The Quantum Noise Of Probe Light In The Medium Of Quantum Memory

Atomic coherent effect caused by the interaction between light and atoms is one of the important methods for quantum information storage. Recently, it has been shown that photons are efficient carriers for quantum information transporting and processing. At the same time, photons are not suitable for information storage because of their high speed and they are difficult to couple with each other. Instead of photons, atoms as a kind of practical partials are widely recognized as a perfect memory cell of quantum information. The interaction between photons and atoms offers an effect process for information to transfer between optical fields and quantum states of practical partials. Therefore it will show great effect on quantum calculation and quantum communication to realize the transporting, storage and picking up of quantum states between light and practical partials by the coherent effect between light field and atoms.For the past a couple of years, a lot of groups has proved the storage function of classical weak pulse signals in the above condition experimentally. However, the realizing of quantum storage requires the retaining of the quantum states at shot noise limit or below the limit. The light fields have quantum states such as coherent states, vertical squeezing states and entangled photon pairs, the quantum properties of such states determine that quantum communication is superior as an information transporting source comparing to the classical secret communication, because restricted to the uncertainty principle in quantum mechanics. Under this condition, any listener-in attempt to filch the information through quantum measurement will disturb the quantum states of the system, therefore exposure themselves. The above theory make the real secret communication be able to come true. Therefore quantum memory is important for further improvement of the information storage capacity and secrecy of quantum communication, and it will enhance the further development of quantum information science. It will greatly improve the development of quantum information processing, quantum secret communication, quantum information control and quantum computing to find a more reasonable and self-contained quantum memory scheme, meanwhile the research of quantum memory will lead us to a deeper understanding and inspection of the basic problems of quantum mechanics, and consummate the research of microcosmic fields of quantum mechanics.In this thesis we experimentally researched the noise property of coherent light field when it is quantum memorized in the atomic coherent medium, and gives a theoretical explanation of the quantum memory of non-classical optical fields with the optimum condition to minimize the quantum noise. The mainly content of this thesis are shown below:1. We introduced the basic and key technology of the light storage experiment with atomic coherent effect, measured the noise of the optical fields that had passed through the EIT medium, and then we give an experimental scheme verifying the property of the quantum memory by measuring the noise.2. We theoretically analysis the quantum memory of squeezed light and give the noise results of the recovered light, which explains the experimental results. The theories show that the total noise of the recovered light contains 3 parts, the amplitude noise of the input field, the phase-to-amplitude converted noise and the atomic noise.The creative works are as follows,1. We measured the noise of the coherent light field recovered from being stored by the EIT medium, after that we give a experimental scheme of measuring the non-classical properties of the recovered non-classical light field.2. We analysis the noise of the coherent light field recovered from EIT medium by all quantum theory, and explained the experiment results by the results.