The Properties Of Polaron And Qubit In Quantum Ring

In this paper,the effect of temperature on the ground state ofpolaron in quantum ring was studied by solving energy eigenequation,LLP unitary transformations and elementary excitation theory method.A qubit was formed by overlying both the ground state and the first excited state of polaron,and the properties of qubit in quantum ring were studied.First of all,the eigenfunction and the eigenenergy of the ground state and the first exited state of the electron in quantum ring were obtained by solving precisely the time-independent Schro|¨dinger equation,and the effect of phonon was studied by using a combinative approach of the LLP unitary transformations and the elementary excitation theory method,and then the energy state of polaron was obtained.The numerical results showed that,on the condition of 0＜T＜T_C,meaning it was in lower temperature,no phonon was excited,and the ground state energy had something to do with temperature. When the temperature arose to T＞T_C,the influence of temperature on the ground energy of polaron was dominant,and the higher temperature,the more number of excited phonons and the larger ground energy could be got.It was also showed that the ground energy decreased with increasing the electron-LO-phonon coupling strength,because the stranger electron-LO-phonon interaction,the larger absolute value of the interaction energy of electron-LO-phonon was,and the smaller ground energy of polaron was.And it was also showed that,the ground energy increased with increasing the confinement strength(increasing the inner radius or decreasing the outer radius of quantum ring),and all these showed that the quantum size effect in quantum ring was very obvious,that is the stronger polaron limited,the greater energy.Secondly,on the condition of electron-LO-phonon strong coupling,the eigenfunction and the eigenenergy of the ground state and the first exited state of the electron in quantum ring were obtained by solving precisely the time-independent Schro|¨dinger equation,and the effect of phonon was studied by using a combinative approach of the LLP unitary transformations and the elementary excitation theory method.A qubit was formed by overlying both the ground state and the first excited state of polaron.The probability density distribution of electron in qubit did periodicity oscillating with time and angle coordinate,and the largest probability density of electron was in the center of ring,and the probability density of electron was zero when it lied in the interface of ring.The oscillating period decreased with increasing,the electron-LO-phonon coupling strength,and it showed that the existence of phonon resulted in decreasing the coherence of qubit.And the oscillating period increased with increasing the inner(or outer) radius of the quantum ring,so the coherence of qubit could be increased by choosing properly the size of quantum ring.