A proposal for experimental detection of amplitude nth-power squeezing

Recently, in several theoretical investigations, amplitude nth-power squeezing has been studied with n = 2, 3, 4, 5. In the present paper, we give a proposal for experimental detection of amplitude nth-power squeezing using ordinary homodyning with coherent light for arbitrary power n and discuss in detail its theory. The proposed scheme requires only repeated measurements of the factorial moments of number of photons in the light obtained after homodyning, with various shifts of phase of coherent light, and involves no approximations, whatsoever. This has advantage over the method proposed by Shchukin and Vogel [Phys. Rev. A 72 (2005) 043808] in that our method requires only one beam splitter and only one photodetector, and also lesser number of repetitions of experiment with phase-shifted coherent light.     

Simultaneous experimental generation of vacuum squeezing and bright amplitude squeezing from a frequency doubler

Both vacuum-squeezed and bright amplitude-squeezed states of light are experimentally generated from a frequency doubler with a semimonolithic Fabry-Perot configuration consisting of a type II nonlinear crystal and a concave mirror. Vacuum squeezing of 3.2 +/- 0.1 dB and amplitude squeezing of 1.3 +/- 0.2 dB are obtained simultaneously at a pump power of 8 mW. The two quadrature-squeezed optical fields that are generated are of identical frequency at 1080-nm wavelength and orthogonal polarization. Optimizing the input pump power by 19 mW yields as much as 5.0 +/- 0.2 dB of maximum vacuum squeezing. The advantages of the system are its simplicity and multiple utility.     

Optical methods for precision measurements

Contactless measuring techniques are becoming increasingly important for industrial applications. The use of a laser, solid-state detector arrays and powerful small computers leads to a very efficient fringe analysis in holography as well as in Moiré and speckle techniques. Due to the computer analysis, much more information can be extracted from interferograms, leading to higher sensitivities and accuracies. The application of different fringe analysis procedures is discussed, together with some potentials of the application of interferometry, holography, and speckle and Moiré techniques.     

Higher-order amplitude squeezing of photons propagating through a semiconductor

Kth power photon amplitude squeezing is studied when the coherent photon propagates through a semiconductor containing the exciton. If the exciton is prepared initially in a coherent state, the photon may become Kth power amplitude squeezed. It is shown that, in the short-time limit, the photon squeezing in the P direction does not appear at all while that in the X direction is possible for all the amplitude powers K. In the latter case, the amount of squeezing is larger for higher power K. The dependences on all the system parameters as well as on the output light detection moment are investigated in detail.     

Single-mode amplitude squeezing in a semiconductor laser at 780 nm

The problem of the creation of a sub-Poissonian radiation source on the basis of a semiconductor laser with an external cavity is considered, which operates, from the viewpoint of quantum optics, in the single-mode regime. The conditions of the generation of sub-Poissonian radiation, under which the whole set of sub-threshold modes, including the nearest modes of the external (long) cavity, is completely suppressed at room temperature, were experimentally revealed and theoretically studied. Single-frequency low-noise lasing is of interest not only for the creation of nonclassical light sources, but also for sensitive spectroscopic applications in the classical domain.     

Kochen-Specker theorem for finite precision spin-one measurements

Unsharp spin-one observables arise from the fact that a residual uncertainty about the actual orientation of the measurement device remains. If the uncertainty is below a certain level, and if the distribution of measurement errors is covariant under rotations, a Kochen-Specker theorem for the unsharp spin observables follows: There are finite sets of directions such that not all the unsharp spin observables in these directions can consistently be assigned approximate truth values in a noncontextual way.     

Light squeezing in optical parametric amplification beyond the slowly-varying amplitude approximation

Optical parametric amplification (OPA) described usually by the coupled-wave equations with the first-order derivatives of the signal and idler waves, is solved under the slowly-varying amplitude approximation (SVA). In this article, by keeping the second-order derivatives in the coupled-wave equations, we obtained an analytical solution for the output signal and idler waves up to the first order of (κ/k)¹; the ratio of coupling constant to the wave number. Furthermore, here the signal and the idler waves are distinguished only by their polarizations with the same frequency. Light squeezing is observed in normally ordered variances of the two quadrature operators of the output combined mode when plotted against κL, where κ is the coupling constant and L the interaction length. The variances have different signs for a range of values of κL and their variations are in opposite directions. We also show that this property is strongly dependent on the relative refractive index of the medium (n). It is worth mentioning that the relative index dependency is not an explicit feature in squeezing of OPA under SVA approximation. Furthermore, the squeezing vanishes when n → 1 and κ/k → 0.     

Progress of precision measurements at JYFLTRAP

This review compiles the results obtained since 2006 by use of the JYFLTRAP Penning trap mass spectrometer. Almost 300 atomic masses of ground or isomeric states of exotic nuclei have been measured. Some of the measurements required the development of new techniques which are briefly mentioned. In addition, JYFLTRAP was applied to a variety of spectroscopic studies and to the production of isobarically or isomerically pure beams.     

真空态多光子Jaynes—Cummings模型中场的振幅N次方压缩

本文研究了一初始处于原子相干态的二能级原子与真空态场相互耦合的ｋ光子Ｊａｙｎｅｓ－Ｃｕｍｍｉｎｇｓ模型中场的振幅Ｎ次方程压缩特性。结果表明，场不仅存在振幅Ｎ＝ｋ次方压缩，而且当ｋ为偶数时，还存在振幅Ｎ＝ｋ／２次方压缩。     

A new Channeltron-detector setup for precision mass measurements at ISOLTRAP

Recent technical developments at ISOLTRAP include the design, installation and characterization of a new Channeltron-detector setup in order to increase the detection efficiency by about a factor of 3. Since a detection efficiency close to 100% is reached, true single-ion experiments can be performed for the first time and exotic nuclides further away from the valley of stability with lower production yields and/or shorter half-lives as compared to previous investigations are accessible. This publication comprises part of the thesis of C. Yazidjian.     

Coherent matter wave inertial sensors for precision measurements in space

We analyze the advantages of using ultra-cold coherent sources of atoms for matter-wave interferometry in space. We present a proof-of-principle experiment that is based on an analysis of results previously published, from which we extract the ratio h/m for ⁸⁷Rb. This measurement shows that a limitation in accuracy arises due to atomic interactions within the Bose–Einstein condensate. Finally, we discuss the promising role of coherent-matter-wave sensors, in particular inertial sensors, in future fundamental physics missions in space. PACS 03.75.-b; 32.80.Pj     

An apparatus for high precision measurements of ultrasonic wave velocity

An automatic gated-carrier pulse superposition system for high precision ultrasonic velocity measurements is described, having better stability and lower cost than previous equipment. The necessary new integrated circuitry, and the method of operation, are described in detail. The principal application is to the measurement of small changes in the velocity of MHz ultrasonic waves, such as occur when materials are subjected to stress. Results are presented confirming a detection sensitivity of 1 part in 10.     

Prospects for precision measurements on ammonia molecules in a fountain

The recent demonstration of cooling and manipulation techniques for molecules offer newpossibilities for precision measurements in molecules. Here, we present the design of a molecularfountain based on a Stark decelerated molecular beam. In this fountain, ammonia molecules aredecelerated to a few meter per second, cooled to sub microKelvin temperatures and subsequentlylaunched. The molecules fly upwards some 30 cm before falling back under gravity, thereby passing amicrowave cavity twice – as they fly up and as they fall back down. The effective interrogationtime in such a Ramsey type measurement scheme includes the entire flight time between the twotraversals through the driving field, which is on the order of a 1/2 second. We present numericalsimulations of the trajectories through the decelerator and estimate the expected count rate. Wepresent an evaluation of the expected stability and accuracy for the inversion transition in¹⁵NH₃ around 22.6 GHz. The estimated frequency instability is , with τ being the measurement time in seconds. With a careful design ofthe interogation zone, systematic frequency shifts are kept below 10^-14. Besides serving as aproof-of-principle, these measurements may be used as a test of the time-variation of fundamentalconstants using the sensitivity of the tunneling motion to a change of the proton-electron massratio.     

Quantum nondemolition measurements in systems with nonstationary squeezing of quantum noise

Summary A Weber detector with optical readout system is considered. The measuring device consists of circulators, homodyne detector and two degenerate parametric amplifiers (or four wave mixers), modifying vacuum fluctuations of the load. In this scheme the greater the squeezing of backaction noise, the smaller the measurable force acting on the mechanical resonator. Postulation of gedanken state reduction is not necessary in our model.

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Riassunto Si considera il rivelatore Weber con sistema di lettura ottico. Lo strumento di misura consiste di circolatori, di un rivelatore omodino e due amplificatori parametrici degenerati (o quattro miscelatori d'onda), che modificano le fluttuazioni nel vuoto del carico. In questo schema, maggiore è la compressione del rumore di retroazione e minore risulta la forza misurabile che agisce sul risonatore meccanico. Nel modello in questione non è necessario postulare la riduzione dello stato concettuale.

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Резюме Рассматривается детектор Вебера с оптической системой считывания. Измерительная аппаратура состоит из циркуляционных насосов, детектора и двух вырожденных параметрических усилителей (или преобразователей четырех волн), преобразуюших вакуумные флуктуации нагрузки. В этой схеме, чем меньше измеряемая сила, действующая на механический резонатор, тем больше подавление шума. В нашей модели не требуется постулирование преобразования состояния.

     

Classical correlations and entanglement in quantum measurements

We analyze a quantum measurement where the apparatus is initially in a mixed state. We show that the amount of information gained in a measurement is not equal to the amount of entanglement between the system and the apparatus, but is instead equal to the degree of classical correlations between the two. As a consequence, we derive an uncertainty-like expression relating the information gain in the measurement and the initial mixedness of the apparatus. Final entanglement between the environment and the apparatus is also shown to be relevant for the efficiency of the measurement.