15 research outputs found
Laser cooling of a diatomic molecule
It has been roughly three decades since laser cooling techniques produced
ultracold atoms, leading to rapid advances in a vast array of fields.
Unfortunately laser cooling has not yet been extended to molecules because of
their complex internal structure. However, this complexity makes molecules
potentially useful for many applications. For example, heteronuclear molecules
possess permanent electric dipole moments which lead to long-range, tunable,
anisotropic dipole-dipole interactions. The combination of the dipole-dipole
interaction and the precise control over molecular degrees of freedom possible
at ultracold temperatures make ultracold molecules attractive candidates for
use in quantum simulation of condensed matter systems and quantum computation.
Also ultracold molecules may provide unique opportunities for studying chemical
dynamics and for tests of fundamental symmetries. Here we experimentally
demonstrate laser cooling of the molecule strontium monofluoride (SrF). Using
an optical cycling scheme requiring only three lasers, we have observed both
Sisyphus and Doppler cooling forces which have substantially reduced the
transverse temperature of a SrF molecular beam. Currently the only technique
for producing ultracold molecules is by binding together ultracold alkali atoms
through Feshbach resonance or photoassociation. By contrast, different proposed
applications for ultracold molecules require a variety of molecular
energy-level structures. Our method provides a new route to ultracold
temperatures for molecules. In particular it bridges the gap between ultracold
temperatures and the ~1 K temperatures attainable with directly cooled
molecules (e.g. cryogenic buffer gas cooling or decelerated supersonic beams).
Ultimately our technique should enable the production of large samples of
molecules at ultracold temperatures for species that are chemically distinct
from bialkalis.Comment: 10 pages, 7 figure
Laguerre-Gaussian wave propagation in parabolic media
We report a new set of Laguerre-Gaussian wave-packets that propagate with
periodical self-focusing and finite beam width in weakly guiding inhomogeneous
media. These wave-packets are solutions to the paraxial form of the wave
equation for a medium with parabolic refractive index. The beam width is
defined as a solution of the Ermakov equation associated to the harmonic
oscillator, so its amplitude is modulated by the strength of the medium
inhomogeneity. The conventional Laguerre-Gaussian modes, available for
homogenous media, are recovered as a particular case.Comment: 11 pages, 5 figure
Laser cooling of a nanomechanical oscillator into its quantum ground state
A patterned Si nanobeam is formed which supports co-localized acoustic and
optical resonances that are coupled via radiation pressure. Starting from a
bath temperature of T=20K, the 3.68GHz nanomechanical mode is cooled into its
quantum mechanical ground state utilizing optical radiation pressure. The
mechanical mode displacement fluctuations, imprinted on the transmitted cooling
laser beam, indicate that a final phonon mode occupancy of 0.85 +-0.04 is
obtained.Comment: 18 pages, 10 figure
Frequency-resolved Monte Carlo
We adapt the Quantum Monte Carlo method to the cascaded formalism of quantum optics, allowing us to simulate the emission of photons of known energy. Statistical processing of the photon clicks thus collected agrees with the theory of frequency-resolved photon correlations, extending the range of applications based on correlations of photons of prescribed energy, in particular those of a photon-counting character. We apply the technique to autocorrelations of photon streams from a two-level system under coherent and incoherent pumping, including the Mollow triplet regime where we demonstrate the direct manifestation of leapfrog processes in producing an increased rate of two-photon emission events
The Quantum Measurement of Gravity for Geodesists and Geophysicists
During the past 30 years a great advancement in low-energy physics, particularly
interactions of atoms with the electromagnetic field, has been achieved. Quoting the
Nobel Prize talk of C. Cohen-Tannoudji, we can say that the development of
electronics and laser techniques has allowed to implement a fine manipulation of
atoms with photons. In this way, following the theory already worked out in the
50s, physicists have learnt how to cool a sample of atoms at the level of the
microkelvin Ă°lk) and, nowadays, even in the range of the nanokelvin (nk).
A wealth of important applications has sprung out from this ability of manipulating
large samples (N of the order of 10 to the seventh) of cold atoms; among them we mention, regarding the improvement of atomic clocks, the creation of atomic gyroscopes and of atomic
gravity meters. This last item is obviously of great interest to geodesists and geophysicists,
particularly for potential applications to space geodesy
Optical manipulation: Trapping ions
The unexpected demonstration of all-optical trapping of ions offers new possibilities in the simulation of quantum spin systems, ultracold chemistry with ions and more