Single-particle entanglement

I give a simple argument that demonstrates that the state parallel to 0 >parallel to 1 >+parallel to 1 >parallel to 0 >, with parallel to 0 > denoting a state with 0 particles (or photons) and parallel to 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.