Dynamics of molecules in pulsed optical lattices and its applications to molecular optics

Mikhail N. Shneider, P. F. Barker, Sergey Gimelshein

Felipe Herrera

Ultracold molecules are expected to find applications in cold chemistry, quantum phases, precision measurements and quantum information. In this thesis three novel applications of cold molecules are studied. First the thesis presents a general method for coherent control of collisions between non-identical particles. It is shown that by preparing two alkali-metal atoms in a superposition of hyperfine states, the elastic-to-inelastic cross section ratio can be manipulated at ultracold temperatures by tuning laser parameters in the presence of a magnetic field. The static field is needed to induce quantum interference between scattering states. Extensions of this scheme for ultracold molecular reactive scattering are discussed. Second, the thesis describes rotational excitons and polarons in molecular ensembles trapped in optical lattices. Rotational excitons can be manipulated using static electric and magnetic fields. For a one-dimensional molecular array with substitutional impurities any localized exciton state can be delocalized by applying a suitable electric field. The electric field induces correlations between diagonal and off-diagonal disorder. It is also shown that the translational motion of polar molecules in an optical lattice can lead to phonons. The lattice dynamics and the phonon spectrum depend on the strength and orientation of a static electric field. An array of polar molecules in an optical lattice can be described by generalized polaron model with tunable parameters including diagonal and off-diagonal exciton-phonon interactions. It is shown that in a strong electric field the system is described by a generalized Holstein model, and at weak electric fields by the Su-Schrieffer-Heeger (SSH) model. The possibility of observing a sharp polaron transition in the SSH model using polar alkali-metal dimers is discussed. Finally, the thesis presents a method to generate entanglement of polar molecules using strong off-resonant laser pulses. Bipartite entanglement between alkali-metal dimers separated by hundreds of nanometers can be generated. Maximally entangled states can be prepared by tuning the pulse intensity and duration. A scheme is proposed to observe the violation of Bell’s inequality based on molecular orientation correlation measurements. It is shown that using a combination of microwave and off-resonant optical pulses, arbitrary tripartite and many-particle states can be prepared.

E. E. Torres-Miyares, L. Cruz Rodríguez, Llinersy Uranga-Piña +1 more

The present study focuses in the investigation of the diffusion of polar molecules on the structures known as optical lattices (a periodic generalization of optical traps); and in the assessment of the influence of a time dependent electromagnetic field on the motion of molecule. To study this phenomenon, the particle is considered to move under the influence of a one-dimensional potential which reproduces the main characteristics of the optical lattice. Starting from the canonical representation of the electromagnetic field, it has been introduce an equivalence between this field and an ensemble of harmonics oscillators. This allows deriving an effective Langevin equation to describe the motion of the particle interacting with the bath oscillators. We analyze the influence, on the diffusion dynamics, of the parameters which determine the shape of the electromagnetic pulses, which constitutes a key ingredient for the design of optimal fields that enable an efficient control of molecular dynamics.

P. F. Barker, Alexis I. Bishop, R. C. Fulton +1 more

P. F. Barker, R. C. Fulton, Alexis I. Bishop +1 more

R. C. Fulton, Alexis I. Bishop, Mikhail N. Shneider +1 more

We describe the deceleration of nitric oxide, benzene and xenon atoms in a molecular beam using one-dimensional pulsed optical lattices created by fields with intensities in the 1012 W cm−2 range. We show that for the same pulse duration and lattice intensity the velocity of the molecules can be controlled by tailoring the lattice velocity. By utilizing the time-dependent oscillatory motion of the molecules within the lattice, we demonstrate the deceleration of nitric oxide from an initial velocity of 400 m s−1 to a final velocity of 290 m s−1 in a single 5.8 ns pulse. Using higher intensities, we measure the deceleration of benzene molecules from 380 m s−1 to 191 m s−1, representing a 75% reduction in the kinetic energy within the lattice over the same duration.