Control of absorptiion and dispersion of light by coherence in a atoms and molecules

Sandeep Sharma, Bimalendu Deb, Tarak Nath Dey

Abstract We theoretically investigate light propagation through a Feshbach-resonant atom–molecule coupled system. We show that when a diatomic molecular state in an electronically ground-state potential is coupled to the continuum of Feshbach-resonant atom–atom scattering states via an excited molecular state with a control (strong) and a probe (weak) laser field, the dispersive behaviour of the medium is significantly influenced by the Feshbach resonance. In particular, a Feshbach resonance helps to make the dispersion characteristics quite sharp, leading to the subluminal propagation of the probe. Our model calculations with realistic parameters show that it is possible to reduce the group velocity to 50 m s −1 with nearly 80% transmission. Furthermore, we demonstrate that it is possible to achieve significant enhancement of the delay-bandwidth product (DBP) of the probe by narrowing the width of the resonance, opening up new prospects for using a resonant atom–molecule coupled medium for efficient slow-light production and applications.

M. Simhony

Jiangbin Gong, Paul W. Brumer

The subtle and fundamental issue of indistinguishability and interference between independent pathways to the same target state is examined in the context of coherent control of atomic and molecular processes, with emphasis placed on possible "which-way" information due to quantum entanglement established in the quantum dynamics. Because quantum interference between independent pathways to the same target state occurs only when the independent pathways are indistinguishable, it is first shown that creating useful coherence between nondegenerate states of a molecule for subsequent quantum interference manipulation cannot be achieved by collisions between atoms or molecules that are prepared in momentum and energy eigenstates. Coherence can, however, be transferred from light fields to atoms or molecules. Using a particular coherent control scenario, it is shown that this coherence transfer and the subsequent coherent phase control can be readily realized by the most classical states of light, i.e., coherent states of light. It is further demonstrated that quantum states of light may suppress the extent of phase-sensitive coherent control by leaking out some which-way information while "incoherent interference control" scenarios proposed in the literature have automatically ensured the indistinguishability of multiple excitation pathways. The possibility of quantum coherence in photodissociation product states is also understood in terms of the disentanglement between photodissociation fragments. Results offer deeper insights into quantum coherence generation in atomic and molecular processes.

Servet Bayram, A. M. Lyyra, Noureddine Melikechi

Wojciech Gawlik

Hussain Ahmad, Ali Akgül, Ghulam Saddiq +1 more

Covalent and photonic interactions between atoms in lattice are controlled by probe absorption and dispersion spectrums. Similarly, information of covalent interaction among atoms within a crystal is extracted by absorption and dispersion spectrums in the range of [Formula: see text]. Localization of atoms and pairs of electron density are controlled by the gradients ([Formula: see text] and [Formula: see text]) variation of absorption and dispersion spectrums of the four-level atomic medium. Additionally, the covalent interaction between atoms are modified using structured light beams in the range of [Formula: see text]. The sharing of electrons between atoms are controlled and modified by the parameters of probe, control fields and the gradients variation of absorption and dispersion. This work will play an important role in the field of quantum enhanced metrology, trapping of atoms, nanolithography and Bose-Einstein condensate.