Graph States and the Variety of Principal Minors

TL;DR

This paper explores the mathematical relationship between quantum graph states and the variety of principal minors of binary symmetric matrices, revealing new symmetries and orbit structures under group actions.

Contribution

It establishes a correspondence between graph states in quantum information and the variety of principal minors, connecting group actions on quantum states to algebraic geometry.

Findings

Identifies the action of local Clifford groups with the action on principal minors.

Translates the action of $SL(2,\mathbb F_2)^{\times n}$ into a symplectic group action.

Analyzes stabilizer groups and states, especially graph states.

Abstract

In Quantum Information theory, graph states are quantum states defined by graphs. In this work we exhibit a correspondence between graph states and the variety of binary symmetric principal minors, in particular their corresponding orbits under the action of $SL(2,\mathbb F_2)^{\times n}\rtimes \mathfrak S_n$. We start by approaching the topic more widely, that is by studying the orbits of maximal abelian subgroups of the $n$-fold Pauli group under the action of $\mathcal C_n^{\text{loc}}\rtimes \mathfrak S_n$, where $\mathcal C_n^{\text{loc}}$ is the $n$-fold local Clifford group: we show that this action corresponds to the natural action of $SL(2,\mathbb F_2)^{\times n}\rtimes \mathfrak S_n$ on the variety $\mathcal Z_n\subset \mathbb P(\mathbb F_2^{2^n})$ of principal minors of binary symmetric $n\times n$ matrices. The crucial step in this correspondence is in translating the action of $SL(2,\mathbb F_2)^{\times n}$ into an action of the local symplectic group $Sp_{2n}^{\text{loc}}(\mathbb F_2)$ on the Lagrangian Grassmannian $LG_{\mathbb F_2}(n,2n)$. We conclude by studying how the former action restricts onto stabilizer groups and stabilizer states, and finally what happens in the case of graph states.