Homodyne-like detection for state-discrimination in the presence of phase noise

We propose an innovative strategy to discriminate between two coherent states affected by either uniform or gaussian phase noise. The strategy is based on a homodyne-like detection scheme with photon-number-resolving detectors in the regime of low-intensity local oscillator. The experimental implementation of the detection scheme involves two hybrid photodetectors, whose outputs are used in post processing to calculate the shot-by-shot photon-number difference. The performance of this strategy is quantified in terms of the error probability in discriminating the noisy coherent signals as a function of the characteristic noise parameters.Comment: 5 pages, 5 figure

Photon-number correlations by photon-number resolving detectors

We demonstrate that by using a pair of photodetectors endowed with internal gain we are able to quantify the correlation coefficient between the two components of a pulsed bipartite state in the mesoscopic intensity regime (less than 100 mean photons)

Subjetividades, lo político y la política : derivas de una discusión teórica

En el trabajo que sigue me propongo poner en tensión una serie de discusiones teóricas en torno a lo que cada una de ellas entiende por procesos de subjetivación, en clave social y política. Para ello, organizo la escritura en dos secciones. La primera discutirá los procesos de construcción subjetiva desde la propuesta de Slavoj Zizek, a partir de su diálogo desde el psicoanálisis lacaniano, pensando sus aportes sobre el renovado lugar del sujeto en el marco del postestructuralismo. En un segundo momento, por otra parte, avanzaré sobre las propuestas de Judith Butler y Ernesto Laclau tomando como contrapunto a Jacques Ranciére, con la idea de resituar el énfasis en torno al proceso de subjetivación como apuesta política. El objetivo principal que persigo con esta lectura crítica consiste en reflexionar, por un lado, sobre el carácter estrictamente político que algunos autores otorgan al proceso de constitución subjetiva misma, mientras que, además, me interesan las posibles divergencias entre quienes examinan dicho proceso en un marco más amplio y complejo de constitución de lo social. El punto de partida de estas reflexiones se encuentra en la diferenciación que una miríada de autores comprometidos con una mirada posfundacional han propuesto entre lo político y la política, pensando el lugar del sujeto en esa arena.In the paper that follows, I propose myself to tense a series of theoretical discussions on what each one of them understand by subjetification processes, in a social and political key. With that purpose in mind, I organize the writing into two sections. The first one will discuss the processes of subjective setting-up from the perspective of Slavoj Zizek taking his dialogue with the lacanian psychoanalysis, thinking on its approaches on the renewed spot of the subject in the postestructuralist frame. In a second moment, I will continue with the proposals of Judith Butler and Ernesto Laclau, taking Jacques Rancière as a counterpoint with the aim of resituate the point on the subjetification process as a political commitment. The main goal I am pursuing with this critique relies on reflecting, on the one hand, on the strictly political character that some authors give to the subjetive constitution process itself, while, on the other hand, I am interested on the possible divergences on those that examine the process in a mayor and more complex frame, related to the constitution of the social. The starting point of this reflections is found on the differences that a myriad of authors compromised with a posfundacional view have proposed between the political and the politics, and on the spot of the subject on that arena

Experimental quantification of non-Gaussianity of phase-randomized coherent states

We present the experimental investigation of the non-Gaussian nature of some mixtures of Fock states by reconstructing their Wigner function and exploiting two recently introduced measures of non-Gaussianity. In particular, we demonstrate the consistency between the different approaches and the monotonicity of the two measures for states belonging to the class of phase randomized coherent states. Moreover, we prove that the exact behavior of one measure with respect to the other depends on the states under investigation and devise possible criteria to discriminate which measure is more useful for the characterization of the states in realistic applications.Comment: 9 pages, 4 figure

Gaussian and Non-Gaussian operations on non-Gaussian state: engineering non-Gaussianity

Multiple photon subtraction applied to a displaced phase-averaged coherent state, which is a non-Gaussian classical state, produces conditional states with a non trivial (positive) Glauber-Sudarshan $P$-representation. We theoretically and experimentally demonstrate that, despite its simplicity, this class of conditional states cannot be fully characterized by direct detection of photon numbers. In particular, the non-Gaussianity of the state is a characteristics that must be assessed by phase-sensitive measurements. We also show that the non-Gaussianity of conditional states can be manipulated by choosing suitable conditioning values and composition of phase-averaged states

Spatial properties of twin-beam correlations at low- to high-intensity transition

It is shown that spatial correlation functions measured for correlated photon pairs at the single-photon level correspond to speckle patterns visible at high intensities. This correspondence is observed for the first time in one experimental setup by using different acquisition modes of an intensified CCD camera in low and high intensity regimes. The behavior of intensity auto- and cross-correlation functions in dependence on pump-beam parameters including power and transverse profile is investigated.Comment: 6 pages, 4 figures, accepted for publication in Optics Expres

Self-consistent characterization of light statistics

We demonstrate the possibility of a self-consistent characterization of the photon-number statistics of a light field by using photoemissive detectors with internal gain simply endowed with linear input/output responses. The method can be applied to both microscopic and mesoscopic photon-number regimes. The detectors must operate in the linear range without need of photon-counting capabilities.Comment: To be published in "Journal of Modern Optics

Absolute calibration of photon-number-resolving detectors with an analog output using twin beams

A method for absolute calibration of a photon-number resolving detector producing analog signals as the output is developed using a twin beam. The method gives both analog-to-digital conversion parameters and quantum detection efficiency for the photon fields. Characteristics of the used twin beam are also obtained. A simplified variant of the method applicable to fields with high signal to noise ratios and suitable for more intense twin beams is suggested.Comment: 4 pages, 3 figure