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Bose-Einstein condensates in 'giant' toroidal magnetic traps

Arnold, A.S., Erling Riis

Published Apr 15, 2002• 12 citations
OpenAlex

Abstract

The experimental realization of gaseous Bose-Einstein condensation (BEC) in 1995 sparked considerable interest in this intriguing quantum fluid. Here, progress towards the development of an 87Rb BEC experiment in a large (, 10cm diameter) toroidal storage ring is reported. A BEC will be formed at a localized region within the toroidal magnetic trap, from whence it can be launched around the torus. The benefits of the system are manifold, as it should readily enable detailed investigations of persistent currents, Josephson effects, phase fluctuations and high-precision Sagnac or gravitational interferometry.

Related papers

Bose-Einstein condensates in 'giant' toroidal magnetic traps

A. S. Arnold, Erling Riis

The experimental realization of gaseous Bose—Einstein condensation (BEC) in 1995 sparked considerable interest in this intriguing quantum fluid. Here, progress towards the development of an 87Rb BEC experiment in a large (≈ 10cm diameter) toroidal storage ring is reported. A BEC will be formed at a localized region within the toroidal magnetic trap, from whence it can be launched around the torus. The benefits of the system are manifold, as it should readily enable detailed investigations of persistent currents, Josephson effects, phase fluctuations and high-precision Sagnac or gravitational interferometry.

arXiv:cond-mat/0110295•Journal of Modern Optics•Apr 1, 2002•17 citations

A Ring with a Spin : Superfluidity in a toroidal Bose-Einstein condensate

Anand K. Ramanathan

Superfluidity is a remarkable phenomenon. Superfluidity was initially characterized by flow without friction, first seen in liquid helium in 1938, and has been studied extensively since. Superfluidity is believed to be related to, but not identical to Bose-Einstein condensation, a statistical mechanical phenomena predicted by Albert Einstein in 1924 based on the statistics of Satyendra Nath Bose, where bosonic atoms make a phase transition to form a Bose-Einstein condensate (BEC), a gas which has macroscopic occupation of a single quantum state. Developments in laser cooling of neutral atoms and the subsequent realization of Bose-Einstein condensates in ultracold gases have opened a new window into the study of superfluidity and its relation to Bose-Einstein condensation. In our atomic sodium BEC experiment, we studied superfluidity and dissipationless flow in an all-optical toroidal trap, constructed using the combination of a horizontal ``sheet''-like beam and vertical ``ring''-like beam, which, like a circuit loop, allows flow around the ring. On inducing a single quantum of circulation in the condensate, the smoothness and uniformity of the toroidal BEC enabled the sustaining of a persistent current lasting 40 seconds, limited by the lifetime of the BEC due to background gas pressure. This success set the stage for further experiments studying superfluidity. In a first set of experiments, we studied the stability of the persistent current by inserting a barrier in the flow path of the ring. The superflow stopped abruptly at a barrier strength such that the local flow velocity at the barrier exceeded a critical velocity, which supported decay via the creation of a vortex-antivortex pair. Our precise control in inducing and arresting superflow in the BEC is a first step toward studying other aspects of superfluidity, such as the effect of temperature and dimensionality. This thesis discusses these experiments and also details partial-transfer absorption imaging, an imaging technique developed in the course of this work.

•Dec 1, 2011•3 citations

A storage ring for Bose-Einstein condensates

Craig Garvie, Aidan S. Arnold, Erling Riis

A vertically-oriented magnetic storage ring for cold atoms has been demonstrated and Bose-Einstein condensates have been formed in a localised section of the torus. The unique design should facilitate high-precision atom interferometry.

Conference on Lasers and Electro-Optics•Jan 1, 2004•0 citations

Toroidal optical dipole traps for two-dimensional Bose-Einstein condensates

Ewan M. Wright, Jochen Arlt, Kishan Dholakia

Summary form only given. The production of tight toroidal traps, or rings, for Bose-Einstein condensates (BECs) opens up the way to a variety of both fundamental and applied studies. By providing tight transverse confinement one can produce a quasi-one-dimensional motion for the BEC on a ring, which allows for studies of vortices and persistent currents. On the applied side, such mesoscopic rings could be used for rotation sensing via the Sagnac effect for counter-propagating atoms around the ring. In this paper, we show that Laguerre-Gaussian (LG) laser modes of high azimuthal mode index l and containing one radial ring can be used to create tight confined optical dipole traps for 2D BECs.

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

A ring trap for ultracold atoms in an RF-dressed state

W H Heathcote, E. Nugent, Benjamin Thomas Sheard +1 more

We combine an RF-dressed magnetic trap with an optical potential to produce a toroidal trapping potential for ultracold 87Rb atoms. We load atoms into this ring trap from a conventional magnetic trap and compare the measured oscillation frequencies with theoretical predictions. This method of making a toroidal trap gives a high degree of flexibility such as a tuneable radius and variable transverse oscillation frequency. The ring trap is ideal for the creation of a multiply connected Bose–Einstein condensate (BEC) and the study of persistent flow and we propose a scheme for introducing a flow of the atoms around the ring.

New Journal of Physics•Apr 10, 2008•98 citations
The experimental realization of gaseous Bose-Einstein condensation (BEC) in 1995 sparked considerable interest in this intriguing quantum fluid. Here, progress towards the development of an 87Rb BEC experiment in a large (, 10cm diameter) toroidal storage ring is reported. A BEC will be formed at a localized region within the toroidal magnetic trap, from whence it can be launched around the torus. The benefits of the system are manifold, as it should readily enable detailed investigations of persistent currents, Josephson effects, phase fluctuations and high-precision Sagnac or gravitational interferometry.
The experimental realization of gaseous Bose—Einstein condensation (BEC) in 1995 sparked considerable interest in this intriguing quantum fluid. Here, progress towards the development of an 87Rb BEC experiment in a large (≈ 10cm diameter) toroidal storage ring is reported. A BEC will be formed at a localized region within the toroidal magnetic trap, from whence it can be launched around the torus. The benefits of the system are manifold, as it should readily enable detailed investigations of persistent currents, Josephson effects, phase fluctuations and high-precision Sagnac or gravitational interferometry.
Superfluidity is a remarkable phenomenon. Superfluidity was initially characterized by flow without friction, first seen in liquid helium in 1938, and has been studied extensively since. Superfluidity is believed to be related to, but not identical to Bose-Einstein condensation, a statistical mechanical phenomena predicted by Albert Einstein in 1924 based on the statistics of Satyendra Nath Bose, where bosonic atoms make a phase transition to form a Bose-Einstein condensate (BEC), a gas which has macroscopic occupation of a single quantum state. Developments in laser cooling of neutral atoms and the subsequent realization of Bose-Einstein condensates in ultracold gases have opened a new window into the study of superfluidity and its relation to Bose-Einstein condensation. In our atomic sodium BEC experiment, we studied superfluidity and dissipationless flow in an all-optical toroidal trap, constructed using the combination of a horizontal ``sheet''-like beam and vertical ``ring''-like beam, which, like a circuit loop, allows flow around the ring. On inducing a single quantum of circulation in the condensate, the smoothness and uniformity of the toroidal BEC enabled the sustaining of a persistent current lasting 40 seconds, limited by the lifetime of the BEC due to background gas pressure. This success set the stage for further experiments studying superfluidity. In a first set of experiments, we studied the stability of the persistent current by inserting a barrier in the flow path of the ring. The superflow stopped abruptly at a barrier strength such that the local flow velocity at the barrier exceeded a critical velocity, which supported decay via the creation of a vortex-antivortex pair. Our precise control in inducing and arresting superflow in the BEC is a first step toward studying other aspects of superfluidity, such as the effect of temperature and dimensionality. This thesis discusses these experiments and also details partial-transfer absorption imaging, an imaging technique developed in the course of this work.
Summary form only given. The production of tight toroidal traps, or rings, for Bose-Einstein condensates (BECs) opens up the way to a variety of both fundamental and applied studies. By providing tight transverse confinement one can produce a quasi-one-dimensional motion for the BEC on a ring, which allows for studies of vortices and persistent currents. On the applied side, such mesoscopic rings could be used for rotation sensing via the Sagnac effect for counter-propagating atoms around the ring. In this paper, we show that Laguerre-Gaussian (LG) laser modes of high azimuthal mode index l and containing one radial ring can be used to create tight confined optical dipole traps for 2D BECs.
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.
We combine an RF-dressed magnetic trap with an optical potential to produce a toroidal trapping potential for ultracold 87Rb atoms. We load atoms into this ring trap from a conventional magnetic trap and compare the measured oscillation frequencies with theoretical predictions. This method of making a toroidal trap gives a high degree of flexibility such as a tuneable radius and variable transverse oscillation frequency. The ring trap is ideal for the creation of a multiply connected Bose–Einstein condensate (BEC) and the study of persistent flow and we propose a scheme for introducing a flow of the atoms around the ring.