I have become an instant fan of Robert J. Sawyer – a science fiction writer out of Mississuga.  I am currently in Volume 3 of his “Neanderthal Parallax” trilogy.  Sawyer seems to do exhaustive research for his books.  His trilogy relies on a particular interpretation of Quantum theory.

Many may be aware of the famous quantum 2-slit experiment.  The results of this experiment cannot be explained away by any means except quantum theory – it cannot be explained at all by classical physics.

Simply stated, you arrange a light source so it shines on a barrier with 2 closely spaced vertical slits.  A screen behind the slits reveals where the light went to as it passed through the slits.  Anyone expecting 2 vertical light bars might be surprised to see the result – it is a whole series of vertical light and dark areas on the screen.  Now it has been proven that light can act like a “wave” – and these bands of light are the “interference pattern” of the 2 sources of light…. much like the interference pattern you might see as water waves collide.  So, if we consider light as an e/m wave – the interference pattern makes perfect classical sense.  So far so good.

However, light can be made to act as particles, the particles known as photons.  So if we take this experiment and dim the light down so that we send a single photon at a time through the slits – what happens?  Again, some may expect to see two vertical bars of light – since the light is going through the apparatus one photon at a time – and there shouldn’t be any interference effects at all.  Yet, when you do the experiment, you do get an interference pattern (although since the photons are arriving one at a time, it takes a while for the interference pattern to emerge).  The inescapable conclusion is that somehow the photon went through both slits simultaneously and interfered with itelf.   What? Something in two places at once – how can that be?

The same effect can be demonstrated with electrons or larger particles (even molecules).

There is a slightly different interpretation.  This one supposes that the universe splits into two realities, one universe where the particle goes through the left slit, and one where it goes through the right slit.  The interference then takes place between these two alternate universes, and when we “observe” the results on the screen, the two universes collapse back into one… but you see the interference patterns as a result.

Curiously enough, if you try to, in any way, determine which slit the particle went though, it removes one of the two alternatives, since you observe the results earlier, the interference does not take place, and you no longer see the interference pattern.

An even more startling effect can be observed if you try to trick mother nature.  You run the experiment as usual, and wait enough time to ensure the particle has passed through the 2 slits, but then – just before the particle hits the screen, you whip it away and reveal apparatus to determine which slit the particle went through.   It will only tell you one or another – you never see it going through both at once.

Now in Sawyers story, there are two alternate universes – the one we know about, and a parallel one where Neanderthals became the dominant human form.  In the Neanderthal world a couple of quantum scientists are building a quantum computer to factor large numbers.  This is of course extremely important since most of our data privacy – the encryption algorithms depend on there being not enough time in the universe to factor a large enough number by classical computing algorithms.  These classical methods basically wind their way through all possible combinations, and typically takes more time than it is worth .

Getting a quantum computer up and running is difficult enough, but keeping it running is quite a problem as well.  You have to isolate the apparatus from the real world to prevent decoherence taking place – which destroys the multiple states of the qubit (much like trying to observe which slit the photon went through).  So naturally in their world the Neanderthals choose the deepest part of the silver mine in Sudbury to construct and run their apparatus.  This eliminates the interference from cosmic rays as well as background radiation from radioctive particles in the rock.  This the same location that we, in this world, built the neutrino detector for similar reasons.

A classical computer depends on bits (binary digit) that can be either in a ’0′ state OR a ’1′ state.  A quantum computer depends on qubits (quantum digit) that can be a “0″ state, a “1″ state, AND in an infinity of in between states – simultaneously.  Weird, but true all the same.  Sawyer’s story relies on the multiple universe interpretation.  The computer “reaches out” into parallel universes to do each of the calculations simultaneously.  Now what happens when it reaches out and basically “runs out of universes”?  Ha – quantum system crash with the unexpected result of linking the Neanderthal world with our world. The exploration of the events that this single events triggers makes for an interesting story, and a HUGO award for Sawyer for his volume 1.

But of course, it is all fiction, (even if based on already known science).  Still, you have to admit, even the reality is all pretty weird.

Erwin Schrödinger’s offered his cat thought experiment to try to show that when you tried to connect the quantum world with the macro world – you get results, that common sense will tell you, just can’t be so.  He puts a radioactive substance in a box, that had a 50-50 chance of decay in the next “n minutes”.  You put a detector in the box that will trigger a hammer if it detects the decay.  The hammer with smash a bottle of deadly poison.  You also place a live cat in the box – and close the lid.  Now wait the “n minutes”.  Quantum theory states the radioactive particle remains in a superimposed state (decayed and not decayed) until observed…. at which time it collapses to one or the other.  Since the cat is part of the system, it is also in a superimposed state (both alive and dead) until you open the box to see the result – at which time it collapses into of the two states.

Ok – you are probably going – no way!  Way.  Ok -prove it.

This is quite difficult to observe experimentally – until now.

New Scientist carries a report that scientists at the University of California at Santa Barbara managed an experiment to show a resonating strip of metal, 60 micrometers long, both oscillating and not oscillating at the same time.  The metal strip is big enough to be visible in a microscope.

The interesting part is how they did it… and this is going to sound familiar.  They constructed one element of a quantum computer – a superconducting qubit and got it oscillating between states at a known frequency.  They were able to then tune the qubit to the resonant frequency of the metal strip, hence transferring the quantum state of the qubit to the metal strip at will.

The physical difficulty of the experiment is that outside interference will result in decoherence very quickly.  Even cooled to 25 millikelvin, the measured results existed only for a few nanoseconds, and could only be measured statisically – but long enough to show the result corresponded to what quantum theory predicted.

So no sooner than I am almost finished reading a fictional account of using a quantum computer to link real worlds, than I am reading an non-fictional account of scientists using a quantum computer to link the micro and macro worlds.

I am reminded of a quote from J. B. S Haldane:

“I have no doubt that in reality the future will be vastly more surprising than anything I can imagine. Now my own suspicion is that the Universe is not only queerer than we suppose, but queerer than we can suppose.“

I read that Arthur C. Clarke wrote “3010″ in the Space Odyssey series because he was tired of real science getting ahead of his fictional accounts.  He figured moving out 1000 years just might keep him ahead of the game.  Good luck to the writers.

Cheers….Hugh