In a new study, physicists have shown a way to establish real entanglement between two identical particles—a topic that has been disputed until now. The results provide a better understanding of the fundamental nature of entanglement between identical particles and have potential applications in quantum information processing.
One of the many strange features of quantum entanglement is that, if two particles are identical, then they automatically appear to be entangled. In this case, "identical" means that the particles are of the same type—for example, any two photons are considered identical because there is no way to tell any particular photon apart from another.
This type of entanglement, which physicists call "entanglement due to indistinguishability," arises because of the standard way that identical particles are labeled. Although the particles are identical, physicists assign them different labels in order to tell them apart. Because of the way that entanglement is determined, with respect to their labels, identical particles inevitably appear to be entangled.
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