Tripartite Entanglement in a Bose Condensate by Stimulated Bragg Scattering

We show that it is possible to entangle three different many-particle states by Bragg spectroscopy with nonclassical light in a Bose condensate of weakly interacting atomic gases. Among these three states, two are of atoms corresponding to two opposite momentum side-modes of the condensate; and the other is of single-mode photons of the output probe beam. We demonstrate strong dependence of the multiparticle entanglement on the quantum statistics of the probe light. We present detailed results on entanglement keeping in view of the possible experimental situation.Comment: 5 pages, 4 figures, Revte

Radio-over-fiber using an optical antenna based on Rydberg states of atoms

We provide an experimental demonstration of a direct fiber-optic link for RF transmission ("radio-over-fiber") using a sensitive optical antenna based on a rubidium vapor cell. The scheme relies on measuring the transmission of laser light at an electromagnetically-induced transparency resonance that involves highly-excited Rydberg states. By dressing pairs of Rydberg states using microwave fields that act as local oscillators, we encoded RF signals in the optical frequency domain. The light carrying the information is linked via a virtually lossless optical fiber to a photodetector where the signal is retrieved. We demonstrate a signal bandwidth in excess of 1 MHz limited by the available coupling laser power and optical density. Our sensitive, non-metallic and readily scalable optical antenna for microwaves allows extremely low-levels of optical power ($\sim 1\, \mu$W) throughput in the fiber-optic link. It offers a promising future platform for emerging wireless network infrastructures

Resonant enhancement of ultracold photoassociation rate by electric field induced anisotropic interaction

We study the effects of a static electric field on the photoassociation of a heteronuclear atom-pair into a polar molecule. The interaction of permanent dipole moment with a static electric field largely affects the ground state continuum wave function of the atom-pair at short separations where photoassociation transitions occur according to Franck-Condon principle. Electric field induced anisotropic interaction between two heteronuclear ground state atoms leads to scattering resonances at some specific electric fields. Near such resonances the amplitude of scattering wave function at short separation increases by several orders of magnitude. As a result, photoaasociation rate is enhanced by several orders of magnitude near the resonances. We discuss in detail electric field modified atom-atom scattering properties and resonances. We calculate photoassociation rate that shows giant enhancement due to electric field tunable anisotropic resonances. We present selected results among which particularly important are the excitations of higher rotational levels in ultracold photoassociation due to electric field tunable resonances.Comment: 14 pages,9 figure

Magneto-optical Feshbach resonance: Controlling cold collision with quantum interference

We propose a method of controlling two-atom interaction using both magnetic and laser fields. We analyse the role of quantum interference between magnetic and optical Feshbach resonances in controlling cold collision. In particular, we demonstrate that this method allows us to suppress inelastic and enhance elastic scattering cross sections. Quantum interference is shown to modify significantly the threshold behaviour and resonant interaction of ultracold atoms. Furthermore, we show that it is possible to manipulate not only the spherically symmetric s-wave interaction but also the anisotropic higher partial-wave interactions which are particularly important for high temperature superfluid or superconducting phases of matter.Comment: 7 pages 3 figures, some minor errors are corrected, Accepted in J. Phys.

A simple functional form for proton-208{}^{208}Pb total reaction cross sections

A simple functional form has been found that gives a good representation of the total reaction cross sections for the scattering from ${}^{208}$Pb of protons with energies in the range 30 to 300 MeV.Comment: 7 pages, 2 figure

Finite temperature effects in light scattering off Cooper-paired Fermi atoms

We study stimulated light scattering off a superfluid Fermi gas of atoms at finite temperature. We derive response function that takes into account vertex correction due to final state interactions; and analyze finite temperature effects on collective and quasiparticle excitations of a uniform superfluid Fermi gas. Light polarization is shown to play an important role in excitations. Our results suggest that it is possible to excite Bogoliubov-Anderson phonon at a large scattering length by light scattering.Comment: 18 pages, 4 figures, Accepted in J. Phys. B: At. Mol. & Opt. Phy

Dispersive probing of driven pseudo-spin dynamics in a gradient field

We have studied the coherent evolution of ultracold atomic rubidium clouds subjected to a microwave field driving Rabi oscillations between the stretched states of the F=1 and F=2 hyperfine levels. A phase winding of the two-level system pseudo-spin vector is encountered for elongated samples of atoms exposed to an axial magnetic field gradient and can be observed directly in state-selective absorption imaging. When dispersively recording the sample-integrated spin population during the Rabi drive, we observe a damped oscillation directly related to the magnetic field gradient, which we quantify using a simple dephasing model. By analyzing such dispersively acquired data from millimeter sized atomic samples, we demonstrate that field gradients can be determined with an accuracy of $\sim25$ nT/mm. The dispersive probing of inhomogeneously broadened Rabi oscillations in prolate samples opens up a path to gradiometry with bandwidths in the kilohertz domain.Comment: 11 pages, 9 figures, 1 video lin