Quantum measurement and information: A new quantum theory of repeated or continuous nondestructive measurements was developed of a single quantum system for which the influence of a previous measurement on a subsequent measurement should be properly formulated. By applying this theory to successive measurements on a single system it was shown that a single wave function cannot be measured. This finding also denies any ontological meaning of the quantum wave function and places a fundamental limit on external force detection with single quantum systems.
Squeezed state: Studies showed that the fluctuation noise is "malleable," that intensity noise can be reduced if the phase noise is allowed to increase, and vice versa. In other words, light can be squeezed. As proof of this concept an efficient semiconductor laser which produces this number/phase squeezing of the states of light was developed.
Cavity quantum electrodynamics: Much was learned about con-trolling spontaneous emission by modifying the electromagnetic field mode using a semiconductor microcavity with a hydrogen-atom-like object "exciton": a positive charge hole as an atomic hydrogen nucleus, and an electron trapped as a hydrogenic wave function. Also, an effort was made to generate both a stimulated coherent light wave and a coherent matter wave, a completely new type of optics. Though first experiments were not successful, much information was learned about such systems.
Mesoscopic physics: The quantum statistical effects involving the scattering of electrons (fermions) and photons (bosoms) were studied. This project demonstrated fermionic interference, mesoscopic electron collisions. This was the first time to observe two particle interference for fermions.
Microscopy and single-atom manipulation: Attempts were made to construct quantum devices at the most basic level: single atoms and particles. One major result was the first experimental observation of the Coulomb blockade in a single atomic junction.