# Seminar "Study of highly entangled quantum spin chains" by Fumihiko Sugino

### Date

Thursday, February 6, 2020 - 14:00 to 15:00

C016-Lab1

### Description

• Date: Thursday, February 6th
• Time: 14:00-15:00
• Venue: C016-Lab1
• Speaker: Fumihiko Sugino, Institute for Basic Science, South Korea

Title: Study of highly entangled quantum spin chains

Abstract:
Quantum entanglement is one of the most surprising features of quantum mechanics.
Ground states of quantum many-body systems with local interactions typically obey
an area law'' meaning the entanglement entropy proportional to the boundary length.
It is exceptional when the system is gapless, and the area law had been believed
to be violated by at most a logarithm for over two decades.

Recent discovery of Motzkin and Fredkin spin chain models is striking, since these
models provide significant violation of the entanglement beyond the belief,
growing as a square root of the volume in spite of local interactions.
Although importance of intensive study of the models is undoubted to reveal novel
features of quantum entanglement, it is still far from their complete understanding.

In this talk, I will explain how such violation of the area law arises mainly in the Motzkin model.
In computation of the Renyi entropy, we observe a novel phase transition never seen in any other
spin chain model studied so far.

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