One team is ahead of the race with 51 qubits.
The 4th International Conference on Quantum Technologies held in Moscow last month was supposed to put the spotlight on Google, who were preparing to give a lecture on a 49-qubit quantum computer they have in the works.
A morning talk presented by Harvard University's
Mikhail Lukin, however, upstaged that evening's event with a small
announcement of his own – his team of American and Russian researchers
had successfully tested a 51-qubit device, setting a landmark in the
race for quantum supremacy.
Quantum computers are considered to be part of the next generation in revolutionary
technology; devices that make use of the odd 'in-between' states of
quantum particles to accelerate the processing power of digital
machines.
The truth is both fascinating and disappointing.
It's unlikely we'll be playing Grand Theft Auto VR8K-3000 on a
quantum-souped Playstation 7 any time soon. Sorry, folks.
Quantum computing isn't all about swapping one kind of chip for a faster one.
What it does do is give us a third kind of bit
where typical computers have only two. In quantum computing, we apply
quantum superposition – that odd cloud of 'maybes' that a particle
occupies before we observe its existence cemented as one of two
different states – to solving highly complex computational problems.
While those kinds of problems are a long, tedious process that tax even our best supercomputers, a quantum computer's "qubit" mix of 1s, 0s, and that extra space in between can make exercises such
as simulating quantum systems in molecules or factorising prime numbers
vastly easier to crunch.
That's not to say quantum computing could never be a useful addition for your home desktop. But to even begin dreaming of
the possibilities, there are a whole number of problems to solve first.
One of them is to ramp up a measly handful of qubits from less than 20 to something that can begin to rival our best classical supercomputers on those trickier tasks.
That number? About 50-odd, a figure that's often referred to in rather rapturous terms as quantum supremacy.
The Harvard device was based on an array of
super-cooled atoms of rubidium held in a trap of magnets and laser
'tweezers' that were then excited in a fashion that allowed their
quantum states to be used as a single system.
The researchers were able to control 51 of these
trapped atoms in such a way that they could model some pretty complex
quantum mechanics, something well out of reach of your everyday desktop
computer.
While the modelling was mostly used to test the
limits of this kind of set-up, the researchers gained useful insights
into the quantum dynamics associated with what's called many-body
phenomena.
Fortunately they were still able to test their
relatively simpler discoveries using classical computers, finding their
technique was right on the money.
The research is currently on the pre-publish
website arXiv.com, awaiting peer review. But the announcement certainly
has the quantum computing community talking about the possibilities and consequences of achieving such limits.
The magical number of 50 qubits is more like a
relative horizon than a true landmark. Not much has changed in the world of quantum computing with the Harvard announcement, and we still have a long way to go before this kind of technology will be useful in making
any significant discoveries.
Google's own plan for a 49-qubit device uses a
completely different process to Lukin's, relying on multiple-qubit
quantum chips that employ a solid-state superconducting structure called a Josephson junction.
They've proven their technology with a simpler 9-qubit version, and plan to gradually step up to their goal.
Without going into detail, each of the technologies has its pros and cons when it comes to scaling and reliability.
A significant problem with quantum computing will
be how to make the system as reliable and error-free as possible. While
classical computing can duplicate processes to reduce the risk of
mistakes, the probabilistic nature of qubits makes this impossible for
quantum calculations.
There's also the question on how to connect a number of units together to form ever larger processors.
Which methods will address these concerns best in the long run is anybody's guess.
"There are several platforms that are very
promising, and they are all entering the regime where it is getting
interesting, you know, system sizes you cannot simulate with classical
computers," Lukin said to Himanshu Goenka from International Business Times.
"But I think it is way premature to pick a winner
among them. Moreover, if we are thinking about truly large scales,
hundreds of thousands of qubits, systems which will be needed for some
algorithms, to be honest, I don't think anyone knows how to go there."
It's a small step on the road to a hundred thousand qubits, but it doesn't make passing this milestone any less significant.
Happy 51, Harvard!
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