An important theoretical aspect of black hole physics is in the context of holography, which is also known as the gauge/gravity correspondence or more traditionally, the AdS/CFT correspondence. According to holography, the physics of a gravitating system in anti-de Sitter  (AdS) spacetime (which is a solution in general relativity with a negative cosmological constant) is completely equivalent to a quantum field  theory without gravity defined on the boundary of the AdS spacetime. This allows us to investigate the properties of gravity using ordinary quantum field theory, and likewise to model some quantum systems (for example, superconductor or strange metal) using specific theories of gravity. For example, the Hawking temperature of the AdS black hole corresponds to the temperature of the field theory under this correspondence. Phase transitions of quantum systems can be studied this way by looking for instability of black holes in the bulk. Though initially developed in the context of string theory, holography has developed into its own field largely independent of string theory.

Recently, partly motivated by black hole information paradox, the ideas from quantum information has been brought into gravitational physics. At CGC, efforts have been made to investigate the quantum information aspects of holography, such as entanglement entropy, complexity, entanglement of purification (EoP) and complexity of purification (CoP). We also pursue some aspects of quantum information in quantum field theory, independent of holography.

A) Probing Phase Transitions via Holographic Information Aspect

The application of gauge/gravity into strongly coupling system has been widely studied in last decade. Especially various phase transitions, including metal/superconductor, insulator/superconductor, metal/insulator, have been well mimicked from the bulk theory. The probe of those transitions is a significant direction. Our center has been madding some efforts on probing various holographic phase transition via information quantities from the bulk side.

B)  Evolution of Holographic Information Aspect in Non-equilibrium Process

Non-equilibrium dynamics and thermalization of a system in quantum field theory can be used to describe processes in various areas of physics. Thermalization is always implemented by a so-called “quench” process which is holographically described by the black hole formation resulted from the gravitational collapse in the bulk. The evolution of holographic information in the thermalization process and their connections with black hole information is another interest of our center.