Super-symmetric informationally complete measurements

TL;DR

This paper investigates the most symmetric SICs in quantum mechanics, revealing their covariance with Heisenberg-Weyl groups and their relation to Clifford groups, providing new insights into symmetric structures in finite quantum systems.

Contribution

It classifies highly symmetric SICs and shows they are covariant with Heisenberg-Weyl groups, linking symmetry properties to foundational quantum structures.

Findings

All most symmetric SICs are covariant with Heisenberg-Weyl groups.

The symmetry groups of these SICs are subgroups of Clifford groups.

Identifies the unique SICs in dimensions 2, 3, and 8 with transitive symmetry groups.

Abstract

Symmetric informationally complete measurements (SICs in short) are highly symmetric structures in the Hilbert space. They possess many nice properties which render them an ideal candidate for fiducial measurements. The symmetry of SICs is intimately connected with the geometry of the quantum state space and also has profound implications for foundational studies. Here we explore those SICs that are most symmetric according to a natural criterion and show that all of them are covariant with respect to the Heisenberg-Weyl groups, which are characterized by the discrete analogy of the canonical commutation relation. Moreover, their symmetry groups are subgroups of the Clifford groups. In particular, we prove that the SIC in dimension~2, the Hesse SIC in dimension~3, and the set of Hoggar lines in dimension~8 are the only three SICs up to unitary equivalence whose symmetry groups act transitively on pairs of SIC projectors. Our work not only provides valuable insight about SICs, Heisenberg-Weyl groups, and Clifford groups, but also offers a new approach and perspective for studying many other discrete symmetric structures behind finite state quantum mechanics, such as mutually unbiased bases and discrete Wigner functions.