Quantum Computing at Room Temperature — Now a Reality
By MATT PECKHAM | @mattpeckham | July 6, 2012 |
Georg Kucsko is a graduate student and one of the lead authors of a
paper that describes a technique that could one day lead to the creation
of a quantum computer at room temperature. Professor Mikhail Lukin (from
left), Georg Kucsko, and Christian Latta are pictured looking at their
lasers in the LISE Building at Harvard University.
You’ve read about the world’s first quantum network built from two atoms
and one proton. You’ve heard about the quantum computer someone plonked
inside a diamond to grapple with something called “quantum decoherence.”
I mean, who hasn’t?
But it’s all crazy Futurama science, right? You’d need costly equipment
capable of cooling those quantum bits (aka “qubits”) to about the
temperature of outer space vacuum, which is to say near absolute zero
(-459.67 F), to get even a primitive quantum computer working, wouldn’t
you? Also: laser beams and mirrors and springs made of light?
Maybe not. In fact, maybe all you need is a team of intrepid researchers
and a little ingenuity to prod a qubit into controlled, quantifiable
action without special cooling.
Like: a group of Harvard scientists, who’ve apparently managed to create
qubits and get them to store information for nearly two seconds at
ambient temperatures. Two seconds may not sound like much, but we’re
talking about a timeframe that the researchers claim is six orders of
magnitude greater than prior attempts.
How’d they do it? With one of the world’s hardest materials, of course.
Like the international team of scientists that recently fiddled with a
tiny diamond chip to get qubits to perform rudimentary calculations, the
Harvard research team, led by physics professor Mikhail Lukin, employed
a custom-crafted diamond to create quantum bits that were able to store
information for nearly two seconds, and — incredibly — do it at room
“What we’ve been able to achieve in terms of control is quite
unprecedented,” said Lukin in a story by Harvard Gazette. “We have a
qubit, at room temperature, that we can measure with very high
efficiency and fidelity. We can encode data in it, and we can store it
for a relatively long time. We believe this work is limited only by
technical issues, so it looks feasible to increase the life span into
the range of hours. At that point, a host of real-world applications
Getting a quantum computer working is like pulling off the world’s least
forgiving Cirque de Soleil act flawlessly. Quantum particles are
susceptible to outside influence. Persuading them to store information,
then measuring that information — much less at room temperature —
involves Herculean feats of isolation and control, like using extremely
expensive equipment to trap particles in a vacuum, then keeping them
perfectly still (as in really-truly: no atomic motion at all) to lower
their temperature to somewhere in the vicinity of absolute zero.
In addition to thermal issues, qubits are prone to decoherence, losing
information quickly as they’re influenced by their environment, thus the
basic quantum science notion that by simply measuring a particle’s state
you’re interacting with it in a way that critically influences your results.
The Harvard team opted to create an ultra-pure, lab-manufactured diamond
containing nitrogen-vacancies, or NVs — impurities at the atomic level
that behave like atoms, allowing them to be controlled and their
The trouble with NVs is that they can’t hold data long enough to
function as quantum computers. Carbon-13 atoms also present in the
diamond, on the other hand, are much less easily influenced and prone to
hanging around longer. But the trouble with them is that those same
upsides make them much more difficult to measure and manipulate.
The solution? It turns out NVs and carbon-13 atoms interact in rather
fascinating ways, such that the former can indicate the state of the
latter. By measuring the NVs, in other words, the team was able to gauge
the spin of the carbon-13 atoms at room temperatures. And by further
isolating the NVs and carbon-13 atoms using lasers, the team was able to
encode information in the carbon-13 atom’s spin and raise its coherence
— the time it’s holding the data — from a millisecond to over two seconds.
Why bother at all, given the effort still involved to produce the
crudest of quantum calculations? Because functional quantum computers
would be unbelievably fast: They take the concept of classical systems,
where information is factored sequentially in “ones” and “zeroes,” and
can represent those states simultaneously, a typically weird-sounding,
parallelistic quantum behavior known as “superposition.”
To give you a sense of what that means, physicist David Deutsch has said
that while your desktop PC today might be processing a single
computation at once in sequential fashion, a quantum computer could be
crunching through a million simultaneously.
The World to Come
What would we do with functional quantum computers (you know, besides
insert a metal prong in the back of our heads and play fisticuffs with a
bunch of Hugo Weaving clones)?
Imagine “quantum cash” channeled through a financial system encrypted
for security purposes at the quantum level, suggests Lukin. Or consider
a topologically quantum network, where qubits facilitate high-speed,
“This research is an important step forward in research toward one day
building a practical quantum computer,” said Georg Kucsko, another
researcher on the Harvard team. “For the first time, we have a system
that has a reasonable timescale for memory and simplicity, so this is
now something we can pursue.”
The Harvard team’s research was recently published in the academic
"Nature, to be commanded, must be obeyed."
~ Francis Bacon
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