The Decoherence Research Of Flux Qubit's Circuit

Superconductivity quantum circuit is one of the most important ways for realizing quantum computation and quantum information. It's more superiority in collection and coupling than other qubit project. However, overcoming decoherence is the key problem for superconductivity electric circuit realizes quantum computation. In this paper, we mainly discussed the electric circuit mutual inductance, the environment circuit element, as well as the driving fields'influence on decoherence of flux qubit.The second chapter introduced a method for analyzing electrical circuit, which is developed recently by Burkard, Koch and Divincenzo et al. also we introduced the Bloch-Redfield master equation for the dynamics of the small quantum system and the environment bath. The third chapter, we used this method analysis electric circuit, and discussed the mutual inductance between the environment circuit elements, as well as the environment circuit element's influence on the decoherent of flux qubit.Chapter four, in the foundation of third chapter, we further discussed the driving fields'influence on decoherence of flux qubit. In the fourth chapter, we solution the Bloch equation to obtain the qubit decoherence time, and comprising the decoherence times of whether there is a driving field. In our research, we mainly draw following conclusion:(l) The decoherence times decreases as the environment and the main circuit, control circuit's mutual inductance increases, and along with the mutual inductance gradual increases, the speed of the decoherence time reduced.(2) The decoherence time decreases as the main circuit and control circuit's mutual inductance increases, and along with the mutual inductance gradual increases, the speed of the decoherence time increased.(3) When the biasing circuit is the RLC electric circuit, the decoherence times increases as resistance Z increases, It indicated that, the current supply's fluctuation is smaller, the decoherence time to be longer. The decoherence time decreases as the capacitance increase.(4) We found the relations between the field-dependent decoherence time and the intrinsic decoherence time.