Guilherme Franzmann

This talk examines how spacetime might emerge from quantum mechanics, drawing on entanglement and quantum error correction. It considers the assumptions about subsystem independence that enter these approaches and what they imply for the emergence of spacetime. The recording includes the discussion that followed.

Last May, ScientiFika became an art space for an evening. Eight researchers and students shared work ranging from Cosmic Cross Stitch and gravitational lensing turned into sound to a scientific paper turned into a black box and mirror. This reflection considers creativity, persistence, vulnerability, and the different demands of science and art.

Some proposed tabletop experiments aim to test whether gravity is quantum by placing two small masses in superpositions of different locations and looking for entanglement between them. This paper examines a usually implicit premise: that the masses and their measurements can be treated as independent subsystems. In perturbative quantum gravity, gauge constraints and each mass’s gravitational field make that separation less exact. The paper explains why this matters for how such experiments are modelled and interpreted, while estimating the effect to be negligible at current experimental sensitivities.

Quantum theory normally lets us divide a larger system into parts and ask what belongs to each part. This invited talk considered why that familiar move becomes difficult in quantum gravity: gravity links matter, location, and the surrounding field, so a subsystem may not have a perfectly sharp, self-contained boundary. The central issue is how to describe quantum-gravitational subsystems without assuming from the outset the independent pieces that the theory is meant to explain.

There are several distinct meanings of “independent” in quantum physics: systems may have separately measurable observables, allow separately chosen states, or combine through a simple product structure. This talk compared those meanings in quantum mechanics and quantum field theory using a common mathematical language for states and observables. It then considered how quantum gravity challenges them and what kinds of revised or approximate subsystem descriptions might be needed.