Light Control And Quantum Correlated Fields In Coherently Prepared Atomic Media

Electromagnetically induced transparency (EIT) is an atomic coherence effect induced by quantum interference. It is available to suppress the resonant absorption of optical field, and to enhance the dispersion and nonlinearity. Recently, EIT has been successfully treated as the unit of information storage and applied in quantum network. With the development of quantum communication, coherently prepared atoms should be widely applied in, such as controlling the optical propagation and preparing the non-classical field. The former is possible to compensate the photon loss and take the role of quantum optics devices in quantum communication; the latter is able to extend the wavelength of quantum correlated beams to atomic resonance, then to realize the efficient information transfer between quantum channel and quantum node. Furthermore, these correlated fields have the advantages of narrow linewidth and long coherence length. Because of no cavity when we use atomic ensemble to obtain quantum correlated fields, high-dimensional quantum correlation is achieved accompanied by multi-mode amplification. Therefore, it is potential to applied in parallel quantum computation, quantum dense coding, and improve the quantum imaging. On the other hand, we do the research in energy levels of the D1 transition of cesium, the corresponding wavelength is 895 nm, which is matching with the exciton emission from InAs quantum dots, for the possible coherent interfaces between atomic and solid-state systems.This article firstly introduces the effects of EIT, electromagnetically induced absorption grating, lasing without inversion, Double and Dual EIT and four-wave mixing and so on, and reviews the research development and application. Then, it presents the main works of experimental and theoretical studies on photonic crystal, EIT with amplification and continuous-wave quantum correlated fields by exploiting hot atomic vapor.1) Optical control of light propagation in photonic crystal based on EITis studied. When the three-level EIT is coupled by a standing wave, the refractive index is periodically modulated to form a one dimensional photonic crystal structure. A similarly dynamic control photonic frequency band gap is opened, because of high efficiency Bragg reflection is obtained as well as the resonant probe field is forbidden. Combining both the characters of EIT and photonic crystal, transfer-matrix theory is taken to simulate the probe transmission and reflection spectrum. Finally, the existence of photonic crystal structure in atoms is fully demonstrated because of the good agreement between theoretical and experimental results.2) High-gain coherent amplification in Tripod-type Dual EIT is studied. Based on the three-level A-EIT, an additional signal field drives the transition between the third ground state and excited state. Two EIT windows is obtained in the probe transmission spectrum with probe frequency scanning. The two windows are coupled when their frequencies are close to equal, then the ground state atomic coherence is enhanced. In the first step, reduce probe absorption with Dual EIT. In the second step, increase the population in the third ground state using the mechanism of spin-exchange induced transfer of population (ToP), thereby amplification with EIT is achieved accompanied by the improvement of pumping rate from signal field. The calculated gain spectrum also shows accurate agreement with experimental result.3) The theoretical part of the generation of EPR entangled fields from four-wave mixing. Stemming from the Hamiltonian of double A three-level field-atom coupled system, the atomic operator is replaced by the product of quantized field operators and a coefficient including the parameters of both pumping field and atoms. The effective Hamiltonian is obtained by making the second order perturbation approximation for field operators and keeping the phase-matching. It describes the amplification intuitively, i.e., the energy of two pumping photons is transferred into a pair of Stokes and anti-Stokes photons through the third-order nonlinearity. According to the EPR entanglement criteria, the two fields are inseparability. The dependence of entanglement on pumping detuning, ground state hyperfine splitting, interaction length, pumping intensity and spontaneous noise is discussed. This study is helpful for the experimental generation of optimal entanglement.4) The experimental preparation for high-dimensional quantum correlated beams in the cesium D1 line is studied. A pair of TEMoiHermit-Gaussian quantum correlated beams are obtained when seeding a TEMoi probe beam into the four-wave mixing amplifier. Extract the sub-modes and measure theirrelative intensity noise correlation, a 2.5 dB high-dimensional correlated beams in both time and spatial domain is obtained. Therefore, these correlated beams is able to encode more information.The innovations are as follows:?.In the viewpoint of photonic crystal, we studied the probe field propagation in electromagnetically induced absorption grating. The theoretical results show a fully demonstration of the co-existence of EIT and photonic crystal structure.?. We firstly realize the coherent amplification with EIT via theDual EIT configuration in experiment. It is indicated that the population of ground state pumped by the signal field is greatly improved through the spin-exchange induced ToP in optically thick medium. Thereby, high gain is occurred with lower pumping intensity.?. Exploiting the second order perturbation approximation and keeping the phase matching condition in four-wave mixing, we firstly present effective Hamiltonian, which is similar to the nondegenerate optical parametric amplification.It is concluded that the key factor of limiting entanglement is the hyperfine splitting between ground states by comparing the two atoms of rubidium and cesium.?. High-dimensional quantum correlated beams with wavelength matching with the cesium absorption line is firstly obtained in experiment,by the means of seeding the four-wave mixing with TEM01 Hermit-Gaussian transverse mode.