Entanglement Sudden Death (ESD)

I love how news outlets ‘sex’ up the news.  In this article the author, when speaking of entanglement, claims that until now, “scientists have assumed such a marriage would endure forever.”  We have?  This seems to imply that all prior entanglement experiments have produced particles that are still entangled which is, of course, not true.  The reality is that a pesky little thing physicists call decoherence has made long time- or distance-scale entanglement difficult.  Decoherence can be caused by lots of things – noisy channels for example.  So, perhaps in an ideal world with no noise, no second law of thermodynamics, etc. we might expect entanglement to last forever.  Certainly there isn’t always a time dependence in the equations of entanglement (depending on what you’re doing).  But the real world is very different.  While I think the paper the article refers to is fascinating and ground-breaking, the MSNBC author has (not surprisingly) been a bit misleading about the whole thing.

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2 Responses to “Entanglement Sudden Death (ESD)”

  1. I just read about that, too. I never got the impression that entanglement decayed away. MSNBC isn’t the only place that reported this. Now I gotta read the paper to see how badly it was mangled.

  2. quantummoxie Says:

    I don’t know if it was that horribly reported. I guess I just think they oversimplified things a bit. Mathematically, there’s nothing that says entanglement should have a time limit to it (it’s just essentially a non-factorable state) so I suspect these guys found something in the math. But realistically they’ve never managed to keep an entangled state for terribly long periods of time (this is one of the limitations on quantum cryptography that they’re trying to remedy).

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