On 9th October, French Physicist Serge Haroche, 68, was taking a walk with his wife when his cell phone rang, and the Swedish country code flashed on the screen –which, at this time of the year,can mean only one thing for a physicist. Luckily, there was a bench nearby where he could sit down.
Haroche has shared this year’s Nobel with American David Wineland. Both work in the field of quantum optics, studying interactions between controlled laser bursts and sub-molecular particles. Both have independently devised “ingenious experiments” over the decades, showing scientists what building blocks of a quantum computer might be like.
Between them, the two laureates have further moved metaphysical mountains,in shattering the central dogma of quantum mechanics, popularly called the observer effect – which purports isolation of quantum states as impossible, since any instrument making measurements tampers with the system. Quantum states are highly unstable, and the slightest interference or interaction with the environment destroys them.
Haroche bounced microwave photons –hypothesized elementary light particles — between two mirrors made of semiconductors and cooled to near absolute zero – when all molecular motion ceases and the quantum world begins. This sustained the photon in our ‘real’ measurable world for nearly a tenth of a second. According to the committee, this “record-long life-time means the photon will have traveled 40,000 kilometers, equivalent to about one trip around the earth.”
The Haroche team built on a way they devised to count the photons, and mapped the stages it went through,from its initial quantum distribution until destruction.This was previously thought impossible.
Wineland had already contributed to quantum computing in the past majorly,having demonstrated ways to break encryption codes beyond the limits of today’s computers. This time,Wineland isolated charged ions from the environment. Then mastered the art of using laser pulses to ‘cool’ the excited ion to its lowest energy state,which caused it to enter the quantum domain, and exhibit the property of ‘superposition’.
Imagine a ball floating in a well that is marked at different depths – representing discrete energy levels. The floating ball is in its natural, un-tampered state. If some occult force causes the ball to take a dive, it can only remain stable at the ‘marked’ depths. Anywhere between, it automatically gravitates to the nearest energy level. This is the classical description.
In the quantum description, the ball occupies multiple energies simultaneously, as if bodily split–including ‘unmarked’ levels in between. This is superposition.
“The race is on,and working out which will win isn’t exactly rocket science.”
Before a measurement is made, the probability of finding the ball at a particular energy can be calculated. Probabilities of finding it around certain markings are higher than others,but at no marking is it completely zero. Once a measurement is made, the tampering causes the ball to be measured at one energy level only.The ball now physically exists in one place. It is the act of measurement, or as Kant would say, the observer that causes the sensual world to actually exist.Take away the observer, and the world dissolves into a sea of un-manifest probabilities.
(NOTE: The well example is a rough analogy, meant to be educative, and should not be taken literally.)
If all this seems counter-intuitive, don’t break sweat.Quantum mechanics has discomfited physicists since its inception, including Einstein who supposedly reacted to it with the words “God does not play dice.” But these peculiar properties of the micro-world make a quantum computer feasible.Universities have already built such devices on a small scale, which outperform traditional computers at some calculations exponentially.
A feasible quantum device relies on a peculiar property manifesting only at subatomic levels, called ‘entanglement’.(Einstein called it “spooky action at a distance”.) If two particles ‘meet’ in the quantum world, they are coupled forever. Changes wrought on one will affect the other simultaneously, even if they are at opposite ends of the galaxy.
When a classical computer, which encodes information as bits– a string of ‘0’s and ‘1’s–performs an operation, it must grind.Consult every conceivable option including the wrong ones, in discrete steps. Thanks to entanglement, a quantum computer–which encodes information as photons or electrons– will do so much faster. If two particles are entangled, and one is measured as a ‘0’, the other will automatically be ‘1’ and vice versa. No separate step is required to confirm this.
Here’s what Seth Lloyd, Mechanical engineering professor at MIT,said to PBS in 2009 –“Suppose I have nine pockets, and my wallet is in one of them. I’ve got to look it up in nine pockets before I find my wallet. Well, a quantum computer could do that in just three operations. If you had 100 pockets, it could do that in 10 operations, or a million pockets, a thousand operations. So a quantum computer could seriously speed up the ability to search a database.”It could further, according to Lloyd, sort through stock market data much faster, and lead to more accurate weather prediction.
Entanglement based protocols will also make data exchange over the net more secure.Today, if you want to upload something privately on the internet for someone, a random alphanumeric key is algorithmically generated; and a third party crack this key, you have no immediate way of knowing. But entanglement ensures any interference generating a ‘ripple’ which notifies both parties involved in the exchange immediately.
Of course, technically realizing a versatile quantum computer capable of all the above is beyond our current reach.Meanwhile, another movement is breaking tantamount revolutionary ground, minus the publicity.
To set the ball rolling, another Seth Lloyd statement from the same interview:“It’s recently been discovered that actual living systems such as photosynthetic bacteria in plants are using funky quantum weirdness techniques to make energy transport in plants and bacteria much, much more efficient. It was kind of a drag because, you know, we discovered all these cool techniques, and then found out, whoa, these bacteria have been doing it for a billion years!”
Enter Toshiyuki Nagakaki, mathematical biologist from Hokkaido University,Japan. Two time winner of the Ig-Nobel Prize, which is awarded for “achievements that first make people laugh, then make them think.”
In 2008, Nagakaki demonstrated how slime mold could solve a maze by efficiently conserving its resources and finding the easiest path to a food source. In 2010, this brainless, primeval organism collectively recreated(without prior knowing) a more efficient version of the Tokyo subway system – establishing that single celled organisms have advanced information processing capacities. The same problem would take humans much longer.Unless there was quantum computing. But if Nagakaki’s method takes a little longer, it is astronomically cheaper.
Then there’s George Church, molecular geneticist from Harvard, who has demonstrated DNA is an effective storage medium. Church’s team encoded his entire book in DNA, with images.Church found one gram of DNA can store more than 450billion gigabytes. And unlike fast changing digital formats, DNA is never obsolete, enduring for millennia under extreme conditions.
This tech is not yet economically feasible,but advances in biotech are lowering DNA coding/reading costs so dramatically, experts predict this medium to outmode digital within a decade. DNA exists as a natural resource, and naturally, is expected to out-compete man-made technologies cost-wise.
The race is on,and working out which will win isn’t exactly rocket science.Scientists like Church and Nagakaki could well be considered for a future Nobel – once they’ve built on these initial discoveries and reached something more buildable.
But only if the Nobel committee decides to majorly overhaul its narrow perspective and instate an award for bioinformatics.
