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J. Ye

Publications and source records attributed to J. Ye.

At least 91 records · Page 5Linked to original sources
arXiv2009

Strong coupling of a mechanical oscillator and a single atom

We propose and analyze a setup to achieve strong coupling between a single trapped atom and a mechanical oscillator. The interaction between the motion of the atom and the mechanical oscillator is mediated by a quantized light field in a laser driven high-finesse cavity. In particular, we show that high fidelity transfer of quantum states between the atom and the mechanical oscillator is in reach for existing or near future experimental parameters. Our setup provides the basic toolbox for coherent manipulation, preparation and measurement of micro- and nanomechanical oscillators via the tools of atomic physics.

quant-ph↗
arXiv2008

Ultracold polar molecules near quantum degeneracy

We report the creation and characterization of a near quantum-degenerate gas of polar $^{40}$K-$^{87}$Rb molecules in their absolute rovibrational ground state. Starting from weakly bound heteronuclear KRb Feshbach molecules, we implement precise control of the molecular electronic, vibrational, and rotational degrees of freedom with phase-coherent laser fields. In particular, we coherently transfer these weakly bound molecules across a 125 THz frequency gap in a single step into the absolute rovibrational ground state of the electronic ground potential. Phase coherence between lasers involved in the transfer process is ensured by referencing the lasers to two single components of a phase-stabilized optical frequency comb. Using these methods, we prepare a dense gas of $4\cdot10^4$ polar molecules at a temperature below 400 nK. This fermionic molecular ensemble is close to quantum degeneracy and can be characterized by a degeneracy parameter of $T/T_F=3$. We have measured the molecular polarizability in an optical dipole trap where the trap lifetime gives clues to interesting ultracold chemical processes. Given the large measured dipole moment of the KRb molecules of 0.5 Debye, the study of quantum degenerate molecular gases interacting via strong dipolar interactions is now within experimental reach.

physics.atom-ph↗
arXiv2008

Global solutions for two-phase Hele-Shaw bubble for a near-circular initial shape

Using a vortex sheet method we prove global existence of a near circular initial bubble in a Hele-Shaw cell with surface tension and generally finite nonzero viscosity ratio between fluids inside and outside the bubble. The circular shape is shown to be asymptotically stable for all sufficiently smooth small perturbation. The initial condition in this case, while smooth, need not be analytic.

math.DS↗
arXiv2008

A High Phase-Space-Density Gas of Polar Molecules

A quantum gas of ultracold polar molecules, with long-range and anisotropic interactions, would not only enable explorations of a large class of many-body physics phenomena, but could also be used for quantum information processing. We report on the creation of an ultracold dense gas of 40K87Rb polar molecules. Using a single step of STIRAP (STImulated Raman Adiabatic Passage) via two-frequency laser irradiation, we coherently transfer extremely weakly bound KRb molecules to the rovibrational ground state of either the triplet or the singlet electronic ground molecular potential. The polar molecular gas has a peak density of 10^12 cm^-3, and an expansion-determined translational temperature of 350 nK. The polar molecules have a permanent electric dipole moment, which we measure via Stark spectroscopy to be 0.052(2) Debye for the triplet rovibrational ground state and 0.566(17) Debye for the singlet rovibrational ground state. (1 Debye= 3.336*10^-30 C m)

quant-ph↗
arXiv2008

Heteronuclear molecules in an optical dipole trap

We report on the creation and characterization of heteronuclear KRb Feshbach molecules in an optical dipole trap. Starting from an ultracold gas mixture of K-40 and Rb-87 atoms, we create as many as 25,000 molecules at 300 nK by rf association. Optimizing the association process, we achieve a conversion efficiency of 25%. We measure the temperature dependence of the rf association process and find good agreement with a phenomenological model that has previously been applied to Feshbach molecule creation by slow magnetic-field sweeps. We also present a measurement of the binding energy of the heteronuclear molecules in the vicinity of the Feshbach resonance and provide evidence for Feshbach molecules as deeply bound as 26 MHz.

cond-mat.other↗
arXiv2008

New Limits on Coupling of Fundamental Constants to Gravity Using $^{87}$Sr Optical Lattice Clocks

The $^1\mathrm{S}_0$-$^3\mathrm{P}_0$ clock transition frequency $ν_\text{Sr}$ in neutral $^{87}$Sr has been measured relative to the Cs standard by three independent laboratories in Boulder, Paris, and Tokyo over the last three years. The agreement on the $1\times 10^{-15}$ level makes $ν_\text{Sr}$ the best agreed-upon optical atomic frequency. We combine periodic variations in the $^{87}$Sr clock frequency with $^{199}$Hg$^+$ and H-maser data to test Local Position Invariance by obtaining the strongest limits to date on gravitational-coupling coefficients for the fine-structure constant $α$, electron-proton mass ratio $μ$ and light quark mass. Furthermore, after $^{199}$Hg$^+$, $^{171}$Yb$^+$ and H, we add $^{87}$Sr as the fourth optical atomic clock species to enhance constraints on yearly drifts of $α$ and $μ$.

physics.atom-ph↗
arXiv2008

Collisional stability of fermionic Feshbach molecules

Using a Feshbach resonance, we create ultracold fermionic molecules starting from a Bose-Fermi atom gas mixture. The resulting mixture of atoms and weakly bound molecules provides a rich system for studying few-body collisions because of the variety of atomic collision partners for molecules; either bosonic, fermionic, or distinguishable atoms. Inelastic loss of the molecules near the Feshbach resonance is dramatically affected by the quantum statistics of the colliding particles and the scattering length. In particular, we observe a molecule lifetime as long as 100 ms near the Feshbach resonance.

cond-mat.other↗
arXiv2008

Ultracold dense gas of deeply bound heteronuclear molecules

Recently, the quest for an ultracold and dense ensemble of polar molecules has attracted strong interest. Polar molecules have bright prospects for novel quantum gases with long-range and anisotropic interactions, for quantum information science, and for precision measurements. However, high-density clouds of ultracold polar molecules have so far not been produced. Here, we report a key step towards this goal. Starting from an ultracold dense gas of heteronuclear 40K-87Rb Feshbach molecules with typical binding energies of a few hundred kHz and a negligible dipole moment, we coherently transfer these molecules into a vibrational level of the ground-state molecular potential bound by >10 GHz. We thereby increase the binding energy and the expected dipole moment of the 40K-87Rb molecules by more than four orders of magnitude in a single transfer step. Starting with a single initial state prepared with Feshbach association, we achieve a transfer efficiency of 84%. While dipolar effects are not yet observable, the presented technique can be extended to access much more deeply bound vibrational levels and ultimately those exhibiting a significant dipole moment. The preparation of an ultracold quantum gas of polar molecules might therefore come within experimental reach.

physics.atom-ph↗
arXiv2007

Precision Test of Mass Ratio Variations with Lattice-Confined Ultracold Molecules

We propose a precision measurement of time variations of the proton-electron mass ratio using ultracold molecules in an optical lattice. Vibrational energy intervals are sensitive to changes of the mass ratio. In contrast to measurements that use hyperfine-interval-based atomic clocks, the scheme discussed here is model-independent and does not require separation of time variations of different physical constants. The possibility of applying the zero-differential-Stark-shift optical lattice technique is explored to measure vibrational transitions at high accuracy.

physics.atom-ph↗
arXiv2006

Compact, thermal-noise-limited optical cavity for diode laser stabilization at 1 x 10-15

We demonstrate phase and frequency stabilization of a diode laser at the thermal noise limit of a passive optical cavity. The system is compact and exploits a cavity design that reduces vibration sensitivity. The sub-Hz laser is characterized by comparison to a second independent system with similar fractional frequency stability (1 x 10-15 at 1 s). The laser is further characterized by resolving a 2 Hz wide, ultranarrow optical clock transition in ultracold strontium.

physics.optics↗
arXiv2006

Narrow Line Photoassociation in an Optical Lattice

With ultracold $^{88}$Sr in a 1D magic wavelength optical lattice, we performed narrow line photoassociation spectroscopy near the $^1$S$_0 - ^3$P$_1$ intercombination transition. Nine least-bound vibrational molecular levels associated with the long-range $0_u$ and $1_u$ potential energy surfaces were measured and identified. A simple theoretical model accurately describes the level positions and treats the effects of the lattice confinement on the line shapes. The measured resonance strengths show that optical tuning of the ground state scattering length should be possible without significant atom loss.

physics.atom-ph↗
arXiv2005

The Cleo Rich Detector

We describe the design, construction and performance of a Ring Imaging Cherenkov Detector (RICH) constructed to identify charged particles in the CLEO experiment. Cherenkov radiation occurs in LiF crystals, both planar and ones with a novel ``sawtooth''-shaped exit surface. Photons in the wavelength interval 135--165 nm are detected using multi-wire chambers filled with a mixture of methane gas and triethylamine vapor. Excellent pion/kaon separation is demonstrated.

physics.ins-det↗
arXiv2001

Single crystal MgB2 with anisotropic superconducting properties

The discovery of superconductor in magnesium diboride MgB2 with high Tc (39 K) has raised some challenging issues; whether this new superconductor resembles a high temperature cuprate superconductor(HTS) or a low temperature metallic superconductor; which superconducting mechanism, a phonon- mediated BCS or a hole superconducting mechanism or other new exotic mechanism may account for this superconductivity; and how about its future for applications. In order to clarify the above questions, experiments using the single crystal sample are urgently required. Here we have first succeeded in obtaining the single crystal of this new MgB2 superconductivity, and performed its electrical resistance and magnetization measurements. Their experiments show that the electronic and magnetic properties depend on the crystallographic direction. Our results indicate that the single crystal MgB2 superconductor shows anisotropic superconducting properties and thus can provide scientific basis for the research of its superconducting mechanism and its applications.

cond-mat.supr-con↗
arXiv2001

Cooling of a single atom in an optical trap inside a resonator

We present detailed discussions of cooling and trapping mechanisms for an atom in an optical trap inside an optical cavity, as relevant to recent experiments. The interference pattern of cavity QED and trapping fields in space makes the trapping wells distinguishable from one another. This adds considerable flexibility to creating effective trapping and cooling conditions and to detection possibilities. Friction and diffusion coefficients are calculated in and beyond the low excitation limit and full 3-D simulations of the quasiclassical motion of a Cs atom are performed.

quant-ph↗
arXiv2000

The Cleo III Ring Imaging Cherenkov Detector

The CLEO detector has been upgraded to include a state of the art particle identification system, based on the Ring Imaging Cherenkov Detector (RICH) technology, in order to take data at the upgraded CESR electron positron collider. The expected performance is reviewed, as well as the preliminary results from an engineering run during the first few months of operation of the CLEO III detector.

hep-ex↗
arXiv1999

Performance of the CLEO III LiF-TEA Ring Imaging Cherenkov Detector in a High Energy Muon Beam

The CLEO III Ring Imaging Cherenkov detector uses LiF radiators to generate Cherenkov photons which are then detected by proportional wire chambers using a mixture of CH$_4$ and TEA gases. The first two photon detector modules which were constructed, were taken to Fermilab and tested in a beam dump that provided high momentum muons. We report on results using both plane and "sawtooth" shaped radiators. Specifically, we discuss the number of photoelectrons observed per ring and the angular resolution. The particle separation ability is shown to be sufficient for the physics of CLEO III.

hep-ex↗
arXiv1999

Evaluation of heating effects on atoms trapped in an optical trap

We solve a stochastic master equation based on the theory of Savard et al. [T.A. Savard, K.M. O'Hara and J.E. Thomas, Phys. Rev. A 56, R1095 (1997)] for heating arising from fluctuations in the trapping laser intensity. We compare with recent experiments of Ye et. al. [J. Ye, D.W. Vernooy and H.J. Kimble, Trapping of single atoms in cavity QED, quant-ph/9908007, Phys. Rev. Lett. (1999 in press)], and find good agreement with the experimental measurements of the distribution of trap occupancy times. The major cause of trap loss arises from the broadening of the energy distribution of the trapped atom, rather than the mean heating rate, which is a very much smaller effect.

quant-ph↗