“Spacetime and Relationalism in Black Box Quantum Information”
by
Stefan Lukas Ludescher
Abstract
In my thesis, I explored the interplay between space-time physics and quantum theory across several directions. First, I investigated Quantum Reference Frames, where colleagues and I quantified the quality of reference-frames. In the special case of clock frames, this provides a quantitative formulation of the Page–Wootters slogan “time replaced by quantum correlations.”
Next, collaborators and I studied rotation boxes: black-box devices that take spatial rotations as inputs and respect rotational symmetry. We characterized a rotation-box random-number generator with two inputs whose randomness certification relies solely on symmetry assumptions, specifically, on bounding a generalized spin, not on the validity of quantum theory. We then analyzed rotation boxes with continuous inputs and found that, for spins {0, 1/2, 1}, the correlation sets of general and quantum rotation boxes coincide, while for spins ≥3/2 a gap appears, which closes again in the infinite-spin limit.
Finally, I examined gravity-mediated entanglement experiments, showing with colleagues, using the language of C*-algebras, that even an infinite-dimensional local classical mediator cannot generate entanglement.
Defense committee:
John H. Selby, Uniwersytet Gdansk, PL (reviewer)
Paolo Perinotti, Università di Pavia, IT (reviewer)
Markus Müller (supervisor)
Caslav Brukner (supervisor)
Thomas Pichler (chair)