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Recently in AAAS Annual Meeting 2012 Category

By Hamish Johnston at the AAAS Annual Meeting, Vancouver, Canada

Depending on how you express it, Moore’s law has held up remarkably well over the past 40 years. In particular, chipmakers have been able to double the number of transistors that can be squeezed onto a chip every two years. This explains why the mobile phone in your pocket is more powerful than the most advanced “supercomputers” of the early 1970s.

Round about 2004 however, one aspect of this exponential growth hit the buffers – it became very difficult to remove the vast amount of heat produced by all these tightly packed circuits. The result being that it is not possible to use all circuits to their full potential. This problem has the ominous moniker of “dark silicon”.

Looking into the not-so-distant future, another problem is expected to crop up when the size of insulating structures in circuits drops below about 4 nm. At this point, electron tunnelling between circuits is expected to put an end to Moore’s law.

One way round this, according to Ralf Cavin of the Semiconductor Research Corporation, is to make the electrons heavier and therefore less likely to tunnel. While this might sound crazy, an electron in a solid has an effective mass that is often greater than its mass in free space. The thing that I don’t understand about this solution is that the speed at which a transistor operates is related to the effective mass of the electrons. The heavier the electron, the slower the speed; so it seems this is at odds with sustaining Moore’s law.

Ultimately, engineers will have to look beyond Moore’s law, and that was the topic of a session where Cavin spoke at the American Association for the Advancement of Science (AAAS) meeting here in Vancouver.

Cavin is keen on in carbo electronics – devices that are based on the remarkably efficient information processing done by living organisms. The benefits, according to Cavin, are many. For one thing, biological molecules such as DNA can store data at much higher densities than the ultimate upper limit of semiconductor devices. Living systems are also highly parallel and extremely energy efficient. On the downside, living circuits are much slower than silicon.

I’m not sure when your mobile phone will contain in carbo devices, if ever, but work has begun in that direction.

Tying qubits in knots

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Photo of a knot

By Hamish Johnston at the AAAS Annual Meeting, Vancouver, Canada

Some of the world’s leading experts on quantum computing are here in Vancouver for the American Association for the Advancement of Science (AAAS) annual meeting – and it’s been great to hear them speak and to also interview some of them.

One topic that has come up several times is the idea of topological quantum computing. A major challenge for those trying to build practical quantum computers is how to protect the “quantumness” of their fragile devices from the destructive effects of environmental noise and heat.

One approach is to take advantage of the topological nature of some quantum states. One example involves quasiparticles called anyons that are predicted to exist in 2D semiconductors. One feature of anyons is that they cannot overlap with each other as they travel through space and time. The result is that the anyons exist in quantum states called “braids” that criss-cross each other.

A key feature of the braids is that they are robust to noise and heat. Indeed, to destroy such a state it must be unravelled much like untying a knot – a process that takes time and effort. This is unlike a more conventional quantum state such as the spin of an electron, which can be destroyed by a simple nudge from a random magnetic field.

Michael Freedman of Microsoft Station Q in Santa Barbara is one of the pioneers in developing the theory of topological computing, and he spoke at the conference. He left the audience with this vision for the future: “There is a serious prospect that quantum computing will change the face of computation.”

Other speakers had a complementary take on this. Scott Aaronson of the Massachusetts Institute of Technology believes that quantum computing and the emergence of quantum computers will give physicists new insights into quantum physics. “Quantum computing has opened a two-way street between physics and the science of computation,” he said.

The essential guide to topological computing can, of course, be found in Physics World.

Ariel hardhat

Building ARIEL

By Hamish Johnston at the AAAS Annual Meeting, Vancouver, Canada

One of the pleasures of my job is that I get to talk to people who are passionate about physics. But nothing prepared me for Lia Merminga, who has to be the most enthusiastic physicist I have ever met. Merminga is head of the accelerator division at TRIUMF in Vancouver – which started as a particle-physics facility back in 1968 but has since branched out into nuclear, medical, biological and condensed-matter physics.

I was at the lab yesterday, dodging the puddles as we toured the campus under leaden skies. The highlight of the tour was getting a close-up look at the cyclotron, which was shut down for maintenance.

You can see the photos I took during the tour on our Flickr page.

I also spoke to Merminga about the Advanced Rare Isotope Laboratory (ARIEL) electron accelerator facility that is currently being built at TRIUMF. Indeed, I suspect much of her enthusiasm comes from the fact that she has what must be a dream job for an accelerator physicist – she’s in charge of building a brand-new accelerator!

I spoke with Merminga about many aspects of ARIEL, so look out for an interview sometime in the future on

Geordie Rose

By Hamish Johnston, reporting from Vancouver, Canada

Yesterday I took a cab out to nearby Burnaby to have a chat with Geordie Rose, a physicist who is co-founder of the quantum-computer maker D-Wave systems. That’s Geordie on the right standing next to one of the firm’s famous black boxes.

What’s inside the box? I had a look. The box itself is a shield that protects its contents from electromagnetic fields that would wreak havoc with D-Wave’s quantum bits (qubits) – which are superconducting flux qubits. In simple terms, each qubit is a little magnet that could easily be perturbed by stray fields.

Also in the box is a dilution refrigerator, which cools the chips to near absolute zero. D-Wave uses “dry” fridges that don’t need to be topped up with costly liquid helium. Indeed, Rose says that the firm has played an important role in the development of dry fridges.

The fridge cools an integrated circuit that contains hundreds of flux qubits. They are arranged in a 2D array where each is coupled with its nearest neighbour, creating an Ising model on a chip.

I also stopped by to chat to D-Wave’s Suzanne Gildert (below), who is developing the firm’s Developer Portal, where programmers can learn about how to write code for the systems. The portal is in a beta version at the moment but a full-blown portal will soon be available to all.

Suzanne Gildert

Coming away from D-Wave, you can’t help thinking that the company has cracked the challenge of creating a viable and scalable quantum computer. Indeed, you can even buy one, if you want. But Rose admits there are lots of challenges ahead before quantum computing goes mainstream – and he thinks the best way forward is to keep building and keep improving the systems.

You can see more photos from my visit on out Flickr page.

View from Vancouver

Snowy mountains and the sea

By Hamish Johnston at the AAAS Annual Meeting, Vancouver, Canada

I have just registered for the American Association for the Advancement of Science (AAAS) meeting in Vancouver. Above is what you see from the convention centre – nice view!

More from Vancouver later, I’m off to D-Wave to talk about quantum computers.

By Hamish Johnston

Tomorrow I will be winging my way to Vancouver to attend the annual meeting of the American Association for the Advancement of Science – the AAAS. I have lots on for the next few days, including a trip to the TRIUMF accelerator lab to find out how physicists there are planning to make medical isotopes using an accelerator rather than having to rely on ageing nuclear reactors.

Geordie Rose

I will also be spending a lot of time talking to people about quantum computing (QC). Indeed, a good chunk of the programme at the AAAS is devoted to QC, a field in which Canadian physicists have excelled.

One such physicist is Geordie Rose (right), founder of the quantum-computer maker D-Wave Systems, which is based in Vancouver. I plan to visit D-Wave on Friday, when I hope to find out what is in that giant box that often appears behind Geordie.

What I’m not looking forward to is the 10-hour flight – if only quantum teleportation worked for macroscopic objects.

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