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Updated: Jul 4, 2026

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference

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Published on: September 5, 2019

Single-copy entanglement in a gapped quantum spin chain.

Christopher Hadley¹

¹Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom.

Physical Review Letters

|June 4, 2008

Summary

Single-copy entanglement in gapped quantum systems, like the spin-S Affleck-Kennedy-Lieb-Tasaki chain, equals the von Neumann entropy. This means all system entanglement can be distilled from just one specimen.

Area of Science:

Quantum Information Theory
Condensed Matter Physics

Background:

Single-copy entanglement quantifies distillable entanglement from one quantum system copy.
For critical spin chains, single-copy entanglement is half the von Neumann entropy.
The behavior of single-copy entanglement in gapped systems remains an open question.

Purpose of the Study:

To investigate single-copy entanglement in gapped quantum systems.
To determine if all entanglement can be distilled from a single specimen in gapped systems.

Main Methods:

Analysis of the spin-S Affleck-Kennedy-Lieb-Tasaki chain, a paradigmatic gapped system.
Comparison of single-copy entanglement with von Neumann entropy.

Main Results:

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A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference

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Published on: September 5, 2019

Nanofabrication of Gate-defined GaAs/AlGaAs Lateral Quantum Dots

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Single-copy entanglement for the spin-S Affleck-Kennedy-Lieb-Tasaki chain is equal to its von Neumann entropy.

This implies that all entanglement in this gapped system is distillable from a single copy.

Conclusions:

The relationship between single-copy entanglement and von Neumann entropy differs between critical and gapped systems.
All entanglement in the studied gapped spin chain can be extracted from a single system instance.