  Entropy production characterizes irreversibility. This viewpoint allows us to
consider the thermodynamic uncertainty relation, which states that a higher
precision can be achieved at the cost of higher entropy production, as a
relation between precision and irreversibility. Considering the original and
perturbed dynamics, we show that the precision of an arbitrary counting
observable in continuous measurement of quantum Markov processes is bounded
from below by Loschmidt echo between the two dynamics, representing the
irreversibility of quantum dynamics. When considering particular perturbed
dynamics, our relation leads to several thermodynamic uncertainty relations,
indicating that our relation provides a unified perspective on classical and
quantum thermodynamic uncertainty relations.
