Thursday, May 08, 2008

Floor that uses kinetic energy to interact with user

Contact is a responsive floor based installation which allows visitors to use their kinetic energy to generate audiovisual forms that will interact with the user, and communicate with each other.

Qutrit breakthrough brings quantum computers closer

Toffoli gate

The folks playing with quantum computers have been claiming for years that their gadgets will one day make today’s supercomputers look like quivering lumps of jelly. But so far, their computers have yet to match the calculating prowess of a 10-year old with ADHD.

The most exciting work so far has been on universal quantum logic gates, the building blocks of any computer. A number of groups have built and demonstrated these and one team even took their gates for the computing equivalent of a run round the block by factorising the number 15.

The trouble is that, to do anything useful with universal quantum gates, you need at least dozens and preferably hundreds of them, all joined together. And because of various errors and problems that creep in, that’s more or less impossible with today’s technology.

Which is why a breakthrough by an Australian group led by Andrew White at the University of Queensland is so exciting. They have built and tested quantum logic gates that are vastly more powerful than those that have gone before by exploiting the higher dimensions available in in quantum mechanics. For example, a qubit can be encoded in a photon’s polarisation. But a photon has other dimensions which can also be used to carry information, such as its arrival time, photon number or frequency. By exploiting these, a photon can easily be used as a much more powerful three level system called a qutrit.

This is how the Ozzie team have exploited the idea: during a computation, their gates convert qubits into qutrits, process the quantum information in this more powerful form and then convert it back into qubits. All using plain old vanilla optics.

That allows a dramatic reduction in the number of gates necessary to perform a specific task. Using only three of the higher dimension logic gates, the team has built and tested a Toffoli logic gate that could only have been constructed using 6 conventional logic gates. And they say that a computer made up of 50 conventional quantum logic gates could be built using only 9 of theirs.

That’s a significant reduction. What’s more, they reckon that these kinds of numbers are possible with today’s linear optics technology.

That means these guys are right now bent over an optical bench with screwdrivers and lens cloths at the ready, attempting to build the world’s most powerful quantum computer. We may see the results–a decent factorisation perhaps–within months.

Could it be that Australia is about to become the center of the quantum computing world?

Ref: Quantum Computing using Shortcuts through Higher Dimensions

Global warming: we have 10 years to avoid catastrophe

Global warming

The arxiv isn’t usually the place where climate scientists make predictions about global warming but yesterday, they made an exception. A group led by James Hansen, one of the world’s leading climate scientists who works at NASA’s Goddard Institute for Space Sciences, warned that global warming is having much worse effects on Earth’s climate than thought. They say without immediate action, humanity is in danger of “seeding irreversible catastrophic effects.”

The background, in case you’ve been stuck on a desert island for the last few years, is that CO2 levels in the atmosphere have doubled from 180 ppm in pre-glacial times to 385 ppm today, most which has come since the industrial age began. “Humanity today, collectively, must face the uncomfortable fact that industrial civilization itself has become the principal driver of global climate,” says Hansen and co.

So what to do? The International Panel on Climate Change suggests that global warming of more than 2-3 degrees C may be dangerous, the EU says we should attempt to limit global warming to no more than 2 degrees C while Hansen himself has said that 1 degree C should be the maximum we should tolerate. This last estimate implies a maximum level of CO2 of 450ppm.

Now Hansen says he was wrong and that we need to aim for a CO2 level of only 350 ppm to be sure of maintaining the climate in the state we’re used to. Because if we carry on as we are, the world is going to change in ways that hard to imagine. I’ll let Hansen do the rest of the talking:

“Present policies, with continued construction of coal-fired power plants without CO2 capture, suggest that decision-makers do not appreciate the gravity of the situation. We must begin to move now toward the era beyond fossil fuels. Continued growth of greenhouse gas emissions, for just another decade, practically eliminates the possibility of near-term return of atmospheric composition beneath the tipping level for catastrophic effects.”

Frightening stuff.

Ref: Target Atmospheric CO2: Where Should Humanity Aim?

Ref: Supporting Material