Theoretical Analysis of Noise Induced Quantum Coherence

Ahsan Nazir

Mark C. Phillips, Hailin Wang, I. Rumyantsev +3 more

We report an experimental demonstration and theoretical analysis of electromagnetically induced transparency in a GaAs quantum well, in which the absorption of an exciton resonance is reduced by more than twentyfold. The destructive quantum interference in this scheme is set up by a control pulse that couples to a resonance of biexcitons. These studies illustrate that many-particle interactions, which are inherent in semiconductors and are often detrimental to quantum coherences, can also be harnessed to manipulate these coherences.

A. N. Omelyanchouk, Sergey E. Savel'ev, Alexandre M. Zagoskin +2 more

We predict theoretically the enhancement of quantum coherence in a superconducting flux qubit by a classical external noise. First, the off-diagonal components of the qubit density matrix are increased. Second, in the presence of both ac drive and noise, the resulting Rabi oscillations survive ``in perpetuity,'' i.e., for times greatly exceeding the Rabi decay time in a noiseless system. The coherence-enhancing effects of the classical noise can be considered as a manifestation of quantum stochastic resonance and are relevant to experimental techniques, such as Rabi spectroscopy.

Jiushu Shao, Christine Zerbe, Peter Hänggi A

Vojtech Szőcs, Harald Friedrich Kauffmann

The optical response of a two-site system driven by a pair of optical pulses in an interferometric set up has been studied theoretically by applying the density operator formalism. The one-exciton approach is taken for modeling two coupled two-level systems (TLS), the external field is presented semiclassically and bath-induced dissipative processes are included. In the δ-pulse limit the population of the excited state has been formulated to the lowest order perturbation expansion in the external field. In the limit of slow luminescence the interferogram of time-integrated total fluorescence has been calculated for pulses with constant relative phase. For phase-randomized pulses the variance of the correlated fluorescence signal as a function of the pulse delay allows direct interrogation of coherent transients and dephasing processes. Our analysis follows the principle of coherence observation by interference noise, COIN [O. Kinrot, I. Sh. Averbukh, and Y. Prior, Phys. Rev. Lett. 75, 3822 (1995)], but is a generalization of this concept to expand on electronically interacting TLS. The theoretical results demonstrate that analysis of fluorescence interference fluctuations may provide a powerful diagnostic tool for probing the initial quantum coherence of energy transfer, i.e., excitation oscillations by employing fs-fluorescence correlation measurements in stable interferometric configurations.

Thomas Betz, Manz, A. Perrin +3 more