Hi all,
Like many have said before, it is a very interesting article.
On the matter, this is my suggestion, a little late but I hope it helps:
1) When you said that his performance has deteriorated, please double-check that it is really due to "lovestruck" and not any other factors. Sometimes the obvious may not necessarily be the source of the problem.
2) This distraction is like any other distractions, e.g., loss of a close family member, depression, financial difficulties, marital problems, children problems, maid problems, mother-in-law problems. So if we begin removing people with problems, very soon we will have to remove all the people in our organization. So what we do, in my opinion, is to tell him straight to his face that it's affecting his job, give him time off to deal with his distraction, and TELL HIM DEFINITELY that it is CRITICAL he comes back to work focused and pulls his own weight. This is no longer just a "lovestruck" issue; it is a DISTRACTION. And it should be handled just like any other distraction. Of course, I am assuming that this "lovestruck" low performance has been persistently happening and it's not just a 2-3 days dry period for him.
3) After the official response to him, take him out for Happy Hour, have a beer or two, and have a buddy talk with him. I'm serious, or the beer thing is just a figure of speech, but I'm sure you know what I mean. For the fact that you know the reason that it's "lovestruck" that is his problem, he must have mentioned it to you, right? So that would mean that at the least you are on good talking terms with him. So be that mentor and friend.
HR is about bringing out people's potential and encouraging them to put in their best and to help them discover talents that sometimes they themselves don't even know existed. This, to me, is what HR is all about. Hiring and firing, any Tom, Dick, and Harry can do it; organizations don't need HR to do it. For us in HR, it's about reaching out, touching people, and getting across to them.
My two cents. Hope it helps.
Smiles and Cheers