Possible Measurements on Quantum Fields

In 1993, Rafael Sorkin published a groundbreaking paper titled "Impossible Measurements on Quantum Fields". In this, he was able to show that under quite generic assumptions, a projective measurement in quantum field theory enables superluminal signaling.

Therefore, such a measurement is unphysical as it cannot be implemented by any physical apparatus. It has been an open question since, how a reasonable theory of measurement in quantum field theory can be constructed in the face of this fundamental obstacle. While there have been a variety of proposals, I will show that a very conservative approach, surprisingly, leads to success. This works for field operators and possibly beyond. This talk is an extended version of the one recently given at RQI-N 2024, in which I hope to present more results and provide considerably more detail.