arXiv subjects

Julien Laurat

Publications and source records attributed to Julien Laurat.

43 records · Page 3Linked to original sources

arXiv2004

Experimental Generation of Large Quadrature EPR Entanglement with a Self-Phase-Locked Type II OPO Below Threshold

We study theoretically and experimentally the quantum properties of a type II frequency degenerate optical parametric oscillator below threshold with a quarter-wave plate inserted inside the cavity which induces a linear coupling between the orthogonally polarized signal and idler fields. This original device provides a good insight into general properties of two-mode gaussian states, illustrated in terms of covariance matrix. We report on the experimental generation of two-mode squeezed vacuum on non-orthogonal quadratures depending on the plate angle. After a simple operation, the entanglement is maximized and put into standard form, \textit{i.e.} quantum correlations and anti-correlations on orthogonal quadratures. A half-sum of squeezed variances as low as $0.33 \pm 0.02$, well below the unit limit for inseparability, is obtained and the entanglement measured by the entropy of formation.

quant-ph↗

arXiv2004

Experimental evidence of spontaneous symmetry breaking in intracavity type-II second harmonic generation with triple resonance

We describe an experiment showing a spontaneous symmetry breaking phenomenon between the intensities of the ordinary and extraordinary components of the fundamental field in intracavity type-II harmonic generation. It is based on a triply resonant dual cavity containing a type II phase matched $χ^{(2)}$ crystal pumped at the fundamental frequency $ω_0$. The pump beam generates in the cavity a second harmonic mode at frequency $2ω_0$ which acts as a pump for frequency degenerate type II parametric down conversion. Under operating conditions which are precisely symmetric with respect to the ordinary and extraordinary components of the fundamental wave, we have observed a breaking of the symmetry on the intensities of these two waves in agreement with the theoretical predictions.

physics.optics↗

arXiv2004

Non-linear and quantum optics of a type II OPO containing a birefringent element Part 1: Classical operation

We describe theoretically the main characteristics of the steady state regime of a type II Optical Parametric Oscillator (OPO) containing a birefringent plate. In such a device the signal and idler waves are at the same time linearly coupled by the plate and nonlinearly coupled by the $χ^{(2)}$ crystal. This mixed coupling allows, in some well-defined range of the control parameters, a frequency degenerate operation as well as phase locking between the signal and idler modes. We describe here a complete model taking into account all possible effects in the system, \emph{i.e.} arbitrary rotation of the waveplate, non perfect phase matching, ring and linear cavities. This model is able to explain the detailed features of the experiments performed with this system.

quant-ph↗

arXiv2004

Non-linear and quantum optics of a type II OPO containing a birefringent element Part 2 : bright entangled beams generation

We describe theoretically the quantum properties of atype-II Optical Parametric Oscillator containing a birefringent plate which induces a linear coupling between the orthogonally polarized signal and idler beams and results in phase locking between these two beams. As in a classical OPO, the signal and idler waves show large quantum correlations which can be measured experimentally due to the phase locking between the two beams. We study the influence of the waveplate on the various criteria characterizing quantum correlations. We show in particular that the quantum correlations can be maximized by using optimized quadratures.

quant-ph↗

arXiv2004

Compact Source of EPR Entanglement and Squeezing at Very Low Noise Frequencies

We report on the experimental demonstration of strong quadrature EPR entanglement and squeezing at very low noise sideband frequencies produced by a single type-II, self-phase-locked, frequency degenerate optical parametric oscillator below threshold. The generated two-mode squeezed vacuum state is preserved for noise frequencies as low as 50 kHz. Designing simple setups able to generate non-classical states of light in the kHz regime is a key challenge for high sensitivity detection of ultra-weak physical effects such as gravitational wave or small beam displacement.

quant-ph↗

arXiv2003

Conditional preparation of a non-classical state in the continuous variable regime: theoretical study

We study the characteristics of the quantum state of light produced by a conditional preparation protocol totally performed in the continuous variable regime. It relies on conditional measurements on quantum intensity correlated bright twin beams emitted by a non-degenerate OPO above threshold. Analytical expressions as well as computer simulations of the selected state properties and preparation efficiency are developed and show that a sub-Poissonian state can be produced by this technique. Projection onto a given trigger value is studied and then extended to a finite band. The continuous variable regime offers the unique possibility to improve dramatically the preparation efficiency by choosing multiple selection bands and thus to generate a great number of sub-Poissonian states in parallel.

quant-ph↗

arXiv2003

Conditional preparation of a quantum state in the continuous variable regime: generation of a sub-Poissonian state from twin beams

We report the first experimental demonstration of conditional preparation of a non classical state of light in the continuous variable regime. Starting from a non degenerate OPO which generates above threshold quantum intensity correlated signal and idler "twin beams", we keep the recorded values of the signal intensity only when the idler falls inside a band of values narrower than its standard deviation. By this very simple technique, we generate a sub-Poissonian state 4.4dB below shot noise from twin beams exhibiting 7.5dB of noise reduction in the intensity difference.

quant-ph↗