Phase retrieval for affine groups over prime fields

TL;DR

This paper investigates phase retrieval using affine group representations over finite fields, establishing conditions for matrix reconstruction from group orbit measurements and providing explicit algorithms and examples.

Contribution

It characterizes vectors enabling matrix recovery via affine group actions, introduces a linear recovery algorithm, and explores the strongest retrieval properties in this context.

Findings

The canonical irreducible representation allows matrix recovery from scalar products with a group orbit.

Explicit vectors are characterized that guarantee the strongest retrieval property.

A linear matrix recovery algorithm is developed with concrete examples.

Abstract

We study phase retrieval for group frames arising from permutation representations, focusing on the action of the affine group of a finite field. We investigate various versions of the phase retrieval problem, including conjugate phase retrieval, sign retrieval, and matrix recovery. Our main result establishes that the canonical irreducible representation of the affine group $\mathbb{Z}_p \rtimes \mathbb{Z}_p^\ast$ (with $p$ prime), acting on the vectors in $\mathbb{C}^{p}$ with zero-sum, has the strongest retrieval property, allowing to reconstruct matrices from scalar products with a group orbit consisting of rank-one projections. We explicitly characterize the generating vectors that ensure this property, provide a linear matrix recovery algorithm and explicit examples of vectors that allow matrix recovery. We also comment on more general permutation representations.