Joint measurements on distant physical systems

          @misc{ pirsa_PIRSA:24090091,
            doi = {10.48660/24090091},
            url = {https://pirsa.org/24090091},
            author = {Pozas Kerstjens, Alejandro},
            keywords = {Quantum Foundations, Quantum Information},
            language = {en},
            title = {Joint measurements on distant physical systems},
            publisher = {Perimeter Institute},
            year = {2024},
            month = {sep},
            note = {PIRSA:24090091 see, \url{https://pirsa.org}}
          }
          

Abstract

It is not explicitly obvious that relativity and quantum mechanics are consistent with each other. Extensive research has shown that quantum states are consistent with relativity, in that they do not allow for faster-than-light transferring of information. In contrast, much less research has been done in quantum measurements, and in fact, naive attempts to put together relativity and quantum measurements lead to signaling between space-like separated regions. In this talk I will describe how this same problem arises in non-relativistic quantum physics, where measurements on systems kept spatially separated in general lead to signalling. By giving away the projection postulate, it is possible to alleviate this problem and measure non-local variables without signaling by exploiting pre-shared entanglement as a resource. I will describe a protocol for implementing any joint measurement in a non-signaling manner, and argue that this leads to a complete classification of all joint quantum measurements, based on the required amount of entanglement necessary to measure them.