Inflation is Not Magic

TL;DR

This paper demonstrates that quantum inflationary perturbations, despite their quantum features, can be efficiently simulated classically because they lack quantum magic, offering insights into the quantum nature of the universe's structure.

Contribution

It shows that quantum inflationary states are stabilizer states with no quantum magic, explaining their classical-like observational signatures and implications for quantum complexity in cosmology.

Findings

Quantum inflationary perturbations are stabilizer states with zero quantum magic.

Wigner negativity from non-Gaussianity is suppressed by squeezing and non-linearity.

Quantum states of early universe perturbations can be classically simulated efficiently.

Abstract

Cosmological perturbations generated during inflation exhibit striking quantum features, including entanglement and high circuit complexity. Yet their observational signatures remain effectively indistinguishable from classical stochastic variables. We quantify this tension by showing that quantum inflationary perturbations are continuous variable stabilizer states with vanishing quantum magic, a necessary resource for universal quantum computation as measured by Wigner negativity. Consequently, despite their quantum origins and description, these states can be efficiently simulated using classical algorithms. We further show that the Wigner negativity arising from primordial non-Gaussianity is suppressed not only by the non-linearity parameter $f_{NL}$, but also by the exponential squeezing of the perturbations. Viewing the early universe as a "high complexity, low magic" regime provides another perspective of what it means for the origin of structure in the universe to be "quantum."