Ground-state entanglement of the BCS model

Area of Science:

• Quantum information theory
• Condensed matter physics

Background:

• Entanglement quantifies correlations in quantum systems.
• Local concurrence measures entanglement between a subsystem and the rest of a quantum system.

Purpose of the Study:

• Investigate local concurrence as an entanglement measure for the BCS model.
• Explore the relationship between average local concurrence (ALC) and system properties.

Main Methods:

• Utilizing the concept of local concurrence.
• Analyzing the ground state of the BCS model in the thermodynamic limit.
• Examining finite systems with fixed particle numbers.

Main Results:

• Local concurrences fully characterize entanglement for the BCS ground state in the thermodynamic limit.
• ALC shows a direct relationship with the order parameter.
• A threshold coupling is identified in finite systems via ALC and condensation energy.

Conclusions:

• ALC is a significant measure for entanglement in the BCS model.
• Entanglement structure is complex in finite systems, with ALC not being the sole significant measure below a threshold coupling.