Principles of Quantum Mechanics was created in 1930.

The distinction is sometimes made to distinguish normal quantum mechanics (which does not incorporate special relativity) and quantum field theory (relativistic quantum mechanics).

Since we know special relativity is correct it is the relativistic form of quantum mechanics which is true, but non-relativistic quantum mechanics is still used, because it is a good approximation at low energies and it is much simpler.

Physics students typically study regular quantum mechanics before moving on to quantum field theory.

The concepts of quantum mechanics were not explored until the 20th century. Newton only lived into the 18th century, so Newton did no work on quantum mechanics.

The mixed state in quantum mechanics is the statistical ensemble of the pure states.

Quantum Mechanics "replaced" Classical Mechanics in particle physics in mid-1930s.