That is, given that destroying the correlation between two entangled particles can't be used to send information between the particles' locations, how could a measurement of whether a system contains entangled particles work? Does it just require all entangled particles to be present for the extra heat transfer to work?
i am still in the process of reading this article (https://arxiv.org/pdf/2408.06418) however entanglement witnesses can be realized in several ways and are one of the underlying aspects of how quantum networking can be made reliable.
under the category of heralded entanglement, one realization uses photons striking photo detectors after they meet in a beamsplitter under the hong-ou-mandel effect scenario. for type 1 entanglement with HOM: if the photons at the two input modes are identical, they always bunch due to quantum interference, and if the photons resulted from emissions in the respective quantum nodes those nodes are now entangled, and the detection is the classical signal that the entangled link was created. the nodes can now transmit information unidirectionally into the entangled qubits. for type 2 entanglement with HOM it's a little bit more complicated although the underlying concept of indistinguishability is what results in the entanglement just the same.
heres one experiment from oxford, https://www.nature.com/articles/s41586-024-08404-x, where they achieved this with high fidelity although the particular details of the beam splitter experiment are not as well detailed.
Mr_Eri_Atlov•4mo ago