  We study quantum coherence in a spin chain with both symmetric exchange and
antisymmetric Dzyaloshinsky-Moriya couplings. Quantum coherence is quantified
using the recently introduced quantum Jensen-Shannon divergence, which has the
property that it is easily calculable and has several desirable mathematical
properties. We calculate exactly the coherence for arbitrary number of spins at
zero temperature in various limiting cases. The $\sigma^{z} \sigma^{z}$
interaction tunes the amount of coherence in the system, and the antisymmetric
coupling changes the nature of the coherence. We also investigate the effect of
non-zero temperature by looking at a two-spin system and and similar behavior,
with temperature dampening the coherence. The characteristic behavior of
coherence resembles that of entanglement and is opposite to that of discord.
The distribution of the coherence on the spins is investigated and found that
it arises entirely due to the correlations between the spins.

Quantum Physics