QUANTUM ZENO EFFECT IN A DOUBLE-WELL POTENTIAL - A MODEL OF A PHYSICAL MEASUREMENT

In this paper we study the quantum Zeno effect in real space due to a position measurement. The motion of a particle is decelerated or comes to a complete stop when its position is observed. Instead of using th e von Neumann collapse hypothesis, we treat a real measurement process . The measurement consists of coupling a two-level atom in a double-we ll potential to a resonant laser beam. Subsequent resonance fluorescen ce can be used to determine the atom's position within the double well , provided the laser wavelength is short enough to ensure a resolvable scattering pattern of the fluorescence photons. Treating this process in the framework of dissipative quantum mechanics, we derive a master equation which describes the measurement process in all relevant deta ils. Solving the master equation analytically as well as numerically w e study the conditions for the decay of the nondiagonal elements. This leads directly to the inhibition of the center-of-mass motion, i.e., to a quantum Zeno effect. Because we treat the measurement process in detail we are able to investigate the conditions for a complete measur ement. In particular, we study the role of the intensity and the wavel ength of the probing laser field.