Effect of environmental noise on coherence of quantum states

In this paper, we study the effect of magnetic field and temperature on the amount of coherence in a two spin Heisenberg system. We show that increasing the temperature always leads to lowering the value of this coherence. We also show that the increase of the amount of the magnetic field, leads to increasing the value of coherence up to a certain value, and ultimately it decreases its value to zero. We also study the same problem for three and four spins in the Heisenberg chain and we show that the same features are also observed for three and four-spin systems. The trends show that these features may be general for Heisenberg chains of arbitrary length.