The Properties And Phonon Effect Of Qubit In Spherical Shell Quantum Dot

The properties and phonon effect of qubit in spherical shell quantum dot are studied by solving the Schrodinger equation and LLP unitary transformation and variation method.The energies and states of electron in spherical shell quantum dot are obtained by solving the Schrodinger equation and a quantum bit (qubit) is formed by overlying both the ground state and an excited state. The numerical results for InAs spherical shell quantum dot indicate that the energy of electron increases when the electron's confinement is strengthened, probability density distribution of electron in qubit has something to do with the electron's position in the spherical shell quantum dot and time, there is a maximum in central spherical surface and zero in boundary surfaces; the probability density of electron in all position makes periodical changing with angle coordinate and periodical oscillating with time, and the oscillating period increases with the outer (or inner) radius increasing.The influence of phonon effect on the energy of polaron and the property of qubit are studied by using LLP unitary transformation and variational method. The numerical results indicate that when inner radius is given, the ground state and excited state energy will decrease with increasing outer radius, which shows that spherical shell quantum dot has apparent quantum size effect. The phonon effect makes the ground energy and the excited states reducing, when inner radius is given, the larger the outer radius is, the more evident the phonon effect is. The phonon effect makes oscillating period shorting, which indicated that phonon effect weakens the coherence of qubit, but it does not change amplitude of probability density.