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A truncated photon
Isak Cecil Onsager Rukan, Jan Gulla, Johannes Skaar·October 24, 2025
Quantum Physics
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Abstract
An elementary particle such as a photon cannot be cut in two pieces. Still it must be possible to truncate a photon with an optical shutter. The result is not another photon or a mix of a photon and a vacuum. Instead it is a superposition and mix of photon numbers up to infinity. This state is rather complicated, but nevertheless locally equivalent to a single photon or vacuum in disjoint regions. Finally we demonstrate how the truncated photon may be illuminating and useful for the understanding of locality and equivalence in quantum field theory.