Three magnetic devices for atom optics

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.)