Quantum boost for artificial intelligence

Quantum computers able to learn could attack larger sets of data than classical computers.

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Programs running on future quantum computers could dramatically speed up complex tasks such as face recognition.

Quantum computers of the future will have the potential to give artificial intelligence a major boost, a series of studies suggests.

These computers, which encode information in 'fuzzy' quantum states that can be zero and one simultaneously, have the ability to someday solve problems, such as breaking encryption keys, that are beyond the reach of ‘classical’ computers.

Algorithms developed so far for quantum computers have typically focused on problems such as breaking encryption keys or searching a list — tasks that normally require speed but not a lot of intelligence. But in a series of papers posted online this month the arXiv preprint server1, 2, 3, Seth Lloyd of the Massachusetts Institute of Technology in Cambridge and his collaborators have put a quantum twist on AI.

The team developed a quantum version of 'machine learning', a type of AI in which programs can learn from previous experience to become progressively better at finding patterns in data. Machine learning is popular in applications ranging from e-mail spam filters to online-shopping suggestions. The team’s invention would take advantage of quantum computations to speed up machine-learning tasks exponentially.

Quantum leap

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At the heart of the scheme is a simpler algorithm that Lloyd and his colleagues developed in 2009 as a way of quickly solving systems of linear equations, each of which is a mathematical statement, such as x + y = 4. Conventional computers produce a solution through tedious number crunching, which becomes prohibitively difficult as the amount of data (and thus the number of equations) grows. A quantum computer can cheat by compressing the information and performing calculations on select features extracted from the data and mapped onto quantum bits, or qubits.

Quantum machine learning takes the results of algebraic manipulations and puts them to good use. Data can be split into groups — a task that is at the core of handwriting- and speech-recognition software — or can be searched for patterns. Massive amounts of information could therefore be manipulated with a relatively small number of qubits.

"We could map the whole Universe — all of the information that has existed since the Big Bang — onto 300 qubits," Lloyd says.

Such quantum AI techniques could dramatically speed up tasks such as image recognition for comparing photos on the web or for enabling cars to drive themselves — fields in which companies such as Google have invested considerable resources. (One of Lloyd's collaborators, Masoud Mohseni, is in fact a Google researcher based in Venice, California.)

“It's really interesting to see that there are new ways to use quantum computers coming up, after focusing mostly on factoring and quantum searches,” says Stefanie Barz at the University of Vienna, who recently demonstrated quantum equation-solving in action. Her team used a simple quantum computer that had two qubits to work out a high-school-level maths problem: a system consisting of two equations4. Another group, led by Jian Pan at the University of Science and Technology of China in Hefei, did the same using four qubits5.

Putting quantum machine learning into practice will be more difficult. Lloyd estimates that a dozen qubits would be needed for a small-scale demonstration.


Nature doi:10.1038/nature.2013.13453

References

• Rebentrost, P., Mohseni, M. & Lloyd, S. preprint at http://arxiv.org/abs/1307.0471 (2013).Show context
• Lloyd, S., Mohseni, M. & Rebentrost, P. preprint at http://arxiv.org/abs/1307.0411 (2013).Show context
• Lloyd, S., Mohseni, M. & Rebentrost, P. preprint at http://arxiv.org/abs/1307.0401 (2013).Show context
• Barz, S. et al. preprint at http://arxiv.org/abs/1302.1210 (2013).Show context
• Pan, J. et al. preprint at http://arxiv.org/abs/1302.1946 (2013).Show context

Related stories and links

From nature.com

• Computing: The quantum company 19 June 2013
• Google and NASA snap up quantum computer 16 May 2013
• Simulation: Quantum leaps 14 November 2012
• Quantum computing: The power of discord 01 June 2011
• Spooky computers closer to reality 28 June 2009
• Nature Insights: Quantum coherence 

From elsewhere

Quantum algorithm zoo

ORIGINAL: Nature

Devin Powell

26 July 2013

Researchers achieve electrical control of quantum bits, paving the way for quantum computers

Image: Arne Laucht

For the first time ever, researchers have encoded quantum information using simple electrical pulses.

Researchers from UNSW in Australia are a big step closer to creating affordable, large quantum computers, after gaining electrical control of quantum bits, or qubits, for the first time.

The team was able to store quantum information in silicon using only simple electrical pulses, instead of pulses of oscillating magnetic fields. This is the same way that the computers we use today encode data, and it means that we now have the ability to cheaply and easily control the quantum computers of the future.

"We demonstrated that a highly coherent qubit, like the spin of a single phosphorus atom in isotopically enriched silicon, can be controlled using electric fields, instead of using pulses of oscillating magnetic fields," said lead author of the study, Arne Laucht from UNSW Engineering, in a press release.

This is something that researchers have been attempting since 1998, and the results have now been published in the open-access journal Science Advances. 

The method works by distorting the shape of the electron cloud attached to the phosphorous atom, quantum engineer Andrea Morello, who also worked on the research, explained in the release.

"This distortion at the atomic level has the effect of modifying the frequency at which the electron responds," he said.

"Therefore, we can selectively choose which qubit to operate. It's a bit like selecting which radio station we tune to, by turning a simple knob. Here, the 'knob' is the voltage applied to a small electrode placed above the atom."

The research suggests that it will be possible to locally control data in a large-scale quantum computers using only inexpensive voltage generators, as opposed to the pricey high-frequency microwave sources that quantum researchers have used to encode information in the past.

It also means that these types of qubits can be manufactured using technology similar to the kind we currently use, which will greatly cut the cost of quantum computers.

The key to the team's success was embedding the phosphorous atom in a thin layer of purified silicon that contains only the silicon-28 isotope, which is non-magnetic and doesn't disturb the qubit.

The UNSW Engineering quantum group was the first in the world to demonstrate single-atom spin qubits in silicon back in 2012, and they also last year showed that they could control these qubits with 99 percent accuracy. Their overall goal is to build the world's first affordable, large-scale quantum computer, and we honestly can't wait.

Love engineering? Find out more about the world-leading research happening at UNSW Engineering.

ORIGINAL: Science Alert

FIONA MACDONALD

11 APR 2015

Scientists Confirm D-Wave's Computer Chips Compute Using Quantum Mechanics

ORIGINAL: IEEE Spectrum
By Jeremy Hsu
Posted 3 Jul 2013 | 18:05 GMT

Photo: Steve Cohn/USC News

A strategy of "show, don't tell" for quantum computing seems to be paying off for Canadian company D-Wave. The latest validation for D-Wave's quantum computer claims comes from a paper published in the June 28 edition of the journal Nature Communications.

Testing of the D-Wave chip—housed at the USC-Lockheed Martin Quantum Computing Center—suggested that the device does use quantum mechanics to solve optimization problems. Once quantum computers scale up to have enough processing power, they could prove much faster than classical computers in tackling certain problems, according to the new paper.

"Our work seems to show that, from a purely physical point of view, quantum effects play a functional role in information processing in the D-Wave processor," says Sergio Boixo, a researcher who led the study while he was a research assistant professor in computer science at the University of Southern California, in a press release.

Most research labs have only succeeded in building quantum computing processors with just a few quantum bits (qubits). Unlike classical computing bits that exist as either a 1 or 0, qubits can exist in multiple states at the same time due to the strange rules of quantum physics that dominate reality at very small scales.

That's why D-Wave initially drew skepticism for claiming to have built quantum processors with hundreds of qubits. But rather than follow research labs in trying to build general-purpose quantum computers, D-Wave has developed specialized quantum annealing devices for solving optimization problems.

The Canadian company has slowly won over some critics by giving independent researchers access to its D-Wave machines and inviting them to test its claims. One such test revealed that D-Wave machines could already beat classical computers in solving certain optimization problems.

D-Wave has also attracted notable tech giants as its first commercial customers. The company made its first commercial sale to Lockheed Martin in 2011, and has sold a second chip to Google for future installation at NASA's Ames Research Center in Moffett Field, California.

Members of the University of California team previously published a paper about D-Wave's quantum computing device on the arXiv preprint server in April. Their new paper in Nature Communications—a test of a D-Wave "Rainier" chip with 108 functional qubits—may give former skeptics fresh hope that quantum computing has, in fact, become a reality.

The USC team has barely paused for breath in its race to study quantum computing. USC's Quantum Computing Center received an upgrade to a new 512-qubit "Vesuvius" chip two months ago—the next machine up for a test drive.