Quantum interference of spontaneous decays: noise reduction in V lasers without inversion

For a four-level double-V laser without inversion we show that the interference of spontaneous decays leads to intensity noise squeezing. The optimum amount of noise reduction is 50%, which is the maximum squeezing in a resonant three-level inversionless Λ-laser with coherent driving and a resonant three-level Raman laser. By transforming into a combination state basis, the Mandel parameter and the output fluctuation spectrum are calculated and the mechanism is interpreted.     

Quantum atomic-fluctuations reduction and squeezed-state generation via forward degenerate four-wave mixing

It is shown that correlation of quantum atomic fluctuations for coupled modes at forward degenerate four-wave mixing leads to atomic noise reduction from the in-phase quadrature variance of the mode which is a linear combination of the coupled signal and probe modes. Thus, quantum atomic fluctuations are not an obstacle for the squeezed-state generation via degenerate four-wave mixing.     

Intensity and frequency noise reduction of a Nd:YAG NPRO via pump light stabilisation

We have shown that pump light intensity stabilisation of a single-mode laser diode pumped Nd:YAG non-planar ring oscillator (NPRO) results in significant intensity noise reduction of the NPRO, as well as frequency noise suppression in the same order of magnitude. This effect does not occur in conventional laser diode array pumped NPROs due to mode beating effects originating in the multi-mode pump. As opposed to individual intensity and frequency stabilisation, pump light stabilisation contributes a simplified stabilisation scheme for single-mode laser diode pumped NPROs for high precision applications. PACS 42.55.Xi; 42.60.By; 42.60.Lh     

High-Lying Vibrational Spectrum of Ammonia via Nonlinear Quantum Theory

We introduce a simple three-parameter model in nonlinear quantum theory-the discrete self-trapping equation to describe the stretching spectrum of ammonia at highlying vibrational states. The model calculations appear to describe the data well. These results obtained are conducive to researching the quantum chaotic manner and the multiphoton processes and isotope separation by multiphoton dissociation of ammonia molecular system.     

Effect of Gaussian references on cross-talk noise reduction in volume holographic memory

We propose and analyze a novel recording and reading scheme for cross-talk noise reduction in volume holographic data storage. Each hologram is recorded with a slightly focused Gaussian reference beam and can be read out by use of the same Gaussian reference. The waist of the reference Gaussian profile can be adjusted based on the required signal-noise ratio and the storage density. Simulation results show the reduced cross-talk noise yielded by the proposed scheme.     

The Quantum R-Matrix via Canonical Quantization in the Liouville Theory

Starting from the classical Liouville theory, we study its quantum theory through canonical quantization. We find that if the Poisson bracket relations between two vectors are,dominated by the classical r-matrix in the classical case, their quantum analogue is replaced by the exchange relations dominated by the quantum R-matrix. The quantum group structure in the quantum LiouviUe theory is studied and the central charge of the quantum Liouville theory is also obtained.     

Alien calculus and non perturbative effects in Quantum Field Theory

In many domains of physics, methods for dealing with non-perturbative aspects are required. Here, I want to argue that a good approach for this is to work on the Borel transforms of the quantities of interest, the singularities of which give non-perturbative contributions. These singularities in many cases can be largely determined by using the alien calculus developed by Jean Écalle. My main example will be the two point function of a massless theory given as a solution of a renormalization group equation.     

Quantum shot noise of conductors and general noise measurement methods

We review the quantum noise properties of phase coherent conductors, in particular the spectacular noise suppression associated with conductance quantization. We describe general techniques used to measure the tiny quantum shot noise current fluctuations at sub-kelvin temperature for low and high frequency.     

Vowel recognition via cochlear implants and noise vocoders: effects of formant movement and duration

Previous work has demonstrated that normal-hearing individuals use fine-grained phonetic variation, such as formant movement and duration, when recognizing English vowels. The present study investigated whether these cues are used by adult postlingually deafened cochlear implant users, and normal-hearing individuals listening to noise-vocoder simulations of cochlear implant processing. In Experiment 1, subjects gave forced-choice identification judgments for recordings of vowels that were signal processed to remove formant movement and/or equate vowel duration. In Experiment 2, a goodness-optimization procedure was used to create perceptual vowel space maps (i.e., best exemplars within a vowel quadrilateral) that included F1, F2, formant movement, and duration. The results demonstrated that both cochlear implant users and normal-hearing individuals use formant movement and duration cues when recognizing English vowels. Moreover, both listener groups used these cues to the same extent, suggesting that postlingually deafened cochlear implant users have category representations for vowels that are similar to those of normal-hearing individuals.     

Quantum effects for parametric X-ray radiation during channeling: Theory and first experimental observation

The theory of X-ray radiation from relativistic channeled electrons at the Bragg angles—parametric X-ray radiation (PXR) during channeling (PXRC)—is developed while accounting for two quantum effects: the initial population of bound states of transverse motion and the transverse “form-factor” of channeled electrons. An experiment was conducted using a 255 MeV electron beam from a linac at the SAGA Light Source. We have identified a difference in the angular distributions of PXR and PXRC and obtained a fairly good agreement between the theoretical and experimental results.     

External non-white noise: Theory and experiment

We consider a system under the influence of an external gaussian noise with a flat spectrum and finite cut-off frequency. The stationery properties of the system are studied as a function of the correlation time of the noise. Theoretical predictions based on an expansion in powers of the correlation time are corroborated by experimental measurements on an electric circuit with a digital noise generator. The two main qualitative properties experimentally observed which can not be explained in a white noise limit theory are: (i) appearance of relative extrema of the stationery distribution for high noise intensity when the correlation time is not too small; (ii) dependence on the noise characteristics of the position of the maximum of the stationary distribution for low noise intensity.     

On spurious and corrupted multifractality: The effects of additive noise, short-term memory and periodic trends

We study the performance of multifractal detrended fluctuation analysis (MF-DFA) applied to long-term correlated and multifractal data records in the presence of additive white noise, short-term memory and periodicities. Such additions and disturbances that can be typically found in the observational records of various complex systems ranging from climate dynamics to physiology, network traffic, and finance. In monofractal records, we find that (i) additive white noise hardly results in spurious multifractality, but causes underestimated generalized Hurst exponents h(q) for all q values; (ii) short-range correlations lead to pronounced crossovers in the generalized fluctuation functions F_q(s) at positions that decrease with increasing moment q, thus causing significantly overestimated h(q) for small q and spurious multifractality; (iii) periodicities like seasonal trends (with standard deviations comparable with the one of the studied process) result in spurious “reversed” multifractality where h(q) increases with increasing q (except for very short time windows). We also show that in multifractal cascades moderate additions of noise, short-range memory, or periodic trends cause flawed results for h(q) with q<2, while h(q) with q>2 remains nearly unchanged.     

Quantum noise of modulation and squeezed states

The reduction of the amount of quantum noise in modulation experiments by the use of two-mode squeezed states is discussed. It is shown that by the use of squeezed radiation instead of coherent radiation, the amount of quantum noise at the modulated frequency can be reduced by many orders of magnitude.