Hoist with Zeno's Petard

[Metaphor Warning: this posting exists in a superposition of metaphorically analogous similes, or analogous metaphorical similes, or... and?]

So - Zeno's Petard? Well, he could have described a shock wave instead of an arrow... if he'd known about explosives... allow me to allow myself a little creative licence.

Anyway, a new problem has arisen, and the problem is that instead of preventing you from being hoist into the air (because the shock wave can never arrive) the Quantum Zeno Effect turns out to have a sting in its tail (though the venom may turn out to be its own antidote - as we shall see later).

Lawrence Krauss has just put up a rather large "Oops?" sign in his latest paper - where he raises the concern that whereas the universe was ticking along nicely, even if it was potentially in a metastable false vacuum, we may have just buggered it up by noticing the fact. All bets are off - our nice little temporarily stable universe may now be a teensy-weensy bit wobblier.

It's like this... The Quantum Zeno Effect tells us that for small t, the probability of decay is proportional to t squared and if we can't quite bring decay (radioactive, quality of TV programming, moral, etc.) to a complete halt, we can at least slow it down by Obsessive Observation (TM) [Tools: Geiger counter, The Ghost of Mary Whitehouse, and, er, The Ghost of Mary Whitehouse]

Normally decay processes are exponential. Example: a while back a Northern Rock share was worth £12, then it became £6, then £3 - anything that halves at regular intervals is undergoing exponential decay. (I can't bear to provide a link.)

But - and here's the fly in the quantum cosmic ointment - for large t, the decay becomes slow again (a Power Law) - meaning apparently that if the decay hasn't happened by then it's really not likely to decay at all.

But, I hear you cry, that's a good thing! It is indeed - if we are living in a wobbly universe. Or it was, until some idiot went and observed the universe before it has reached the transition point (actually I'm not sure that the timing was that important) from Exponential to Power Law because at that point his observation reset everything (trust a bloke to start fiddling with (qu)bits of fundamental existence) - and we are back on the slippery slope of Exponential decay again.

Oh dear, as I seem to find myself exclaiming more and more these days (as in, "Oh dear. Where are my slippers," or "Oh dear, I've snagged my nice new cardigan,", or even "Oh Dear!The Windows Vista Update - KB938797 if you want to know - that Microsoft recommended for my PC is not, in fact, valid for my PC", etcetera, etcetera, etcetera.)

It may not all end in tears, but (oops - didn't plan this one, honestly) it could all end in tears, rips, splits and general cosmic hyperactivity disorder as the false vacuum (have I explained that one yet? No? Ah.) collapses to a new all time low of vacuity (c.f. UK government data protection assurances (random but relevant link), Northern Rock share valuation, usw.) and Life the Universe and Everything goes "Poof!".

Now I'm in a bit of a quandary as to what to recommend. Live long and prosper but get overrun in the end, or accept that everyone dies young (good or bad - remember to tell the kids "Only the good die young" at the same time you tell them Santa keeps a list of Naughty and Nice) cosmologically speaking.

However, getting back in the saddle of my tame French ovine, if we have indeed put an observational spanner in the cosmic works, we have the answer in hand: the Quantum Zeno Effect, the cause of the problem in the first place.

Whoever made that ill-advised observation of some remote supernova and noticed that the universe is accelerating "outwards" - thereby effecting the observation of a false vacuum - should be glued to his telescope and forced to keep watching... and his children... and his children's children... and his children's children's children (etcetera, etcetera, etcetera ad infinitum - if we want there to be one) to make sure that it doesn't decay. Seems fair to me.

However, two other considerations to take into account.

a) Death of Universe = No Invasion of the Boltzmann Brains (not a bad thing, IYAM)

and (more fundamentally)

b) How in the name of Dick Emery can one part of a quantum system "observe" another part of a quantum system in such a way as to affect the decay probability of the system as a whole?

Answer that if you can! Personally - Oh dear, I really should stop thinking about such things - I'm now more concerned about The Boltzmann Brains From Another Universe observing ours (universe that is) - that really could upset the cosmo-quantum apple-cart and dump several unattractively large flies in our collective soup (ah... you are wondering now, "Did he say ointment or soup earlier?"). The BBFAU may already have observed us - or done so long ago - and it's all over bar the shouting.

Or just perhaps, the plethora of BB's in the multiverse ensures that we are always observed, and thus safe for the foreseeable future.

What was that old Chinese curse? May you live in interesting times.

Here's hoping we live through these interesting times... personally I'm planning to stick around.

Watch me.

[PS A False Vacuum - one which talks about you behind your back]
[PPS If the Quantum Zeno Effect is both doom and salvation doesn't it just cancel itself out, or does it mean it's all kindofuncertain in a satisfyingly-quantum-sort-of-way? Over to you Nicey]

White Rabbit

It's all coming together now.

Remember the sage advice (if no else is going to blow my trumpet, I'll do it myself) on how to ensure that things are not in the last place you look?

Good. Now, have you read about the Quantum Zeno Effect? No? Consider it part of the required reading list.

What about the Stuff on Boltzmann Brains (I and II)? Really! Do you think I am doing all this for my benefit? Come back when you have...

OK... I can now reveal that I have

a) An explanation for things (previously) being in the last place you looked
b) A viable defence against the Invasion of the Boltzmann Brains (and one that doesn't involve destroying the whole universe, which is handy)
c) An explanation for the complete failure of my previous quantum teleportation experiment.

Choosing, at random, to begin with (c) ... once upon a time, I was sitting in the bath pondering the inconvenience of the "teleportation booths" in the film The Fly, i.e. how annoying it was that one had to pre-position a receiving booth in order to be able to travel somewhere. What if one wants to go to e.g. Alpha Centauri? With current technology it would take thousands of years to get the receiver in place, and I for one don't want to wait ("current technology" obviously now including quantum teleportation but excluding other Faster Than Light travel...)

Anyway, there I was, in the bath and I thought I'd try an experiment to see if there was a way around this problem - you can try it too, maybe you'll have better luck?

Sit in bath (water temperature irrelevant, but science doesn't have to be a pain in the arse, make yourself comfy)

Place a bar of soap/bottle of shampoo/rubber duck (I rather like the idea that the first macroscopic object to be teleported should be a rubber duck)/other convenient object in your outstretched left hand

Now, hold out out your right hand and observe very, very carefully... can you see the soap/shampoo/duck? No? Keep trying...

The idea was that since everything has a finite, but tiny probability of being everywhere else, if you looked often enough in a particular place you could raise that probability to as close to unity as you wanted.

No, I never succeeded either - I thought the problem was that I didn't know how to quantum mechanically observe a macroscopic object, but now I am beginning to suspect that the Quantum Zeno Paradox is a better explanation. Because I was looking in my right hand continuously, that was the one place the soap was never going to appear.

Which also possibly explains why things are always in the last place you look(ed)

But! Aha! Here comes the clever bit. So, we can't observe and teleport in this way. However, we can proceed by elimination. Wherever an object is, it is also actually spread out, so all we need to to is to exclude the destination from our observations i.e. observe absolutely everything else and so prevent the object from going there.

Believe it or not, this would actually work - but probably only for tiny things like photons at the moment - and we can teleport those anyway.

[Side note - however... I can see how one could apply the principles to create dynamic "photonic crystals", i.e with switched apertures... hope I got the right license type.. that could be worth something!]

On the other hand, it could turn out Quantum Mechanically to be the equivalent of not thinking about a White Rabbit.

No - not the one in The Matrix.

Or Harvey.

Or the Jefferson Airplane song.

Or The White Rabbit in Alice in Wonderland

Any White Rabbit at all. (this link gives a helpful list of some major associations of White Rabbit to avoid)

Let me know when you haven't thought about one for a couple of minutes...

Oh - I nearly forgot. Boltzmann Brains: they appear from fluctuations in the vacuum - if you keep watching you can suppress them. So, if we all dedicate ourselves to observing the (increasingly) empty universe from now until eternity we can stave off the invasion... what would Camus have made of that?

Aaah! I think I've done my bit for the blogosphere today.

Doh! The Quantum Zeno Effect

"Doh!" as in, beaten to it again!

A long time ago (though I doubt as far back as 1977) I humorously proposed what is apparently called the Quantum Zeno Effect - a way of inhibiting state changes by obsessive observation.

I say humorously because I was proposing it as a way of handling nuclear waste - and one that is not as far as I can see at all practical (Worried about radioactive decay? Just keep an eye on it - and it won't! How one could appropriately "observe" a large mass of diverse composition I wasn't - and still amn't - sure).

And, as this is the way of things, I find out today (thanks of course to the New Scientist article here - subscription required to read the whole article online) that George Sudarshan and Baidyanaith Misra of the University of Texas apparently described this phenomenon way back when I was 16. It's since been established experimentally too.

The reason it works is that for small t, the probability of a transition is proportional to t squared...

I found a nice demonstration of the idea here (a pdf of a presentation by Wayne Itano of NIST) but, for those of you impatient for the Technical Stuff the maths bit looks like this...

So, there you have it: a watched superposition never decays.

(Of course in practice you can't make the absolutely necessary infinite number of observations to completely stop decay, but you ought to be able to slow things right down)