495 research outputs found
Finite-time thermodynamics of port-Hamiltonian systems
In this paper, we identify a class of time-varying port-Hamiltonian systems
that is suitable for studying problems at the intersection of statistical
mechanics and control of physical systems. Those port-Hamiltonian systems are
able to modify their internal structure as well as their interconnection with
the environment over time. The framework allows us to prove the First and
Second laws of thermodynamics, but also lets us apply results from optimal and
stochastic control theory to physical systems. In particular, we show how to
use linear control theory to optimally extract work from a single heat source
over a finite time interval in the manner of Maxwell's demon. Furthermore, the
optimal controller is a time-varying port-Hamiltonian system, which can be
physically implemented as a variable linear capacitor and transformer. We also
use the theory to design a heat engine operating between two heat sources in
finite-time Carnot-like cycles of maximum power, and we compare those two heat
engines.Comment: To appear in Physica D (accepted July 2013
Classical and fluctuation-induced electromagnetic interactions in micronscale systems: designer bonding, antibonding, and Casimir forces
Whether intentionally introduced to exert control over particles and
macroscopic objects, such as for trapping or cooling, or whether arising from
the quantum and thermal fluctuations of charges in otherwise neutral bodies,
leading to unwanted stiction between nearby mechanical parts, electromagnetic
interactions play a fundamental role in many naturally occurring processes and
technologies. In this review, we survey recent progress in the understanding
and experimental observation of optomechanical and quantum-fluctuation forces.
Although both of these effects arise from exchange of electromagnetic momentum,
their dramatically different origins, involving either real or virtual photons,
lead to different physical manifestations and design principles. Specifically,
we describe recent predictions and measurements of attractive and repulsive
optomechanical forces, based on the bonding and antibonding interactions of
evanescent waves, as well as predictions of modified and even repulsive Casimir
forces between nanostructured bodies. Finally, we discuss the potential impact
and interplay of these forces in emerging experimental regimes of
micromechanical devices.Comment: Review to appear on the topical issue "Quantum and Hybrid Mechanical
Systems" in Annalen der Physi
Coherent control and feedback cooling in a remotely-coupled hybrid atom-optomechanical system
Cooling to the motional ground state is an important first step in the
preparation of nonclassical states of mesoscopic mechanical oscillators.
Light-mediated coupling to a remote atomic ensemble has been proposed as a
method to reach the ground state for low frequency oscillators. The ground
state can also be reached using optical measurement followed by feedback
control. Here we investigate the possibility of enhanced cooling by combining
these two approaches. The combination, in general, outperforms either
individual technique, though atomic ensemble-based cooling and feedback cooling
each individually dominate over large regions of parameter space.Comment: 28 pages, 5 figures, 2 tables. Updated to include exemplary
experimental parameters and expanded discussion of noise source
Gravitational wave detection beyond the standard quantum limit using a negative-mass spin system and virtual rigidity
Gravitational wave detectors (GWDs), which have brought about a new era in
astronomy, have reached such a level of maturity that further improvement
necessitates quantum-noise-evading techniques. Numerous proposals to this end
have been discussed in the literature, e.g., invoking frequency-dependent
squeezing or replacing the current Michelson interferometer topology by that of
the quantum speedmeter. Recently, a proposal based on the linking of a standard
interferometer to a negative-mass spin system via entangled light has offered
an unintrusive and small-scale new approach to quantum noise evasion in GWDs
[Phys. Rev. Lett. , 031101 (2018)]. The solution proposed therein
does not require modifications to the highly refined core optics of the present
GWD design and, when compared to previous proposals, is less prone to losses
and imperfections of the interferometer. In the present article, we refine this
scheme to an extent that the requirements on the auxiliary spin system are
feasible with state-of-the-art implementations. This is accomplished by
matching the effective (rather than intrinsic) susceptibilities of the
interferometer and spin system using the virtual rigidity concept, which, in
terms of implementation, requires only suitable choices of the various
homodyne, probe, and squeezing phases.Comment: Minor typos fixed, minor editing; 12 pages, 5 figure
Monte Carlo Simulations
Monte Carlo computer simulations are virtually the only way to analyze the
thermodynamic behavior of a system in a precise way. However, the various
existing methods exhibit extreme differences in their efficiency, depending on
model details and relevant questions. The original standard method, Metropolis
Monte Carlo, which provides only reliable statistical information at a given
(not too low) temperature has meanwhile been replaced by more sophisticated
methods which are typically far more efficient (the differences in time scales
can be compared with the age of the universe). However, none of the methods
yields automatically accurate results, i.e., a system-specific adaptation and
control is always needed. Thus, as in any good experiment, the most important
part of the data analysis is statistical error estimation.Comment: 17 pages, 1 figure, 42nd IFF Spring School "Macromolecular Systems in
Soft and Living Matter", Forschungszentrum Juelich, 14-25 February 201
Quantum Measurement Theory in Gravitational-Wave Detectors
The fast progress in improving the sensitivity of the gravitational-wave (GW)
detectors, we all have witnessed in the recent years, has propelled the
scientific community to the point, when quantum behaviour of such immense
measurement devices as kilometer-long interferometers starts to matter. The
time, when their sensitivity will be mainly limited by the quantum noise of
light is round the corner, and finding the ways to reduce it will become a
necessity. Therefore, the primary goal we pursued in this review was to
familiarize a broad spectrum of readers with the theory of quantum measurements
in the very form it finds application in the area of gravitational-wave
detection. We focus on how quantum noise arises in gravitational-wave
interferometers and what limitations it imposes on the achievable sensitivity.
We start from the very basic concepts and gradually advance to the general
linear quantum measurement theory and its application to the calculation of
quantum noise in the contemporary and planned interferometric detectors of
gravitational radiation of the first and second generation. Special attention
is paid to the concept of Standard Quantum Limit and the methods of its
surmounting.Comment: 147 pages, 46 figures, 1 table. Published in Living Reviews in
Relativit
Plasma Electronics
Contains reports on nine research projects.U. S. Air Force under Air Force Contract AF 19(604)-7400National Science Foundation under Grant G-9330U.S.Navy(Office of Naval Research)under Contract Nonr-1841(78)U. S. ArmyLincoln Laboratory, Purchase Order DDL B-00337U. S. Nav
Introduction to Quantum Noise, Measurement and Amplification
The topic of quantum noise has become extremely timely due to the rise of
quantum information physics and the resulting interchange of ideas between the
condensed matter and AMO/quantum optics communities. This review gives a
pedagogical introduction to the physics of quantum noise and its connections to
quantum measurement and quantum amplification. After introducing quantum noise
spectra and methods for their detection, we describe the basics of weak
continuous measurements. Particular attention is given to treating the standard
quantum limit on linear amplifiers and position detectors using a general
linear-response framework. We show how this approach relates to the standard
Haus-Caves quantum limit for a bosonic amplifier known in quantum optics, and
illustrate its application for the case of electrical circuits, including
mesoscopic detectors and resonant cavity detectors.Comment: Substantial improvements over initial version; include supplemental
appendices
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