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Optica Applicata

Production of spinor condensates of 87 Rb released from a magnetic trap

R. Gartman, Marcin Piotrowski, J. Szczepkowski, Marcin Witkowski, M. Zawada, Wojciech Gawlik

Published Jan 1, 2010• 0 citations
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Abstract

Most of spinor condensates studied so far were produced in situ in dipole optical traps. Our new method allows production of spinor condensates in an expanding atomic cloud. Since the spinor condensate is created outside the trap, the Bose –E instein condensate can be prepared in any trap, either magnetic or optical dipole, which significantly extends the experimental flexibility. The described method permits also study of collisions between low density spinor condensates.

Related papers

Production and study of spinor condensates of 87Rb released from a magnetic trap

R. Gartman, Marcin Piotrowski, J. Szczepkowski +4 more

Most of spinor condensates studies so far, were produced in situ in dipole magnetic and optical traps. Atomic densities are then too big to allow observation of weak dipolar interaction within the spinor condensate of alkali atoms. This paper studies about spinor condensates in the F=2 state of87Rb produced in an atomic cloud expanding after realising from a magnetic trap. The method used in this research allows production of spinor condensates in an expanding atomic cloud where density is low enough to permit such studies. This method is based on appropriate sequence of magnetic perturbations. Preliminary results indicate dynamics of mixing between various magnetic sublevels MFcontrolled by duration and strength of magnetic perturbation.

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)•Jun 1, 2009•0 citations

Bose-Einstein condensates in a large-volume optical trap

Axel Görlitz, T. L. Gustavson, A. E. Leanhardt +7 more

Summary form only given. Bose-Einstein condensates (BEC) are generally produced by evaporative cooling of laser cooled atomic samples in magnetic traps. Though magnetic traps are indispensable for the production of a BEC, they pose restrictions on the possible studies with a BEC. Previous experiments of our group have demonstrated that it is possible to trap a BEC in the circular focus of a far-detuned infrared laser beam. This first realization of an optical dipole trap (ODT) for BEC was used to prepare and investigate spinor condensates of Na atoms in the F=1 hyperfine manifold. However, the initial peak density in this ODT after loading from the magnetic trap reached 10/sup 15/ atoms/cm/sup 3/, leading to rapid losses due to three-body collisions. To realize an ODT capable of storing large condensates for a long time, we have used a laser beam with an elliptical beam profile. The optical trap is loaded by superimposing the light field onto the magnetic trap and then slowly turning off the magnetic fields. The transfer efficiency is close to 100%, and thus more than 10/sup 7/ Bose-condensed atoms can be loaded into the ODT.

Quantum Electronics and Laser Science Conference•Nov 13, 2002•0 citations

A simple recipe for rapid all-optical formation of spinor Bose–Einstein condensates

Chih-Yuan Huang, Chun-Chia Chen, Li-An Sun +4 more

Abstract We present a simple recipe for the rapid formation of spinor Bose–Einstein condensates of 87 Rb atoms in a three-beam crossed optical dipole trap (ODT). Two laser Gaussian beams were crossed at a small angle to form an effective single potential in the intersection region with an independent and widely tunable trap volume and aspect ratio, for both efficient atom loading and number density enhancement. A third Gaussian beam was then introduced to create a potential dimple at the trap center to further increase the atom number density and collision rate, which enabled rapid evaporation to a Bose condensation. In this configuration, 2 × 10 6 atoms were loaded into the three-beam crossed trap from a vapor cell magneto-optical trap, and condensates of 3 × 10 4 – 4.5 × 10 4 atoms were created after 3–5 s of rapid evaporation. The demonstration of efficient and robust BEC production in this ODT suggests the applicability of this trapping geometry to lasers with any far off-resonant wavelengths. To prepare the spinor condensates with a wide tunability of spin population, control of the magnetic fields was first employed during evaporation to polarize the spin states, and the tuning mechanism is discussed. Spinor condensates with an arbitrary spin population were then created via multiple microwave pulses driving the ground hyperfine transitions.

Journal of Physics B Atomic Molecular and Optical Physics•Jun 14, 2017•8 citations

All-Optical Formation of an Atomic Bose-Einstein Condensate

M. D. Barrett, J. A. Sauer, Michael Chapman

We have created a Bose-Einstein condensate (BEC) of ${}^{87}\mathrm{Rb}$ atoms directly in an optical trap. We employ a quasielectrostatic dipole force trap formed by two crossed ${\mathrm{CO}}_{2}$ laser beams. Loading directly from a sub-Doppler laser-cooled cloud of atoms results in initial phase space densities of $\ensuremath{\sim}1/200$. Evaporatively cooling through the BEC transition is achieved by lowering the power in the trapping beams over $\ensuremath{\sim}2\mathrm{s}$. The resulting condensates are $F\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1$ spinors with $3.5\ifmmode\times\else\texttimes\fi{}{10}^{4}$ atoms distributed between the ${m}_{F}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(\ensuremath{-}1,0,1)$ states.

arXiv:cond-mat/0106027•Physical Review Letters•Jun 19, 2001•635 citations

All-optical 87Rb Bose-Einstein condensate apparatus: construction and operation

I. L. H. Humbert

Research on degenerate quantum gases of dilute atomic gases has become a well established field in modern physics and revealed many astonishing phenomena. The first experiments on Bose and Fermi gases at low temperatures aimed to prove the predictions of quantum mechanics on a macroscopic scale. Since then we make use of Bose and Fermi gases and mixtures of any combination to model other many body systems. A property of Bose Einstein condensates is superfluidity which we want to investigate further in toroidal potentials with a new apparatus which can produce an all-optical BEC. This means trapping thermal atoms in an optical dipole trap and cooling the sample by evaporation into the quantum degenerate regime. This new technique was first successfully demonstrated by M.D. Barrett et al. in 2001 and promises to be faster and simpler than the well established and common way of evaporation in magnetic traps. A new apparatus was built by the author and we report on the experimental details of the trapping of 87Rb atoms from a hot vapour and cooling them in a magneto-optical trap, and further evaporation to quantum degeneracy in a crossed optical dipole trap operating at a wavelength of l = 1064nm, with accurate control of the power in both beams via a feedback loop. The evaporation of neutral atoms of 87Rb in far red detuned optical dipole traps using linearly polarised laser light is spin independent, and mixed spinor condensates of the F=1 manifold can be formed. As an empirical technique we found by applying a magnetic gradient field during the final evaporation that we can selectively populate mF spin states or prepare mixtures. This intriguing mechanism was found earlier as well by M. S. Chang, but is yet not fully understood and subject of our future research. We can now routinely prepare an almost pure condensate containing up to 7000 atoms in the condensed phase purely in the mF = 0 spin state. This thesis contains the theoretical framework of Bose-Einstein condensation with in mean-field theory, the concepts of cooling of atoms in magneto-optical traps, the trapping and evaporation in optical dipole traps and the experimental realisation. In the future this experiment will be extended by a fast scanning dipole trap to apply arbitrary time averaged potentials of more complex geometries, such as toroidal traps to study the effects of superfluidity in a periodic potential. The production of toroidal traps and cold atoms in such a trap are outlined in this thesis.

•Jan 1, 2012•0 citations

All-Optical Spinor Bose-Einstein Condensation and the Spinor Dynamics-Driven Atom Laser

Nathan E. Lundblad

Optical trapping as a viable means of exploring the physics of ultracold dilute atomic gases has revealed a new spectrum of physical phenomena. In particular, macroscopic and sudden occupation of the ground state below a critical temperature—-a phenomenon known as Bose-Einstein condensation—-has become an even richer system for the study of quantum mechanics, ultracold collisions, and many-body physics in general. Optical trapping liberates the spin degree of the BEC, making the order parameter vectorial (‘spinor BEC’), as opposed to the scalar order of traditional magnetically trapped condensates. The work described within is divided into two main efforts. The first encompasses the all-optical creation of a Bose-Einstein condensate in rubidium vapor. An all-optical path to spinor BEC (as opposed to transfer to an optical trap from a magnetic-trap condensate) was desired both for the simplicity of the experimental setup and also for the potential gains in speed of creation; evaporative cooling, the only known path to dilute-gas condensation, works only as efficiently as the rate of elastic collisions in the gas, a rate that starts out much higher in optical traps. The first all-optical BEC was formed elsewhere in 2001; the years following saw many groups worldwide seeking to create their own version. Our own all-optical spinor BEC, made with a single-beam dipole trap formed by a focused CO₂ laser, is described here, with particular attention paid to trap loading, measurement of trap parameters, and the use of a novel 780 nm high-power laser system. The second part describes initial experiments performed with the nascent condensate. The spinor properties of the condensate are documented, and a measurement is made of the density-dependent rate of spin mixing in the condensate. In addition, we demonstrate a novel dual-beam atom laser formed by outcoupling oppositely polarized components of the condensate, whose populations have been coherently evolved through spin dynamics. We drive coherent spin-mixing evolution through adiabatic compression of the initially weak trap. Such dual beams, nominally number-correlated through the angular momentum-conserving collision m=0 + m=0 ⇌ m=+1 + m=-1 have been proposed as tools to explore entanglement and squeezing in Bose-Einstein condensates.

•May 30, 2006•0 citations
Most of spinor condensates studied so far were produced in situ in dipole optical traps. Our new method allows production of spinor condensates in an expanding atomic cloud. Since the spinor condensate is created outside the trap, the Bose –E instein condensate can be prepared in any trap, either magnetic or optical dipole, which significantly extends the experimental flexibility. The described method permits also study of collisions between low density spinor condensates.
Most of spinor condensates studies so far, were produced in situ in dipole magnetic and optical traps. Atomic densities are then too big to allow observation of weak dipolar interaction within the spinor condensate of alkali atoms. This paper studies about spinor condensates in the F=2 state of87Rb produced in an atomic cloud expanding after realising from a magnetic trap. The method used in this research allows production of spinor condensates in an expanding atomic cloud where density is low enough to permit such studies. This method is based on appropriate sequence of magnetic perturbations. Preliminary results indicate dynamics of mixing between various magnetic sublevels MFcontrolled by duration and strength of magnetic perturbation.
Summary form only given. Bose-Einstein condensates (BEC) are generally produced by evaporative cooling of laser cooled atomic samples in magnetic traps. Though magnetic traps are indispensable for the production of a BEC, they pose restrictions on the possible studies with a BEC. Previous experiments of our group have demonstrated that it is possible to trap a BEC in the circular focus of a far-detuned infrared laser beam. This first realization of an optical dipole trap (ODT) for BEC was used to prepare and investigate spinor condensates of Na atoms in the F=1 hyperfine manifold. However, the initial peak density in this ODT after loading from the magnetic trap reached 10/sup 15/ atoms/cm/sup 3/, leading to rapid losses due to three-body collisions. To realize an ODT capable of storing large condensates for a long time, we have used a laser beam with an elliptical beam profile. The optical trap is loaded by superimposing the light field onto the magnetic trap and then slowly turning off the magnetic fields. The transfer efficiency is close to 100%, and thus more than 10/sup 7/ Bose-condensed atoms can be loaded into the ODT.
Abstract We present a simple recipe for the rapid formation of spinor Bose–Einstein condensates of 87 Rb atoms in a three-beam crossed optical dipole trap (ODT). Two laser Gaussian beams were crossed at a small angle to form an effective single potential in the intersection region with an independent and widely tunable trap volume and aspect ratio, for both efficient atom loading and number density enhancement. A third Gaussian beam was then introduced to create a potential dimple at the trap center to further increase the atom number density and collision rate, which enabled rapid evaporation to a Bose condensation. In this configuration, 2 × 10 6 atoms were loaded into the three-beam crossed trap from a vapor cell magneto-optical trap, and condensates of 3 × 10 4 – 4.5 × 10 4 atoms were created after 3–5 s of rapid evaporation. The demonstration of efficient and robust BEC production in this ODT suggests the applicability of this trapping geometry to lasers with any far off-resonant wavelengths. To prepare the spinor condensates with a wide tunability of spin population, control of the magnetic fields was first employed during evaporation to polarize the spin states, and the tuning mechanism is discussed. Spinor condensates with an arbitrary spin population were then created via multiple microwave pulses driving the ground hyperfine transitions.
We have created a Bose-Einstein condensate (BEC) of 87Rb{}^{87}\mathrm{Rb}87Rb atoms directly in an optical trap. We employ a quasielectrostatic dipole force trap formed by two crossed CO2{\mathrm{CO}}_{2}CO2​ laser beams. Loading directly from a sub-Doppler laser-cooled cloud of atoms results in initial phase space densities of $\ensuremath{\sim}1/200$. Evaporatively cooling through the BEC transition is achieved by lowering the power in the trapping beams over $\ensuremath{\sim}2\mathrm{s}$. The resulting condensates are F=1F\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1F=1 spinors with $3.5\ifmmode\times\else\texttimes\fi{}{10}^{4}$ atoms distributed between the ${m}_{F}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(\ensuremath{-}1,0,1)$ states.
Research on degenerate quantum gases of dilute atomic gases has become a well established field in modern physics and revealed many astonishing phenomena. The first experiments on Bose and Fermi gases at low temperatures aimed to prove the predictions of quantum mechanics on a macroscopic scale. Since then we make use of Bose and Fermi gases and mixtures of any combination to model other many body systems. A property of Bose Einstein condensates is superfluidity which we want to investigate further in toroidal potentials with a new apparatus which can produce an all-optical BEC. This means trapping thermal atoms in an optical dipole trap and cooling the sample by evaporation into the quantum degenerate regime. This new technique was first successfully demonstrated by M.D. Barrett et al. in 2001 and promises to be faster and simpler than the well established and common way of evaporation in magnetic traps. A new apparatus was built by the author and we report on the experimental details of the trapping of 87Rb atoms from a hot vapour and cooling them in a magneto-optical trap, and further evaporation to quantum degeneracy in a crossed optical dipole trap operating at a wavelength of l = 1064nm, with accurate control of the power in both beams via a feedback loop. The evaporation of neutral atoms of 87Rb in far red detuned optical dipole traps using linearly polarised laser light is spin independent, and mixed spinor condensates of the F=1 manifold can be formed. As an empirical technique we found by applying a magnetic gradient field during the final evaporation that we can selectively populate mF spin states or prepare mixtures. This intriguing mechanism was found earlier as well by M. S. Chang, but is yet not fully understood and subject of our future research. We can now routinely prepare an almost pure condensate containing up to 7000 atoms in the condensed phase purely in the mF = 0 spin state. This thesis contains the theoretical framework of Bose-Einstein condensation with in mean-field theory, the concepts of cooling of atoms in magneto-optical traps, the trapping and evaporation in optical dipole traps and the experimental realisation. In the future this experiment will be extended by a fast scanning dipole trap to apply arbitrary time averaged potentials of more complex geometries, such as toroidal traps to study the effects of superfluidity in a periodic potential. The production of toroidal traps and cold atoms in such a trap are outlined in this thesis.
Optical trapping as a viable means of exploring the physics of ultracold dilute atomic gases has revealed a new spectrum of physical phenomena. In particular, macroscopic and sudden occupation of the ground state below a critical temperature—-a phenomenon known as Bose-Einstein condensation—-has become an even richer system for the study of quantum mechanics, ultracold collisions, and many-body physics in general. Optical trapping liberates the spin degree of the BEC, making the order parameter vectorial (‘spinor BEC’), as opposed to the scalar order of traditional magnetically trapped condensates. The work described within is divided into two main efforts. The first encompasses the all-optical creation of a Bose-Einstein condensate in rubidium vapor. An all-optical path to spinor BEC (as opposed to transfer to an optical trap from a magnetic-trap condensate) was desired both for the simplicity of the experimental setup and also for the potential gains in speed of creation; evaporative cooling, the only known path to dilute-gas condensation, works only as efficiently as the rate of elastic collisions in the gas, a rate that starts out much higher in optical traps. The first all-optical BEC was formed elsewhere in 2001; the years following saw many groups worldwide seeking to create their own version. Our own all-optical spinor BEC, made with a single-beam dipole trap formed by a focused CO₂ laser, is described here, with particular attention paid to trap loading, measurement of trap parameters, and the use of a novel 780 nm high-power laser system. The second part describes initial experiments performed with the nascent condensate. The spinor properties of the condensate are documented, and a measurement is made of the density-dependent rate of spin mixing in the condensate. In addition, we demonstrate a novel dual-beam atom laser formed by outcoupling oppositely polarized components of the condensate, whose populations have been coherently evolved through spin dynamics. We drive coherent spin-mixing evolution through adiabatic compression of the initially weak trap. Such dual beams, nominally number-correlated through the angular momentum-conserving collision m=0 + m=0 ⇌ m=+1 + m=-1 have been proposed as tools to explore entanglement and squeezing in Bose-Einstein condensates.