Matter-light entanglement with cold atomic ensembles

In this thesis I present the investigations of matter-light entanglement in cold atomic samples. Particularly, entanglement of mixed species ensembles and bichromatic light fields is proposed and demonstrated experimentally. This approach avoids the use of two interferometrically separate paths for qubits entanglement distribution. I also present the first implementation of multiplexed quantum memory, and experimentally demonstrate entanglement involving arbitrary pairs of elements within this memory array. Finally, quantum interference of electromagnetic fields emitted by remote quantum memory elements separated by 5.5 m is realized.Ph.D.Committee Chair: Kuzmich, Alex; Committee Member: Chapman, Michael; Committee Member: Citrin, David; Committee Member: Kennedy, T. A. Brian; Committee Member: Raman, Chandr

Laser Cooling of 85Rb Atoms to the Recoil Temperature Limit

We demonstrate the laser cooling of 85Rb atoms in a two-dimensional optical lattice. We follow the two-step degenerate Raman sideband cooling scheme [Kerman et al., Phys. Rev. Lett. 84, 439 (2000)], where a fast cooling of atoms to an auxiliary state is followed by a slow cooling to a dark state. This method has the advantage of independent control of the heating rate and cooling rate from the optical pumping beam. We operate the lattice at a Lamb-Dicke parameter eta=0.45 and show the cooling of spin-polarized 85Rb atoms to the recoil temperature in both dimension within 2.4 ms with the aid of adiabatic cooling

Transporting long-lived quantum spin coherence in a photonic crystal fiber

Confining particles in hollow-core photonic crystal fibers has opened up new prospects to scale up the distance and time over which particles can be made to interact with light. However, maintaining long-lived quantum spin coherence and/or transporting it over macroscopic distances in a waveguide remain challenging. Here, we demonstrate coherent guiding of ground-state superpositions of 85Rb atoms over a centimeter range and hundreds of milliseconds inside a hollow-core photonic crystal fiber. The decoherence is mainly due to dephasing from residual differential light shift (DLS) from the optical trap and the inhomogeneity of ambient magnetic field. Our experiment establishes an important step towards a versatile platform that can lead to applications in quantum information networks and matter wave circuit for quantum sensing.Comment: Accepted by Physical Review Letter

Dark-state sideband cooling in an atomic ensemble

We utilize the dark state in a {\Lambda}-type three-level system to cool an ensemble of 85Rb atoms in an optical lattice [Morigi et al., Phys. Rev. Lett. 85, 4458 (2000)]. The common suppression of the carrier transition of atoms with different vibrational frequencies allows them to reach a subrecoil temperature of 100 nK after being released from the optical lattice. A nearly zero vibrational quantum number is determined from the time-of-flight measurements and adiabatic expansion process. The features of sideband cooling are examined in various parameter spaces. Our results show that dark-state sideband cooling is a simple and compelling method for preparing a large ensemble of atoms into their vibrational ground state of a harmonic potential and can be generalized to different species of atoms and molecules for studying ultracold physics that demands recoil temperature and below

Influence of the Coriolis force in atom interferometry

In a light-pulse atom interferometer, we use a tip-tilt mirror to remove the influence of the Coriolis force from Earth's rotation and to characterize configuration space wave packets. For interferometers with large momentum transfer and large pulse separation time, we improve the contrast by up to 350% and suppress systematic effects. We also reach what is to our knowledge the largest spacetime area enclosed in any atom interferometer to date. We discuss implications for future high performance instruments.Comment: 4 pages, 5 figures, 1 tabl

High-resolution atom interferometers with suppressed diffraction phases

We experimentally and theoretically study the diffraction phase of large-momentum transfer beam splitters in atom interferometers based on Bragg diffraction. We null the diffraction phase and increase the sensitivity of the interferometer by combining Bragg diffraction with Bloch oscillations. We demonstrate agreement between experiment and theory, and a 1500-fold reduction of the diffraction phase, limited by measurement noise. In addition to reduced systematic effects, our interferometer has high contrast with up to 4.4 million radians of phase difference, and a resolution in the fine structure constant of $\delta \alpha/\alpha=0.25\,$ppb in 25 hours of integration time.Comment: Added appendix and explanations. 6 pages, 4 figure

Quantum-Enhanced Velocimetry with Doppler-Broadened Atomic Vapor

Traditionally, measuring the center-of-mass (c.m.) velocity of an atomic ensemble relies on measuring the Doppler shift of the absorption spectrum of single atoms in the ensemble. Mapping out the velocity distribution of the ensemble is indispensable when determining the c.m. velocity using this technique. As a result, highly sensitive measurements require preparation of an ensemble with a narrow Doppler width. Here, we use a dispersive measurement of light passing through a moving room temperature atomic vapor cell to determine the velocity of the cell in a single shot with a short-term sensitivity of 5.5 $\mu$m s$^{-1}$ Hz$^{-1/2}$. The dispersion of the medium is enhanced by creating quantum interference through an auxiliary transition for the probe light under electromagnetically induced transparency condition. In contrast to measurement of single atoms, this method is based on the collective motion of atoms and can sense the c.m. velocity of an ensemble without knowing its velocity distribution. Our results improve the previous measurements by 3 orders of magnitude and can be used to design a compact motional sensor based on thermal atoms

Long Light Storage Time in an Optical Fiber

Light storage in an optical fiber is an attractive component in quantum optical delay line technologies. Although silica-core optical fibers are excellent in transmitting broadband optical signals, it is challenging to tailor their dispersive property to slow down a light pulse or store it in the silica-core for a long delay time. Coupling a dispersive and coherent medium with an optical fiber is promising in supporting long optical delay. Here, we load cold Rb atomic vapor into an optical trap inside a hollow-core photonic crystal fiber, and store the phase of the light in a long-lived spin-wave formed by atoms and retrieve it after a fully controllable delay time using electromagnetically-induced-transparency (EIT). We achieve over 50 ms of storage time and the result is equivalent to 8.7x10^-5 dB s^-1 of propagation loss in an optical fiber. Our demonstration could be used for buffering and regulating classical and quantum information flow between remote networks

Bi-color atomic beam slower and magnetic field compensation for ultracold gases

Transversely loaded bidimensional-magneto-optical-traps (2D-MOT) have been recently developed as high flux sources for cold strontium atoms to realize a new generation of compact experimental setups. Here, we discuss on the implementation of a cross-polarized bi-color slower for a strontium atomic beam improving the 2D-MOT loading, and increasing the number of atoms in a final MOT by eleven times. Our slowing scheme addresses simultaneously two excited Zeeman substates of the 88Sr 1S0->1P1 transition at 461 nm. We also realized a 3-axis active feedback control of the magnetic field down to the microgauss regime. Such a compensation is performed thanks to a network of eight magnetic field probes arranged in a cuboid configuration around the atomic cold sample, and a pair of coils in Helmholtz configuration along each of three Cartesian directions. Our active feedback is capable of efficiently suppressing most of the magnetically-induced position fluctuations of the 689~nm intercombination-line MOT.Comment: 8 pages, 6 figure

Gravitational Redshift, Equivalence Principle, and Matter Waves

We review matter wave and clock comparison tests of the gravitational redshift. To elucidate their relationship to tests of the universality of free fall (UFF), we define scenarios wherein redshift violations are coupled to violations of UFF ("type II"), or independent of UFF violations ("type III"), respectively. Clock comparisons and atom interferometers are sensitive to similar effects in type II and precisely the same effects in type III scenarios, although type III violations remain poorly constrained. Finally, we describe the "Geodesic Explorer," a conceptual spaceborne atom interferometer that will test the gravitational redshift with an accuracy 5 orders of magnitude better than current terrestrial redshift experiments for type II scenarios and 12 orders of magnitude better for type III.Comment: Work in progress. 11 page