I am interested in learning some details of quantum computers inner working, what are the limitation etc. in order to understand quantum computation more. Can some one refer me to some good materials in this regard? I have a PhD in theoretical physics, so technical documents won't be an issue.
Here are some useful materials with respect to superconducting qubits that I found to be helpful:
A Quantum Engineer’s Guide to Superconducting Qubits, P. Krantz, M. Kjaergaard, F. Yan, T.P. Orlando, S. Gustavsson, and W. D. Oliver
Tutorial: Gate-based superconducting quantum computing, Sangil Kwon, Akiyoshi Tomonaga, Gopika Lakshmi Bhai, Simon J. Devitt, Jaw-Shen Tsai
Superconducting Quantum Computing: A Review, He-Liang Huang,Dachao Wu, Daojin Fan, Xiaobo Zhu
Superconducting Qubits: A Short Review, M. H. Devoret, A. Wallraff, and J. M. Martinis
Superconducting Qubits and the Physics ofJosephson Junctions , John M. Martinis and Kevin Osborne
Superconducting Qubits: Current State of Play. Morten Kjaergaard, Mollie E. Schwartz, Jochen Braumüller, Philip Krantz, Joel I-Jan Wang, Simon Gustavsson, William D. Oliver
Fast, Accurate State Measurement in Superconducting Qubits PhD thesis of Daniel Sank
It largely depends on the technology you're interested in. If you want to learn about photonic quantum computing you can check out this video which summarizes very well how it works. If you want to learn more then I would suggest going to the Strawberry Fields website, specially this page. Also going through the demos and tutorials is a great way to get a better understanding of how this works.
I hope this helps!