Speaker
Caslav Brukner
Description
Quantum theory denies jointly well-defined outcomes for incompatible measurements, but still assumes jointly well-defined Born probabilities. We argue that this second form of joint definiteness relies on the idealization of a classical reference frame. If relative frequencies are defined with respect to a finite quantum reference frame, their large-run limits can become incompatible observables, obeying uncertainty relations and violating Bell inequalities. This suggests that, where ideal reference frames are unavailable, the quantum state may need to encode a “probability of probabilities.” We close by discussing why such a possibility may be relevant for quantum gravity.
Author
Caslav Brukner