# Superconducting atomchip

##### Recent publications

♦ Microwave probes dipole blockade and van der Waals forces in a cold Rydberg gas

R. Celestrino Teixeira, C. Hermann-Avigliano, T.L. Nguyen, T. Cantat-Moltrecht, J.M. Raimond, S. Haroche and M. Brune

Phys. Rev. Lett 115, 013001 (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 and M. Brune

Phys. Rev. A 90, 040502 (2014)

**PEOPLE**

**Permanents:** Clément Sayrin, Michel Brune, Jean-Michel Raimond, Serge Haroche

**PhDs:** Thanh Long Nguyen, Tigrane Cantat-Moltrecht, Rodrigo Cortiñas

## Superconducting Atomchip for Rydberg atoms

Thanks to their large electric polarizabilities, Rydberg atoms interact very strongly through dipole-dipole interactions. At a few micrometres distance, this interaction can be still as big as several MHz. The so-called dipole blockade is one of the most striking consequences of this interaction strength: the presence of a Rydberg atom prevents the excitation of a subsequent Rydberg atom in its immediate proximity.

Rydberg atoms, which can be laser-excited from alkali atoms in their ground states, and which are long-lived (several 100µs lifetime), are thus ideal candidates for the study of spin-spin interactions in dense systems. In particular, they can be used to realise a quantum simulator of condensed-matter systems.

In our group, we prepare a gas of Rydberg atoms in the vicinity of a superconducting atomchip. Rydberg atoms are excited from a gas of laser-cooled Rubidium-87 atoms, initially trapped in a magnetic trap created by the atomchip. Our work focuses on the study of the interaction between the Rydberg atoms. We can, in particular, control the mean interatomic distance between the Rydberg excitation and probe the interactions through, e.g., microwave spectroscopy. This should, e.g., enable the preparation of spin chains and the study of the quantum transport of energy along it.

# Dipole blockade and microwave spectroscopy

##### Publications

♦ Microwaves Probe Dipole Blockade and van der Waals Forces in a Cold Rydberg Gas

R. Teixeira, C. Hermann-Avigliano, T.-L. Nguyen, T. Cantat-Moltrecht, J.-M. Raimond, S. Haroche, S. Gleyzes, M. Brune

Phys. Rev. Lett. 115, 013001 (2015)

##### Supplementary Materials

Because of their strong electric polarizability, Rydberg atoms interact very strongly through dipole-dipole interaction. During a resonant laser excitation of Rydberg levels in a dense atomic cloud, the strength of the interaction leads to the so-called dipole blockade effect [Lukin et al. (2001)]: every Rydberg atoms is surrounded by a blockade sphere into which no other Rydberg atom can be excited. At saturation, the distance between the Rydberg atoms then corresponds to the radius of this sphere, the so-called blockade radius. However, when the laser excitation is detuned from resonance, the dipole interaction can facilitate the excitation of a Rydberg atom at a distance called facilitation radius from an initial Rydberg seed. The value of the facilitation radius is controlled via the detuning of the excitation light.

In our experiments, we have been recently able to demonstrate that the relative distance between Rydberg atoms excited in a cold gas of atoms, trapped in the vicinity of our atomchip, can be controlled via the detuning of the excitation laser. Using microwave spectroscopy, we have measured directly the interaction energy distribution of the Rydberg gas, from which we can deduce the Rydberg atoms spatial distribution. By recording the time evolution of the interaction energy distribution, we have also observed the dynamics of the Rydberg gas, which expands due to the strong repulsive interaction between the atoms. In particular, we have been able to observe the breakdown of the frozen gas approximation, few µs only after the preparation of the Rydberg gas.