Coherent transport of cold atoms in angle-tuned optical lattices

Optical lattices with a large spacing between the minima of the optical potential can be created using the angle-tuned geometry where the 1-D periodic potential is generated by two propagating laser beams intersecting at an angle different from $\pi$. The present work analyzes the coherent transport for the case of this geometry. We show that the potential depth can be kept constant during the transport by choosing a magic value for the laser wavelength. This value agrees with that of the counterpropagating laser case, and the magic wavelength does not depend of the optical lattice geometry. Moreover, we find that this scheme can be used to implement controlled collision experiments under special geometric conditions. Finally we study the transport of hyperfine-Zeeman states of rubidium 87.Comment: 8 pages, 5 figures, one section added, in press in Phys. Rev.

Contextual Realization of the Universal Quantum Cloning Machine and of the Universal-NOT gate by Quantum Injected Optical Parametric Amplification

A simultaneous, contextual experimental demonstration of the two processes of cloning an input qubit and of flipping it into the orthogonal qubit is reported. The adopted experimental apparatus, a Quantum-Injected Optical Parametric Amplifier (QIOPA) is transformed simultaneously into a Universal Optimal Quantum Cloning Machine (UOQCM) and into a Universal NOT quantum-information gate. The two processes, indeed forbidden in their exact form for fundamental quantum limitations, will be found to be universal and optimal, i.e. the measured fidelity of both processes F<1 will be found close to the limit values evaluated by quantum theory. A contextual theoretical and experimental investigation of these processes, which may represent the basic difference between the classical and the quantum worlds, can reveal in a unifying manner the detailed structure of quantum information. It may also enlighten the yet little explored interconnections of fundamental axiomatic properties within the deep structure of quantum mechanics. PACS numbers: 03.67.-a, 03.65.Ta, 03.65.UdComment: 27 pages, 7 figure

Manipulation of ultracold atomic mixtures using microwave techniques

We used microwave radiation to evaporatively cool a mixture of of 133Cs and 87Rb atoms in a magnetic trap. A mixture composed of an equal number (around 10^4) of Rb and Cs atoms in their doubly polarized states at ultracold temperatures was prepared. We also used microwaves to selectively evaporate atoms in different Zeeman states.Comment: 9 pages, 6 figure

Resonantly enhanced tunneling of Bose-Einstein condensates in periodic potentials

We report on measurements of resonantly enhanced tunneling of Bose-Einstein condensates loaded into an optical lattice. By controlling the initial conditions of our system we were able to observe resonant tunneling in the ground and the first two excited states of the lattice wells. We also investigated the effect of the intrinsic nonlinearity of the condensate on the tunneling resonances.Comment: accepted for publication in Phys. Rev. Letter

Dynamical control of matter-wave tunneling in periodic potentials

We report on measurements of dynamical suppression of inter-well tunneling of a Bose-Einstein condensate (BEC) in a strongly driven optical lattice. The strong driving is a sinusoidal shaking of the lattice corresponding to a time-varying linear potential, and the tunneling is measured by letting the BEC freely expand in the lattice. The measured tunneling rate is reduced and, for certain values of the shaking parameter, completely suppressed. Our results are in excellent agreement with theoretical predictions. Furthermore, we have verified that in general the strong shaking does not destroy the phase coherence of the BEC, opening up the possibility of realizing quantum phase transitions by using the shaking strength as the control parameter.Comment: 5 pages, 3 figure

Observation of photon-assisted tunneling in optical lattices

We have observed tunneling suppression and photon-assisted tunneling of Bose-Einstein condensates in an optical lattice subjected to a constant force plus a sinusoidal shaking. For a sufficiently large constant force, the ground energy levels of the lattice are shifted out of resonance and tunneling is suppressed; when the shaking is switched on, the levels are coupled by low-frequency photons and tunneling resumes. Our results agree well with theoretical predictions and demonstrate the usefulness of optical lattices for studying solid-state phenomena.Comment: 5 pages, 3 figure

Sympathetic cooling and collisional properties of a Rb-Cs mixture

We report on measurements of the collisional properties of a mixture of $^{133}$Cs and $^{87}$Rb atoms in a magnetic trap at $\mu\mathrm{K}$ temperatures. By selectively evaporating the Rb atoms using a radio-frequency field, we achieved sympathetic cooling of Cs down to a few $\mu\mathrm{K}$. The inter-species collisional cross-section was determined through rethermalization measurements, leading to an estimate of $a_s=595 a_0$ for the s-wave scattering length for Rb in the $|F=2, m_F=2>$ and Cs in the $|F=4, m_F=4>$ magnetic states. We briefly speculate on the prospects for reaching Bose-Einstein condensation of Cs inside a magnetic trap through sympathetic cooling

Dressed matter waves

We suggest to view ultracold atoms in a time-periodically shifted optical lattice as a "dressed matter wave", analogous to a dressed atom in an electromagnetic field. A possible effect lending support to this concept is a transition of ultracold bosonic atoms from a superfluid to a Mott-insulating state in response to appropriate "dressing" achieved through time-periodic lattice modulation. In order to observe this effect in a laboratory experiment, one has to identify conditions allowing for effectively adiabatic motion of a many-body Floquet state.Comment: 9 pages, 4 figures, to be published in: J. Phys.: Conference Serie

The Use of Both Therapeutic and Prophylactic Vaccines in the Therapy of Papillomavirus Disease

Human papillomavirus (HPV) is the most common sexually transmitted virus. The high-risk HPV types (i.e., HPV16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59) are considered to be the main etiological agents of genital tract cancers, such as cervical, vulvar, vaginal, penile, and anal cancers, and of a subset of head and neck cancers. Three prophylactic HPV vaccines are available that are bivalent (vs. HPV16, 18), tetravalent (vs. HPV6, 11, 16, 18), and non-avalent (vs. HPV6, 11, 16, 18, 31, 33,45, 52, 58). All of these vaccines are based on recombinant DNA technology, and they are prepared from the purified L1 protein that self-assembles to form the HPV type-specific empty shells (i.e., virus-like particles). These vaccines are highly immunogenic and induce specific antibodies. Therapeutic vaccines differ from prophylactic vaccines, as they are designed to generate cell-mediated immunity against transformed cells, rather than neutralizing antibodies. Among the HPV proteins, the E6 and E7 oncoproteins are considered almost ideal as targets for immunotherapy of cervical cancer, as they are essential for the onset and evolution of malignancy and are constitutively expressed in both premalignant and invasive lesions. Several strategies have been investigated for HPV therapeutic vaccines designed to enhance CD4+ and CD8+ T-cell responses, including genetic vaccines (i.e., DNA/ RNA/virus/ bacterial), and protein-based, peptide-based or dendritic-cell-based vaccines. However, no vaccine has yet been licensed for therapeutic use. Several studies have suggested that administration of prophylactic vaccines immediately after surgical treatment of CIN2 cervical lesions can be considered as an adjuvant to prevent reactivation or reinfection, and other studies have described the relevance of prophylactic vaccines in the management of genital warts. This review summarizes the leading features of therapeutic vaccines, which mainly target the early oncoproteins E6 and E7, and prophylactic vaccines, which are based on the L1 capsid protein. Through an analysis of the specific immunogenic properties of these two types of vaccines, we discuss why and how prophylactic vaccines can be effective in the treatment of HPV-related lesions and relapse

AC-induced superfluidity

We argue that a system of ultracold bosonic atoms in a tilted optical lattice can become superfluid in response to resonant AC forcing. Among others, this allows one to prepare a Bose-Einstein condensate in a state associated with a negative effective mass. Our reasoning is backed by both exact numerical simulations for systems consisting of few particles, and by a theoretical approach based on Floquet-Fock states.Comment: Accepted for publication in Europhysics letters, 6 pages, 4 figures, Changes in v2: reference 7 replaced by a more recent on