Longitudinal-mode-partition noise in a semiconductor-laser-based interferometer

We observed a periodic intensity-noise variation in the output of a Mach-Zehnder interferometer as we changed the arm-length difference in the range of several millimeters. We found that the period of the variation coincided with that expected for the longitudinal-mode separation of the semiconductor laser. The origin of the huge excess noise of a bright fringe (approximately 30 dB above the shot-noise level) was the longitudinal-mode-partition noise that was due to the selective destructive interference of side modes.     

Parametric oscillatory instability on axially-symmetrical test mass elastic modes in Advanced LIGO interferometer

We discuss the importance of accurate calculation of axially-symmetrical elastic modes frequencies and forms in test masses (mirrors) of Advanced LIGO interferometer using the method of superposition to analyse the effect of parametric oscillatory instability. This method consists in possibility to construct analytical expressions for partial solutions of media motion equation in the cylindrical coordinates which allow to satisfy all zero boundary conditions. Obtained results allow to predict more exactly (in comparison with numerical calculations) the number of combinations of optical and elastic modes that can create undesirable effect of parametric oscillatory instability.     

Holographic ballistic gravimeter with the fixation of the angular position of a test mass

We have reported on the results of an experimental simulation of a holographic absolute ballistic gravimeter with the minimal (down to 0.5 mm) length of the trajectory of a falling test mass and rigid stabilization of its angular position. Gravimeters of this type ensure the mobile measurement of the free fall acceleration and are intended for the application in a new field of research, i.e., HF gravimetry.     

Radiation noise of an active interferometer

 An investigation of the behaviour of amplitude and frequency noise of radiation of an active interferometer in the regime of amplified optical bistability is presented. The phenomenon of non-amplification of external signal noise at sharp amplification of the external signal is established. The impact of strong amplitude fluctuations is studied. Our results have shown that the active interferometer allows an effective separation of the valid signal from the amplitude noise. The spectral density of a fluctuation of the field frequency in the active interferometer is shown to fall sharply in comparison with the “quantum limit”. The linewidth of radiation is determined by the spectral density at zero frequency and is equal to the natural linewidth of the external signal. The influence of quantum noise of the amplifying and absorbing media of the active interferometer is discussed. Received: 26 January 1996     

Phase sensitive shot noise in an Andreev interferometer

We investigate nonequilibrium noise in a diffusive Andreev interferometer, in which currents emerging from two normal metal/superconductor (N-S) interfaces can interfere. We observe a modulation of the shot noise when the phase difference between the two N-S interfaces is varied by a magnetic flux. This is the signature of phase-sensitive fluctuations in the normal metal. The effective charge inferred from the shot noise measurement is close to q(eff) = 2e but shows phase-dependent deviations from 2e at finite energy, which we interpret as being due to pair correlations. Experimental data are in good agreement with predictions based on an extended Keldysh Green's function approach.     

Accuracy analysis of parallel plate interferometer for angular displacement measurement

The measurement accuracy of a parallel-plate interferometer for angular displacement measurement is analyzed. The measurement accuracy of angular displacement is not only related to the accuracy of phase extraction, but also related to initial incident angle, refraction index and thickness of plane-parallel plate as well as wavelength's stability of laser diode, etc. Theoretical analysis and computer simulation show that the measurement error of the angular displacement bears a minimum value when choosing an optimal initial incident angle in a large range. These analytical results serve as a guide in practical measurement. In this interferometer, reducing the refraction index or increasing the thickness of the parallel plate can improve the measurement accuracy; and the relative error of the phase measurement is 3.0×10⁻⁴ corresponding to 1 °C temperature variation. Based on these theoretical and experimental results, the measurement accuracy of the parallel-plate interferometer is up to an order of 10⁻⁸ rad.     

Implementing the Deutsch's algorithm with spin-orbital angular momentum of photon without interferometer

Deutsch's algorithm is the simplest quantum algorithm which shows the acceleration of quantum computer. In this paper, we theoretically advance a scheme to implement quantum Deutsch's algorithm in spin-orbital angular momentum space. Our scheme exploits a newly developed optical device called "q-plate", which can couple and manipulate the spin-orbital angular momentum simultaneously. This experimental setup is of high stability and efficiency theoretically for there is no interferometer in it.     

Thermoelastic-damping noise from sapphire mirrors in a fundamental-noise-limited interferometer

We report the first high-precision interferometer using large sapphire mirrors, and we present the first direct, broadband measurements of the fundamental thermal noise in these mirrors. Our results agree well with the thermoelastic-damping noise predictions of Braginsky, et al. and Cerdonio et al., which have been used to predict the astrophysical reach of advanced interferometric gravitational wave detectors.     

Low-coherent light-source angular interferometer using a square prism and the angular-scanning technique

An interferometer based on using low-coherent light source, a square prism, and the angular-scanning technique is proposed for absolute angular-displacement determinations. An angular displacement of the square prism shifts the correlogram, which is modulated by an envelope function, of the interference signal of the beams passing through the prism. This angle can thus be discovered by detecting the shifting of the envelope peak. A setup constructed to validate the interferometer is used. The results of using this setup are then presented.     

便携式泰曼格林型干涉仪装调方法研究

 为满足光学系统对高精度检测的要求,依据一种新型便携式干涉仪的设计方案,研究了装调方法。该型干涉仪基于改进的泰曼-格林光路结构,其设计测试精度达到λ/10（P-V,λ=630 nm）,具有参考镜离轴、体积小巧、便携、精度较高、成本低及便于批量装备等新特点。针对该新型干涉仪的结构特点,研究了以两个互相垂直的光轴为基准对整体结构进行装调的新方法,并用装调完善的干涉仪进行了实测试验和比对试验。试验结果表明,该新型干涉仪器对已知面型精度为λ/10（P-V,λ=630 nm）的标准球面镜进行检测,其精度可达到0.09 λ;在相同的测试条件下进行比对实验时,该新型干涉仪对普通标准球面镜的检测结果为0.053 λ（RMS,λ=630 nm）,ZYGO干涉仪的检测结果为0.051 λ（RMS,λ=632.8 nm）,两者测量能力较为接近。采用新装调方法进行装调的该新型便携式干涉仪的实际检测精度达到了设计要求,新装调方法可以满足该新型干涉仪的指标要求。     

A simple high-sensitivity interferometric position sensor for test mass control on an advanced LIGO interferometer

A small Michelson interferometer has been configured as a tracking mirror displacement sensor in order to achieve both large dynamic range (2.1 mm) and excellent sensitivity across a broad frequency range (6Hz–3 kHz). The interferometer is illuminated by a simple LED, uses broadband, non-polarising beamsplitters and contains no lensing optics. A DC-coupled balanced detector provides an error signal that is used to position the tracking mirror of the Michelson interferometer so as to maintain an interferometer operating position close to the centre of a particular fringe. The total interferometric sensor provides a small, simple and cost-effective means of achieving high-resolution displacement measurements.     

基于半导体光放大器的干涉型器件中噪声特性的分析

分析了基于半导体光放大器(SOA)的干涉仪分别处于“开”、“关”两种工作状态时的输出信噪比及噪声指数,发现当干涉仪处于“开”态时输出信噪比有所恶化,并导出了附加噪声因子的表达式。实验结果进一步证明了理论分析的正确性。     

Photon-assisted Shot noise of the double quantum dot interferometer in weak Kondo regime

The shot noise of a parallel double quantum dot (DQD) system under the perturbation of microwave fields is investigated in the weak Kondo regime. Peak-valley structures exhibit in the differential conductance and shot noise, and side resonant peaks emerge around the Kondo peak due to the absorption and emission of photons. The shot noise is sensitively dependent on the adjusting approach through changing the gate voltages. Large resonant Fano factor accompanying photon-induced side peaks appear by simultaneously varying the two gate voltages. The photon suppression and enhancement of shot noise have been evaluated corresponding to the coherent and incoherent current correlation. The destructive interference causes the suppression of shot noise by changing the Aharonov–Bohm phase.     

Shot noise in a double-quantum-dot Aharonov-Bohm interferometer under the perturbation of ac fields

We have investigated the shot noise spectral density in the parallel double-quantum-dot (DQD) interferometer threaded with an Aharonov-Bohm (AB) flux under the perturbation of ac fields. The derivations are based on the nonequilibrium Green’s function (NGF) technique in the Coulomb blockade regime. The AB flux and the perturbation of ac fields together provide a photon-assisted AB interferometer for controlling the shot noise efficiently. The signature of the shot noise reflects the intrinsic microstructure of the DQD system, which plays important roles for the enhancement and suppression of shot noise. The versatile resonant structures of shot noise, Fano factor have been revealed to exhibit the sub-Poissonian and super-Poissonian types of shot noise by adjusting the gate voltages sequentially.     

Influence of dephasing on shot noise in an electronic Mach-Zehnder interferometer

We analyze shot noise under the influence of dephasing in an electronic Mach-Zehnder interferometer, of the type that was realized recently [Nature (London) 422, 415 (2003)]]. Using a model of dephasing by a fluctuating classical field, we show how the usual partition noise expression T(1-T) is modified. We study the dependence on the power spectrum of the field, which is impossible in simpler approaches such as the dephasing terminal, against which we compare. We remark on shot noise as a tool to distinguish thermal smearing from genuine dephasing.     

利用Sagnac干涉仪实现光子轨道角动量分束器

光子轨道角动量量子态具有高维和光学涡旋特性, 在经典和量子领域展示出了巨大的应用潜力, 目前对其的研究已成为物理学的一个热点. 本实验研究了利用Sagnac干涉仪干涉的方法将具有不同轨道角动量的光束无破坏地分离到不同的路径, 即实现光子轨道角动量分束器. 实验中利用此分束器验证了对几种不同轨道角动量态(包含叠加态)的分离, 得到了与理论预期相符的实验结果. 这种对轨道角动量态的区分的方法相比已有的其他区分方法具有较好的稳定性, 而且可用于区分叠加态, 也可以达到单光子水平, 最重要的是实现了不同的轨道角动量本征态无破坏的与路径比特耦合. 这种新方法对高密度通信、量子纠缠、量子保密通信、量子计算与量子信息等方面有着重要的意义.     

Shot noise in the hybrid triple-quantum-dot interferometer coupled to superconductor and normal terminals

The shot noise of a hybrid triple-quantum-dot (TQD) interferometer has been investigated by employing the nonequilibrium Green's function method, and the general shot noise formula has been derived. The oscillation behaviors of transmission coefficients and shot noise versus the Aharonov–Bohm phase ?   exhibit asymmetric Fano resonance structure and blockade effect. Sub-Poissonian and super-Poissonian behaviors of shot noise appear in different regimes of terminal bias e_Vγ$e{V}_{\gamma }$ contributed by the Andreev reflection, and correlation of Andreev tunneling with the normal electron transport. The inverse resonance and resonance structures emerge in the shot noise and Fano factor with respect to one of the gate voltages in different regimes of e_Vγ$e{V}_{\gamma }$. The asymmetric structure can be enhanced by modifying the energy levels and gate biases of the TQD. The self-correlation and cross-correlation of current components contribute to the enhancement and suppression of shot noise.     

Wide-band measurement of mechanical thermal noise using a laser interferometer

We have measured the displacement thermal noise of a mechanical cantilever, made of phosphor bronze, using a laser interferometer. The measured noise spectrum agrees well with an estimation based on the fluctuation–dissipation theorem with a mechanical-admittance measurement. The frequency range where we could measure the thermal noise was from 50  to 500 Hz; this range is important for the noise characterization of interferometric gravitational wave detectors.     

An angular correlation test of time-reversal invariance

A test of time-reversal invariance in electromagnetic transitions is proposed in which all possible two-gamma angular correlations in a triple cascade are measured. The results can be combined to yield a term proportional to cos η.