Scattering of polarized laser light by an atomic gas in free space: a QSDE approach

Implementing quantum stochastic differential equations on a quantum computer

We study how to implement quantum stochastic differential equations (QSDEs) on a quantum computer. This is illustrated by an implementation of the QSDE that couples a laser driven two-level atom to the electromagnetic field in the vacuum state on the IBMqx4 Tenerife computer. We compare the resulting master equation and quantum filtering equations to existing theory. In this way we characterize the performance of the computer.

量子线性系统理论

Quantum Linear Systems Theory

本文综述了量子线性系统理论的最新成果，探讨了基于相干量子反馈控制的H∞最优控制器设计，并讨论了线性量子系统物理可实现性问题。

Field-free molecular alignment induced by elliptically polarized laser pulses: non invasive 3 dimensional characterization

An investigation of field-free molecular alignment produced by elliptically polarized laser pulses is reported. Experiments are conducted in CO$_2$ at room temperature. A non invasive all-optical technique, based on the cross defocusing of a probe pulse, is used to measure the alignment along two orthogonal directions that is sufficient to provide a 3 dimensional characterization. The field-free molecular alignment produced by a laser of elliptical polarization is in good agreement in terms of amplitude and shape with theoretical predictions. It turns out to be almost equivalent to the superpo…

Spin polarized electron-positron pair production via elliptical polarized laser fields

We study nonperturbative multiphoton electron-positron pair creation in ultrastrong electromagnetic fields formed by two counterpropagating pulses with elliptic polarization. Our numerical approach allows us to take into account the temporal as well as the spatial variation of the standing electromagnetic field. The spin and momentum resolved pair creation probabilities feature characteristic Rabi oscillations and resonance spectra. Therefore, each laser frequency features a specific momentum distribution of the created particles. We find that, depending on the relative polarization of both pu…

Electron-positron pair production in an arbitrary polarized ultrastrong laser field

Electron-positron pair production in an arbitrary polarized ultrastrong laser field is investigated in the first order perturbation approximation in which the Volkov states are used for convenient calculation of scattering amplitude and cross section. It is found surprisingly that the optimal pair production depends strongly on the polarization. For some cases of field parameters, the optimal field is elliptically polarized or evenly circularly polarized one, rather than the usual linear polarization as indicated by previous works. Some insights into pair generation are given and some interest…

Femtosecond-Laser-Induced Spin-Polarized Electron Emission from a GaAs Tip

It is shown that focusing circularly-polarized 800 nm light pulses of 100 fs duration on the tips of p-GaAs crystalline shards having no negative electron affinity (NEA) activation results in electron emission that is both fast and spin-polarized. The 400 fs duration of the emission process was determined by pump/probe measurements. The three samples we investigated produced electron polarizations of 13.1(9)%, 13.3(7)%, and 10.4(2)%. Emission currents ranged between 50 pA and 3 nA with a sample bias of -100V and average laser power of 100 mW. The electron emission exhibited linear dichroism an…