A microtrap consisting of two concentric circular wire loops having radii of 300 and 660 μm, respectively, is demonstrated. The three-dimensional trap has a maximum depth of more than 1 mK, and the trap center position as measured below the atom chip surface can be adjusted by applying a small-bias magnetic field. More than 105 Rb87 atoms were transferred into the microtrap from a magneto-optical trap and remained trapped for several hundred milliseconds, which is limited by the background pressure. The loading of a linear array of three microtraps is also demonstrated. The trap dimensions are readily scaled to micrometer size, which is of interest for creating a one- and two-dimensional array of neutral atom traps on a single atom chip.A microtrap consisting of two concentric circular wire loops having radii of 300 and 660 μm, respectively, is demonstrated. The three-dimensional trap has a maximum depth of more than 1 mK, and the trap center position as measured below the atom chip surface can be adjusted by applying a small-bias magnetic field. More than 105 Rb87 atoms were transferred into the microtrap from a magneto-optical trap and remained trapped for several hundred milliseconds, which is limited by the background pressure. The loading of a linear array of three microtraps is also demonstrated. The trap dimensions are readily scaled to micrometer size, which is of interest for creating a one- and two-dimensional array of neutral atom traps on a single atom chip.

Bulletin of the American Physical SocietyJun 5, 20130 citations

Double-Loop Microtrap Array for Ultracold Atoms

Bin Jian

A novel kind of magnetic microtrap is demonstrated for ultracold neutral atoms. It consists of two concentric loops of radii $r_1$ and $r_2$ having oppositely oriented currents. A magnetic field minimum is generated in three dimensions that can be used to trap the atoms with a trap depth of about 1 mK using a current of 2.6 A. The condition $r_2/r_1$ = 2.2 maximizes the restoring force on the atoms toward the trap center. Unlike conventional magnetic microtraps, an external bias field is not required. Moreover, a one dimensional array of double-loop microtraps can be created by daisy chaining single microtrap circuits. \nA linear array of three microtraps having $r_1$ = 300 $\\mu$ m was fabricated as part of an atom chip. The following three techniques were developed to load the microtrap array: 1) atoms initially contained in a magneto-optical trap (MOT) were transported to the atom chip by a conventional magnetic trap, 2) atoms were first loaded into a mirror MOT and 3) atoms were initially loaded in a far off resonance optical dipole trap (FORT). Each technique loaded greater than $10^5$ $^{87}$ Rb atoms into the microtrap array. The lowest temperature of 30 $\\mu$ K for the microtrapped atom cloud was achieved using FORT loading. The strength and the position of the microtrap could be precisely adjusted over a range from 300 to 50 $\\mu$ m above the atom chip surface by applying an external bias magnetic field. The lifetime of the atoms trapped in the microtrap array was measured to be 350 ms which was limited by the collisions with residual background gas.A novel kind of magnetic microtrap is demonstrated for ultracold neutral atoms. It consists of two concentric loops of radii $r_1$ and $r_2$ having oppositely oriented currents. A magnetic field minimum is generated in three dimensions that can be used to trap the atoms with a trap depth of about 1 mK using a current of 2.6 A. The condition $r_2/r_1$ = 2.2 maximizes the restoring force on the atoms toward the trap center. Unlike conventional magnetic microtraps, an external bias field is not required. Moreover, a one dimensional array of double-loop microtraps can be created by daisy chaining single microtrap circuits. \nA linear array of three microtraps having $r_1$ = 300 $\\mu$m was fabricated as part of an atom chip. The following three techniques were developed to load the microtrap array: 1) atoms initially contained in a magneto-optical trap (MOT) were transported to the atom chip by a conventional magnetic trap, 2) atoms were first loaded into a mirror MOT and 3) atoms were initially loaded in a far off resonance optical dipole trap (FORT). Each technique loaded greater than $10^5$ $^{87}$Rb atoms into the microtrap array. The lowest temperature of 30 $\\mu$K for the microtrapped atom cloud was achieved using FORT loading. The strength and the position of the microtrap could be precisely adjusted over a range from 300 to 50 $\\mu$m above the atom chip surface by applying an external bias magnetic field. The lifetime of the atoms trapped in the microtrap array was measured to be 350 ms which was limited by the collisions with residual background gas.

May 6, 20140 citations

A linear array of 11 double-loop microtraps for ultracold atoms

Bin Jian, William Arie van Wijngaarden

A linear array of 11 closely spaced microtraps was demonstrated. Each microtrap was created using the magnetic field generated by two concentric circular wire loops having radii of 60 and 132 μ m carrying oppositely oriented currents as well as a bias magnetic field oriented perpendicular to the atom chip surface containing the microwire loops. 87 Rb atoms were initially cooled using either a surface magneto-optical trap (MOT) or a far off resonance optical dipole trap (FORT) created using an infrared laser directed along the microtrap array axis. The microtrap current was turned on and over 12 000 atoms were loaded into each microtrap. The advantage of FORT loading was that the 11 microtraps were about equally populated and the microtrapped atom temperature of 11 μ K was one quarter of that obtained using the MOT.A linear array of 11 closely spaced microtraps was demonstrated. Each microtrap was created using the magnetic field generated by two concentric circular wire loops having radii of 60 and 132 μ m carrying oppositely oriented currents as well as a bias magnetic field oriented perpendicular to the atom chip surface containing the microwire loops. 87 Rb atoms were initially cooled using either a surface magneto-optical trap (MOT) or a far off resonance optical dipole trap (FORT) created using an infrared laser directed along the microtrap array axis. The microtrap current was turned on and over 12 000 atoms were loaded into each microtrap. The advantage of FORT loading was that the 11 microtraps were about equally populated and the microtrapped atom temperature of 11 μ K was one quarter of that obtained using the MOT.

Journal of Physics B Atomic Molecular and Optical PhysicsOct 15, 20144 citations

Manipulation of ultracold atoms using double-loop microtraps

William Arie van Wijngaarden, Bin Jian, Andrei Mouraviev

Abstract Ultracold atoms created using microtraps are being used in an increasing number of diverse applications. This paper reviews the double-loop microtrap which consists of two concentric circular wire loops carrying oppositely oriented currents. This generates a magnetic field configuration that traps a magnetic dipole in three-dimensions. The position of the trapped atoms relative to the atom chip surface containing the microwire loops, can be precisely controlled by applying different currents in the two loops or alternatively using a so called bias magnetic field oriented perpendicular to the chip surface. Double-loop microtraps can be daisy chained in series to create a one- or two-dimensional microtrap array. Experiments that have demonstrated a double-loop microtrap array are discussed. Future possibilities are presented as to how atoms can be transferred between adjacent microtraps as well as the use of an additional micro sized Ioffe coil to create a trap having a nonzero magnetic field minimum to reduce atom loss by suppressing Majorana transitions.Abstract Ultracold atoms created using microtraps are being used in an increasing number of diverse applications. This paper reviews the double-loop microtrap which consists of two concentric circular wire loops carrying oppositely oriented currents. This generates a magnetic field configuration that traps a magnetic dipole in three-dimensions. The position of the trapped atoms relative to the atom chip surface containing the microwire loops, can be precisely controlled by applying different currents in the two loops or alternatively using a so called bias magnetic field oriented perpendicular to the chip surface. Double-loop microtraps can be daisy chained in series to create a one- or two-dimensional microtrap array. Experiments that have demonstrated a double-loop microtrap array are discussed. Future possibilities are presented as to how atoms can be transferred between adjacent microtraps as well as the use of an additional micro sized Ioffe coil to create a trap having a nonzero magnetic field minimum to reduce atom loss by suppressing Majorana transitions.

Physica ScriptaApr 13, 20160 citations

Single layer atom chip for magnetically trapping one-dimensional array of ultracold atoms

Cheng Feng, Bo Yan, Ke Min +1 more

We propose a wire configuration to create a one-dimensional (1D) array of magnetic microtraps for trapping ultracold atoms. The configuration is formed by replacing the central part of the Z-wire pattern with a zigzag wire. We simulate the performance of this pattern by the finite element method which can take both the width and depth of the wire into consideration. The result of simulation shows that this configuration can create magnetic microtraps which can be separated and combined by changing the bias magnetic field. We manage to split the Z-wire trap and prove that a similar result can occur for the new wire configuration. The fabrication processes of the atom chip are also introduced. Finally we discuss the loading method.We propose a wire configuration to create a one-dimensional (1D) array of magnetic microtraps for trapping ultracold atoms. The configuration is formed by replacing the central part of the Z-wire pattern with a zigzag wire. We simulate the performance of this pattern by the finite element method which can take both the width and depth of the wire into consideration. The result of simulation shows that this configuration can create magnetic microtraps which can be separated and combined by changing the bias magnetic field. We manage to split the Z-wire trap and prove that a similar result can occur for the new wire configuration. The fabrication processes of the atom chip are also introduced. Finally we discuss the loading method.

Chinese Physics BAug 1, 20101 citation

One-dimensional lattice of permanent magnetic microtraps for ultracold atoms on an atom chip

Mahima Singh, Michael Volk, A. M. Akulshin +3 more

We report on the loading and trapping of ultracold atoms in a one-dimensional permanent magnetic lattice of period 10 µm produced on an atom chip. The grooved structure which generates the magnetic lattice potential is fabricated on a silicon substrate and coated with a perpendicularly magnetized multilayered TbGdFeCo/Cr film of effective thickness 960 nm. Ultracold atoms are evaporatively cooled in a Z-wire magnetic trap and then adiabatically transferred to the magnetic lattice potential by applying an appropriate bias field. Under our experimental conditions trap frequencies of up to 90 kHz in the magnetic lattice are measured and the atoms are trapped at a distance of less than 5 µm from the surface with a measured lifetime of about 450 ms. These results are important in the context of studies of quantum coherence of neutral atoms in periodic magnetic potentials on an atom chip.We report on the loading and trapping of ultracold atoms in a one-dimensional permanent magnetic lattice of period 10 µm produced on an atom chip. The grooved structure which generates the magnetic lattice potential is fabricated on a silicon substrate and coated with a perpendicularly magnetized multilayered TbGdFeCo/Cr film of effective thickness 960 nm. Ultracold atoms are evaporatively cooled in a Z-wire magnetic trap and then adiabatically transferred to the magnetic lattice potential by applying an appropriate bias field. Under our experimental conditions trap frequencies of up to 90 kHz in the magnetic lattice are measured and the atoms are trapped at a distance of less than 5 µm from the surface with a measured lifetime of about 450 ms. These results are important in the context of studies of quantum coherence of neutral atoms in periodic magnetic potentials on an atom chip.

arXiv:0801.0624Journal of Physics B Atomic Molecular and Optical PhysicsMar 10, 200849 citations

A novel kind of magnetic microtrap is demonstrated for ultracold neutral atoms. It consists of two concentric loops of radii

r_1

and

r_2

having oppositely oriented currents. A magnetic field minimum is generated in three dimensions that can be used to trap the atoms with a trap depth of about 1 mK using a current of 2.6 A. The condition

r_2/r_1

= 2.2 maximizes the restoring force on the atoms toward the trap center. Unlike conventional magnetic microtraps, an external bias field is not required. Moreover, a one dimensional array of double-loop microtraps can be created by daisy chaining single microtrap circuits. \nA linear array of three microtraps having

r_1

= 300

\\mu

m was fabricated as part of an atom chip. The following three techniques were developed to load the microtrap array: 1) atoms initially contained in a magneto-optical trap (MOT) were transported to the atom chip by a conventional magnetic trap, 2) atoms were first loaded into a mirror MOT and 3) atoms were initially loaded in a far off resonance optical dipole trap (FORT). Each technique loaded greater than

10^5

^{87}

Rb atoms into the microtrap array. The lowest temperature of 30

\\mu

K for the microtrapped atom cloud was achieved using FORT loading. The strength and the position of the microtrap could be precisely adjusted over a range from 300 to 50

\\mu

m above the atom chip surface by applying an external bias magnetic field. The lifetime of the atoms trapped in the microtrap array was measured to be 350 ms which was limited by the collisions with residual background gas.