## About this Research Topic

The world is at the dawn of the era of quantum technologies. Quantum cryptography systems already are in use to secure the exchange of information, and the first quantum computers are becoming accessible. And ambitious plans to interconnect the world via a network of secure quantum channels - the so-called ...

The world is at the dawn of the era of quantum technologies. Quantum cryptography systems already are in use to secure the exchange of information, and the first quantum computers are becoming accessible. And ambitious plans to interconnect the world via a network of secure quantum channels - the so-called quantum internet - are taking shape.

This technological progress is accompanied by unprecedented new insight into the foundations of quantum mechanics. Perhaps the most spectacular example of the new theoretical advances is the emerging relation between spacetime and quantum entanglement, which sheds completely new light on the over-one-hundred-year-long problem of formulating a quantum theory of gravitational interactions, of understanding the fundamentally quantum nature of spacetime itself and, possibly, of explaining its emergence from non-spatiotemporal quantum entities. Moreover, exploration of black holes has allowed us to examine the properties of quantum mechanics to their limits, for example, considering the no-cloning theorem in the context of a black hole horizon. In a similar vein, frameworks have been developed for quantum theory on indefinite causal structures as well as to reveal the general set of causal relations both classically and quantumly. The progress in basic research is not only correlated with technological advances but can also be its direct consequence, an example of which are the first quantum simulations of gravitational systems performed in the last two years.

The crucial conclusion emerging out of the above and numerous additional results, is the significance of quantum information in understanding gravitational phenomena and possibly in the very foundations of quantum spacetime. The objective of this Research Topic is to stimulate further, broad exploration and discussion in this domain at the level of both theoretical investigation and utility of quantum technologies in understanding gravitational physics.

We welcome the submission of articles on the following topics:

- Quantum information aspects of black holes

- Entanglement in quantum gravity states

- Non-contextuality in quantum gravity

- Quantum simulations of Planck scale physics

- Emergence of spacetime and gravity from quantum many-body systems

- Entanglement/Gravity duality

- Tensor networks for quantum gravitational systems

- Holographic description of gravity

- Experiments at the interplay between quantum physics and gravity

- Quantum error correction models of spacetime

- Quantum metrology for gravitational experiments

- Effects of gravity on quantum key distribution protocols

- Quantum causality

- Geometric methods for quantum complexity

- Quantum formalism and the structure of space-time

- Quantum information on indefinite causal structures

The cover image is an original artist's impression of the subject of the Research Topic by Kaća Bradonjić.

**Keywords**:
Quantum gravity, Spacetime, Quantum information, Quantum technologies

**Important Note**:
All contributions to this Research Topic must be within the scope of the section and journal to which they are submitted, as defined in their mission statements. Frontiers reserves the right to guide an out-of-scope manuscript to a more suitable section or journal at any stage of peer review.