Physics of ultracold atoms in Russia: topical research

In the last decade, significant advances have been made in the laser cooling and trapping of atoms and ions. The most widespread schemes are those employing magneto-optical and optical traps for neutral atoms and RF traps for ions, which allow one to reach translational motion temperatures of atoms and ions below 100 μK. The use of ultracold trapped atoms and ions opens up new possibilities for diverse basic and applied studies in atomic spectroscopy owing to the spatial localisation of atoms and ions in a small volume, without transit-time or Doppler broadening. For example, in the case of cold atoms the time of interaction with probe light is determined by the lifetime of an atom in a trap, which reaches tens of seconds. At a low density of atoms, the width of some optical resonances in the atoms can be less than a fraction of a hertz, which allows one to envisage a new generation of atomic frequency standards, with a relative uncertainty less than 10^-18. At the same time, at a high density of atoms resonances should broaden and shift as a result of collisions and interatomic interactions, so laser and microwave spectroscopies can be used to follow collisional and collective processes in ensembles of cold atoms. Finally, cold atoms and ions are thought to be promising objects for producing a quantum computer's qubits.