Embezzlement as a "Self-Test" for Infinite Copies of Entangled States

We investigate the operator-algebraic structure underlying entanglement embezzlement, a phenomenon where a fixed entangled state (the catalyst) can be used to generate arbitrary target entangled states without being consumed. We show that the ability to embezzle a target state g imposes strong internal constraints on the catalyst state f: specifically, f must contain infinitely many mutually commuting, locally structured copies of g. This property is formalized using C*-algebraic tools and is analogous to a form of self-testing, certifying the presence of infinite copies of g within f. Using this infinite-copy certification. Our results clarify the structural requirements for embezzlement and provide new conceptual tools for analyzing state certification in infinite-dimensional quantum systems.