Abstract
The idea of holography in string theory provides a simple geometric computation of entanglement entropy. This generalizes the well-known Bekenstein-Hawking formula of black hole entropy and strongly suggests that a gravitational spacetime consists of many bits of quantum entanglement. After a brief discussion of an interpretation of AdS/CFT with an emphasis on the computational complexity and quantum entanglement, I will explain progresses on a recently introduced quantity called pseudo entropy, which generalizes the entanglement entropy and has a manifest gravity dual. This opens up a further understanding of emergence of spacetime in gravity.