OSERC Seminars

Title:  Collective Atom-Photon Interactions toward a Hybrid Quantum System

Speaker:  Dr. Jongmin Lee, Joint Quantum Institute, University of Maryland and National Institute of Standards and Technology, College Park, Maryland, USA

Location:  Room 616, Physics Building

Time: 13:30-15:00, Thursday, May 8, 2014

Abstract:
The nanofiber-based optical lattices with a large optical depth have been demonstrated for 87Rb atoms using two-color (red- and blue-detuned) evanescent trapping fields of 750nm and 1064nm lights. 87Rb atoms in our lattices experience light shifts (to the blue) on 5P3/2 to all upper transitions, and the absorption profile is shifted to the blue. In addition, the ellipticity of a HE11 mode leads to strong Zeeman broadening, both on 5P3/2 and 5S1/2, due to the vector light shifts. Here, I present a qualitative study of this inhomogeneous broadening based on light shifts, atomic temperature distribution, and population redistribution.

Using an optical waveguide (silicon nitride), an integrated optical dipole trap uses two-color traveling evanescent wave fields to trap cold neutral atoms. An integrated optical waveguide coupler provides a potential gradient along the beam propagation direction sufficient to confine atoms without optical lattices. Its quasi-TE0 waveguide mode has an advantage over the HE11 mode of a nanofiber, with little inhomogeneous Zeeman broadening at the trapping region. The longitudinal confinement eliminates the need for a 1D optical lattice, reducing collisional blockaded atomic loading, potentially producing larger ensembles. The waveguide trap allows for scalability and integrability with nano-fabrication technology. The potential performance of such scalable atom traps and the current research progress towards a fiber-coupled silicon nitride optical waveguide integrable with atom chips will be addressed. A centimeter long silicon nitride nanophotonic waveguide with inverse-tapered ends (for higher input couplings of 750nm and 1064nm lights) has been developed to address and trap many cold neutral atoms for studying collective atom-photon interactions toward a scalable quantum system.

The nanofiber / nanophotonic atom traps have been studied as the AMO/CM interface toward a hybrid quantum system and coherent quantum conversion, exploiting the magnetic dipole coupling between trapped cold neutral atoms and superconducting circuits. A novel protection layer of superconductivity has been considered because optical / magnetic atom traps near the superconducting circuits has practical limitation because of its vulnerability to those trapping fields. A nanophotonic atom trap can locate trapped atoms near the superconducting circuits, minimizing residual light scattering. Here, the dielectric and lossy multi-wavelength Bragg layers are proposed to protect the superconducting circuits from optical photons of two-color near-infrared trapping fields and from a broadband blackbody radiation of a nanophotonic device, considering the maximal back-transmission of electro-magnetic fields of the circuits through this protection layer and the heat transfer to the circuits through the protection layer from absorbed scattered photons.

In addition, a dual-wavelength high-finesse cavity system having homogeneous atom-cavity coupling and high cavity finesses (180,000 for 780nm and 120,000 for 1560nm) has been studied for the collective atom-cavity interactions such as the pseudo-spin-squeezing toward the atomic sensor application (quantum metrology), the macroscopic self-trapping behavior toward the macroscopic Schrodinger cat state generation, and Raman lasing with atomic gain medium toward a sub-Hz linewidth laser will be addressed.