Controlling the shape of a quantum wavefunction

Gabriel Turinici, HERSCHEL A. RABITZ

Gabriel Turinici, HERSCHEL A. RABITZ

P. H. Bucksbaum, Douglass W. Schumacher, Dan Pinkos +3 more

We used a computer controlled LCD to shape the spectrum of a short laser pulse which was then used to excite a shaped atomic wavepacket. We use amplified programmable shaped optical pulses to engineer Rydberg wavefunctions. The method employs a computer-controlled liquid crystal pulse shaper[l]. The wavefunctions, which are nonstationary states, are monitored by observing temporal interference via the optical Ramsey method[2,3].

Claudius Gros

Kazuki Koshino, Hajime Ishihara

Exploiting the field-amplification effect of a cavity, the possibility of optical nonlinearity by only two photons was indicated experimentally. In the present article, we review our recent analysis of the two-photon dynamics in a cavity quantum electrodynamics (QED) system. Since a cavity-QED system is highly dispersive around its resonances, the shapes of photonic pulses are significantly deformed through interaction with the system. Thus, the present analysis is based on a formalism beyond single-mode approximations. The external photon field is treated rigorously as a continuum, which enables us to handle the two-photon wavefunction in the space representation. The degree of optical nonlinearity in a two-photon state is quantified by comparing the output wavefunction with the linear output wavefunction. It is revealed that the semiclassical optical response theory can be applied for evaluation of the two-photon optical nonlinearity. The two-photon nonlinearity appears not purely as a phase shift in the output wavefunction. The degradation of the fidelity between the output wavefunction and the linear output wavefunction always occurs, which hinders the application of this nonlinear effect as a quantum phase gate. The optimum condition for maximizing the two-photon nonlinearity is clarified, suggesting that pulse shape control is more essential than the Q-value control of the cavity QED system.