|
|
Date: Oct. 15, 2007: Prof. Markus Greiner, Harvard Title: “Quantum Gas Microscopy:
Towards Lattices with Optical Addressability” |
|
|
Date:
Oct. 22, 2007: Dr. Pascal Naidon, NIST Title: “Two-Body Transients in
Coupled Atom-Molecule Bose-Einstein Condensates” |
|
|
Abstract: Ultracold atoms can be
associated into diatomic molecules by applying a resonant laser. This two-body
process, known as photoassociation, may be limited
at high laser intensities by
the unitarity of the S-matrix. In the case of a
Bose- Einstein condensate of atoms, many-body models have predicted
that the conversion to molecules may be limited at even lower
intensities, because of molecules breaking up into noncondensate
atoms, a process called "rogue dissociation". In the talk, I will show that there are three regimes of photoassociation in a Bose-Einstein condensate, and that they all can be understood on
the basis of time-dependent two-body theory.
In particular, the rogue dissociation is not a many-body effect, but results from a "universal"
transient response of individual atom pairs.
Finally, I will illustrate how the three regimes could be observed by photoassociating condensates of alkaline-earth atoms. |
|
|
Date
Oct. 29, 2007: Dr. Ippei Danshita,
NIST: Title: “Quantum Phases of Ultracold Bosons in Double Well Optical Lattices.” |
|
|
Abstract: Recently, the experimental realization of double-well
optical lattices has attracted much
interest [1]. In this talk, I will discuss the superfluid
and insulating phases of bosons in double-well optical lattices and
focus on the specific example of a two-legged ladder, which is currently
accessible in experiments. Applying both
mean-field and time-evolving block decimation [2] techniques to the two-leg Bose-Hubbard Hamiltonian, the
zero-temperature phase diagrams are obtained.
The critical points separating the insulating and superfluid phases at
commensurate fillings, where the Berezinskii-Kosterlitz-Thouless transition occurs, are determined. I will show that the phase diagram depends significantly on the interchain hopping and tilt between double wells.
In particular, the insulating phase at unit filling exhibits a non-monotonic behavior as a function of the tilt
parameter, producing a reentrant phase transition
between superfluid and insulating phases. [1] J. Sebby-Strabley et al., Phys.
Rev. A 73, 033605 (2006); M. Anderlini et al., Nature ( [2] G. Vidal, Phys. Rev. Lett. 93,
040502 (2004); ibid. 98, 070201 (2007). |
|
|
Date:
Nov. 5, 2007: Dr. Hua-Gen Yu, BNL Title: Strategies to Study Large Amplitude
Motions in Molecular Spectroscopy |
|
|
Abstract: Molecules in highly excited vibrational states undergo large amplitude motions (LAM). These motions often make molecular spectra complicated through the anharmonicity of potential energy surfaces, and/or the quantum nonadiabatic effects. Therefore, it becomes a challenge to study the large amplitude motions of molecules in quantum dynamics calculations, especially, for many-body systems. This is also partially due to the failure of traditional theories such as the normal mode picture and perturbation approaches. In this talk, we will discuss a few of strategies to deal with the LAMs for polyatomic molecules. They include the coherent discrete variable representation (ZDVR)[1], the two-layer Lanczos iterative diagonalization algorithm[2], and the orthogonal scattering coordinates[3-4] together with applications. [1] H.-G. Yu, J. Chem. Phys., 122 (2005) 164107. [2] H.-G. Yu, J. Chem. Phys., 120 (2004) 2270. [3] H.-G. Yu, J.T. Muckerman, and T.J. Sears, J. Chem. Phys., 116 (2002) 1435. [4]
H.-G. Yu, and J. T. Muckerman, J. Mol. Spectrosc. 214 (2002) 11. |
|
|
Date:
Nov. 12 and 15, 2007: Prof. Pierre Meystre,
University of Nov. 12: Title: “Matter-Wave Superradiance” Nov. 15: Title: “Polar Condensates” |
|
|
|
|
|
|
|
|
Date: Nov. 26,
2007: Prof. Chris Search, Stevens Institute of Technology Title: Spin Current from Quantum Dots Embedded
in a Microcavity Abstract: Experiments with self-assembled quantum dots have recently progressed towards electrical control of the charge state of dots embedded in microcavities. At the same time, a number of experiments have shown strong coupling to a single optical microcavity mode while others have studied the conductance and current noise through self-assembled dots. These parallel avenues of research have motivated us to study theoretically how electrical transport through a quantum dot would be effected by coupling to a cavity mode. We have developed a model for quantum dots coupled to a lead at zero bias with one of the Zeeman states lying below the Fermi level of the lead and the other above. Raman transitions involving a pump laser and a quantized cavity mode induce spin flips inside the dot that result in a pure spin current flowing from the dot. We have studied the characteristics of the spin current generated by this quantum dot spin battery as well as the associated current noise. The spin current is strongly correlated with the photon current associated with photons leaking out of the cavity as are their associated noise spectra. We find that in our system, the spin current can be significantly larger than for the case of spin flips induced by electron spin resonance. The spin current noise spectra show clear structures that are a result of the discrete nature of photon states in the cavity. For the case of a driven cavity mode, the spin current also exhibits bistability as a function of the laser amplitude that drives the cavity. |
|
|
Date: Dec. 3, 2007 (4:00 PM in S-141):
Ana Maria Rey, Harvard Title:
Quantum magnetism in optical superlattices Abstract:
By loading spinor atoms in optical lattices it is now possible to simulate
quantum spin models in controlled environments and to study quantum magnetism in strongly correlated systems. In this
talk I will describe
a technique that allows one to prepare, detect
and control superexchange interactions in ultra-cold spinor atoms loaded in optical superlattices. I will focus this discussion
in the context of recent experiments that measured for the first time such super-exchange interactions. I shall also discuss the many-body
dynamics arising from coherent coupling
between singlet-triplet pairs in adjacent double-wells, in
particular the generation of complex magnetic and maximally entangled states by non-equilibrium
dynamics. |
|
|
Date: Friday, Dec.
7, 2007 (2:45 PM in S-141) Prof. Anatoly Kuklov,
CUNY Title:
"Strongly interacting quantum phases of ultracold
atomic mixtures in optical
lattices" I will
discuss mixtures of non-convertible atomic species in optical lattices. The case of integer total filling
per site with strong repulsion
may lead to so called supercounterfluidity which
finds analogy in spin systems in the case of
two-component mixtures. In general,
it is a state characterized by zero net transfer of atoms and superfluid counterflows of all species. Depending on interactions,
the order parameter may feature quasi-molecular complexes
consisting of several atomic units and can be characterized by additional symmetries. Results of Monte-Carlo simulations for
phase diagram of a two-component bosonic
mixture are presented. Detection
scheme relying on the noise analysis of the absorption image is discussed. Possibilities of inducing phases
characterized by broken lattice symmetries are considered as well. |
|
|
Date: Friday, Dec. 14,
2007 (3:00 PM in S141): Kyung Soo Choi, Caltech Title:
“A reversible matter-light quantum interface for mapping
entanglement” Abstract:
In the field of quantum information science, a considerable activity has been
focused on the development of scalable quantum network. A promising
architecture for quantum network is composed of quantum nodes for storing and
processing information, and photonic channels which link the remote nodes for
distributing entanglement [1]. In this talk, I will briefly review progresses
towards this goal utilizing the interactions of single photons with atomic
ensembles (as a quantum node), and show a recent experimental demonstration
of coherent conversion of photonic entanglement into and out of atomic
memories. In contrast to (probabilistic) progresses to date, this strategy
allows the intrinsically deterministic creation and subsequent state-transfer
of the entangled state. Thus, this protocol provides a promising avenue to
generate photonic entanglement, and distribute the entanglement between
matter and light in a “push-button” fashion for quantum networks. [1]
H. J. Briegel, W. Dur, J.
I. Cirac and P. Zoller, Phys.
Rev. Lett. 81, 5932 (1998) |
|
|
|
|
|
|
|
|
|
|
|
|