SciBlogs

Archive 2012

Sir Paul Callaghan Roger Hanson Mar 26

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Farewell to Paul Callaghan a proud New Zealander and world-class scientist, whose knowledge, style and modesty provided inspiration to many scientists, myself included.

Quantum Physics #3 Roger Hanson Mar 13

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The meaning of information loss

Ralf Landauer demonstrated that if an operation is information reversible, that is, in a logic gate the output can be inferred from the input and the input can be inferred from the output (see earlier Quantum Physcis #2) , then because information is not destroyed no heat is emitted from the device. If a system doesn’t lose information then it doesn’t interact with the environment. Systems, when they are quantum do not exchange energy with environment, that is, they do not release information. This is the same as saying that they are not “measured” by the environment. In the early days of modern quantum physics (if you get my meaning), it was inferred that measurement required the presence of a human or a human made device. This of course isn’t true. Whether humans are present or not doesn’t matter. To briefly explore this issue more I want to give a few paragraphs on the meaning of information.

Seth Lloyd of MIT notes: “all physical systems are computers: rocks process information: every electron, photon, elementary particle stores bits of data. Every time two particles interact the bits are transformed, physical existence and information contents are inextricably linked”.

The way to convert a container full of steam into one of ice is allow the container to lose heat. By doing so it loses information.  A container of ice is a much simpler system than one of steam. David Deutsch of Oxford University says that an information rich system is one that would require a much bigger computer program to simulate, than an information poor system. If I was asked to program a computer to precisely simulate the contents of the container, the water present as ice would a much simpler system and hence would require a much shorter program to simulate it than the same container and the same water in the form of steam. The information difference has been lost as heat, just as Ralf Landauer’s principle identified.

Profoundly, Sean Carrol of Caltech, defines information in the following way: “processing information allows us to extract useful work from a system in ways that would have otherwise been impossible”. As a thermodynamicist, this hits the bullseye for me.

If you agree with the above argument then hold tight (can you wait?- OK maybe you can) for the next installment. If you agree or disagree with the line of thought so far, it would be great to hear from you. Establishing these ground rules, I can progress onto more controversial issues.

Quantum Physics #2 Roger Hanson Mar 06

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I intend to post a series of blogs introducing the beginner to quantum physics. This is the second such blog. I ‘ll eventually move on to more contentious issues and ask the Brains Trust out there for feedback.

The first “eureka” moment for in the journey to make sense of quantum physics is described in the following.

Anyone who has seen a supercomputer is immediately struck by the enormous amount of cooling equipment these computers require. That raises a question: why does the process of computing generate so much heat? The answer reaches into fundamental physics, a proper understanding of which will eventually deliver computers that require no power to process information; the ultimate energy conservation device.

Imagine a black box with an input connection on the left had side and an output connection on the right hand side. The input is connected to a device that generates an electrical pulse. The electronic circuits inside the box interpret this pulse as a ‘1’ and take that and flip it so that a ‘0’ is delivered at the output. Alternatively, if a ‘0’ is sent into the box, a ‘1’ is delivered at the output. In summary: Input 0 → Output 1; Input 1 → Output 0.

An opaque partition screen is placed across the middle of the box so if you sit on the input side you cannot see the output or me sitting at the output side. If we both know that the internals are designed to flip the input signal then if I see a “1″ appear at my side (the output), I can infer that a “0″ must have entered the input, on your side. This is called a reversible operation because purely by examining the output value, the input value can be deduced and vice-versa.

The black box is replaced with a different one. It has two input connections on the left hand side and one output connection on the right hand side. With the opaque partition in place, we run the following experiment. The circuitry inside this new box is configured such that if both of the two inputs is a “1″, then and only then, will the sole output deliver a “1″. This means that if I (sitting at the output) see a “1″, I can immediately infer that a “1″ must have been sent into each of the two input lines on your side of the partition. So far so good. However if a “0″ appears at the output then I cannot correctly infer what the individual inputs must have been because three separate combinations of input can deliver a “0″ at the output: these are (1 and 0) or (0 and 1) or (0 and 0). It is impossible for the person at the output to infer by seeing the “0″ which of the three possible combinations were actually input. This is called an irreversible operation because the input cannot be inferred by only examining the output.

The interesting feature of this irreversible operation is that heat is given off when it is performed. However, no heat is given off when reversible information processing is performed. The reason is that information was lost during the processing of the irreversible operation. We know that is true: the input had two pieces of information and that information could not be correctly inferred purely by examining the output; information was lost.

There is a fundamental connection between information loss and heat loss. Energy is lost if information is erased. This phenomenon was first identified by Rolf Landauer, an engineer with IBM in the 1960s. The two operations in the black boxes referred to earlier are used in computer logic (that is, how computers perform calculations). The exciting feature of this is that if you made a computer whose information processing was based entirely on reversible systems (like the first black box noted above), then no heat would be lost, hence no power consumed, by the calculation process. Reversible computing is energy free information processing.

Reversible computer logic is currently being used but there are technical difficulties with its universal use. For example, if a computer processes billions of bits of information and must not erase any, then all that information has to be stored somewhere, so the sheer size of these computers would make them uneconomic.

However, the fact that reversible information processing is energy free is being used to at least limit the power consumption of some computers. In gadgets that need to process information but be miserly with their power consumption, then reversible computing is very useful. Dramatically improved computing efficiency with the extensive use of reversible information processing could be the next big revolution in computing. More importantly to me, it provides an insight between energy loss and information processing, because reversible information processing is the world of quantum physics.

Quantum Physics #1 Roger Hanson Feb 16

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Quantum Physics for Beginners # 1

Until the 20th century, the only physics humankind was aware of was that which involved energy and time. The science that successfully describes these processes is called thermodynamics. This is based on the very reasonable idea that any activity in this Universe requires energy to be expended and takes time to complete. Alas this isn’t true. At the beginning of the 20th century Einstein completely revised the traditional thinking on time. Time had always been thought of as universal, one time for all; however Einstein showed that your time is different from mine. Indeed your time depends on the speed you’ve been travelling, the acceleration you’ve been subjected to, and the gravitational field you’ve been living in. But Einstein’s theory of relativity is incomplete; it provides a mathematically useful geometric analysis of time and space but by-passes the fundamental science completely.

Until the 20th century we thought that thermodynamics and relativity described everything there was to know about the Universe, or perhaps more accurately, the fabric of the Universe. Max Planck in 1900 had fired the first warning shot that showed that all wasn’t so cosy when he discovered that light can absorb and admit radiation only in energy bundles (later called quanta) whose size was proportional to the frequency of radiation. It ranks as one of the greatest discoveries in science but Planck hated his idea. He was obsessed with thermodynamics (particularly the second law), his problem was that for his quanta to work they had to temporarily break the second law (for reasons to be explained in later posts). Photographs show a miserable Planck at the time — yes, really miserable. The discovery won him a Noble Prize in 1918 but that didn’t cheer him up, I guess you can’t please everyone.

The wonderful (I use the term advisedly) thing is that thermodynamics and relativity are not the underlying truth of the Universe; they are just special cases of a more fundamental physics. That physics is called quantum physics. Quantum physics does away with the pesky inconvenience of time and energy, indeed any particle that finds itself in the quantum world will be everywhere simultaneously. Don’t laugh — life, including you, couldn’t exist if for significant periods the sub-atomic particles that you are made of don’t temporarily appear everywhere in the Universe simultaneously. You don’t have to take my word for this, the great Richard Feynman (Nobel Prize in 1965) spent a large chunk of his career demonstrating it.

Next article I’ll get down to specifics, and if you don’t agree with any of it or don’t understand it then please comment.

Science in New Zealand Roger Hanson Feb 02

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Here’s the dream: New Zealand continues its superbly innovate and world beating work in the dairying industry and continues to star in Hollywood thanks to the amazing efforts of Weta Workshop and Peter Jackson. These two outstanding examples show that NZ can take on the world and win. But this is not enough; we need more world class companies, we need knowledge based companies. Forget trying to stitch clothes together in sweat factories or make low grade steel in coal and gas fired mills; we’ll never compete with Asia on that front. We need knowledge based companies powered by science-trained brains.

Professor Sir Paul Callaghan in his excellent series shown on Stratos TV last year, interviewed some captains of industry and presented thoughts of his own on what New Zealand needed to do to raise its game. For example, on almost any measure, an electronics factory beats the dairy industry heads down; cleaner and greener, smaller area required, bigger income per employee and so on. Australia gets its GNP largely from digging bits of it up and flogging it overseas, and good on them, but that for many reasons can be a long term curse. New Zealand is not in that position, at least not to the same extent, so we must in the future take the German, Korean and Japanese route. We must make money by adding value. Get this right and it sends you into financial orbit (Apple are currently sitting on a cash pile of US$100 billion and Samsung Q4 2011 profits are up 17% to US$3.5 billion).

Can New Zealand be the source of another Apple or Samsung? You bet it can. Ask any Kiwi 20 years ago if one of the most powerful people in Hollywood, James Cameron, director of Avatar would go out of his way to fly to Wellington to discuss future projects with a Wellington based visual effects company and you would be looked at as if you were insane. The Wellington film industry came from nowhere to world class player, so don’t say New Zealand can’t enter the global science based knowledge community.

As an almost evangelical fan of quantum physics, I can see an enormous scientific and technological juggernaut heading towards the human species with the words ‘Quantum Physics’ emblazoned on it.  Of course quantum physics based technologies exist today: lasers, flat screen TVs, medical scanners, are all based on quantum physics laws, however, marvellous as these devices are, this is at the level of tinkering compared with what must be possible. The real action is still to come. For example: understanding and exploiting the quantum aspects of living organisms; developing quantum computing and above all, evading time by engineering processes to do their stuff in the quantum universe not the thermodynamic universe. It ain’t going to be easy; to use the old cliché, if it was then someone would have already done it, but that can be said about any technology from car engines to GPS units.

I’ll finish with the thought that the Universe we are aware of, that is, the structures and activities we detect with our senses and with our instruments, is merely the front-stage. Being unable to detect something doesn’t mean it doesn’t exist. More than that, the  Universe itself has a limit to what it can detect. We know that limit precisely. Behind this world of detection is a hidden world, a world where quantum physics plays where the impossible is possible. Experiments allow us to glimpse at this. This is not science fiction. What goes on there makes anything existing electronics can do infantile in comparison. Lifting the quantum veil will reveal a whole new playground for science and technology.

The dream: the person who does this, the next Bill Gates, calls New Zealand home.

In future blog posts I’d like to clarify some quantum issues for the beginner and draw attention to what is possible.

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