The Quantum Noise Of The Probe Field In Electromagnetically Induced Transparency Medium

As the basis of quantum communication and computing, the investigation of the interaction between the light and atomic is very important. Which including coherent population trapping (CPT), electromagnetically induced transparency (EIT), quantum storage, slow light, laser without inversion (LWI) and so on. Due to its unique absorption and dispersion properties, EIT have a wide range of applications in many areas. EIT effect can reduce the absorption loss of light in the medium while enhancing the dispersion, thus it can be used in slowing the group velocity of the light, quantum storage, laser without inversion and many other aspects. In quantum communication, the reliability of quantum information processing depends on the measurement of the noise. The research of quantum noise properties of probe light field in Electromagnetically induced transparency has a significant role in improving the reliability of quantum information.First, we review the background knowledge of EIT, which including discovery and physical mechanism, development, and applications of EIT. Secondly, we analyze the absorption and dispersion properties of a two-level atomic system resonance medium and Λ-type three-level atomic system EIT medium through Semi-classical theory. Through comparison we can find that Λ-type three-level EIT atomic system has strong dispersion and weak absorption at the resonance. It’s different from the two-level atomic system: which has strong dispersion and strong absorption. This feature of EIT makes many phenomena possible. So EIT has been well used in many areas.Finally, this paper focuses on the experimental study of quantum noise properties of the probe field in EIT medium. Through the absorption and dispersion properties of EIT we analyze the sources of additional noise of probe field. We applied some relevant knowledge in the experiment, such as the technology of saturated absorption, low noise AC/DC detector and balanced homodyne detection system. These are the basis of the experiment of the interaction between light and atoms. We use balanced homodyne detection and self-homodyne detection respectively to measure the quadrature amplitude and quadrature phase noise spectra of the probe field in electromagnetic induced transparency medium. Through adjusting the voltage of the piezoelectric ceramic transducer, we change the optical path of the local light, thus change the relative phase of the local light and the probe light in the balanced homodyne detection. Then we measure the noise components of the probe light with the different phase. In the experiment, we observe that the coupling of the probe light and the coupling light lead to the increase of the noise of the probe light in electromagnetic induced transparency medium. And we find that the induced extra noise of the different quadrature components of the probe field is different for the different detuning of the coupling laser. Simultaneously, we give the relationship between the noise of the probe field and the power of the coupling light and analysis frequency. The analysis to quantum noise properties of light field in EIT medium can be used as the basis of the reliability of quantum information process and the method of phase noise measurement of the light field.