  We investigate the feasibility of performing quantum non-demolition (QND)
measurements in relativistic quantum systems, using the one-dimensional Dirac
oscillator as a specific example. We derive general expressions for its QND
observables and find that they are intricate combinations of the position,
momentum, and spin operators, which makes them challenging to realize
experimentally in general. However, the situation is considerably simplified in
both the weakly and strongly relativistic limits, where their experimental
realization will be possible.
