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Transporting, splitting and merging of atomic ensembles in a chip trap

Peter Hommelhoff, W. Hänsel, T. Steinmetz, Theodor W. Hänsch, Jakob Reichel

Published Nov 2, 2004• 51 citations
OpenAlex

Abstract

We present a toolbox for cold atom manipulation with time-dependent magnetic fields generated by an atom chip. Wire layouts, detailed experimental procedures and results are presented for the following experiments: Use of a magnetic conveyor belt for positioning of cold atoms and Bose-Einstein condensates with a resolution of two nanometers; splitting of thermal clouds and BECs in adjustable magnetic double well potentials; controlled splitting of a cold reservoir. The devices that enable these manipulations can be combined with each other. We demonstrate this by combining reservoir splitter and conveyor belt to obtain a cold atom dispenser. We discuss the importance of these devices for quantum information processing, atom interferometry and Josephson junction physics on the chip. For all devices, absorption-image video sequences are provided to demonstrate their time-dependent behaviour.

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Transporting, splitting and merging of atomic ensembles in a chip trap

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We present a toolbox for cold atom manipulation with time-dependent magnetic fields generated by an atom chip. Wire layouts, detailed experimental procedures and results are presented for the following experiments: use of a magnetic conveyor belt for positioning of cold atoms and Bose–Einstein condensates (BECs) with a potential resolution of 2 nm; splitting of thermal clouds and BECs in adjustable magnetic double-well potentials; and controlled splitting of a cold reservoir. The devices that enable these manipulations can be combined with each other. We demonstrate this by combining reservoir splitter and conveyor belt to obtain a cold atom dispenser. We discuss the importance of these devices for quantum information processing, atom interferometry and Josephson junction physics on the chip. For all devices, absorption-image video sequences are provided to demonstrate their time-dependent behaviour.

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Have been demonstrated: a beam splitter, a conveyor belt, and a switch. Just as electrons drive electronics and photons drive photonics, many researchers hope that cold, neutral atoms will drive a future “atomtronics.” To process information, atoms will need to be manipulated on or near an “atom chip” using atom-based analogs of mirrors, lenses, waveguides, gratings, and other devices. The new devices reported here all exploit the interaction between a neutral atom’s magnetic moment and an external magnetic field with a gradient strong enough to create microscopic potentials. Jörg Schmiedmayer of the University of Heidelberg and his colleagues have designed a beam splitter for guided atoms, using a Y-shaped current-carrying wire nanofabricated on a surface. Depending on how current is sent through the Y, atoms can be directed to the output arms with any desired ratio. A group at the Max Planck Institute for Quantum Optics in Munich has been able to confine atom clouds in separate potential wells and transport them with 800-nm precision near a surface having time-dependent currents in a lithographically patterned conductor. The researchers have used their “magnetic conveyor belt” to merge separate clouds; their evidence shows that the process is adiabatic and can be reversed to coherently split wavepackets. Also using lithography, and following their own beam splitter, a group at the University of Colorado and NIST in Boulder has devised a switch that can direct a guided beam of neutral atoms to either of two output ports separated by 8 mm. Both the incoming and outgoing atoms are guided between two parallel wires having current flowing in the same direction. In the switch region, the atoms are guided alongside two wires with oppositely flowing current. (D. Cassettari et al., Phys. Rev. Lett. 85, 5483, 2000 http://dx.doi.org/10.1103/PhysRevLett.85.5483 . W. Hänsel et al., Phys. Rev. Lett. 86, 608, 2001 http://dx.doi.org/10.1103/PhysRevLett.86.608 . D. Müller et al., Opt. Lett. 25, 1382, 2000 http://dx.doi.org/10.1364/OL.25.001382 ; D. Müller et al., Phys. Rev. A , in press.)© 2001 American Institute of Physics.

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We report on progress for a couple of experiments on manipulating cold atoms on a chip for quantum sensing. The first experiments are directed towards developing a compact atom interferometer on an atom chip using a double-well potential. The interferometer uses 87Rb atoms magnetically confined in an atomic waveguide produced by wires on the surface of a lithographically patterned chip. Finite element modeling of combinations of different current configurations with various external bias fields indicated a means of coherently splitting the atomic cloud through dynamically adjusting the currents and bias fields. In these experiments we investigate real-time transformations between different double-well configurations adiabatically and non-adiabatically, and study their effects on the initially trapped atoms. Coherence properties of the two atomic wavepackets are examined. In another set of experiments we investigate the properties of bosons confined to (quasi) one dimension in our magnetic waveguide. When the atom-atom repulsive interaction becomes much larger than the kinetic energy, bosons confined in one dimension can enter a new state of matter, the Tonks-Girardeau gas, in which they behave like non-interacting fermions. However, the bosons can still occupy the same momentum state and therefore the gas cannot be fully described by either Bose-Einstein or Fermi-Dirac statistics. This transition has been observed in optical lattices but not in magnetic atom chip waveguides. We discuss the conditions for obtaining a Tonks-Girardeau gas with 87Rb atoms in our atom chip waveguide as well as a novel signature for observing the transition in our system.

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Magnetic microchip traps and single–atom detection

Romain Long, T. Steinmetz, Peter Hommelhoff +3 more

Microchip traps provide a promising approach to quantum information processing and communication (QIPC) with neutral atoms: strong and complex potentials can be produced for acting on the qubit atoms, and the potentials can be scaled to higher qubit numbers by virtue of the microfabrication process. We describe experimental results that are relevant to use in QIPC, such as the transport of Bose-Einstein-condensed atomic ensembles along the chip surface with the help of a magnetic conveyor belt. The second part of the paper is devoted to single-atom detection on the chip.

Philosophical Transactions of the Royal Society A Mathematical Physical and Engineering Sciences•Jul 15, 2003•46 citations
We present a toolbox for cold atom manipulation with time-dependent magnetic fields generated by an atom chip. Wire layouts, detailed experimental procedures and results are presented for the following experiments: Use of a magnetic conveyor belt for positioning of cold atoms and Bose-Einstein condensates with a resolution of two nanometers; splitting of thermal clouds and BECs in adjustable magnetic double well potentials; controlled splitting of a cold reservoir. The devices that enable these manipulations can be combined with each other. We demonstrate this by combining reservoir splitter and conveyor belt to obtain a cold atom dispenser. We discuss the importance of these devices for quantum information processing, atom interferometry and Josephson junction physics on the chip. For all devices, absorption-image video sequences are provided to demonstrate their time-dependent behaviour.
We present a toolbox for cold atom manipulation with time-dependent magnetic fields generated by an atom chip. Wire layouts, detailed experimental procedures and results are presented for the following experiments: use of a magnetic conveyor belt for positioning of cold atoms and Bose–Einstein condensates (BECs) with a potential resolution of 2 nm; splitting of thermal clouds and BECs in adjustable magnetic double-well potentials; and controlled splitting of a cold reservoir. The devices that enable these manipulations can be combined with each other. We demonstrate this by combining reservoir splitter and conveyor belt to obtain a cold atom dispenser. We discuss the importance of these devices for quantum information processing, atom interferometry and Josephson junction physics on the chip. For all devices, absorption-image video sequences are provided to demonstrate their time-dependent behaviour.
We demonstrate an integrated magnetic ``atom chip'' which transports cold trapped atoms near a surface with very high positioning accuracy. Time-dependent currents in a lithographic conductor pattern create a moving chain of magnetic potential wells; atoms are transported in these wells while remaining confined in all three dimensions. We achieve fluxes up to 10^6 /s with a negligible heating rate. An extension of this ``atomic conveyor belt'' allows the merging of magnetically trapped atom clouds by unification of two Ioffe-Pritchard potentials. Under suitable conditions, the clouds merge without loss of phase space density. We demonstrate this unification process experimentally.
We demonstrate an integrated magnetic device which transports cold atoms near a surface with very high positioning accuracy. Time-dependent currents in a lithographic conductor pattern create a moving chain of potential wells; atoms are transported in these wells while remaining confined in all three dimensions. We achieve mean fluxes up to 10(6) s(-1) with a negligible heating rate. An extension of this device allows merging of atom clouds by unification of two Ioffe-Pritchard potentials. The unification, which we demonstrate experimentally, can be performed without loss of phase space density. This novel, all-magnetic atom manipulation offers exciting perspectives, such as trapped-atom interferometry.
Have been demonstrated: a beam splitter, a conveyor belt, and a switch. Just as electrons drive electronics and photons drive photonics, many researchers hope that cold, neutral atoms will drive a future “atomtronics.” To process information, atoms will need to be manipulated on or near an “atom chip” using atom-based analogs of mirrors, lenses, waveguides, gratings, and other devices. The new devices reported here all exploit the interaction between a neutral atom’s magnetic moment and an external magnetic field with a gradient strong enough to create microscopic potentials. Jörg Schmiedmayer of the University of Heidelberg and his colleagues have designed a beam splitter for guided atoms, using a Y-shaped current-carrying wire nanofabricated on a surface. Depending on how current is sent through the Y, atoms can be directed to the output arms with any desired ratio. A group at the Max Planck Institute for Quantum Optics in Munich has been able to confine atom clouds in separate potential wells and transport them with 800-nm precision near a surface having time-dependent currents in a lithographically patterned conductor. The researchers have used their “magnetic conveyor belt” to merge separate clouds; their evidence shows that the process is adiabatic and can be reversed to coherently split wavepackets. Also using lithography, and following their own beam splitter, a group at the University of Colorado and NIST in Boulder has devised a switch that can direct a guided beam of neutral atoms to either of two output ports separated by 8 mm. Both the incoming and outgoing atoms are guided between two parallel wires having current flowing in the same direction. In the switch region, the atoms are guided alongside two wires with oppositely flowing current. (D. Cassettari et al., Phys. Rev. Lett. 85, 5483, 2000 http://dx.doi.org/10.1103/PhysRevLett.85.5483 . W. Hänsel et al., Phys. Rev. Lett. 86, 608, 2001 http://dx.doi.org/10.1103/PhysRevLett.86.608 . D. Müller et al., Opt. Lett. 25, 1382, 2000 http://dx.doi.org/10.1364/OL.25.001382 ; D. Müller et al., Phys. Rev. A , in press.)© 2001 American Institute of Physics.
We report on progress for a couple of experiments on manipulating cold atoms on a chip for quantum sensing. The first experiments are directed towards developing a compact atom interferometer on an atom chip using a double-well potential. The interferometer uses 87Rb atoms magnetically confined in an atomic waveguide produced by wires on the surface of a lithographically patterned chip. Finite element modeling of combinations of different current configurations with various external bias fields indicated a means of coherently splitting the atomic cloud through dynamically adjusting the currents and bias fields. In these experiments we investigate real-time transformations between different double-well configurations adiabatically and non-adiabatically, and study their effects on the initially trapped atoms. Coherence properties of the two atomic wavepackets are examined. In another set of experiments we investigate the properties of bosons confined to (quasi) one dimension in our magnetic waveguide. When the atom-atom repulsive interaction becomes much larger than the kinetic energy, bosons confined in one dimension can enter a new state of matter, the Tonks-Girardeau gas, in which they behave like non-interacting fermions. However, the bosons can still occupy the same momentum state and therefore the gas cannot be fully described by either Bose-Einstein or Fermi-Dirac statistics. This transition has been observed in optical lattices but not in magnetic atom chip waveguides. We discuss the conditions for obtaining a Tonks-Girardeau gas with 87Rb atoms in our atom chip waveguide as well as a novel signature for observing the transition in our system.
Microchip traps provide a promising approach to quantum information processing and communication (QIPC) with neutral atoms: strong and complex potentials can be produced for acting on the qubit atoms, and the potentials can be scaled to higher qubit numbers by virtue of the microfabrication process. We describe experimental results that are relevant to use in QIPC, such as the transport of Bose-Einstein-condensed atomic ensembles along the chip surface with the help of a magnetic conveyor belt. The second part of the paper is devoted to single-atom detection on the chip.