In the last several years considerable efforts have been devoted to developing Bose-Einstein-condensatebased devices for applications such as fundamental research, precision measurements, and integrated atom optics. Such devices, capable of complex functionality, can be designed from simpler building blocks as is done in microelectronics. One of the most important components of microelectronics is a transistor. We demonstrate that a Bose-Einstein condensate in a three-well potential structure where the tunneling of atoms between two wells is controlled by the population in the third shows behavior similar to that of an electronic field-effect transistor. Namely, it exhibits switching and both absolute and differential gain. The role of quantum fluctuations is analyzed, and estimates of the switching time and parameters for the potential are presented.
The operation of cold-atom beam splitters is analyzed in the context of Bose-Einstein condensate interferometry. We introduce two representative geometries of the splitting region and study influence of nonlinearity and nonadiabaticity on the splitting and the recombination of the condensate for both geometries.
The operation of a BEC based atom interferometer, where the atoms are held in a weaklyconfining magnetic trap and manipulated with counter-propagating laser beams, is analyzed. A simple analytic model is developed to describe the dynamics of the interferometer. It is used to find the regions of parameter space with high and low contrast of the interference fringes for both single and double reflection interferometers. We demonstrate that for a double reflection interferometer the coherence time can be increased by shifting the recombination time. The theory is compared with recent experimental realizations of these interferometers.
We describe the design and function of a circular magnetic waveguide produced
from wires on a microchip for atom interferometry using deBroglie waves. The
guide is a two-dimensional magnetic minimum for trapping weak-field seeking
states of atoms or molecules with a magnetic dipole moment. The design consists
of seven circular wires sharing a common radius. We describe the design, the
time-dependent currents of the wires and show that it is possible to form a
circular waveguide with adjustable height and gradient while minimizing
perturbation resulting from leads or wire crossings. This maximal area geometry
is suited for rotation sensing with atom interferometry via the Sagnac effect
using either cold atoms, molecules and Bose-condensed systems
Cold-atom interferometers use guiding potentials that split the wave function of the Bose-Einstein condensate and then recombine it. We present a theoretical analysis of the wave-function recombination instability that is due to the weak nonlinearity of the condensate. It is most pronounced when the accumulated phase difference between the arms of the interferometer is close to an odd multiple of and consists in exponential amplification of the weak ground state mode by the strong first excited mode. The instability exists for both trapped-atom and beam interferometers.
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