Realization Of Coherent Control Of Light Field And Self-sufficient Heat Engine Based On Multi-level Atoms

The interaction between light and atom is the main content of quantum optics researches.The common research methods include the semi-classical theory which only quantizes the atom,and the quantum theory which quantizes both the light field and the atom.The interaction between photons and atoms displays numbers of unique quantum phenomena,such as Rabi oscillation,coherent population trapping,slow light and Rydberg blockade.In this dissertation,we pay main attention to the changes of light field as well as the behavior of atom during the process of the interaction between light field and atom.It mainly divides into two parts:one is the coherent manipulation of classical light field and its application;the other is the self-contained thermal machine composed of single atom within the interaction.The coherent control of light is a method to realize the modulation of various properties of light by the interaction between light and atom,which by means of natural or artificial atom as the medium.In the researches of quantum computer and quantum communication,photon has been widely concerned as the best carrier of quantum information.Different from electronic,there is no direct interaction between photons.Given that we must rely on atoms as the medium to achieve coherent control of light.In addition,the atom also plays an important role in the photon generation and storage.Self-contained thermal machine is a kind of special quantum thermal machine.It can realize the functions of refrigerator and heat engine only by contacting with heat baths at different temperatures without any external power.Specifically,the dissertation has arrived at the following results:1.Using the principle of Electromagnetically Induced Transparency,we study the polarization response of △-type three-levelartificial atom to two weak fields in the system of coherent coupling of three classical light fields and parity breaking three-level atom,and propose a cross phase modulation scheme.The unique cyclic transition structure of △-type three-level atom makes the relative phase of the three light fields have an obvious influence on the polarization of the atom.Adjusting the relative phase can sensitively change the absorption and dispersion of the weak fields.In our scheme,the probe field can propagate transparently without absorption.With the help of the relative phase of the multi-optical field,we can increase the cross phase modulation of the auxiliary field to the probe field and restrain the self phase modulation of the probe field.In addition,the dispersion curves of the probe field and the auxiliary field in the medium are basically the same,which shows that they have similar group velocity.2.A more completed all-optical switch scheme is proposed.In our scheme,by simply opening or closing the weak auxiliary field,controlling the closure or destruction of the cyclic transition structure,we can make the probe field in the state of transparent propagation or absorption.Then,we explain this phenomenon by solving the steady-state solution of the system:when the auxiliary field is opened,the closed cyclic transition structure makes the nonlinear effect greatly enhanced,which is enough to eliminate the absorption brought by the linear effect.We also compared this scheme with the electromagnetically induced transparency scheme.3.A new theoretical scheme of self-contained quantum thermal machine is proposed.In this scheme,we realize the cooling of the target qubit,and discuss the influence of the coupling strength between the thermal machine and the target qubit on the cooling effect and efficiency.It is found that strong coupling helps to cool the target qubit to a lower temperature faster.However,the coupling strength has no significant effect on the critical temperature.It should be noted that our scheme can be used to cool the target qubits of any frequency without replacing the thermal machine.