Four Postulates of Quantum Mechanics Are Three
Abstract
The tensor product postulate of quantum mechanics states that the Hilbert space of a composite system is the tensor product of the components' Hilbert spaces. All current formalizations of quantum mechanics that do not contain this postulate contain some equivalent postulate or assumption (sometimes hidden). Here we give a natural definition of a composite system as a set containing the component systems and show how one can logically derive the tensor product rule from the state postulate and from the measurement postulate. In other words, our Letter reduces by one the number of postulates necessary to quantum mechanics.
 Publication:

Physical Review Letters
 Pub Date:
 March 2021
 DOI:
 10.1103/PhysRevLett.126.110402
 arXiv:
 arXiv:2003.11007
 Bibcode:
 2021PhRvL.126k0402C
 Keywords:

 Quantum Physics
 EPrint:
 4 pages+supplementary information. Final version accepted for publication on Phys. Rev. Lett