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Archive for April, 2011

A peculiar thing popped up in a Google search when I looked up Dr. Tommaso Calarco, whom I was preparing to interview for the IQC video library. Amid the websites listing his research achievements and awards, of which there are many, was a YouTube video called “Don’t Let My Qubit Decohere on Me.”

Much to my surprise and delight, the video depicted Calarco (wearing a pair of pink sunglasses and doing his best Elton John schtick) singing a song with a band of fellow scientists. Lyrically, the song is a loving ode to a qubit, and a lament that the qubit may fall prey to decoherence (that evil-undoer of quantumness).

Here’s an excerpt:

Forged with light,
On atoms in a vacuum,
Ones and zeros – but not so black and white.
Quantum computing,
comes rushing round the corner,
Building here,
On the thoughts of many minds
Qubit,
We’ve almost got you working,
Your coherence could change our way of life,
But please don’t couple,
To noise you’re not supposed to:
Randomise, or just decay into the light…

Don’t let my qubit decohere on me
Though I seek coherence it’s often something else I see,
Don’t allow my system to behave – classically!
Oh, I want that quantum thing,
Don’t let my qubit decohere on me!

When I mentioned to Calarco that I had seen this clip, he laughed uproariously for several minutes, punctuating his laughter with embarrassed cries of “Oh dear” and “Oh goodness.” He explained that “some guy unfortunately recorded” that video at the final soiree of a quantum information research network he had helped build. Although he is a little bashful knowing the video is floating around YouTube, he explained that it actually represents an important aspect of physics. “Physicists are crazy and they should be,” he told me. “It’s important to let them be crazy. Because if they do some craziness they also might develop something important.”

Developing something important is exactly what Calarco does when he’s not imitating Elton John. He is a respected quantum computing researcher who is working to build collaborative research networks across Europe. He is excited and enthusiastic about the potential of quantum information research, as you’ll see from our interview with him.

But first, enjoy his brief stint as a quantum rock star, singing Don’t Let My Qubit Decohere on Me:

And now our interview with Dr. Tommaso Calarco — Understanding Quantum Computing:

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In the winter of 2010, IQC Director Raymond Laflamme delivered a talk at the inaugural (and awesome) TEDxWaterloo conference, in which he explained how researchers are learning to control the quantum world to create technologies of unprecedented power.

His talk, like the popular TED talks that have spawned hundreds of TEDx conferences in cities around the world, was intended to pique curiosity and inspire imagination.

While the full 18-minute talk can be viewed here, we also wanted to provide a somewhat shorter version with some supplementary visuals (keep an eye out for Schrodinger’s living-dead cat, who makes a cameo).  IQC had a big presence at this year’s TEDxWaterloo too, so stay tuned to QuantumFactory for a new video from that event.

In the meantime, enjoy Laflamme at TEDxWaterloo: The Director’s Cut.

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In the quest to a build quantum processor, we are still at the point of investigating several different systems. You see, no “holy grail” system as been found yet. There is always a small caveat. Example: nuclear magnetic resonance is tremendously good at controlling the state of the qubits and has low decoherence (the nasty tendency of quantum systems to lose their “quantumness”), but its scalability is jeopardized by the low polarization of the nuclear spins. Another promising system, electron spins in quantum dots, has a strong scalability potential, but work still needs to be done to contain decoherence (though major improvements have been made). Also, photons do not decohere much, but entanglement is challenging to generate (but again, new discoveries are made frequently). For uninitiated readers, quantum entanglement is the ability of multiple quantum systems to share very strong correlations, but that would be the subject of another post entirely…

Trapped ions are contenders — along with the quantum dots, photons, superconducting nanocircuits and few others — as the bases of a scalable system. Many interesting and significant results have been demonstrated in the past few years, including the experimental realization of quantum error correction, quantum simulation and steady improvement in the control of qubits.

One of the biggest challenges is to create and keep large entangled states. Decoherence really doesn’t like entanglement, and conspires to destroy it whenever possible.  In 2005, the trapped ion group in Austria led by Dr. Rainer Blatt demonstrated the generation of entanglement in an 8-qubit ion trap system — a world record at the time and quite an achievement.

Photo: University of Innsbruck

Recently, while reading Physical Review Letters, I was impressed to see that they have cranked up that number to 14 entangled qubits!  To learn the details of the experiment, visit PRL 106 130506 (2011). Although I’m exited by this result, I should comment that it is still a little too early to conclude that we now have a 14-qubit quantum processor. You see, while they are able to create specific entangled states, you must have the ability to produce any entangled state but in order to perform universal quantum computation in the circuit model.

Nonetheless, this kind of result can be paramount in the study of entanglement decoherence in larger systems (which they also did in their article) and the type of entangled state they created is at the heart of building the next generation of measurement and sensing tools.

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Quantum mechanics only applies to the realm of the invisibly, infinitesimally small, right? Not necessarily!

Andrew Cleland, UC Santa Barbara

In what was deemed by the journal Science to be last year’s “Breakthrough of the Year,” a team of researchers at the University of California at Santa Barbara achieved quantum effects on the macro scale with a device they dubbed a “quantum paddle” — which can basically be in two states at the same time. Until now, such quantum effects were exclusive to the world of atoms, electrons and other unimaginably puny particles.  The team’s device is still rather “small,” in the sense that it’s just barely visible to the naked eye, but that’s gigantic in quantum terms.

One of the researchers behind the discovery, Andrew Cleland, recently visited the Institute for Quantum Computing, and we sat him down in front of a camera to pick his brain about his work and its implications.  In this clip, he explains how his team achieved quantum effects with their device — and why it’s still not possible for a person to be in two places at the same time (which is probably for the best anyway, judging by the final season of Lost).

 

 

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