Optical experiments have demonstrated cases in which mirror symmetry in stable atoms is broken during the absorption or emission of light. Such results, which are in conflict with quantum electrodynamics, support the theory of unification of the electromagnetic and weak interactions. The interpretation of the experimental results is based on exchanges of weak neutral bosons between the electrons and the nucleus of the atom. A concise review of these phenomena in atomic physics is presented. The role of precise caesium parity-violation experiments, as a source of valuable information about electroweak physics, is illustrated by examples pertaining to experimental conditions which, in some cases, are not accessible to accelerator experiments. We give the basic principles of experiments, some under way and others completed, where a quantitative determination of the nuclear weak charge, , which plays for the exchange the same role as the electric charge for the Coulomb interaction is to be, or has been achieved. In the most recent and most precise experiment the accuracy on is limited to 1 % by the uncertainty due to atomic physics calculations. Such a result challenges specialists in atomic theory and nuclear structure, since a more accurate determination of would mean more stringent constraints upon possible extensions of the standard model. Moreover, clear evidence has recently been obtained for the existence of the nuclear anapole moment, which describes the valence electron interaction with a chiral nuclear-magnetization component induced by the parity-violating nuclear forces. In writing this review, our hope was to make clear that any improvement in atomic parity-violation measurements will allow the exploration of new areas of electroweak physics.

http://iopscience.iop.org/article/10.1088/0034-4885/60/11/004/pdf

Parity violation in atoms

The design of a diode laser frequency stabilization system using the Zeeman effect is described. Various regimes of operation are analyzed using the Jones matrix approach. The system is different from the original Joint Institute for Laboratory Astrophysics design in that the magnetic fields are fully contained and thus it can be used in proximity of magnetically sensitive instruments.

Laser frequency stabilization using linear magneto-optics

Two identical femtosecond pulses are used to create a coherent superposition of two vibrational wave packets in a bound electronic state of cesium dimers. The oscillations of these two wave packets are further detected after photoionization of the system. Quantum interferences between the two wave packets result in a temporal coherent control of the ionization probability. The interferogram exhibits the following features as a function of the time delay between the two laser pulses: high-frequency oscillation corresponding to Ramsey fringes (at the Bohr frequency of the transition) modulated by a slow envelope corresponding to the oscillations of vibrational wave packets (vibrational recurrences). Here the control parameter is the time delay between the two laser pulses which can be used to control the preparation of a wave packet in a quantum system and monitor its evolution. The detailed theory of this experiment is presented and compared with the pump-probe experiment. The temporal coherent control exp...

Temporal coherent control in the photoionization of cs2: theory and experiment

Using ultrashort laser pulses, we have observed quadrature squeezing and parametric gain in quasi-phasematched KTiOPO4 waveguides. Using a local oscillator pulse that is 2.5 times shorter than the squeezed pulse, we observed noise reduction of 12 6 1% below the shot-noise level. Parametric amplification and deamplification of a coherent seed pulse have also been observed, with no indication of gain-induced diffraction.

Quadrature squeezing with ultrashort pulses in nonlinear-optical waveguides.

We review the progress made in the determination of the weak charge, QW, of the cesium nucleus which raises the status of Atomic Parity Violation measurements to that of a precision electroweak test. Not only is it necessary to have a precision measurement of the electroweak asymmetry in the highly forbidden 6S–7S transition, but one also needs a precise calibration procedure. The 1999 precision measurement by the Boulder group implied a 2.5 σ deviation of QW from the theoretical prediction. This triggered many particle physicist suggestions as well as examination by atomic theoretical physicists of several sources of corrections. After about three years, the disagreement was removed without appealing to "New Physics". Concurrently, an original experimental approach was developed in our group for more than a decade. It is based on detection by stimulated emission with amplification of the left–right asymmetry. We present our decisive, recent progress together with our latest results. We emphasize the important impact for electroweak theory, of future measurements in cesium possibly pushed to the 0.1% level. Other possible approaches are currently explored in several atoms.

https://hal.archives-ouvertes.fr/hal-00004505/document

Atomic parity violation: principles, recent results, present motivations

Reaching the shot noise limit in the polarization measurement of individual nanosecond light pulses

High precision balanced mode polarimetry with a pulsed laser beam

Experimental progress using nonlinear optics for precision measurements of the nuclear weak charge in the 6S-7S Cs transition

Magnification of a tiny polarisation rotation by a dichroic plate in balanced mode polarimetry

We describe an ongoing experiment to measure parity violation in atomic caesium, based on detection by stimulated emission. Our goal is to measure to 1 a left-right asymmetry of to test electroweak theory and look for new physics beyond the Standard Model. The Cs highly forbidden transition, , is excited in a vapour (5-10 mtorr) by a pump laser pulse in a longitudinal electric field . The PV asymmetry resulting from the weak interaction during optical excitation is converted into an anisotropy in the gain of a probe laser pulse which stimulates the allowed transition , and manifests itself as a tiny -odd rotation of the probe's linear polarization. Differential polarimetry allows dark-field detection of the rotation angle with a baseline defined to better than and discrimination between true and pseudo-rotation. Lineshape-independent angle calibration is performed using a parity-conserving -even anisotropy. To isolate the parity-violating effect, we exploit the symmetry of revolution of the experiment by (i) rotating pump and probe linear polarizations around the beam axis and (ii) reversing in a cylindrically symmetric cell. After describing the apparatus and data acquisition procedure, we summarize the current experimental status and short-term prospects.

https://iopscience.iop.org/article/10.1088/1355-5111/10/6/006/pdf

Ph. Jacquier

Papers

Reaching the shot noise limit in the polarization measurement of individual nanosecond light pulses

High precision balanced mode polarimetry with a pulsed laser beam

Experimental progress using nonlinear optics for precision measurements of the nuclear weak charge in the 6S-7S Cs transition

Magnification of a tiny polarisation rotation by a dichroic plate in balanced mode polarimetry

Sensitive pulsed pump-probe atomic polarimetry for parity-violation measurements in caesium