Decoherence in Josephson vortex quantum bits

We investigate decoherence of a Josephson vortex quantum bit (qubit) in a dissipative and noisy environment. We use the perturbed sine-Gordon equation to describe the two-state system as the Josephson vortex qubit (JVQ) is fabricated by using a long Josephson junction. We compute the coherence time T2 by estimating the effects of quasiparticle dissipation and weakly fluctuating bias currents on the relaxation time and on the dephasing time. We show that an ultra-long T2 may be obtained from JVQ by using experimentally accessible value of physical parameters.