Optimizing Single-Photon Cooling

Single-photon cooling is a recently introduced method to cool atoms and molecules for which standard methods might not be applicable. We numerically examine this method in a two-dimensional wedge trap as well as in a two-dimensional harmonic trap. An element of the method is a small optical box with ``diodic'' walls which moves slowly through the external potential and catches atoms irreversibly. We show that the cooling efficiency of the method can be improved by optimizing the trajectory of this box.Single-photon cooling is a recently introduced method to cool atoms and molecules for which standard methods might not be applicable. We numerically examine this method in a two-dimensional wedge trap as well as in a two-dimensional harmonic trap. An element of the method is a small optical box with ``diodic'' walls which moves slowly through the external potential and catches atoms irreversibly. We show that the cooling efficiency of the method can be improved by optimizing the trajectory of this box.

arXiv:1204.0352Physical Review AOct 24, 20123 citations

Single-photon molecular cooling

Edvardas Narevicius, Stephen Travis Bannerman, Mark G. Raizen

We propose a general method to cool the translational motion of molecules. Our method is an extension of single photon atomic cooling which was successfully implemented in our laboratory. Requiring a single event of absorption followed by a spontaneous emission, this method circumvents the need for a cycling transition and can be applied to any paramagnetic or polar molecule. In our approach, trapped molecules would be captured near their classical turning points in an optical dipole or RF-trap following an irreversible transition process.We propose a general method to cool the translational motion of molecules. Our method is an extension of single photon atomic cooling which was successfully implemented in our laboratory. Requiring a single event of absorption followed by a spontaneous emission, this method circumvents the need for a cycling transition and can be applied to any paramagnetic or polar molecule. In our approach, trapped molecules would be captured near their classical turning points in an optical dipole or RF-trap following an irreversible transition process.

arXiv:0808.1383New Journal of PhysicsMay 14, 200928 citations

Single-photon cooling in a wedge billiard

Seok Jin Choi, Bala Sundaram, Mark G. Raizen

Single-photon cooling (SPC), noted for its potential as a versatile method for cooling a variety of atomic species, has recently been demonstrated experimentally. In this paper, we study possible ways to improve the performance of SPC by applying it to atoms trapped inside a wedge billiard. The main feature of the wedge billiard for atoms, also experimentally realized recently, is that the nature of atomic trajectories within it changes from stable periodic orbit to random chaotic motion with the change in wedge angle. We find that a high cooling efficiency is possible in this system with a relatively weak dependence on the wedge angle and that chaotic dynamics, rather than a regular orbit, is more desirable for enhancing the performance of SPC.Single-photon cooling (SPC), noted for its potential as a versatile method for cooling a variety of atomic species, has recently been demonstrated experimentally. In this paper, we study possible ways to improve the performance of SPC by applying it to atoms trapped inside a wedge billiard. The main feature of the wedge billiard for atoms, also experimentally realized recently, is that the nature of atomic trajectories within it changes from stable periodic orbit to random chaotic motion with the change in wedge angle. We find that a high cooling efficiency is possible in this system with a relatively weak dependence on the wedge angle and that chaotic dynamics, rather than a regular orbit, is more desirable for enhancing the performance of SPC.

arXiv:1008.1255Physical Review ASep 16, 20104 citations

Cavity cooling and spectroscopy of a bound atom-cavity system

Peter Maunz

Cooling is indispensable for trapping and observing single free atoms.In atomic physics, this can be achieved efficiently by laser cooling.Conventional methods to laser cool atoms are based on repeated optical pumping cycles followed by spontaneous emission of a photon from the atom.Such pumping schemes can only be applied to certain atomic species, which have a closed optical transition.Drawbacks caused by photons spontaneously emitted from the atom can be avoided in the strongly coupled atom-cavity system in which energy and entropy can be removed by photons lost from the cavity.This thesis reports on the first observation of this cooling mechanism which does not rely on spontaneous emission.In the experiment, a single atom is captured in an intracavity dipole trap.Illuminating the system with a weak, slightly blue-detuned light beam extends the storage time of the atom in the trap.The observed cooling force is at least five times larger than the force achieved by free-space cooling methods at comparable excitation of a two-level atom.Utilising cavity cooling, single atoms are prepared strongly-coupled to the mode of a high-finesse cavity.This allows to observe two well-resolved normal-mode peaks in both the cavity transmission as well as in the trap lifetime.The experiment is in agreement with a Monte Carlo simulation, demonstrating the localisation of the atom to within a tenth of a wavelength.The ability to individually excite the normal modes opens new possibilities to use this system for applications in quantum information science, including the realisation of quantum-logic gates.In the future cavity cooling might be applied to systems which cannot be cooled by conventional methods as for instance molecules or an atom carrying a quantum bit.Cooling is indispensable for trapping and observing single free atoms.In atomic physics, this can be achieved efficiently by laser cooling.Conventional methods to laser cool atoms are based on repeated optical pumping cycles followed by spontaneous emission of a photon from the atom.Such pumping schemes can only be applied to certain atomic species, which have a closed optical transition.Drawbacks caused by photons spontaneously emitted from the atom can be avoided in the strongly coupled atom-cavity system in which energy and entropy can be removed by photons lost from the cavity.This thesis reports on the first observation of this cooling mechanism which does not rely on spontaneous emission.In the experiment, a single atom is captured in an intracavity dipole trap.Illuminating the system with a weak, slightly blue-detuned light beam extends the storage time of the atom in the trap.The observed cooling force is at least five times larger than the force achieved by free-space cooling methods at comparable excitation of a two-level atom.Utilising cavity cooling, single atoms are prepared strongly-coupled to the mode of a high-finesse cavity.This allows to observe two well-resolved normal-mode peaks in both the cavity transmission as well as in the trap lifetime.The experiment is in agreement with a Monte Carlo simulation, demonstrating the localisation of the atom to within a tenth of a wavelength.The ability to individually excite the normal modes opens new possibilities to use this system for applications in quantum information science, including the realisation of quantum-logic gates.In the future cavity cooling might be applied to systems which cannot be cooled by conventional methods as for instance molecules or an atom carrying a quantum bit.

Mar 1, 20053 citations

Continuous all-optical deceleration and single-photon cooling of molecular beams

Andrew M. Jayich, Amar C. Vutha, Matthew T. Hummon +2 more

Ultracold molecular gases are promising as an avenue to rich many-body physics, quantum chemistry, quantum information, and precision measurements. This richness, which flows from the complex internal structure of molecules, makes the creation of ultracold molecular gases using traditional methods (laser plus evaporative cooling) a challenge, in particular due to the spontaneous decay of molecules into dark states. We propose a way to circumvent this key bottleneck using an all-optical method for decelerating molecules using stimulated absorption and emission with a single ultrafast laser. We further describe single-photon cooling of the decelerating molecules that exploits their high dark state pumping rates, turning the principal obstacle to molecular laser cooling into an advantage. Cooling and deceleration may be applied simultaneously and continuously to load molecules into a trap. We discuss implementation details including multilevel numerical simulations of strontium monohydride. These techniques are applicable to a large number of molecular species and atoms with the only requirement being an electric dipole transition that can be accessed with an ultrafast laser.Ultracold molecular gases are promising as an avenue to rich many-body physics, quantum chemistry, quantum information, and precision measurements. This richness, which flows from the complex internal structure of molecules, makes the creation of ultracold molecular gases using traditional methods (laser plus evaporative cooling) a challenge, in particular due to the spontaneous decay of molecules into dark states. We propose a way to circumvent this key bottleneck using an all-optical method for decelerating molecules using stimulated absorption and emission with a single ultrafast laser. We further describe single-photon cooling of the decelerating molecules that exploits their high dark state pumping rates, turning the principal obstacle to molecular laser cooling into an advantage. Cooling and deceleration may be applied simultaneously and continuously to load molecules into a trap. We discuss implementation details including multilevel numerical simulations of strontium monohydride. These techniques are applicable to a large number of molecular species and atoms with the only requirement being an electric dipole transition that can be accessed with an ultrafast laser.

arXiv:1312.4499Physical Review AFeb 21, 201429 citations

Optimizing the efficiency of evaporative cooling in optical dipole traps

Abraham J. Olson, Robert Niffenegger, Yong P. Chen

We present a combined computational and experimental study to optimize the efficiency of evaporative cooling for atoms in optical dipole traps. By employing a kinetic model of evaporation, we provide a strategy for determining the optimal relation between atom temperature, trap depth, and average trap frequency during evaporation given experimental initial conditions. We then experimentally implement a highly efficient evaporation process in an optical dipole trap, showing excellent agreement between the theory and experiment. This method has allowed the creation of pure Bose-Einstein condensates of ${}^{87}$ Rb with $2\ifmmode\times\else\texttimes\fi{}{10}^{4}$ atoms starting from only $5\ifmmode\times\else\texttimes\fi{}{10}^{5}$ atoms initially loaded in the optical dipole trap, achieving an evaporation efficiency ${\ensuremath{\gamma}}_{\mathrm{eff}}$ of 4.0 during evaporation.We present a combined computational and experimental study to optimize the efficiency of evaporative cooling for atoms in optical dipole traps. By employing a kinetic model of evaporation, we provide a strategy for determining the optimal relation between atom temperature, trap depth, and average trap frequency during evaporation given experimental initial conditions. We then experimentally implement a highly efficient evaporation process in an optical dipole trap, showing excellent agreement between the theory and experiment. This method has allowed the creation of pure Bose-Einstein condensates of ${}^{87}$Rb with $2\ifmmode\times\else\texttimes\fi{}{10}^{4}$ atoms starting from only $5\ifmmode\times\else\texttimes\fi{}{10}^{5}$ atoms initially loaded in the optical dipole trap, achieving an evaporation efficiency ${\ensuremath{\gamma}}_{\mathrm{eff}}$ of 4.0 during evaporation.

arXiv:1211.3469Physical Review AMay 20, 201344 citations

{}^{87}

Rb with $2\ifmmode\times\else\texttimes\fi{}{10}^{4}$ atoms starting from only $5\ifmmode\times\else\texttimes\fi{}{10}^{5}$ atoms initially loaded in the optical dipole trap, achieving an evaporation efficiency ${\ensuremath{\gamma}}_{\mathrm{eff}}$ of 4.0 during evaporation.