Implementation Of Quantum Computing Via Foerster Resonance In Rydberg Atoms

In this thesis,we mainly study the implementation of quantum information processing via Stark-tuned Foerster resonance in Rydberg atoms.In the first chapter,we first briefly introduce the research background of quantum computing,and then introduce the Rydberg atom system and the basic principal of the Foerster resonant interaction,we finally describe the methods used in this thesis for the implementation of quantum logic gates,i.e.adiabatic passage and Landau-Zener transition.In Chapter 2,we study the implementation of quantum logic gates by adiabatically modulating the Foerster interaction in Rydberg atoms.In combination with the adiabatic rapid passage and Stark-tuned Foerster resonance,we propose schemes for implementing a controlled-Z gate(CZ)and a controlled-NOT gates(CNOT).In this scheme,the variation of dipolar interaction strength between the two atoms can be achieved by continuously changing the angle between the quantization axis and the internuclear axis on one hand;on the hand,the energy defect is adiabatically modulated to and back from the resonance by using the electric field induced Stark effect.Since our scheme requires only to reach the Foerster resonance once,the operation time of the logic gates is greatly reduced and the fidelity remains high.Finally,we discuss in detail the experimental feasibility and analyze the effects of parameter fluctuations and the Zeeman effect on the fidelity of quantum logic gates.In comparison with the double adiabatic passage scheme,our scheme proposes another method for constructing high-fidelity quantum logic gates,which lays the theoretical basis for the experimental study of quantum information processing with Rydberg atoms.In chapter 3,the implementation of a two-qubit logic gates by periodic modulation of the Foerster interaction is discussed.We consider the two collective states participating the Foerster interaction as a two-level system,the coupling strength between the levels is kept unchanged,and a periodic external driving field is used to modulate the Foerster energy defect.The dynamics of the system can be described by the standard model of the Landau-Zener transition.Under optimal driving conditions,the system after time evolution returns to the initial state with the population and the accumulated phase retained in stable value for a certain time scale,which favors the implementation of near-deterministic operation of quantum logic gates.We also discuss in detail the effects of parameter fluctuations and the atomic spontaneous emission on the fidelity of gates.Compared with the scheme via double adiabatic passage,we used a driving field of the periodic cosine function,which is easy to access in experiment;although the acquired phase and population of the state in our scheme is non-deterministic,but it is highly robust against a certain degree of time deviation with a similar gate operation time.Therefore,our scheme provides a simple and effective method for realizing quantum computation via modulating the Foerster interaction.