Stratification of the space of density matrices via invariant theory and Uhlmann's connection
Abstract
The space of n× n density matrices is the full state space of an n-level quantum system. While it has been asserted in the literature on quantum information theory that decomposing this state space into equirank pieces yields a Whitney stratification, rigorous proofs have remained absent. Using methods from invariant theory, this work provides a proof that the rank decomposition of the matrix algebra constitutes a (b)-regular stratification in the sense of Whitney. Furthermore, we demonstrate how the Uhlmann connection - which describes the adiabatic holonomy of mixed states and reduces to the Berry connection on pure states - can be geometrically treated as a stratified connection on a stratified vector bundle. Finally, our appendix provides a self-contained exposition of stratified fiber bundles and the new concept of stratified connections, which may be of independent interest.
Related
- Connection matrices and Berry phases on the homogeneous spaces 𝒟J1 and 𝒳J1 attached to Jacobi groups
- Finite-rank multiplicative perturbations of rotationally invariant non-Hermitian random matrices
- Spectral properties of deterministic matrices multiplied by rotationally invariant random non-Hermitian ensembles
- Quantum minimum description of density matrices
- Spectral density estimation for normal matrices
BibTeX
@misc{jordan2026stratification,
title = {{Stratification of the space of density matrices via invariant theory and Uhlmann's connection}},
author = {Howy Jordan and Markus J. Pflaum and Gerd Rudolph},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.02773},
eprint = {2610.02773},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.02773},
}
RIS
TY - UNPB
TI - Stratification of the space of density matrices via invariant theory and Uhlmann's connection
AU - Howy Jordan
AU - Markus J. Pflaum
AU - Gerd Rudolph
PY - 2026
DA - 2026/10/02
PB - arXiv
DO - 10.48550/arxiv.2610.02773
UR - https://arxiv.org/abs/2610.02773
AB - The space of n× n density matrices is the full state space of an n-level quantum system. While it has been asserted in the literature on quantum information theory that decomposing this state space into equirank pieces yields a Whitney stratification, rigorous proofs have remained absent. Using methods from invariant theory, this work provides a proof that the rank decomposition of the matrix algebra constitutes a (b)-regular stratification in the sense of Whitney. Furthermore, we demonstrate how the Uhlmann connection - which describes the adiabatic holonomy of mixed states and reduces to the Berry connection on pure states - can be geometrically treated as a stratified connection on a stratified vector bundle. Finally, our appendix provides a self-contained exposition of stratified fiber bundles and the new concept of stratified connections, which may be of independent interest.
ER -