Matthieu Viteau

Observation of collective excitation of two individual atoms in the Rydberg blockade regime

When two single Rydberg atoms—those with electrons in highly excited states—interact, one can be used to control the quantum state of the other. Two independent experiments demonstrate such ‘Rydberg blockade’, an effect that might make long-range quantum gates between neutral atoms possible.

Optical pumping and vibrational cooling of molecules.

The methods producing cold molecules from cold atoms tend to leave molecular ensembles with substantial residual internal energy. For instance, cesium molecules initially formed via photoassociation of cold cesium atoms are in several vibrational levels ν of the electronic ground state. We applied a broadband femtosecond laser that redistributes the vibrational population in the ground state via a few electronic excitation/spontaneous emission cycles. The laser pulses are shaped to remove the excitation frequency band of the ν = 0 level, preventing re-excitation from that state. We observed a fast and efficient accumulation (∼70% of the initially detected molecules) in the lowest vibrational level, ν = 0, of the singlet electronic state. The validity of this incoherent depopulation pumping method is very general and opens exciting prospects for laser cooling and manipulation of molecules.

High-fidelity quantum driving

Transforming a quantum system with high fidelity is usually a trade-off between an increase in speed—thereby minimizing decoherence—and robustness against fluctuating control parameters. Protocols at these two extreme limits are now demonstrated and compared using Bose–Einstein condensates in optical traps.

Electric-field induced dipole blockade with Rydberg atoms.

High resolution laser Stark excitation of np (60<n<85) Rydberg states of ultracold cesium atoms shows an efficient blockade of the excitation attributed to long-range dipole-dipole interaction. The dipole blockade effect is observed as a quenching of the Rydberg excitation depending on the value of the dipole moment induced by the external electric field. Effects of ions which could match the dipole blockade effect are discussed in detail but are ruled out for our experimental conditions. Analytic and Monte Carlo simulations of the excitation of an ensemble of interacting Rydberg atoms agree with the experiments and indicate a major role of the nearest neighboring Rydberg atom.

Efficient formation of deeply bound ultracold molecules probed by broadband detection

SUMMARY Using a non-selective broadband detection scheme we discovered an efficient mechanism of formation of ultracold Cs

Kinetic Monte Carlo modeling of dipole blockade in Rydberg excitation experiment

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Cooperative excitation and many-body interactions in a cold Rydberg gas.

molecules in deeply bound levels (

Photoionization spectroscopy of excited states of cold caesium dimers

v=1-9

Controllable Interactions between Rydberg Atoms and Ultracold Plasmas

) of their electronic ground state X

Entanglement of two ground state neutral atoms using Rydberg blockade

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