Carla Hermann
Early Stage Researcher

Centre National de la Recherche Scientifique, Paris, France

Academic Background

I studied physics (2005-2009) at the University of Concepcion, Chile (Universidad de Concepción). After that I started my PhD at the same university. Then, in the second year I came to Paris for an internship in experimental physics at the Laboratoire Kastler Brossel under the supervision of Pr. Jean-Michel Raimond. As a result of this, I was accepted to begin my PhD thesis in Paris during 3 years in a co-supervision system of both universities.  I have been working since September 2010 in an experiment on Rydberg atoms on superconducting atom chips. The topic of my thesis is: “Deterministic preparation of single Rydberg atoms and applications to quantum information

Description of Work

The aim of this thesis will be to investigate a deterministic source of circular Rydberg atoms for quantum information processing experiments. Circular Rydberg atoms and superconducting cavities are remarkable tools for the exploration of basic quantum phenomena and for the realization of quantum information processing sequences. They realize the simplest, matter-field system, with a single atom coupled to a single field mode containing only a few photons.

The ENS experiments used so far a laser excitation of a weak atomic beam to produce Rydberg atoms at thermal velocities. All parameters of an atomic sample are under control (velocity, preparation time, etc) but the number of atoms in the sample obeys a random Poisson statistics. This is a severe limitation for quantum information experiments, in which the qubits must be prepared deterministically. The goal of this PhD work is to remove this limitation. On the experimental side, the first objective is to investigate the dipole blockade mechanism in a dense, small sample of ground state atoms. Due to the very strong dipole-dipole interaction between two Rydberg atoms, the laser excitation frequency for preparing two atoms in the sample is noticeably shifted with respect to that of the first excitation (a few hundred MHz for atoms at a distance of a few microns). The resonant laser excitation of a small cloud of atoms is thus bound to result in the deterministic preparation of a single Rydberg atom. The proper conditions for the observation of the dipole blockade mechanism are met with atoms on a superconducting atom chip. A few hundred atoms can be trapped in a Ioffe-Pritchard trap, with transverse dimensions below 1 μm and a length of a few μm. The first part of the work will be to optimize the chip design to get a trapped atom cloud with the proper shape. We will then perform detailed laser spectroscopy of the Rydberg line in the trap. After that we plan to look for spectral evidence of the dipole-dipole interaction. We will then investigate the dipole blockade mechanism. A high efficiency field-ionization detector will be used to count the number of Rydberg atoms prepared and to measure the performance of the deterministic source.

Publications

A scheme for efficient generation of mesoscopic field states superposition in cavity QED
C. Hermann-Avigliano, N. Cisternas, M. Brune, J.M. Raimond, C. Saavedra
Phys. Rev. A 91, 013815 (2015)

Long coherence times for Rydberg qubits on a superconducting atom chip
C. Hermann-Avigliano, R. Celstrino-Teixeira, T.L. Nguyen, T. Cantat-Moltrecht, G. Nogues, I. Dotsenko, S. Gleyzes, J.M. Raimond, S. Haroche, M. Brune
Phys. Rev. A 90, 040502 (2014)

Conclusive discrimination among N equidistant pure states
Luis Roa, Carla Hermann-Avigliano,  R. Salazar, and A. B. Klimov
Physical Review A 84, 014302 (2011).