Ultra-cold at NUS
Our research focuses on the use of ultra-cold atoms for neutral atom quantum information applications.  We investigate the use of micro-fabricated magnetic traps (atom chips) and optical lattices as a means to trap and manipulate large arrays of atoms (qubits).  To provide the necessary interaction between individual atoms we will investigate the use of micro-cavities.

Atom Chips

The magnetic fields generated by current carrying wires can be used to trap atoms.  Using micro-fabrication techniques these traps can be made extremely small and large complex arrays of traps can be easily fabricated onto a single chip. A number of groups around the world have demonstrated many of the building blocks needed for quantum information applications.  The image to the right shows a magnified image of a micro-fabricated Ioffe trap.  The wires are 5 micron wide and the field of view is approximately 0.5mm. (learn more about atom chips)
Optical Lattices

The electromagnetic field of a laser beam can also be used to trap and manipulate atoms.  A retro-reflected laser beam creates a standing wave that provides a linear array of micro-potentials as indicated in the figure.  Placing an atom at each trapping site then results in a 1-D lattice of ultra-cold atoms.  Such a lattice can be used as a quantum register/memory.  By intersecting beams from other directions 2-D and 3-D lattices can be easily made. (learn more about optical lattices)

  
Micro-cavities

For quantum information processing we require a means to couple two atoms.  This interaction can be mediated by photons but in order to provide a sufficiently strong coupling the photon must be confined to a cavity.  The smaller the cavity the stronger the interaction.  The micro-toroid shown to the right is one such cavity.  Other possibilities include micro-mirrors, fibre based cavities and photon band gap cavities. (learn more about cavity QED for quantum information)

  

     Image taken from  PRL 97, 243905 (2006)
Bose Einstein Condensation

Bose Einstein Condensates are at the extreme limit of ultra-cold temperatures.  They are thus very sensitive probes of small energy variations and a useful diagnostic tool of fabrication imperfections in atom chips.  They also provide the means to initialize an optical lattice to one atom per site. (learn more about BEC and it's applications).

        

      Bose              Einstein