Excess optical quantum noise in atomic sensors

Enhanced nonlinear optical response of a coherent atomic medium is the basis for many atomic sensors, and their performance is ultimately limited by the quantum fluctuations of the optical readout. Here we demonstrate that the off-resonant interactions, with the aid of the near-resonant process, can significantly modify the quantum noise of a coherent light field, even when its effect on the mean signal is negligible. The altered quantum optical noise distribution results in excess noise in the measurement quantity. We illustrate this concept by using an atomic magnetometer based on the nonlinear Faraday effect. These results show the existence of previously unnoticed factors in fundamental limitations in atomic magnetometry and could have impact in a wide range of atom-light-based precision measurements

Metáfora y fraseología. Estudio tipológico contrastivo entre el chino y el español

En este trabajo se realiza un análisis contrastivo de los mecanismos semánticos metafóricos que funcionan en las unidades fraseológicas del chino y del español, y también se muestra la clasificación tipológica de las metáforas presentes en dichas unidades con objeto de hallar una sistematicidad en los procedimientos productores de las fraseologías y de las metáforas.In this work we carry out a contrastive analysis about metaphoric semantic mechanisms which work in the Chinese and Spanish phraseology. Also we show the typological classification of the metaphors which are present in the phraseological unities, in order to find a systematic order in the producing process of phraseologies and metaphors

Coherence assisted resonance with sub-lifetime-limited linewidth

We demonstrate a novel approach to obtain resonance linewidth below that limited by coherence lifetime. Cross correlation between induced intensity modulation of two lasers coupling the target resonance exhibits a narrow spectrum. 1/30 of the lifetime-limited width was achieved in a proof-of-principle experiment where two ground states are the target resonance levels. Attainable linewidth is only limited by laser shot noise in principle. Experimental results agree with an intuitive analytical model and numerical calculations qualitatively. This technique can be easily implemented and should be applicable to many atomic, molecular and solid state spin systems for spectroscopy, metrology and resonance based sensing and imaging.Comment: 5 pages 5 figure

Two-axis-twisting spin squeezing by multi-pass quantum erasure

Many-body entangled states are key elements in quantum information science and quantum metrology. One important problem in establishing a high degree of many-body entanglement using optical techniques is the leakage of the system information via the light that creates such entanglement. We propose an all-optical interference-based approach to erase this information. Unwanted atom-light entanglement can be removed by destructive interference of three or more successive atom-light interactions, with only the desired effective atom-atom interaction left. This quantum erasure protocol allows implementation of Heisenberg-limited spin squeezing using coherent light and a cold or warm atomic ensemble. Calculations show that significant improvement in the squeezing exceeding 10 dB is obtained compared to previous methods, and substantial spin squeezing is attainable even under moderate experimental conditions. Our method enables the efficient creation of many-body entangled states with simple setups, and thus is promising for advancing technologies in quantum metrology and quantum information processing.Comment: 10 pages, 4 figures. We have improved the presentation and added a new section, in which we have generalized the scheme from a three-pass scheme to multi-pass schem

Metáfora y fraseología. Estudio tipológico contrastivo entre el chino y el español

En este trabajo se realiza un análisis contrastivo de los mecanismos semánticos metafóricos que funcionan en las unidades fraseológicas del chino y del español, y también se muestra la clasificación tipológica de las metáforas presentes en dichas unidades con objeto de hallar una sistematicidad en los procedimientos productores de las fraseologías y de las metáforas.In this work we carry out a contrastive analysis about metaphoric semantic mechanisms which work in the Chinese and Spanish phraseology. Also we show the typological classification of the metaphors which are present in the phraseological unities, in order to find a systematic order in the producing process of phraseologies and metaphors