Quantum Operations on Conformal Nets

TL;DR

This paper introduces quantum operations on conformal nets, characterizes their fixed points, and establishes a Galois correspondence between intermediate nets and subhypergroups, extending prior results in conformal field theory.

Contribution

It defines quantum operations on conformal nets, analyzes their fixed points, and links intermediate subnets to subhypergroups, broadening the understanding of symmetries in conformal field theory.

Findings

Fixed point subnet under quantum operations is the Virasoro net.

Quantum operations fixing a subnet form a hypergroup.

Intermediate conformal nets correspond to subhypergroups.

Abstract

On a conformal net $\mathcal{A}$, one can consider collections of unital completely positive maps on each local algebra $\mathcal{A}(I)$, subject to natural compatibility, vacuum preserving and conformal covariance conditions. We call \emph{quantum operations} on $\mathcal{A}$ the subset of extreme such maps. The usual automorphisms of $\mathcal{A}$ (the vacuum preserving invertible unital *-algebra morphisms) are examples of quantum operations, and we show that the fixed point subnet of $\mathcal{A}$ under all quantum operations is the Virasoro net generated by the stress-energy tensor of $\mathcal{A}$. Furthermore, we show that every irreducible conformal subnet $\mathcal{B}\subset\mathcal{A}$ is the fixed points under a subset of quantum operations. When $\mathcal{B}\subset\mathcal{A}$ is discrete (or with finite Jones index), we show that the set of quantum operations on $\mathcal{A}$ that leave $\mathcal{B}$ elementwise fixed has naturally the structure of a compact (or finite) hypergroup, thus extending some results of [Bis17]. Under the same assumptions, we provide a Galois correspondence between intermediate conformal nets and closed subhypergroups. In particular, we show that intermediate conformal nets are in one-to-one correspondence with intermediate subfactors, extending a result of Longo in the finite index/completely rational conformal net setting [Lon03].