Single-particle entanglement

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.