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I give a simple argument that demonstrates that the state 0⟩1⟩+1⟩0⟩, with 0⟩ denoting a state with 0 particles (or photons) and 1⟩ a one-particle state, is entangled in spite of recent claims to the contrary. I also discuss viewpoints on the old controversy about whether the above state can be said to display single-particle or single-photon nonlocality.
S. J. van Enk (Thu,) studied this question.