Showing papers on "Noise (electronics) published in 2016"

Sub-Femto-g Free Fall for Space-Based Gravitational Wave Observatories: LISA Pathfinder Results

Abstract: We report the first results of the LISA Pathfinder in-flight experiment. The results demonstrate that two free-falling reference test masses, such as those needed for a space-based gravitational wave observatory like LISA, can be put in free fall with a relative acceleration noise with a square root of the power spectral density of 5.2 +/- 0.1 fm s(exp -2)/square root of Hz, or (0.54 +/- 0.01) x 10(exp -15) g/square root of Hz, with g the standard gravity, for frequencies between 0.7 and 20 mHz. This value is lower than the LISA Pathfinder requirement by more than a factor 5 and within a factor 1.25 of the requirement for the LISA mission, and is compatible with Brownian noise from viscous damping due to the residual gas surrounding the test masses. Above 60 mHz the acceleration noise is dominated by interferometer displacement readout noise at a level of (34.8 +/- 0.3) fm square root of Hz, about 2 orders of magnitude better than requirements. At f less than or equal to 0.5 mHz we observe a low-frequency tail that stays below 12 fm s(exp -2)/square root of Hz down to 0.1 mHz. This performance would allow for a space-based gravitational wave observatory with a sensitivity close to what was originally foreseen for LISA.

Measurement noise 100 times lower than the quantum-projection limit using entangled atoms

Abstract: Quantum metrology uses quantum entanglement--correlations in the properties of microscopic systems--to improve the statistical precision of physical measurements. When measuring a signal, such as the phase shift of a light beam or an atomic state, a prominent limitation to achievable precision arises from the noise associated with the counting of uncorrelated probe particles. This noise, commonly referred to as shot noise or projection noise, gives rise to the standard quantum limit (SQL) to phase resolution. However, it can be mitigated down to the fundamental Heisenberg limit by entangling the probe particles. Despite considerable experimental progress in a variety of physical systems, a question that persists is whether these methods can achieve performance levels that compare favourably with optimized conventional (non-entangled) systems. Here we demonstrate an approach that achieves unprecedented levels of metrological improvement using half a million (87)Rb atoms in their 'clock' states. The ensemble is 20.1 ± 0.3 decibels (100-fold) spin-squeezed via an optical-cavity-based measurement. We directly resolve small microwave-induced rotations 18.5 ± 0.3 decibels (70-fold) beyond the SQL. The single-shot phase resolution of 147 microradians achieved by the apparatus is better than that achieved by the best engineered cold atom sensors despite lower atom numbers. We infer entanglement of more than 680 ± 35 particles in the atomic ensemble. Applications include atomic clocks, inertial sensors, and fundamental physics experiments such as tests of general relativity or searches for electron electric dipole moment. To this end, we demonstrate an atomic clock measurement with a quantum enhancement of 10.5 ± 0.3 decibels (11-fold), limited by the phase noise of our microwave source.

Ultralow-noise mode-locked fiber lasers and frequency combs: principles, status, and applications

Abstract: We review the most recent progress in ultralow-noise mode-locked fiber lasers and fiber-based frequency-comb sources. With the rapid progress in theory, measurement, and control of noise in passively mode-locked fiber lasers, we have reached the point where the residual carrier–envelope-offset phase jitter (when stabilized) and pulse timing jitter performance of such laser sources can be fully optimized to the unprecedented levels of attoseconds regime. In this paper, first, major principles in building such low-noise passively mode-locked fiber lasers are reviewed. We then define noise in mode-locked fiber lasers and present the basic theoretical and numerical framework for analyzing the noise in mode-locked fiber lasers. More detailed discussions on theory, measurement methods, state-of-the-art performances, and stabilization methods of intensity noise, timing jitter, and comb-line frequency noise follow. Finally, we overview today’s most representative applications of such ultralow-noise mode-locked fiber lasers and frequency-comb sources. As an already powerful tool for various high-precision applications, ultralow-noise mode-locked fiber lasers will keep finding more exciting applications in optical science and photonic technology in the coming years.

On Probabilistic Shaping of Quadrature Amplitude Modulation for the Nonlinear Fiber Channel

Abstract: Different aspects of probabilistic shaping for a multispan optical communication system are studied. First, a numerical analysis of the additive white Gaussian noise (AWGN) channel investigates the effect of using a small number of input probability mass functions (PMFs) for a range of signal-to-noise ratios (SNRs), instead of optimizing the constellation shaping for each SNR. It is shown that if a small penalty of at most 0.1 dB SNR to the full shaping gain is acceptable, just two shaped PMFs are required per quadrature amplitude modulation (QAM) over a large SNR range. For a multispan wavelength division multiplexing optical fiber system with 64QAM input, it is shown that just one PMF is required to achieve large gains over uniform input for distances from 1400 to 3000 km. Using recently developed theoretical models that extend the Gaussian noise (GN) model and full-field split-step simulations, we illustrate the ramifications of probabilistic shaping on the effective SNR after fiber propagation. Our results show that, for a fixed average optical launch power, a shaping gain is obtained for the noise contributions from fiber amplifiers and modulation-independent nonlinear interference (NLI), whereas shaping simultaneously causes a penalty as it leads to an increased NLI. However, this nonlinear shaping loss is found to have a relatively minor impact, and optimizing the shaped PMF with a modulation-dependent GN model confirms that the PMF found for AWGN is also a good choice for a multi-span fiber system.

Reduced Sensitivity to Charge Noise in Semiconductor Spin Qubits via Symmetric Operation.

Abstract: We demonstrate improved operation of exchange-coupled semiconductor quantum dots by substantially reducing the sensitivity of exchange operations to charge noise. The method involves biasing a double dot symmetrically between the charge-state anticrossings, where the derivative of the exchange energy with respect to gate voltages is minimized. Exchange remains highly tunable by adjusting the tunnel coupling. We find that this method reduces the dephasing effect of charge noise by more than a factor of 5 in comparison to operation near a charge-state anticrossing, increasing the number of observable exchange oscillations in our qubit by a similar factor. Performance also improves with exchange rate, favoring fast quantum operations.

Noise Suppression Using Symmetric Exchange Gates in Spin Qubits

Abstract: We demonstrate a substantial improvement in the spin-exchange gate using symmetric control instead of conventional detuning in GaAs spin qubits, up to a factor of six increase in the quality factor of the gate. For symmetric operation, nanosecond voltage pulses are applied to the barrier that controls the interdot potential between quantum dots, modulating the exchange interaction while maintaining symmetry between the dots. Excellent agreement is found with a model that separately includes electrical and nuclear noise sources for both detuning and symmetric gating schemes. Unlike exchange control via detuning, the decoherence of symmetric exchange rotations is dominated by rotation-axis fluctuations due to nuclear field noise rather than direct exchange noise.

A micrometre-sized heat engine operating between bacterial reservoirs

Abstract: Artificial microscale heat engines are prototypical models to explore the mechanisms of energy transduction in a fluctuation-dominated regime(1,2). The heat engines realized so far on this scale have operated between thermal reservoirs, such that stochastic thermodynamics provides a precise framework for quantifying their performance(3-6). It remains to be seen whether these concepts readily carry over to situations where the reservoirs are out of equilibrium(7), a scenario of particular importance to the functioning of synthetic(8,9) and biological(10) microscale engines and motors. Here, we experimentally realize a micrometre-sized active Stirling engine by periodically cycling a colloidal particle in a time-varying optical potential across bacterial baths characterized by different degrees of activity. We find that the displacement statistics of the trapped particle becomes increasingly non-Gaussian with activity and contributes substantially to the overall power output and the effciency. Remarkably, even for engines with the same energy input, differences in non-Gaussianity of reservoir noise results in distinct performances. At high activities, the effciency of our engines surpasses the equilibrium saturation limit of Stirling effciency, the maximum effciency of a Stirling engine where the ratio of cold to hot reservoir temperatures is vanishingly small. Our experiments provide fundamental insights into the functioning of micromotors and engines operating out of equilibrium.

Magnetless Microwave Circulators Based on Spatiotemporally Modulated Rings of Coupled Resonators

Abstract: Nonreciprocal components are ubiquitous in electronic and optical systems. To date, the use of magneto-optical materials has been the prevailing method to achieve nonreciprocity. However, magnetic-based devices are accompanied by several drawbacks, such as the requirement of bulky biasing devices and their incompatibility with semiconductor technology, which make their integration challenging. Recently, strong magnetless nonreciprocity was demonstrated in spatiotemporally modulated coupled-resonator networks as a result of an effective spin imparted to the structure by an RF signal. These structures can be easily integrated, and they potentially exhibit good power and noise performance, as any parametric device. Here, we develop an analytical theory for such devices, which allows determining the conditions for designing them with optimum characteristics, and present two designs based on lumped- and distributed-element circuits for applications at the very high-frequency and wireless-communications bands, respectively. The circulators exhibit large isolation and low insertion loss within reasonable modulation requirements. Furthermore, they can be realized with a modulation frequency substantially lower than the input frequency, significantly simplifying the design. Measurements for the lumped-element design are provided and show good agreement with theory and full-wave simulations. The nonlinear characteristics of the presented designs are also studied, and possible ways to reduce nonlinear distortion by increasing the static bias of the varactors or using advanced varactor topologies are explored.

Quantum phase magnification

Abstract: Quantum metrology exploits entangled states of particles to improve sensing precision beyond the limit achievable with uncorrelated particles. All previous methods required detection noise levels below this standard quantum limit to realize the benefits of the intrinsic sensitivity provided by these states. We experimentally demonstrate a widely applicable method for entanglement-enhanced measurements without low-noise detection. The method involves an intermediate quantum phase magnification step that eases implementation complexity. We used it to perform squeezed-state metrology 8 decibels below the standard quantum limit with a detection system that has a noise floor 10 decibels above the standard quantum limit.

Approaching the Heisenberg Limit without Single-Particle Detection.

Abstract: We propose an approach to quantum phase estimation that can attain precision near the Heisenberg limit without requiring single-particle-resolved state detection. We show that the "one-axis twisting" interaction, well known for generating spin squeezing in atomic ensembles, can also amplify the output signal of an entanglement-enhanced interferometer to facilitate readout. Applying this interaction-based readout to oversqueezed, non-Gaussian states yields a Heisenberg scaling in phase sensitivity, which persists in the presence of detection noise as large as the quantum projection noise of an unentangled ensemble. Even in dissipative implementations-e.g., employing light-mediated interactions in an optical cavity or Rydberg dressing-the method significantly relaxes the detection resolution required for spectroscopy beyond the standard quantum limit.

Dynamics and coherence resonance of tri-stable energy harvesting system

Abstract: To improve the efficiency of energy harvesting, this paper presents a tri-stable energy harvesting device, which can realize inter-well oscillation at low-frequency base excitation and obtain a high harvesting efficiency by tri-stable coherence resonance. First, the model of a magnetic coupling tri-stable piezoelectric energy harvester is established and the corresponding equations are derived. The formula for the magnetic repulsion force between three magnets is given. Then, the dynamic responses of a system subject to harmonic excitation and Gaussian white noise excitation are explored by a numerical method and validated by experiments. Compared with a bi-stable energy harvester, the threshold for inter-well oscillation to occur can be moved forward to the low frequency, and the tri-stable device can create a dense high output voltage and power at the low intensity of stochastic excitation. Results show that for a definite deterministic or stochastic excitation, the system can be optimally designed such that it increases the frequency bandwidth and achieves a high energy harvesting efficiency at coherence resonance.

Plasmonic Trace Sensing below the Photon Shot Noise Limit

Abstract: Plasmonic sensors are important detectors of biochemical trace compounds, but those that utilize optical readout are approaching their absolute limits of detection as defined by the Heisenberg uncertainty principle in both differential intensity and phase readout. However, the use of more general minimum uncertainty states in the form of squeezed light can push the noise floor in these sensors below the shot noise limit (SNL) in one analysis variable at the expense of another. Here, we demonstrate a quantum plasmonic sensor whose noise floor is reduced below the SNL in order to perform index of refraction measurements with sensitivities unobtainable with classical plasmonic sensors. The increased signal-to-noise ratio can result in faster detection of analyte concentrations that were previously lost in the noise. These benefits are the hallmarks of a sensor exploiting quantum readout fields in order to manipulate the limits of the Heisenberg uncertainty principle.

Reduced sensitivity to charge noise in semiconductor spin qubits via symmetric operation

Abstract: We demonstrate improved operation of exchange-coupled semiconductor quantum dots by substantially reducing the sensitivity of exchange operations to charge noise. The method involves biasing a double dot symmetrically between the charge-state anticrossings, where the derivative of the exchange energy with respect to gate voltages is minimized. Exchange remains highly tunable by adjusting the tunnel coupling. We find that this method reduces the dephasing effect of charge noise by more than a factor of 5 in comparison to operation near a charge-state anticrossing, increasing the number of observable exchange oscillations in our qubit by a similar factor. Performance also improves with exchange rate, favoring fast quantum operations.

Constructions and Noise Threshold of Hyperbolic Surface Codes

Abstract: We show how to obtain concrete constructions of homological quantum codes based on tilings of 2-D surfaces with constant negative curvature (hyperbolic surfaces). This construction results in 2-D quantum codes whose tradeoff of encoding rate versus protection is more favorable than for the surface code. These surface codes would require variable length connections between qubits, as determined by the hyperbolic geometry. We provide numerical estimates of the value of the noise threshold and logical error probability of these codes against independent $X$ or $Z$ noise, assuming noise-free error correction.

Low-noise kinetic inductance traveling-wave amplifier using three-wave mixing

Abstract: We have fabricated a wide-bandwidth, high dynamic range, low-noise cryogenic amplifier based on a superconducting kinetic inductance traveling-wave device. The device was made from NbTiN and consisted of a long, coplanar waveguide on a silicon chip. By adding a DC current and an RF pump tone, we are able to generate parametric amplification using three-wave mixing (3WM). The devices exhibit gain of more than 15 dB across an instantaneous bandwidth from 4 to 8 GHz. The total usable gain bandwidth, including both sides of the signal-idler gain region, is more than 6 GHz. The noise referred to the input of the devices approaches the quantum limit, with less than 1 photon excess noise. We compare these results directly to the four-wave mixing amplification mode, i.e., without DC-biasing. We find that the 3WM mode allows operation with the pump at lower RF power and at frequencies far from the signal. We have used this knowledge to redesign the amplifiers to utilize primarily 3WM amplification, thereby allowing for direct integration into large scale qubit and detector applications.

Implementation of a quantum cubic gate by an adaptive non-Gaussian measurement

Abstract: We present a concept of non-Gaussian measurement composed of a non-Gaussian ancillary state, linear optics, and adaptive heterodyne measurement, and on the basis of this we also propose a simple scheme of implementing a quantum cubic gate on a traveling light beam. In analysis of the cubic gate in the Heisenberg representation, we find that nonlinearity of the gate is independent from nonclassicality; the nonlinearity is generated solely by a classical nonlinear adaptive control in a measurement-and-feedforward process, while the nonclassicality is attached by the non-Gaussian ancilla that suppresses excess noise in the output. By exploiting the noise term as a figure of merit, we consider the optimum non-Gaussian ancilla that can be prepared within reach of current technologies and discuss performance of the gate. It is a crucial step towards experimental implementation of the quantum cubic gate.

Comparison of low frequency charge noise in identically patterned Si/SiO2 and Si/SiGe quantum dots

Abstract: We investigate and compare the charge noise in Si/SiO2 and Si/SiGe gate defined quantum dots with identically patterned gates by measuring the low frequency 1/f current noise through the biased quantum dots in the coulomb blockade regime. The current noise is normalized and used to extract a measurement of the potential energy noise in the system. Additionally, the temperature dependence of this noise is investigated. The measured charge noise in Si/SiO2 compares favorably with that of the SiGe device as well as previous measurements made on other substrates suggesting Si/SiO2 is a potential candidate for spin based quantum computing.

Quantized conductance coincides with state instability and excess noise in tantalum oxide memristors

Abstract: Tantalum oxide memristors can switch continuously from a low-conductance semiconducting to a high-conductance metallic state. At the boundary between these two regimes are quantized conductance states, which indicate the formation of a point contact within the oxide characterized by multistable conductance fluctuations and enlarged electronic noise. Here, we observe diverse conductance-dependent noise spectra, including a transition from 1/f(2) (activated transport) to 1/f (flicker noise) as a function of the frequency f, and a large peak in the noise amplitude at the conductance quantum GQ=2e(2)/h, in contrast to suppressed noise at the conductance quantum observed in other systems. We model the stochastic behaviour near the point contact regime using Molecular Dynamics-Langevin simulations and understand the observed frequency-dependent noise behaviour in terms of thermally activated atomic-scale fluctuations that make and break a quantum conductance channel. These results provide insights into switching mechanisms and guidance to device operating ranges for different applications.

Force sensing based on coherent quantum noise cancellation in a hybrid optomechanical cavity with squeezed-vacuum injection

Abstract: We propose and analyse a feasible experimental scheme for a quantum force sensor based on the elimination of backaction noise through coherent quantum noise cancellation (CQNC) in a hybrid atom-cavity optomechanical setup assisted with squeezed vacuum injection. The force detector, which allows for a continuous, broadband detection of weak forces well below the standard quantum limit (SQL), is formed by a single optical cavity simultaneously coupled to a mechanical oscillator and to an ensemble of ultracold atoms. The latter acts as a negative-mass oscillator so that atomic noise exactly cancels the backaction noise from the mechanical oscillator due to destructive quantum interference. Squeezed vacuum injection enforces this cancellation and allows sub-SQL sensitivity to be reached in a very wide frequency band, and at much lower input laser powers.

Low frequency gravitational wave detection with ground-based atom interferometer arrays

Abstract: We propose a new detection strategy for gravitational waves (GWs) below few Hertz based on a correlated array of atom interferometers (AIs). Our proposal allows to reject the Newtonian Noise (NN) which limits all ground based GW detectors below few Hertz, including previous atom interferometry-based concepts. Using an array of long baseline AI gradiometers yields several estimations of the NN, whose effect can thus be reduced via statistical averaging. Considering the km baseline of current optical detectors, a NN rejection of factor 2 could be achieved, and tested with existing AI array geometries. Exploiting the correlation properties of the gravity acceleration noise, we show that a 10-fold or more NN rejection is possible with a dedicated configuration. Considering a conservative NN model and the current developments in cold atom technology, we show that strain sensitivities below $1\times 10^{-19}/\sqrt{Hz}$ in the $ 0.3-3 \ Hz$ frequency band can be within reach, with a peak sensitivity of $3\times 10^{-23} /\sqrt{Hz}$ at $2 \ Hz$. Our proposed configuration could extend the observation window of current detectors by a decade and fill the gap between ground-based and space-based instruments.

The Switch in a Genetic Toggle System with Lévy Noise.

Abstract: A bistable toggle switch is a paradigmatic model in the field of biology. The dynamics of the system induced by Gaussian noise has been intensively investigated, but Gaussian noise cannot incorporate large bursts typically occurring in real experiments. This paper aims to examine effects of variations from one protein imposed by a non-Gaussian Levy noise, which is able to describe even large jumps, on the coherent switch and the on/off switch via the steady-state probability density, the joint steady-state probability density, and the mean first passage time. We find that a large burst of one protein due to the Levy noises can induce coherent switches even with small noise intensities in contrast to the Gaussian case which requires large intensities for this. The influences of the stability index, skewness parameter and noise intensity on the on/off switch are analyzed, leading to an adjustment of the concentrations of both proteins and a decision which stable point to stay most. The mean first passage times show complex effects under Levy noise, especially the stability index and skewness parameter. Our results also imply that the presence of non-Gaussian Levy noises has fundamentally changed the escape mechanism in such a system compared with Gaussian noise.

Systematic biases in low-frequency radio interferometric data due to calibration: the LOFAR-EoR case

Abstract: The redshifted 21 cm line of neutral hydrogen is a promising probe of the epoch of reionization (EoR). However, its detection requires a thorough understanding and control of the systematic errors. We study two systematic biases observed in the Low-Frequency Array-EoR residual data after calibration and subtraction of bright discrete foreground sources. The first effect is a suppression in the diffuse foregrounds, which could potentially mean a suppression of the 21 cm signal. The second effect is an excess of noise beyond the thermal noise. The excess noise shows fluctuations on small frequency scales, and hence it cannot be easily removed by foreground removal or avoidance methods. Our analysis suggests that sidelobes of residual sources due to the chromatic point spread function (PSF) and ionospheric scintillation cannot be the dominant causes of the excess noise. Rather, both the suppression of diffuse foregrounds and the excess noise can occur due to calibration with an incomplete sky model containing predominantly bright discrete sources. The levels of the suppression and excess noise depend on the relative flux of sources which are not included in the model with respect to the flux of modelled sources. We predict that the excess noise will reduce with more observation time in the same way as the thermal noise does. We also discuss possible solutions such as using only long baselines to calibrate the interferometric gain solutions as well as simultaneous multifrequency calibration along with their benefits and shortcomings.

Long-Range Distributed Vibration Sensing Based on Phase Extraction From Phase-Sensitive OTDR

Abstract: Distributed fiber-optic vibration sensors based on phase-sensitive optical time-domain reflectometry ( $\phi$ -OTDR) have found many applications in various fields. In this paper, we analyze the phase noise of $\phi$ -OTDR, which is the main limiting factor of the measurement range. We found that the laser phase noise and phase extraction error caused by the intensity noise in photodetection contribute to the total phase noise. By introducing a series of auxiliary weak reflection points along the fiber, we develop a phase-noise-compensated $\phi$ -OTDR and realize a long-range distributed vibration sensing based on the phase extraction. Furthermore, a statistical analysis was proposed to maintain the vibration measurement sensitivity along the whole fiber. In the experiment, vibrations at 30 km were measured with a linear response, which confirmed the validity of our proposed system.

Linear Massive MIMO Precoders in the Presence of Phase Noise—A Large-Scale Analysis

Abstract: We study the impact of phase noise on the downlink performance of a multiuser multiple-input–multiple-output (MIMO) system, where the base station (BS) employs a large number of transmit antennas $M$ . We consider a setup where the BS employs $M_{\mathrm{osc}}$ free-running oscillators, and $M/M_{\mathrm{osc}}$ antennas are connected to each oscillator. For this configuration, we analyze the impact of phase noise on the performance of zero forcing (ZF), regularized ZF, and matched filter precoders when $M$ and the number of users $K$ are asymptotically large, whereas the ratio $M/K=\beta$ is fixed. We analytically show that the impact of phase noise on the signal-to-interference-plus-noise ratio (SINR) can be quantified as an effective reduction in the quality of the channel state information (CSI) available at the BS when compared with a system without phase noise. As a consequence, we observe that as $M_{\mathrm{osc}}$ increases, the SINR performance of all considered precoders degrades. On the other hand, the variance of the random phase variations caused by the BS oscillators reduces with increasing $M_{\mathrm{osc}}$ . Through Monte Carlo simulations, we verify our analytical results and compare the performance of the precoders for different phase noise and channel noise variances. For all considered precoders, we show that when $\beta$ is small, the performance of the setup where all BS antennas are connected to a single oscillator is superior to that of the setup where each BS antenna has its own oscillator. However, the opposite is true when $\beta$ is large and the signal-to-noise ratio (SNR) at the users is low.

A global view of velocity fluctuations in the corona below 1.3r⊙ with comp

Abstract: The Coronal Multi-channel Polarimeter (CoMP) has previously demonstrated the presence of Doppler velocity fluctuations in the solar corona. The observed fluctuations are thought to be transverse waves, i.e., highly incompressible motions whose restoring force is dominated by the magnetic tension, some of which demonstrate clear periodicity. We aim to exploit CoMP’s ability to provide high cadence observations of the off-limb corona to investigate the properties of velocity fluctuations in a range of coronal features, providing insight into how (whether) the properties of the waves are influenced by the varying magnetic topology in active regions, quiet Sun and open field regions. An analysis of Doppler velocity time-series of the solar corona from the 10747 A Iron XIII line is performed, determining the velocity power spectrum and using it as a tool to probe wave behavior. Further, the average phase speed and density for each region are estimated and used to compute the spectra for energy density and energy flux. In addition, we assess the noise levels associated with the CoMP data, deriving analytic formulae for the uncertainty on Doppler velocity measurements and providing a comparison by estimating the noise from the data. It is found that the entire corona is replete with transverse wave behavior. The corresponding power spectra indicate that the observed velocity fluctuations are predominately generated by stochastic processes,with the spectral slope of the power varying between the different magnetic regions. Most strikingly, all power spectra reveal the presence of enhanced power occurring at ∼3 mHz, potentially implying that the excitation of coronal transverse waves by p-modes is a global phenomenon.

Squeezed states of light and their applications in laser interferometers

Abstract: According to quantum theory the interactions between physical systems are quantized. As a direct consequence, measurement sensitivities are fundamentally limited by quantization noise, or just `quantum noise' in short. Furthermore, Heisenberg's Uncertainty Principle demands measurement back-action for some observables of a system if they are measured repeatedly. In both respects, squeezed states are of high interest since they show a `squeezed' uncertainty, which can be used to improve the sensitivity of measurement devices beyond the usual quantum noise limits including those impacted by quantum back-action noise. Squeezed states of light can be produced with nonlinear optics, and a large variety of proof-of-principle experiments were performed in past decades. As an actual application, squeezed light has now been used for several years to improve the measurement sensitivity of GEO600 -- a laser interferometer built for the detection of gravitational waves. Given this success, squeezed light is likely to significantly contribute to the new field of gravitational-wave astronomy. This Review revisits the concept of squeezed states and two-mode squeezed states of light, with a focus on experimental observations. The distinct properties of squeezed states displayed in quadrature phase-space as well as in the photon number representation are described. The role of the light's quantum noise in laser interferometers is summarized and the actual application of squeezed states in these measurement devices is reviewed.

Allan Deviation Plot as a Tool for Quartz-Enhanced Photoacoustic Sensors Noise Analysis

Abstract: We report here on the use of the Allan deviation plot to analyze the long-term stability of a quartz-enhanced photoacoustic (QEPAS) gas sensor. The Allan plot provides information about the optimum averaging time for the QEPAS signal and allows the prediction of its ultimate detection limit. The Allan deviation can also be used to determine the main sources of noise coming from the individual components of the sensor. Quartz tuning fork thermal noise dominates for integration times up to 275 s, whereas at longer averaging times, the main contribution to the sensor noise originates from laser power instabilities.

Signal Detection In Non Gaussian Noise

Abstract: A solution to get the problem off, have you found it? Really? What kind of solution do you resolve the problem? From what sources? Well, there are so many questions that we utter every day. No matter how you will get the solution, it will mean better. You can take the reference from some books. And the signal detection in non gaussian noise is one book that we really recommend you to read, to get more solutions in solving this problem.

Noise performance of low-dose CT: comparison between an energy integrating detector and a photon counting detector using a whole-body research photon counting CT scanner.

Abstract: Photon counting detector (PCD)-based computed tomography (CT) is an emerging imaging technique. Compared to conventional energy integrating detector (EID)-based CT, PCD-CT is able to exclude electronic noise that may severely impair image quality at low photon counts. This work focused on comparing the noise performance at low doses between the PCD and EID subsystems of a whole-body research PCD-CT scanner, both qualitatively and quantitatively. An anthropomorphic thorax phantom was scanned, and images of the shoulder portion were reconstructed. The images were visually and quantitatively compared between the two subsystems in terms of streak artifacts, an indicator of the impact of electronic noise. Furthermore, a torso-shaped water phantom was scanned using a range of tube currents. The product of the noise and the square root of the tube current was calculated, normalized, and compared between the EID and PCD subsystems. Visual assessment of the thorax phantom showed that electronic noise had a noticeably stronger degrading impact in the EID images than in the PCD images. The quantitative results indicated that in low-dose situations, electronic noise had a noticeable impact (up to a 5.8% increase in magnitude relative to quantum noise) on the EID images, but negligible impact on the PCD images.

Stochastic resonance subject to multiplicative and additive noise: The influence of potential asymmetries

Abstract: The influence of potential asymmetries on stochastic resonance (SR) subject to both multiplicative and additive noise is studied by using two-state theory, where three types of asymmetries are introduced in double-well potential by varying the depth, the width, and both the depth and the width of the left well alone. The characteristics of SR in the asymmetric cases are different from symmetric ones, where asymmetry has a strong influence on output signal-to-noise ratio (SNR) and optimal noise intensity. Even optimal noise intensity is also associated with the steepness of the potential-barrier wall, which is generally ignored. Moreover, the largest SNR in asymmetric SR is found to be relatively larger than the symmetric one, which also closely depends on noise intensity ratio. In addition, a moderate cross-correlation intensity between two noises is good for improving the output SNR. More interestingly, a double SR phenomenon is observed in certain cases for two correlated noises, whereas it disappears for two independent noises. The above clues are helpful in achieving weak signal detection under heavy background noise.