
information is technically difficult to implement, showing that the inefficient
(but practical) signal-to-noise estimation of the parameter is usually
superior. We also describe other technical advantages unique to imaginary weak
value amplification techniques, focusing on beam deflection measurements. In
this case, we discuss combined noise types (such as detector transverse jitter,
angular beam jitter before the interferometer and turbulence) for which the
interferometric weak value technique gives higher Fisher information over
conventional methods. We go on to calculate the Fisher information of the
recently proposed photon recycling scheme for beam deflection measurements, and
show it further boosts the Fisher information by the inverse postselection
probability relative to the standard measurement case
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