Thanks to the classical work of Bekenstein and Hawking we have learnt that gravity is holographic. This means that the quantum degrees of freedom of gravity are connected to surfaces, and not to volumes enclosed by such surfaces. Based on this idea the term Holographic Principle has been coined. The first mathematically precise implementation of this principle was inside string theory. This is the famous AdS/CFT correspondence. Later the idea of holography separated from string theory. This was due to the striking results of quantum information theory which is  is based on the phenomenon of entanglement regarded as a new resource. Soon entanglement based articulation of  ideas provided new insight on considerations of the nature of gravity. The first step was the combination of the idea of holography with the idea of entanglement. In this context it was realized that even classical spacetime geometry is an emergent concept, inherently of quantum origin.

 

In this talk in the simplest holographic scenario we put strings back into the mix [1]. We show that the world sheets of classical strings regarded as objects testing classical spacetime geometry encode quantum information geometric data. Data which is not necessarily directly related to entanglement.

 

[1]: Bercel Boldis and Péter Lévay: "Segmented strings and holography", Phys. Rev. D 109, 046002 – Published 5 February 2024