Talk on Spin measurements in relativistic quantum reference frames

Friday 19 October at 15.00 in Sala Cortini
Talk on Spin measurements in relativistic quantum reference frames by Flaminia Giacomini, IQOQI, Vienna

Flaminia Giacomini is a PhD student of the Chaslav Brukner’s team at the INSTITUTE FOR QUANTUM OPTICS AND QUANTUM INFORMATION VIENNA

Although the spin is regarded as a fundamentally quantum property, there is still no generally accepted relativistic spin operator for massive particles. The origin of the difficulties in finding a proper relativistic spin operator lies in the fact that, on the one hand, the spin gets entangled with the momentum in boosted reference frames, and on the other hand, spin is operationally defined through a Stern-Gerlach measurement only in the rest frame. Here, we answer the question of how we can recover the information about the spin in its rest frame by performing an experiment in the laboratory frame. To this end, we find a quantum reference frame transformation (“quantum Lorentz boost”) which allows us to ‘jump’ into the rest frame of a particle that is in a superposition of relativistic momenta with respect to the laboratory frame. We then transform the set of possible measurements in the rest frame back to an isomorphic set in the laboratory frame, where one can define a ”relativistic Stern-Gerlach” measurement, and find a set of observables satisfying the spin su(2) algebra.