Ground-State Entanglement of the BCS Model

2004/11/04 by Clare Dunning, Jon Links, Huan-Qiang Zhou · 1 voice
Computer Science · Physics and Astronomy · #Quantum Computing Algorithms and Architecture #Quantum Information and Cryptography #Quantum many-body systems #cond-mat.str-el #hep-th #quant-ph

paper · pdf · doi:10.1103/physrevlett.94.227002

published as Phys.Rev.Lett. 94 (2005) 227002 · 5 pages, 3 figures. V2: added new results & discussion on crossover regime

arxiv published 2004/11/04 · arxiv created 2005/03/17 · arxiv updated 2005/03/17 · openalex publication_date 2005/06/07 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

The concept of local concurrence is used to quantify the entanglement between a single qubit and the remainder of a multiqubit system. For the ground state of the BCS model in the thermodynamic limit the set of local concurrences completely describes the entanglement. As a measure for the entanglement of the full system we investigate the average local concurrence (ALC). We find that the ALC satisfies a simple relation with the order parameter. We then show that for finite systems with a fixed particle number, a relation between the ALC and the condensation energy exposes a threshold coupling. Below the threshold, entanglement measures besides the ALC are significant.

Citations

• Theory of Superconductivity
• Energy as an entanglement witness for quantum many-body systems
• Entanglement of a Pair of Quantum Bits
• Thermodynamics and the measure of entanglement
• Distributed Entanglement

Discussions

• The relevant state is probably the BCS ground state? Though it is an ansatz arxiv.org/abs/quant-ph... so it’s macroscopic in that it’s a large number of things that are like copper pairs. [bsky, 2 points, 1 comments]