Phase control on an atomic system

Qing Yang Xu, Xiangming Hu, J. W. Yin

M. A. Bouchène, Mahmoud Abdel‐Aty

We propose a method to control the atomic dynamics in the presence of electromagnetic fields. Instead of measuring the population dynamics, we focus on the possibility of controlling the Pancharatnam phase. For a two-level system we find that this phase can be optically induced and controlled by the phase shift. More importantly, the nonlinear interaction between the atom and the field leads to an enhanced sensitivity for the control of the atomic phase evolution and system dynamics.

Halyne Silva Borges, Celso J. Villas-Bôas

We theoretically investigate the implementation of a quantum controlled-phase gate in a system constituted by a single atom inside an optical cavity, based on the electromagnetically induced transparency effect. First we show that a probe pulse can experience a $\ensuremath{\pi}$ phase shift due to the presence or absence of a classical control field. Considering the interplay of the cavity-EIT effect and the quantum memory process, we demonstrated a controlled-phase gate between two single photons. To this end, first one needs to store a (control) photon in the ground atomic states. In the following, a second (target) photon must impinge on the atom-cavity system. Depending on the atomic state, this second photon will be either transmitted or reflected, acquiring different phase shifts. This protocol can then be easily extended to multiphoton systems, i.e., keeping the control photon stored, it may induce phase shifts in several single photons, thus enabling the generation of multipartite entangled states. We explore the relevant parameter space in the atom-cavity system that allows the implementation of quantum controlled-phase gates using the recent technologies. In particular, we have found a lower bound for the cooperativity of the atom-cavity system which enables the implementation of phase shift on single photons. The induced shift on the phase of a photonic qubit and the controlled-phase gate between single photons, combined with optical devices, enable one to perform universal quantum computation.

Dimitrios Charalambidis, Natalia E. Karapanagioti, D. Xenakis +8 more

Viswanath Ramakrishna, Raimund J. Ober, HERSCHEL A. RABITZ

Wang Li, Gen‐Quan Li, Xiao Shao-Wu +1 more

In this paper, we have calculated the absorption of the probing field in a N-type four-level atomic system with three dipole transitions using density matrix equation. The results indicate that the absorption or amplification of the probing field depends on the Rabi phases of the control field and signal field under introducing laser field Rabi phase, and the absorption or amplification periodically changes with the Rabi phases of the control field and the signal field at a period of 2π. The Rabi phase change of the probe field has no effect on the absorption. In addition, the effect of the signal field Rabi phase on absorption is the same as that of the control field Rabi phase on absorption. Rabi phase has an effect mainly on atomic coherence but little on atomic population.