90,246 research outputs found
Quantum Metrology with Cold Atoms
Quantum metrology is the science that aims to achieve precision measurements
by making use of quantum principles. Attribute to the well-developed techniques
of manipulating and detecting cold atoms, cold atomic systems provide an
excellent platform for implementing precision quantum metrology. In this
chapter, we review the general procedures of quantum metrology and some
experimental progresses in quantum metrology with cold atoms. Firstly, we give
the general framework of quantum metrology and the calculation of quantum
Fisher information, which is the core of quantum parameter estimation. Then, we
introduce the quantum interferometry with single and multiparticle states. In
particular, for some typical multiparticle states, we analyze their ultimate
precision limits and show how quantum entanglement could enhance the
measurement precision beyond the standard quantum limit. Further, we review
some experimental progresses in quantum metrology with cold atomic systems.Comment: 53 pages, 9 figures, revised versio
A low cost scheme for high precision dual-wavelength laser metrology
A novel method capable of delivering relative optical path length metrology
with nanometer precision is demonstrated. Unlike conventional dual-wavelength
metrology which employs heterodyne detection, the method developed in this work
utilizes direct detection of interference fringes of two He-Ne lasers as well
as a less precise stepper motor open-loop position control system to perform
its measurement. Although the method may be applicable to a variety of
circumstances, the specific application where this metrology is essential is in
an astrometric optical long baseline stellar interferometer dedicated to
precise measurement of stellar positions. In our example application of this
metrology to a narrow-angle astrometric interferometer, measurement of
nanometer precision could be achieved without frequency-stabilized lasers
although the use of such lasers would extend the range of optical path length
the metrology can accurately measure. Implementation of the method requires
very little additional optics or electronics, thus minimizing cost and effort
of implementation. Furthermore, the optical path traversed by the metrology
lasers is identical with that of the starlight or science beams, even down to
using the same photodetectors, thereby minimizing the non-common-path between
metrology and science channels.Comment: 17 pages, 4 figures, accepted for publication in Applied Optic
Experimental comparison of dynamic tracking performanceof iGPS and laser tracker
External metrology systems are increasingly being integrated with traditional industrial articulated robots, especially in the aerospace industries, to improve their absolute accuracy for precision operations such as drilling, machining and jigless assembly. While currently most of the metrology assisted robotics control systems are limited in their position update rate, such that the robot has to be stopped in order to receive a metrology coordinate update, some recent efforts are addressed toward controlling robots using real-time metrology data. The indoor GPS is one of the metrology systems that may be used to provide real-time 6DOF data to a robot controller. Even if there is a noteworthy literature dealing with the evaluation of iGPS performance, there is, however, a lack of literature on how well the iGPS performs under dynamic conditions. This paper presents an experimental evaluation of the dynamic measurement performance of the iGPS, tracking the trajectories of an industrial robot. The same experiment is also repeated using a laser tracker. Besides the experiment results presented, this paper also proposes a novel method for dynamic repeatability comparisons of tracking instrument
The GRAVITY metrology system: modeling a metrology in optical fibers
GRAVITY is the second generation VLT Interferometer (VLTI) instrument for
high-precision narrow-angle astrometry and phase-referenced interferometric
imaging. The laser metrology system of GRAVITY is at the heart of its
astrometric mode, which must measure the distance of 2 stars with a precision
of 10 micro-arcseconds. This means the metrology has to measure the optical
path difference between the two beam combiners of GRAVITY to a level of 5 nm.
The metrology design presents some non-common paths that have consequently to
be stable at a level of 1 nm. Otherwise they would impact the performance of
GRAVITY. The various tests we made in the past on the prototype give us hints
on the components responsible for this error, and on their respective
contribution to the total error. It is however difficult to assess their exact
origin from only OPD measurements, and therefore, to propose a solution to this
problem. In this paper, we present the results of a semi-empirical modeling of
the fibered metrology system, relying on theoretical basis, as well as on
characterisations of key components. The modeling of the metrology system
regarding various effects, e.g., temperature, waveguide heating or mechanical
stress, will help us to understand how the metrology behave. The goals of this
modeling are to 1) model the test set-ups and reproduce the measurements (as a
validation of the modeling), 2) determine the origin of the non-common path
errors, and 3) propose modifications to the current metrology design to reach
the required 1nm stability.Comment: 20 pages, 19 figures. Proceeding of SPIE 9146 "Optical and Infrared
Interferometry IV
Calibration and alignment of metrology system for the Nuclear Spectroscopic Telescope Array mission
A metrology system to measure the on-orbit movement of a ten
meter mast has been built for the Nuclear Spectroscopic Telescope Array (NuSTAR) x-ray observatory. In this paper, the metrology system is described, and the performance is measured. The laser beam stability is discussed in detail. Pre-launch alignment and calibration are also described. The invisible infrared laser beams must be aligned to their corresponding detectors without deploying the telescope in Earth’s gravity. Finally, a possible method for in-flight calibration of the metrology system is described
Intelligent sampling for the measurement of structured surfaces
Uniform sampling in metrology has known drawbacks such as coherent spectral aliasing and a lack of efficiency in terms of measuring time and data storage. The requirement for intelligent sampling strategies has been outlined over recent years, particularly where the measurement of structured surfaces is concerned. Most of the present research on intelligent sampling has focused on dimensional metrology using coordinate-measuring machines with little reported on the area of surface metrology. In the research reported here, potential intelligent sampling strategies for surface topography measurement of structured surfaces are investigated by using numerical simulation and experimental verification. The methods include the jittered uniform method, low-discrepancy pattern sampling and several adaptive methods which originate from computer graphics, coordinate metrology and previous research by the authors. By combining the use of advanced reconstruction methods and feature-based characterization techniques, the measurement performance of the sampling methods is studied using case studies. The advantages, stability and feasibility of these techniques for practical measurements are discussed
Quantum metrology
We point out a general framework that encompasses most cases in which quantum
effects enable an increase in precision when estimating a parameter (quantum
metrology). The typical quantum precision-enhancement is of the order of the
square root of the number of times the system is sampled. We prove that this is
optimal and we point out the different strategies (classical and quantum) that
permit to attain this bound.Comment: 4 pages, 2 figure
Nonlinear metrology with a quantum interface
We describe nonlinear quantum atom-light interfaces and nonlinear quantum
metrology in the collective continuous variable formalism. We develop a
nonlinear effective Hamiltonian in terms of spin and polarization collective
variables and show that model Hamiltonians of interest for nonlinear quantum
metrology can be produced in Rb ensembles. With these Hamiltonians,
metrologically relevant atomic properties, e.g. the collective spin, can be
measured better than the "Heisenberg limit" . In contrast to other
proposed nonlinear metrology systems, the atom-light interface allows both
linear and non-linear estimation of the same atomic quantities.Comment: 8 pages, 1 figure
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