This week we welcomed Dr. Weibin Li from the University of Nottingham who spoke about “Rydberg excitation in thermal Rydberg gases”. The abstract for this AMOPP seminar can be found below.
Rydberg excitation in thermal Rydberg gases
The creation of optical nonlinearities in atomic gases become a challenging task with increasing temperature, due to large Doppler effects. We study single photon excitation of electronically high-lying Rydberg states by nanosecond laser pulses that propagate in a high density thermal gas of alkali atoms. Fast Rabi flopping and strong Rydberg atom interactions, both in the order of GHz, overcome Doppler effects and dephasing due to thermal collisions between Rydberg electrons and surrounding atoms. The latter has not been taken into account appropriately so far. We show that a sizable dispersive nonlinearity is generated by strong interactions between Rydberg atoms. Despite the Rydberg optical nonlinearity, solitary propagation, i.e., self-induced transparency (SIT), of the light pulse can still occur. The existence of SIT allows to implement a conditional optical phase gate in the thermal gas through harvesting strong interactions. Our study paves the route to study nonlinear optics in thermal Rydberg gases and directly contributes to the current effort in realising scalable quantum information and communication devices with glass cell technologies.
This weeks AMOPP seminar was given by Dr. German Sinuco-Leon from the University of Sussex on the topic of “Spatial and internal control of atomic ensembles with radiofrequency and microwave driving”. The abstract for this talk can be found below.
Spatial and internal control of atomic ensembles with radiofrequency and microwave driving
The ability to apply well-controlled perturbation to quantum systems is essential to modern methodologies to study their properties (e.g. in high-precision-spectroscopy), and developing quantum technologies (e.g. atomic-clocks and quantum processors). In most of the experimental platforms available today, such perturbations arise from the interaction of a quantum system with electromagnetic radiation, which creates harmonically oscillating couplings between the states of the system. Within this context, in this talk, I will describe our recent studies of the use of low-frequency electromagnetic radiation to control the external and internal degrees of freedom of ultracold atomic ensembles [1,2]. I will outline the relation of this problem with Floquet Engineering and the more general issue of describing the dynamic of the driven quantum systems. Finally, I will explain the challenges of describing the quantum dynamics of systems driven and highlight eh need for developing new conceptual and mathematical tools to identify universal characteristics and limitation of their dynamics.
 G. A. Sinuco-Leon, B. M. Garraway, H. Mas, S. Pandey, G. Vasilakis, V. Bolpasi, W. von Klitzing, B. Foxon, S. Jammi, K. Poulios, T. Fernholz, Microwave spectroscopy of radio-frequency dressed alkali atoms, Physical Review A, accepted (2019). [ArXiv:1904.12073].
 G. Sinuco-León and B.M. Garraway, Addressed qubit manipulation in radio-frequency dressed lattices, New Journal of Physics. 18, 035009 (2016)