Whimsley

Quantum Breathing

Chris next door works at the Perimeter Institute; he is a physicist in the field of quantum information and I've been trying to read some of his papers. Interesting, if a bit beyond an ex-chemist. But reading quantum things again reminded me of The Best Quantum Thing I Ever Learned, which - outside chemists - seems little known. So I'll tell the story here as briefly as I can - Wikipedia now has a good set of entries on this if you want to know more, including fancy moving pictures: start at haemoglobin. All the images here are borrowed from Wikipedia.

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Breathe in.

What's going on? You draw oxygen into your lungs; from there it passes to the bloodstream; from there to muscles and nerves. To make that journey oxygen molecules (O₂) stick to molecules of haemoglobin in red blood cells, which carry them until they get to a place where they are needed, at which point the oxygen molecules hop off the haemoglobin to do their work.

More precisely, an oxygen molecule sticks to an iron atom at the centre of one of four "haem" or "heme" groups that are part of each haemoglobin molecule. Here is a picture of a haem group with its iron atom (Fe) surrounded by four nitrogen atoms. There is actually a fifth Nitrogen atom at right angles to the diagram ("behind" the Fe), that is in turn attached to the long "globin" chain.

If haemoglobin was just a passive lump onto which oxygen molecules stick then breathing would not work. The first oxygen molecule to bump into a haemoglobin can attach to one of four iron atoms, and so would tend attach more frequently than the second (which has only three spots to attach to), which would attach more frequently than the third and the fourth. So unless oxygen was present in great excess, there would be empty seats left on each haemoglobin as it stops by the lungs to collect its passengers. In the same way, when the oxygen molecules step off from the haemoglobin at the end of the line, the last one would have the least tendency to leave - haemoglobins may have some passengers returning for a round trip. We would have to breathe much harder than we do to get the oxygen to our muscles.

But, as Max Perutz found out a few decades ago, haemoglobin is much more than a passive lump.

When haemoglobin is empty of oxygen, the haem groups - each of which is attached to one of the four "globin" strands that wrap themselves up to form the blob-shaped haemoglobin molecule - are near to the surface of the blob but are not openly exposed. When the first oxygen molecule attaches, it triggers a slight change in the local structure of the haem group, and this in turn tugs on the globin so that the other haem sites are exposed, and more easily attract oxygen molecules. It's this opening up as oxygen attaches that is the root of haemoglobin's efficiency, and the switch that triggers it is a quantum one.

Before the oxygen attaches, the iron sits slightly out of the plane of the four nitrogen atoms. But when the oxygen attaches, the iron atom moves into the plane of the ring. This slight movement is the switch, triggering the rearrangement of the globin chain and the exposing of the other haem binding sites. Here is a sideways view, in elaborate ASCII text graphics, of the iron moving into the haem plane.

          N
          |                               N
         Fe                               |
N-----N======N-------N           N-----N==Fe==N-----N
                                          |                                                                                 |
                                          O

What happens to the iron atom to shift it into the plane? To understand that you have to know a bit about how the electrons around the iron atom are arranged.

Electrons are arranged in shells of course, and each shell holds different numbers of electrons. The innermost shell holds two electrons, the second holds eight, and the third shell can hold 18 electrons. Iron has 14 electrons in the third shell and two electrons in the fourth shell. In haemoglobin, the iron exists as Fe²⁺, with the two electrons in the 4s orbital removed. We can focus on the 14 electrons in the 3 shell to understand the switch.

The 3 shell has a single orbital with zero angular momentum (3s) that, like any orbital, can hold two electrons (one "spin up", one "spin down"). It has three 3p orbitals (6 electrons) with an angular momentum of one and a slightly higher energy. And it has five 3d orbitals with an angular momentum of two and a slightly higher energy still. There are 6 electrons spread among the 3d orbitals (leaving four unoccupied spaces) and these d electrons are the key to the switch.

When six electrons occupy the five 3d orbitals they avoid pairing up if at all possible, and they have spins "pointing" the same way (Hund's Rule: a consequence of the Pauli Exclusion Principle). By occupying separate orbitals, which generally occupy different regions of space, they keep out of each others' way and this lets the negatively-charged get a little closer to the positively-charged nucleus (become more tightly bound) without repelling each other. So the 3d energy levels of an iron atom are like this (the vertical lines are electrons, the horizontal line shows an empty slot where an electron could fit).

    ^
E   |        ||  |-  |-  |-  |- 
    |

(The unpaired electrons here, all lined up with spins "pointing" the same way, are the reason that iron is magnetic.)

This labelling of orbitals as 3s, 3p, 3d, 4s and so on is precise only for isolated atoms. But place an iron in a cage and not all the 3d orbitals are at the same energy: there is a "ligand field" effect that raises the energy of some orbitals more than others. The Nitrogen atoms have a partial negative charge, and (like charges repel) electrons in orbitals that are located largely close to these atoms rise in energy. Those that are mainly distributed away from the Nitrogen atoms will be lower in energy.

The shape of the cage determines the change in energy levels (as well as a mixing among them which we can put to one side). Here is an iron atom in a square cage. The five 3d orbitals (in a line on the left of the diagram) have split into distinct levels on the right, with different energies. To untangle the configurations of orbitals in different environments you need to apply group theory ideas to quantum mechanics.

If the split between the energy levels is small then Hund's Rule still applies and the electrons will tend to occupy orbitals singly, with spins aligned: this is called the "high-spin" case.  If the split is bigger then the electrons pair up in the lower-energy orbitals: the "low-spin" case. In the haem group the iron is high-spin. But as the oxygen atom binds to it, bringing another negative charge close to the iron, the pattern changes and (crucially) the magnitude of the splitting among the energy levels increases, and the iron changes to being a low-spin case. And, to cut the story slightly short, this switch to a low-spin Fe²⁺ ion causes the iron to fit into the plane of the haem group instead of protruding from it, and it drags the fifth nitrogen atom and the globin chain along with it.

So breathing, in the end, works only because of a fine balance between magnetism and electron level splittings in iron atoms; it works because quantum mechanics says that electrons occupy discrete energy levels and because we can calculate the order and energy of those levels. What I like is that (unlike most popular quantum topics, which focus on weirdness) this phenomenon that lies behind every breath is no longer a mystery - it's a triumph of understanding and brings the most abstract topics, group theory and quantum mechanics, down to earth.

If That's All Right With You - A Modest Manifesto

My "Happy Shoes" series seems to have faded out one episode before I meant it to. Oh well, maybe I'll get back to it soon. Meanwhile, here is a something a little different, which owes a lot to various posts by Chris Dillow at Stumbling and Mumbling.

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The names of Vasili Arkhipov and Stanislav Petrov do not appear in most lists of 20th century heroes, but they should. After all, who else could claim to have literally saved the world?

Arkhipov's moment came during the Cuban Missile Crisis on October 27, 1962, when he was an officer on a Soviet nuclear-armed submarine. When the submarine was bombarded by an American ship an intelligence officer on board thought "that's it - the end" and the captain gave the order to prepare to fire a nuclear missile. Had the missile launched, nuclear war would have begun, but firing a nuclear warhead required the approval of three officers and Arkhipov prevailed on his fellow officers to wait -- and things calmed down. When the story became public in 2002 Thomas Blanton, director of the US National Security Archive, said simply: "A guy called Vasili Arkhipov saved the world".

In 1983, Stanislav Petrov was monitoring the Soviet early warning satellites for signs of a US attack. His instructions were clear: if he detected missiles targeting the USSR he was "to push the button and launch a counter-offensive". But when the system showed five missile launches in the US all headed towards the USSR, sirens blared and warning lights flashed, and a room full of people waited for him to push the button, he didn't. It didn't look right to him and he reported the alarm to his superiors but declared it false. Petrov was right: the signal was a false alarm triggered by the satellite itself, and a war was averted.

You could hardly find two more unheroic heroes. They were not powerful generals or strong warriors, they were mid-level functionaries in the Soviet military: small cogs in a very big machine, far from the centres of political power. And their actions were not the decisive, bold gestures that we expect from heroes but were cautious and sceptical. When others demanded action their heroic response was to say "let's wait and see".

We should value modest people such as Arkhipov and Petrov more highly. It is time for modest people to get the credit they deserve.

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Look around. It is easy to see what kind of character traits we value. We nourish "leaders" all the way from elementary school (where programs select "leaders of tomorrow") through university scholarships and on into the adult world. We heap admiration on those who succeed in reaching positions of power. We encourage single-minded ambition with every book or show or speaker that tells you to "find your passion" or "follow your dream". We applaud extroverts for their gregariousness and self-confidence.

On the other hand, we undervalue traits such as meekness, generosity, doubt, introversion, a sense of balance, gentleness, irony and competence. In short, we reward arrogance and punish modesty. (I don't mean modesty as in women covering up their bodies so that men don't get excited, of course, I mean modesty as in a sense of limits, lack of pretension).

These unbalanced values distort many aspects of our culture. Consider heroism. We search for our heroes among those who are "exceptional" (climb higher mountains, score more goals, make more money...) but a different and better idea of heroism is possible, in which heroic acts are those that reveal our humanity. Arkhipov and Petrov are two examples. For another, consider the 17th century inhabitants of the village of Eyam (rhymes with dream) in Derbyshire, England. I heard of this from John Trevor's song "Roses of Eyam", as sung by the wonderful Roy Bailey. The song records how the villagers gave up their lives when bubonic plague arrived in Eyam by sealing themselves off to make sure the  disease did not spread to the surrounding areas. The number who died varies according to the telling: some say 259 of 333, some 318 from 350, but there was no doubt that those who sealed themselves off had little chance of survival. There was nothing grandiose here - no rewards, no trophies, no immortality save of the most simple kind. And yet how much more heroic these unknown people are than, say, Bill Gates or Bono.

James Joyce realized that our common humanity is at the core of heroism. By building the greatest novel of the twentieth century around a day in the life of a Leopold Bloom -- a middle-aged, cuckolded, advertising salesman -- Joyce highlighted the epic nature of everyday life. And he is right; the great things in life are universal. Birth and death, giving birth, caring for others: you don't need to explore the remote corners of the world to find these things, yet what can be greater? As Chris Dillow reminds us, Thomas Gray knew the value of modest lives. In his "Elegy Written in a Country Churchyard" he surveyed the graves of the "rude Forefathers" of a hamlet:

Let not Ambition mock their useful toil,
Their homely joys, and destiny obscure;
Nor Grandeur hear with a disdainful smile
The short and simple annals of the Poor

The poet reminds us of the importance and nobility of modest work compared to the contributions of those who enjoy "the pomp of power".  Dillow again: "All the essentials of life come from the little people who clean the streets and make our food. The humblest binman has done more good for me in the last 10 years than [Tony] Blair's managed." Or, as I read in a cookbook, "The discovery of a new dish does more for human happiness than the discovery of a star".

We would have better politicians and CEOs if a sense of service - an inherently modest quality - rather than "leadership quality" was seen as a character trait to be rewarded, and if they recognized that their success comes as much from luck and the quirks of history as from merit. And even those who do reach the pinnacles with good motives must be treated with suspicion. Power of all strands does, after all, corrupt, and those who see power are the most vulnerable to corruption.

Public discourse suffers from the same warped perspective. Those who parade bold visions and big ideas gain much of the limelight, but such efforts often have more to say about the vanity and presumption of their authors than about the reach of their intellects. A discourse based on big ideas is prone to being diverted by demagogues. Flashy writing and speaking does have its place, but mainly as popularization, and it means little if not built on cautious and detailed work carried out by those with more modest aims. The devil is often in the details and the world can more often be seen by looking closely at a grain of sand than by scanning the far horizon.

Vanity is linked to what must be The Word For 2007: "passionate". At every turn it seems that we are told that the way to happiness is to "find your passion". Companies boast that they have a "passion for excellence". Be all you can be. Follow your dream.

Such ideas are literally self-centred, and are the opposite of the modest life. When you are the star of your own life, those around you are reduced to supporting roles. Who, I cannot help but wonder, is paying for that dream? Who is finding the children's clothes while you are busy finding your passion? Usually it is the family members who have to suffer the absences (physical and mental) of the dreamer. Conor Cruise O'Brien has been called "the greatest living Irishman", yet in a trip to Toronto in the 1990s he was without his family for once, and he was at a loss. Why? Because his family members usually handled the money, the arrangements, the mundane details of his trips. Surely no one who gets those around him to do the drudge work can be considered "great".

Passion not only leads to a self-centred life; it is also the enemy of scepticism, of doubt, and of reflection. To be passionate is to be blinkered. Evangelists, monomaniacs, and demagogues are as passionate as anyone, and follow their dream wherever it takes them. But they are terrible role models. We would do better to emulate those who make and accept the compromises of a modest life; those who treat people around them with respect, who accept that others have dreams too and that, if we all give a little, we may not reach our dream but we may have a better world.

It's not that we should cast down the extrovert and immodest. Every parade needs a leader and, as the saying goes, "you can't lead a parade if you think you look funny sitting on a horse". Movies need stars and some rock bands benefit from a little swagger, but the point is that the starring role, while it grabs the spotlight, is just one of many that combine to produce the finished event. The star cannot shine without a supporting cast. Every great band needs its rhythm section, every orchestra its second fiddles. No politician gets elected without dedicated campaign workers and no matter how comfortable you feel on a horse, you can't lead a parade all on your own because that's not a parade. We need to remember that music, parades, and other events are collective efforts, and value those who feel more comfortable behind the scenes together with those who revel in the spotlight.

Of all roles, perhaps that of the spectator is least appreciated. Being a spectator is seen as passive and uninspired: how often do you hear the phrase "mere spectator" contrasted with "active participant"? Yet us spectators have an essential part to play too, because great events are made great by their spectators. What is a cup final without the fans? A rock concert without the crowd? A festival without the festival-goers? Or consider books: novelist Zadie Smith recently wrote that "A novel is a two-way street, in which the labour  required on either side is, in the end, equal... Reading is a skill and an art and readers should take pride in their abilities and have no shame in cultivating them if for no other reason than the fact that writers need you".

Extroverts, as Jonathan Rauch says in a widely-read essay, dominate public life. "This is a pity", he goes on, "If introverts ran the world, it would no doubt be a calmer, saner,  more peaceful sort of place." Yet introverts get little respect:   

Extroverts are seen as bighearted, vibrant, warm, empathic. "People person" is a compliment. Introverts are described with words like "guarded", "loner", "reserved", "taciturn", "self-contained", "private" - narrow, ungenerous words.

There are good reasons for this. Extroverts, after all, are in a good position to spread the idea that being outgoing is a good thing. Introverts, on the other hand, are not well suited to evangelize the virtues of quiet.

Restoring a balance will not be easy, because it demands immodest behaviour of modest people. It is difficult to promote the quiet virtues in a world drowning in the verbiage of the loudmouthed. Does it even make sense to stage an outspoken demand for modesty (if that's all right with you?), a brash call for humility, a blunt demand for subtlety, an uncompromising plea for flexibility? Can we be unequivocally on the side of doubt? Does it make sense to spout a monologue on the benefits of shutting the hell up?

Probably not. The very idea of a manifesto is, of course, immodest. But I think it could be saved by something that is lacking in this attempt, which is irony. Perhaps someone else can do a better job.

We should be able to speak up while accepting the limits of our own arguments if we acknowledge (with Leonard Cohen) that "there is a crack in everything. That's how the light gets in." Contradiction is an opportunity to learn rather than a debate to be fought. Thesis and antithesis are the beginning of synthesis. In exploring both sides of contradictions and arguments we learn to see both sides of a dispute, empathize with hurts and griefs that are not our own, and start to see the cracks in our own beliefs. And that must surely be a goal of any modest agenda - although not before we get the immodest down off their high horses and get them to shut up for a minute.

Bard of Salford

Procrastinating at  YouTube I type in sentimental search terms in hope of dredging up long lost gems.

And I am not disappointed. The magnificent  John Cooper Clarke is there - about 50 separate videos,some original, others homages to the man.

For those who have not had the pleasure, here are a few nasal rhymes from a true original:

Health Fanatic

Beasley Street

I mustn't go down to the sea again

Finney passes to Nugent

For the first time in my lifetime (just) a PNE player has scored for England. I know it was Andorra, but still.

Now for the premiership.

Link: BBC SPORT | Football | Internationals | Finney delighted with Nugent goal.

Sir Tom Finney has spoken of his pride at seeing David Nugent become the first Preston North End player to score for England in 49 years.

"It was only a tap in but nevertheless he scored and that was very important on his debut," Finney told BBC Sport.

"It gives me a bit of a thrill to see a Preston player wearing an England shirt - the club itself will be very proud."

Finney was the last Preston player to score for England when he found the net against Northern Ireland in 1958.

Tims Spey Way Challenge

This post is for anyone who knew me from PHGS and who is as out of touch with people from school as I am.

I went to Friends Reunited for the first time in ages to look through people's entries, and was shocked to see that Tim Lester has recently been diagnosed with motor neuron disease. A couple of weeks ago he set off on a fundraising walk through the highlands of Scotland, where he now lives, so go donate at http://www.justgiving.com/timsspeywaychallenge and show your support for Tim. There's a clickable link in the right hand column of this page as well.

Here's what he has to say at Justgiving - Tims Spey Way Challenge.

On Wednesday 29th November 2006 I was diagnosed as having Motor Neuron Disease - www.scotmnd.org.uk . Once I had picked myself up off the floor I thought I had to do something positive and decided in a moment of lucid thought that I would walk the Spey Way and try and raise some money for charity along the way. This is one of four designated long distance footpaths in Scotland and follows the course of the great River Spey from it's source in the Cairngorms to where it enters the Moray Firth (just down the road from where we now live, see photo opposite). More information from www.speysideway.org . I probably won't be able to do a Jayne Tomlinson but as long as I can put one foot in front of the other I will keep going (and even if I have to end it in a wheelchair I will). As Motor Neuron Disease is very close to my heart I would like to raise some money for them to do more research in to this little understood disease, and also Meningitis Research. This is a charity that we have done our little bit for over the years, our son Alex having survived its' ravages at an early age, and it would be good if we could raise some funds for them too. Walking will commence on the 3rd March, and don't worry I won't be galloping to the end! Your support, both monetary and in person if you can make it this far North, would be appreciated as it would be great to share some time together on this adventure. Donating through this site is simple, fast and totally secure. It is also the most efficient way to sponsor me: Scottish Motor Neurone Disease Association will receive your money faster and, if you are a UK taxpayer, an extra 28% in tax will be added to your gift at no cost to you. So please sponsor me now! Many thanks for your support.

He also has a myspace page for the walk and there's a newspaper story here.

I haven't seen Tim in many years, but - if you read this Tim - when we were at school you seemed like one of the few people in our year who actually had it all together. At least, after you got rid of the Ziggy Stardust haircut. First, you had the rugby thing going. Then, you had the music thing going with Mike Parker and Jim Hogarth. And then you were dating Barbara Armstrong, who had emerged from some kind of an invisible cocoon she was hiding in for years to suddenly become attractive-and-outspoken-and-Oxford-bound Jo Armstrong.

So you managed to be one of the cool people in school without getting an attitude about it, and always seemed just as happy to spend time with those of us who were less cool as with those who were more so. I hope you've carried on being as admirable - I'm sure you have. It's a hell of a thing to get that diagnosis, but taking on the walk sounds like just the kind of thing you'd do - no messing, getting out and do something useful. Best wishes to you in the walk and everything else, my friend.

Where are the Canadian Essays?

I spent part of this snowy morning reading Zadie Smith's 5,000 word essay in the Guardian about writing, and what writers do and don't know about it. It's a fine example of an essay. It's not journalism: there is nothing current about it, nothing that ties it to 2007 rather than 2002 or 2012. It's also not academic: there are no footnotes, no references to others. It is personal and yet well thought out, so that it contributes something original (something I have not seen elsewhere anyway) in an individualistic sense. Like the best essays, it is a contribution to a continuing conversation from someone you like to listen to.

Which got me thinking, where could you find a 5,000 word essay in Canada? Not a piece of journalism, not creative non-fiction, not research, not issue-focused writing, not as short as an op-ed, but a real essay? The Walrus, I suppose, but where else? I've seen occasional pieces elsewhere, but rarely of this length. And certainly not in widely-read publications. Seems to me this is a real lack of the Canadian public sphere. I'd be glad to be proved wrong.

Here's a brief excerpt from the middle of the piece to give you a sense of its content and tone.

Link: Fail better | Review | Guardian Unlimited Books.

First things first: writers do not have perfect or even superior knowledge about the quality or otherwise of their own work - God knows, most writers are quite deluded about the nature of their own talent. But writers do have a different kind of knowledge than either professors or critics. Occasionally it's worth listening to. The insight of the practitioner is, for better or worse, unique. It's what you find in the criticism of Virginia Woolf, of Iris Murdoch, of Roland Barthes. What unites those very different critics is the confidence with which they made the connection between personality and prose. To be clear: theirs was neither strictly biographical criticism nor prescriptively moral criticism, and nothing they wrote was reducible to the childish formulations "only good men write good books" or "one must know a man's life to understand his work". But neither did they think of a writer's personality as an irrelevance. They understood style precisely as an expression of personality, in its widest sense. A writer's personality is his manner of being in the world: his writing style is the unavoidable trace of that manner. When you understand style in these terms, you don't think of it as merely a matter of fanciful syntax, or as the flamboyant icing atop a plain literary cake, nor as the uncontrollable result of some mysterious velocity coiled within language itself. Rather, you see style as a personal necessity, as the only possible expression of a particular human consciousness. Style is a writer's way of telling the truth. Literary success or failure, by this measure, depends not only on the refinement of words on a page, but in the refinement of a consciousness, what Aristotle called the education of the emotions.

2006 Best of the Year List

You may have noticed that my normally far-from-hectic posting rate has gone from snail-like to glacial over the last few weeks. Well, be assured that it's going to stay that way for the remainder of 2006. I intend to have even less to say than usual.

Whether we like it or not, this is a season of consumption and so, for no good reason, here is a list of some of the best things I consumed in 2006.

Best fiction I read. Three Junes by Julia Glass. Not my kind of book at all, which makes it all the more remarkable that I found it unputdownable.

Best non-fiction I read. Consciousness Explained by Daniel Dennett, who is my new intellectual hero. It was published back in 1991, but my interest in this kind of stuff is relatively recent. I was put onto it via Susan Blackmore's excellent Consciousness, A Very Short Introduction. A book I'll be reading again in the next couple of weeks, and one that changed how I look at life & death.

Best movie I watched. Hidden (Cache), directed by Michael Haneke. Watching movies or TV is usually thought to be a passive act. But with this movie you are absolutely engaged from the first shot, wondering what it is you are seeing. Are you the watcher? Are you watching the watcher? Are you a spectator watching the watched? It's riveting. Then there is that one scene in the middle where, all of a sudden, everyone who sees it just gasps or swears. And to finish it off, there is the four-minute long final shot, which you scan from corner to corner for clues. Are there answers to the puzzles the movie poses? Who cares? Not me. Great stuff.

Best TV Series I watched. Intelligence. It's unusual to be able to watch a Canadian drama series and realize that it's not "good, considering" but just really really good. From the makers of Da Vinci's Inquest, and shown on CBC on Tuesdays, the multiple plotlines, shady deals, double crossing, and excellent acting from the leads (Ian Tracey and Klea Scott) as well as from the big supporting cast make this the best series I've seen since Oz.

Best radio show I listened to. Continues to be Writers and Company, where Eleanor Wachtel does a great job of interviewing writers. She gives them space to talk, doesn't get in the way, and as a result I've found several authors I like from this show.

Best restaurant I visited. Brars. Who knew that in the middle of the warehouses and  machine shops of the light-industry wasteland that is Brampton, in one of a million mini-malls scattered around Toronto airport, there is a vegetarian Indian restaurant that serves up to a thousand people in an evening, provides good value (it's a buffet for $13), and the great atmosphere of many people enjoying their company and their food. Big tables, lots of rooms, and lots of food (and on the evening I was there, great company too). Being the only non-subcontinent people in the restaurant was a bit of an eye-opener as well - I guess I have some things to learn about this place I live.

Best food shop I bought from - The usual culprits in Kitchener Waterloo are the gourmet places, like Vincenzo's, who are pretty good I must admit. But this was the year I discovered Onkar Food & Spices on Hazelglen Road in Kitchener. Good Indian ingredients at good prices. Plus I get to walk the dog through Monarch Woods when I go there.

Best other shop in K-W: J&J Cards and Collectibles on Weber Street, just south of University. Some years ago it was a place that sold Pokemon cards for the kids, Magic Cards and Dungeons and Dragons paraphernalia for the teenagers, and so on. In the last couple of years it has expanded, and it now has a great selection of board games, chess stuff, and lots more. The Brothers J have done a great job with this place.

Best book launch of 2006 - No One Makes You Shop at Wal-Mart, at Words Worth books back in June. Great that so many people came out (and bought books). A belated thanks to everyone.

Quantum Computing Revisited

So, following on from my recent gripe about quantum computing, it turns out that there are others who have thought along similar lines, and actually done the work of going beyond generalized grumbles.

Specifically, Scott Aaronson at Shtetl-Optimized posts about a paper by M. I. Dyakonov called Is Fault-Tolerant Quantum Computation Really Possible? Dyakonov goes on about the theory of error-correction in (hypothetical) quantum computers, which I know nothing of, and in particular criticizes the "threshold theorem", but he also makes some more elementary points that I did, so here are a few excerpts from Mr/Ms Dyakonov's paper just to show I'm not completely out to lunch.

The enormous literature devoted to [fault-tolerant quantum computation]... is purely mathematical. It is mostly produced by computer scientists with a limited understanding of physics and a somewhat restricted perception of quantum mechanics as nothing more than unitary transformations in Hilbert space plus "entanglement".

[on decoherence] While the relaxation of two-level systems was thoroughly studied during a large part of the 20th century, and is quite well understood, in the quantum computing literature there is a strong tendency to make it look as an obscure quantum phenomenon.

Elsewhere, Dyakonov takes aim at the assumptions of ideal behaviour that permeate discussions of the feasibility of quantum computing, and to my mind does a pretty good job of bringing a little reality into the discussion. Click the  Shtetl-Optimized link above for some more discussion of the paper.

Quantum Computing: Gripes from a Quantum Fuddy-Duddy

Waterloo is an interesting place to live these days for an ex-quantum-mechanic, mainly because of all that techno-geek BlackBerry money that is being splashed around. When I bike to work I go past the Perimeter Institute in Theoretical Physics at the beginning of my ride, and then go within a stone's throw of the Institute for Quantum Computing at the end, both of which are making waves these days. All these brainy young things pushing the boundaries of what we know and don't know, it's fun to watch.

The main media event recently has been the publication of the book "The Trouble with Physics" by the Perimeter Insitute's Lee Smolin, which is a criticism of String Theory and its 30-year failure to prove itself as something more than a promising candidate for a theory of everything. Smolin's book has been widely reviewed, often in conjunction with Peter Woit's "Not Even Wrong" which argues much the same thing. The title "Not Even Wrong" was a devastating putdown coined by Enrico Fermi of another physicist's work - the implication being it was so mistaken that you couldn't even show why and how it was incorrect. My own work was in the relatively mundane work of molecules rather than cosmological elementary particles; that is, it was quantum, but on our side of the Heisenberg Uncertainty Principle, not the other side. Both books argue that String Theory has become so removed from experiment that it has ceased to be science, and has become prone to building elaborate edifices on an insufficiently sound physical basis.

While PI has made the biggest splash locally, the Institute for Quantum Computing is a rising star too. And Quantum Computing is something that I feel I can get more of a handle on than String Theory, so I've been reading a bit about it. And what I see either exposes me for a quantum fuddy-duddy or suggests that Quantum Computing (QC from here on) could do with listening to the critiques of Smolin and applying it to themselves.

So here is what's wrong with quantum computing from what I can see. (Disclaimer: these opinions are based on a number of popular articles, my attempts to follow Scott Aaronson's excellent weblog Shtetl-Optimized, and the bit I have read of Jozef Gruska's 1999 text "Quantum Computing", which I actually got out of the library last week. These opinions are worth exactly what you paid for them.)

Reading a QC book is an odd thing for a regular physics type. Where are the Hamiltonians? Few and far between, it seems ("Hamiltonian" is mentioned in only a literal handful of places -- five -- in Gruska). Everything is about the action of unitary operators on states. For anyone reading this who is not a physicist, here's what that means. In physics, when things interact, that interaction is described by a Hamiltonian. If you're trying to solve a problem, your first step is to construct a Hamiltonian operator that describes the interaction you are studying, and then solve the equations that come from that. Unitary operators, on the other hand, describe a change in a quantum system from one state to another, which may sound like the same thing but isn't. In regular computers, circuits consist of many gates that carry out elementary operations (AND, OR, and so on). If you had a quantum "gate" then a unitary operator describes the change from input to output (that's the change in state), and ignores the way in which the system gets from the one end of the gate to the other. The Hamiltonian would describe the actual physical operation that happens as the light or electron or nuclear spin goes from the input to the output.

That still might not be very clear, so here's the end result: the theory of QC is built in a manner that has become deliberately divorced from the real world. The "implementation" or the actual building of a computer is consciously separated from the theory of the logic and algorithms that you would build on top of this computer. There is a division of labour between theory and experiment that is present right down to the way the theory is constructed, and that is a bit of a problem because it means that every single thing that the theorists say is conditional. All the theorems they prove need a big asterisk next to them saying "as long as someone can make a computer". As a footnote Richard Feynman, who knew what he was doing, did some early explorations in Quantum Computing and did approach it by building Hamiltonians and putting together Schrodinger equations - just what you'd expect a physicist to do.

You can see why the discipline has gone in this manner. Regular old classical computing, after all, followed a similar path. It started off with mathematicians (von Neumann and Turing) who set out a logical architecture of computers and algorithms, and this work was followed (loosely speaking, and as best I understand) by the engineers once the transistor was invented. And it makes sense that those interested in exploring algorithms can do so without needing to know all about welding - this stuff is complicated enough as it is. But we should keep in mind that there is always the possibility that the success of regular computing will not be repeated. The proof of the pudding and all that.

The second thing that bothers me about QC is related to this division of labour. Everywhere you look they are talking about "entanglement" and all the things that go along with it: Bell's inequalities, EPR experiments and so on. In Gruska's book Everett (of the "many-worlds interpretation") is mentioned as many times as Hamiltonian. Again, for a quantum fuddy-duddy this raises red flags. The wierdness of the quantum world is seductive - enough that my 1st year lecturer (the late Peter Dawber) felt he had to warn us "this is interesting, but it's interpretation. My advice is learn how to calculate and solve problems, and don't get stuck in the philosophical quicksand". Good advice that has been repeated by many a lecturer, I'm sure. And yet here are these QC-ers diving headlong into entangled states, and spending more time on them than on things with actual Hamiltonians. Looking in Gruska's index again, entanglement merits 42 mentions. Perhaps this is mainly a rhetorical point, but I do think it is worth making because entanglement is built into the culture of quantum computing.

Entanglement is connected to what happens when you prepare a multi-particle quantum state and then let the particles become separated. So you get paragraphs like this:

Prepare a system with two particles, each of which can have two values of spin, and send them off in opposite directions. Then measure one of the particles to find its spin. This measurement then immediately fixes the spin of the other particle, even though it's a long way away. The state of the two particles is entangled.

But you could also write this paragraph this way.

Prepare a system with two particles, each of which can have two values of spin, and send them off in opposite directions. Then measure the state of the system by checking one particle. This measurement tells you the spin of both particles.

The difference is that in the second phrasing avoids mention of entanglement, and focuses on the fact that this is a single quantum system we are talking about here, and that however far apart the two particles end up being, they still have to comprise a single quantum system, and that means no messing from the classical world. The two paragraphs refer to the same operations and mathematics, but the second avoids extraneous weirdness.

The two most mature methods of actually preparing quantum computers are NMR spectroscopy and ion traps. Ion traps deal with fine control of isolated quantum systems (as required for "entanglement") and involves very exotic and incredibly precise experimental apparatus. This is what you would expect if you are dealing with single systems: the expense of dealing with them grows as the size of the separation grows. NMR deals with many systems (coffee cups, for example - the link is to a PDF file) and uses the fancy techniques of pulsed magnetic resonance to give these systems a variety of kicks. It's recently been extended to 12 "qubits" (individual spins), which is the biggest quantum computer to date.

But here is the odd thing, this most successful technique is not based on the single systems that are needed for entanglement. In fact, these same multi-pulse NMR experiments have been carried out for some years and the word "entanglement" never raised its head so far as I know until the Quantum Computation people got interested. In NMR you are dealing with qubits that are not spatially separated (they are nuclei on the same molecule) and you are not dealing with a single quantum system described by a single state vector (you are dealing with a thermodynamic ensemble of quantum systems described by a density matrix). Myself, I could never follow the theory of multi-pulse NMR, but I'm pretty sure there was no mention of many-world interpretations in it.

So QC should realise that the consequences of "entanglement" are limited to inherently exotic systems with which you are unlikely to be able to build a real computer. It's useful in PR material to highlight the weirdness of the quantum world, but when talking science you should follow Occam, who said "avoid talking weirdness whenever possible". For example, when QC people talk about "maximally entangled states" or "Bell states" they simply mean a state in which you've measured spin along one axis when you're going to measure spin along another axis later. This can be talked about without reference to Bell or entanglement.

This thing with entanglement shows up in all kinds of popular articles by the practitioners of WC. As one example, here is a popular piece by some of the theorists (Steane and van Dam) who have demonstrated that you can use entanglement to enhance communication - that you can exploit the entanglement of a quantum state together with regular messages among observers at different places to get more efficient communications. The article reads in a fun enough way (it's about participants at a game show who each carry their own little qubit into a separate cubicle and then pass messages). But it's not possible. You can't carry a qubit around because in order to exploit entanglement you have to have a single quantum system. This kind of writing comes from thinking about measurement according to the first way I wrote the paragraph above (measure the particle) as opposed to the second (measure the system).

Perhaps I'm being overly picky about this because it is, after all, just a popular article (although it works in some concepts you would need undergraduate physics to understand before the end). But I can imagine QCers saying, "well, it's possible in principle". But like a lot of "in principle" arguments I don't buy it. I think Daniel Dennett dealt with this kind of argument in his brilliant "Consciousness Explained " when discussing the idea of a "brain in a vat" (aka the Matrix) where philosophers argue that you could "in principle" recreate the sensations of the world by stimulating the right portions of the brain. Dennett basically calls their bluff and accuses them of not thinking through the magnitude of the problem, and takes some time to spell out just how hugely implausible it is. Now it's not a proof, but I think the same kind of thing applies to these popularizations of entanglement. You can "in principle" have widely separated parts of a single quantum state outside a hugely expensive laboratory only if you don't think too hard about what the endeavour entails. In a sense, we're back to the use of Unitary operators by the theorists so they don't have to think about implementations.

Well, this has been more rambling than I expected, so here's a summary of what I see as the main points.

• The split between abstract theory and physical implementation in the structure of quantum computing is a dangerous game. It means that everything that quantum computing theory says needs to be taken with a big pinch of salt until realistic quantum computers are demonstrated.
• The widespread use of the rhetoric of entanglement and other ideas that focus on the non-intuitive parts of quantum mechanics exacerbates the problem by pulling QC theory further away from actual implementations.
• The fact that the biggest quantum computers to date are NMR based demonstrates how little entanglement adds to the actual theory of QC. And the fact that the best alternative is the inherently exotic approach of ion traps is disheartening.

I hope I'm wrong. There's a lot of smart people working on quantum computing who I'm sure have thought through these issues more than I have, and they look like in some ways they are making progress (see here). But here are two predictions that will show whether I'm right or wrong in a few years. One is that what constitutes a major advance will be redefined. The participants in a field are always enthusiastic about the major advances that are happening, but if we see major experimental advances that are phrased in terms like "enhance the understanding of what is necessary for quantum computation" rather than "actually compute something" then watch out. Second, the goals (PDF)  set out by some people in the field will not be achieved.

Well, that's my Canadian Thansgiving ramble. Now I'm going to plant some tulips, which, with a bit of luck, will appear simultaneously, as if by magic, in a coherent fashion next spring.

Update: A recent post at Shtetl Optimized discusses a paper that has some of the same criticisms as my post here, except done properly: "Is Fault-Tolerant Quantum Computation Really Possible? by M. I. Dyakonov." Fuddy-duddies unite!

No Attack On Iran

It is important that Seymour Hersh exposes the rumblings from various parts of the US government about a potential attack on Iran, but on this occasion I've felt for some time that it's not going to happen. It's not that Bush, Cheney, Rumsfeld and so on wouldn't do such a thing - personally I think they'd do it in a heartbeat if it gained them a few points in the polls - but that they can't even if they want to. It's getting close to the end of Bush's second term, he doesn't have the personal clout any more, and Iraq is such a complete and utter catastrophe that the response to any further military adventurism would, I think, be swift and damning. Now this wouldn't reassure me if I was sitting in Tehran, but that's how it looks from here.

And now someone with some actual knowledge says the same thing. The Yorkshire Ranter is someone who seems to know his military logistics stuff, and also comes from God's Own County, so he can hardly be wrong, and he argues that the US just doesn't have the needed stuff in the area to carry out any attack on Iran.

His recent posts have been excellent - I especially like his unified theory of stupidity on terrorism  where he starts off with this:

I'm beginning to think that it's possible to discern so many similarities between really stupid opinions on terrorism that we can call it a theory. Specifically, if you're talking about state sponsorship, you're probably wrong, unless overwhelming evidence contradicts this. As far as I can tell, the modern version of this theory originated in the late 1970s or early 1980s. It had been about - Shakespeare has a character in Richard II allege that "all the troubles in our lands/have in false Bolingbroke their first head and spring" - but the strong form seems to have originated then.

Key features are that 1) terrorist or guerrilla activity is never the work of the people who appear to carry it out, 2) instead it is the work of a Sponsor, 3) that only action against the Sponsor will be effective, 4) even if there is no obvious sign of the Sponsor's hand, this only demonstrates their malign skill, and 5) there is evidence, but it is too secret to produce. In the strong form, it is argued that all nonconventional military activity is the work of the same Sponsor.

and his Recidivist with alert populations, where he says this:

try out the following quote from one Robert Mocny, director of the USVISIT program at DHS:

"We cannot allow to impediment our progress the privacy rights of known criminals."

The law is what I say it is, and you're either with us, or you're with the terrorists. Perhaps literally with them, in the cells. Joseph Sensibaugh, manager of biometric interoperability for the FBI, meanwhile opines that "It helps the Department of Homeland Security determine who's a good guy and who's a bad guy," targeting "suspected terrorists" and "remaining recidivist with alert populations". Not to mention the president of Bolivia and a dead bluesman, apparently.

Why does it specifically have to be illiterate authoritarianism, by the way? What does that last phrase actually mean, anyone? Anyway. Enquiring minds want to know more. What was this "pilot project"? Whose records were given to the DHS? Will they be told? What are the safeguards? Where are the guarantees?

Good questions Alex.