Quantum phase transitions manifest themselves in various forms, each with their own features. In particular, criticality is known to be a resource for quantum enhanced sensitivity. In this talk, we investigate various forms of criticality in both closed and open quantum systems to find out what features in these phase transitions are responsible for achieving quantum enhanced sensitivity. In particular, we explore Stark localization [1], symmetry protected topological systems [2], Floquet systems for both DC [3] and AC [4] and boundary time crystals [5]. While phase transition in these systems may have different origins, there is one common feature among all of them: gap closing. This suggests that gap closing is the main feature in phase transitions which is responsible for quantum enhanced sensitivity. 

References: 
[1] X. He, R. Yousefjani, A. Bayat, Phys. Rev. Lett. 131, 010801(2023)
[2] S. Sarkar, C. Mukhopadhyay, A. Alase, A. Bayat, Phys. Rev. Lett. 129, 090503 (2022)
[3] U. Mishra, A. Bayat, Phys. Rev. Lett. 127, 080504 (2021)
[4] U. Mishra, A. Bayat, Scientific Reports 12, 14760 (2022)
[5] V. Montenegro, M. G. Genoni, A. Bayat, M. G. A. Paris, Commun. Phys. 6, 304 (2023)

Abolfazl Bayat is a professor of Physics at the Institute of Fundamental and Frontier Sciences at University of Electronic Science and Technology of China in Chengdu. After completing his PhD in 2008 from Sharif University of Technology in Iran, he did his postdocs at University College London (2008-2011 and 2013-2017) and University of Ulm in Germany (2011-2013). His research interest includes: quantum simulation, quantum sensing and many-body physics.