https://doi.org/10.1140/epjp/s13360-025-06320-1
Regular Article
Entanglement Islands from Hilbert space reduction
1
Indian Institute of Technology, 208016, Kanpur, India
2
Shing-Tung Yau Center and School of Physics, Southeast University, 210096, Nanjing, China
3
School of Physics and Technology, Wuhan University, 430072, Wuhan, Hubei, China
Received:
7
May
2024
Accepted:
13
April
2025
Published online:
9
May
2025
In this paper, we propose a mechanism to generate entanglement islands in quantum systems from a purely quantum information perspective. More explicitly we show that, if we impose certain constraints on a quantum system by projecting out certain states in the Hilbert space, it is possible that for all the states remaining in the reduced Hilbert space, there exist subsets 
whose states are encoded in the states of another subset 
. Then, the subsets 
are just the entanglement islands of the corresponding subsets 
. We call such a system self-encoded and find that the entanglement entropy in such systems should be calculated by a new island formula. We give a comparison between our new island formula and island formula in gravitational theories. Inspired by our mechanism, we propose a simulation of the AdS/BCFT correspondence and the island phases in this context via a holographic 
with a special Weyl transformation.
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Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
