Recent progress on the manipulation of single atoms in optical tweezers for quantum computing

This paper summarizes our recent progress towards using single rubidium atoms trapped in an optical tweezer to encode quantum information. We demonstrate single qubit rotations on this system and measure the coherence of the qubit. We move the quantum bit over distances of tens of microns and show that the coherence is reserved. We also transfer a qubit atom between two tweezers and show no loss of coherence. Finally, we describe our progress towards conditional entanglement of two atoms by photon emission and two-photon interferences.Comment: Proceedings of the ICOLS07 conferenc

Optical Trapping of an Ion

For several decades, ions have been trapped by radio frequency (RF) and neutral particles by optical fields. We implement the experimental proof-of-principle for trapping an ion in an optical dipole trap. While loading, initialization and final detection are performed in a RF trap, in between, this RF trap is completely disabled and substituted by the optical trap. The measured lifetime of milliseconds allows for hundreds of oscillations within the optical potential. It is mainly limited by heating due to photon scattering. In future experiments the lifetime may be increased by further detuning the laser and cooling the ion. We demonstrate the prerequisite to merge both trapping techniques in hybrid setups to the point of trapping ions and atoms in the same optical potential.Comment: 5 pages, 3 figure

Inserting single Cs atoms into an ultracold Rb gas

We report on the controlled insertion of individual Cs atoms into an ultracold Rb gas at about 400 nK. This requires to combine the techniques necessary for cooling, trapping and manipulating single laser cooled atoms around the Doppler temperature with an experiment to produce ultracold degenerate quantum gases. In our approach, both systems are prepared in separated traps and then combined. Our results pave the way for coherent interaction between a quantum gas and a single or few neutral atoms of another species

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

The dipole blockade between Rydberg atoms has been proposed as a basic tool in quantum information processing with neutral atoms. Here we demonstrate experimentally the Rydberg blockade of two individual atoms separated by 4 $\mu$m. Moreover, we show that, in this regime, the single atom excitation is enhanced by a collective two-atom behavior associated with the excitation of an entangled state. This observation is a crucial step towards the deterministic manipulation of entanglement of two or more atoms using the Rydberg dipole interaction.Comment: 5 pages, 4 figure

Two-dimensional transport and transfer of a single atomic qubit in optical tweezers

Quantum computers have the capability of out-performing their classical counterparts for certain computational problems1. Several scalable quantum-computing architectures have been proposed. An attractive architecture is a large set of physically independent qubits arranged in three spatial regions where (1) the initialized qubits are stored in a register, (2) two qubits are brought together to realize a gate and (3) the readout of the qubits is carried out2, 3. For a neutral-atom-based architecture, a natural way to connect these regions is to use optical tweezers to move qubits within the system. In this letter we demonstrate the coherent transport of a qubit, encoded on an atom trapped in a submicrometre tweezer, over a distance typical of the separation between atoms in an array of optical traps4, 5, 6. Furthermore, we transfer a qubit between two tweezers, and show that this manipulation also preserves the coherence of the qubit

ELECTRON SPIN RESONANCE EXPERIMENTS AT HIGH FREQUENCY AND HIGH MAGNETIC FIELD ON THE RANDOM SYSTEM CsMn1- xCoxCl3.2H2O

ESR and AFMR experiments have been performed at high frequencies and magnetic fields on the random antiferromagnetic mixture with competing spin anisotropies CsMn1-xCoxCl3.2H2O. The frequency vs. field plots of the resonance points are presented for several concentrations x and are analysed within the framework of usual antiferromagnetic theory

ELECTRON SPIN RESONANCE IN THE DISORDERED SYSTEM Mg1-xCoxCl2

Electron spin resonance experiments performed on a single crystal sample of the site diluted planar magnet Mg0.79Co0.21Cl2 are reported. A number of resonance lines has been observed. From the analysis of the experiments, a model for the clustering of the magnetic atoms below the percolation concentration is obtained

Low-field and anomalous high-field Hall effect in (TMTSF)2ClO 4

We report the study of the Hall effect, at low temperature, in (TMTSF) 2ClO4 (slow-cooled state), up to 80 kOe, with the field perpendicular to the (a-b) plane. We show that the linear field dependence of the weak Hall resistance, up to 40 kOe, supports the interpretation of the conducting phase in terms of a quasi planar Fermi surface with a density of carriers corresponding to the stoechiometry of the salt. At higher field, a strong and sharp increase of the Hall constant, is the signature of a phase transition to a semi-metallic state. The transition magnetic field is very temperature dependent. Below 0.7 K, in the semi-metallic state, remarkable steps and plateaux, of the Hall resistance are observed, suggesting either the quantization of the Hall constant of carriers in weakly coupled (a-b) planes or the existence of a sequence of electron-hole instabilities (excitonic phases).Nous présentons une étude de l'effet Hall effectuée à basse température dans (TMTSF)2ClO4 après refroidissement lent, jusqu'à un champ de 80 kOe placé perpendiculairement au plan (a-b). La très faible résistance de Hall dépendant linéairement du champ magnétique jusqu'à 40 kOe indique l'existence d'un conducteur à surface de Fermi quasi-planaire et une densité de porteurs correspondant à la stoechiométrie. La croissance très brutale de la constante de Hall observée en champ élevé correspondant à une transition vers un état semi-métallique. Les marches et plateaux de la résistance de Hall observés dans l'état semi-métallique au-dessous de 0,7 K suggèrent soit la quantification de la constante de Hall des porteurs bidimensionnels dans les plans (a-b ) soit l'existence d'une série de transitions du type instabilité électron-trou (phases excitoniques)