Unitarization of Pseudo-Unitary Quantum Circuits in the S-matrix Framework

TL;DR

This paper introduces a new diagrammatic method for transforming S-matrices into T-matrices within pseudo-unitary quantum circuits, enabling advanced analysis and potential applications in scattering theory and No-Go theorems.

Contribution

It proposes a novel partial inversion operation with diagrammatic representation, deformed metrics, and a renormalized-growth algorithm for pseudo-unitary circuit analysis.

Findings

Defined a partial inversion operation with diagrammatic representation

Developed deformed metrics and dot products preserving physical constraints

Introduced a renormalized-growth algorithm for T-matrix construction

Abstract

Pseudo-unitary circuits are recurring in both S-matrix theory and analysis of No-Go theorems. We propose a matrix and diagrammatic representation for the operation that maps S-matrices to T-matrices and, consequently, a unitary group to a pseudo-unitary one. We call this operation ``partial inversion'' and show its diagrammatic representation in terms of permutations. We find the expressions for the deformed metrics and deformed dot products that preserve physical constraints after partial inversion. Subsequently, we define a special set that allows for the simplification of expressions containing infinities in matrix inversion. Finally, we propose a renormalized-growth algorithm for the T-matrix as a possible application. The outcomes of our study expand the methodological toolbox needed to build a family of pseudo-unitary and inter-pseudo-unitary circuits with full diagrammatic representation in three dimensions, so that they can be used to exploit pseudo-unitary flexibilization of unitary No-Go Theorems and renormalized circuits of large scattering lattices.