Quantum Communications pp 77-129 | Cite as

# Elements of Quantum Mechanics

## Abstract

Quantum Mechanics will be formulated assuming four *postulates*: Postulate 1: gives the universal model of any physical system: a Hilbert space on the field of complex numbers. Postulate 2: models the temporal evolution of a *closed* physical system that is not influenced by other physical systems. Postulate 3: regards the *information* that can be extracted (through a *quantum measurement*) from a quantum system at a given time instant. Postulate 4: formalizes the interaction among physical systems through a combination of multiple Hilbert spaces into a single Hilbert space. The mathematical tool of this formulation is given by the tensor product. Considering that our final objective is *Quantum Communications*, some aspects of Quantum Mechanics will not be further expanded, such as the consequences of Postulate 2 on the evolution of a quantum system, while other points, in particular *quantum measurements* (Postulate 3) will be exhaustively investigated.

## Keywords

Hilbert Space Quantum Mechanics Quantum System Coherent State Pure State## References

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