Non-resonant Action of π-Pulses

G. P. Berman, David K Campbell, V. I. Tsifrinovich

The problems of error correction in a spin quantum computer are discussed. For digital processing in the Ising and Heisenberg chains driven by a resonant electromagnetic field, the simple schemes are suggested which provide correction of errors caused by imperfect \ensuremath{\pi} pulses, and prevent the most significant errors caused by the nonresonant action of \ensuremath{\pi} pulses. The probability of error caused by the Heisenberg interaction during the action of \ensuremath{\pi} pulses is estimated. For quantum computations in spin systems a principal opportunity to correct the phase errors, based on Steane's three quantum-bits scheme, is described.

Marlan O. Scully, Shi-Yao Zhu, Muhammad Suhail Zubairy

Tonghao Xing, Jiang Zhang, Guilu Long

Andrey L. Vershinin, A E Dmitriev, Oleg M. Parshkov

The quasi-resonance interaction of a laser pulse with an inhomogeneously broadened quantum transition is numerically simulated under conditions corresponding to the experiment on the study of self-induced transparency in rubidium vapours. It is shown that the experimental shift of the pulse spectrum is caused by the initial stage of the formation of a precursor pulse and the influence of irreversible relaxation. It is found that the precursor pulse is more stable to the destructive action of relaxation than the 2π pulse and appears even in the case when the input pulse area is insufficient for the formation of the 2π pulse.

S.R. Barone, S. Chi

Zeyu Zhao, Wei Zhang, Yin Hui Huang +1 more

The formation of ultracold Cs 2 molecules via photoassociation (PA) with a spectral π-jump laser pulse is theoretically investigated by solving the time-dependent Schrödinger equation using the mapped Fourier grid method. Numerical calculations show that the population distributions of associated molecules mainly result from the off-resonant excitation of the π-jump laser pulse. Compared with the transform-limited pulse, an efficient population accumulation in the PA process is achieved with the π-jump pulse. An oscillation pattern appears in the population on the vibrational levels of the state owing to the action of the post-half-pulse in the π-jump pulse. The PA efficiency is related to the Rabi angle of the laser pulse. A π-jump pulse can be used to enhance more effectively the PA efficiency than a transform-limited pulse with the same Rabi angle.