Integrated Information Theory (IIT) posits that consciousness is a fundamental property of physical systems, determined by their capacity to integrate information. Consciousness is measured by phi which is the degree to which a system’s cause-effect power is irreducible to its individual parts. The theory asserts that consciousness exists wherever a system forms a unified, highly differentiated whole, and the specific quality of an experience is identical to the complex, multidimensional mathematical geometry of that integrated network.

Other Resources:
http://www.scholarpedia.org/article/Integrated_information_theory
https://en.wikipedia.org/wiki/Integrated_information_theory

Does Integrated Information Theory (IIT) feel too woo-woo to anyone?
byu/Prestigious_Hope2082 inconsciousness