According to Thomas Astruc, "[The Quantic Universe] is the extended universe in which live Ladybug and Cat Noir. Ladybug is to Quantic Universe what Spider-Man is to the Marvel-verse, or Batman to the DC-verse. Quantic Universe is filled of super-heroes in all countries, alien races, magic... Ladybug is just a tiny part of it. Hopefully, if the series is successful, we'll be able to explore it."
At San Diego Comic-Con International 2016, it was revealed that the universe is being expanded as a comic book universe, which will feature other Miraculous holders and other types of heroes in the world.
Previously, according to Astruc, it was also possible that Félix, the first version of Cat Noir before Adrien, still existed in some way there. However, Astruc later stated that Félix will never appear.
Majestia Issue #56, a comic appearing in "Ladybug & Cat Noir (Origins - Part 1)", is published by the company Quantic Comics, which is a reference to the Quantic Universe.
Real people from history, such as Jeanne d'Arc and Tomoe Gozen, and mythological figures, such as Herakles and Cernunnos, exist in this universe as Miraculous holders. Whether their histories and legends are the same or they have been modified has yet to be seen.
If he isn't able to explore the Miraculous universe, Thomas has another universe he's creating.