  We introduce Kadanoff-Ceva order-disorder operators in the quantum Ising
model. This approach was first used for the classical planar Ising model and
recently put back to the stage. This representation turns out to be equivalent
to the loop expansion of Sminorv's fermionic observables and is particularly
interesting due to its simple and compact formulation. Using this approach, we
are able to extend different results known in the classical planar Ising model,
such as the conformal invariance/covariance of correlations and the
energy-density, to the spin-representation of the (1+1) dimensional quantum
Ising model.
