Quartic quantum theory: an extension of the standard quantum mechanics

TL;DR

This paper introduces a novel extended quantum theory where the number of parameters scales as the fourth power of distinguishable states, expanding the standard quantum framework through embedding classical probability distributions into higher-dimensional quantum states.

Contribution

It presents a new extended quantum theory with a higher parameter count, embedding classical distributions into quantum states, and shows how constraints recover standard quantum and classical theories.

Findings

Extended quantum states form a higher-dimensional convex set.

Standard quantum theory is a special case with K=N^2.

Classical theory is recovered under stronger constraints.

Abstract

We propose an extended quantum theory, in which the number K of parameters necessary to characterize a quantum state behaves as fourth power of the number N of distinguishable states. As the simplex of classical N-point probability distributions can be embedded inside a higher dimensional convex body of mixed quantum states, one can further increase the dimensionality constructing the set of extended quantum states. The embedding proposed corresponds to an assumption that the physical system described in N dimensional Hilbert space is coupled with an auxiliary subsystem of the same dimensionality. The extended theory works for simple quantum systems and is shown to be a non-trivial generalisation of the standard quantum theory for which K=N^2. Imposing certain restrictions on initial conditions and dynamics allowed in the quartic theory one obtains quadratic theory as a special case. By imposing even stronger constraints one arrives at the classical theory, for which K=N.