# Is it correct to say that matter and antimatter are opposite in all quantum properties that are conserved?

Matter and Antimatter are always created in pairs, with the exception of CP Symmetry Violation. Thus, in order for some quantum properties to be conserved, these properties must be opposite in the particle and antiparticle created.

An example of that is electrical charge, which is a conserved quantum property. When a particle-antiparticle pair is created, they must have opposite charges for charge to be conserved.

Therefore, is it right to conclude and define an antiparticle as a particle with opposite conserved quantum properties?

• I think mass is an exception, because the sum of their energy should be energy which produced them. All the others, yes. – peterh - Reinstate Monica Feb 12 '17 at 3:33
• CP symmetry isn't the symmetry between matter and antimatter, it's CPT symmetry, which hasn't been found to be violated experimentally. – David Elm Feb 12 '17 at 7:38

Note that antiparticles are required to ensure that a theory is causal. In other words, a measurement at $x$ should not affect a measurement at $y$ if the separation between the two coordinates is space-like [i.e., $(x-y)^2<0$]. One finds that for correlations between observables to vanish like this, each particle $\chi$ must have a corresponding antiparticle $\overline{\chi}$ with the same mass, but opposite internal quantum numbers.