Quantum Computing Making Strides – Maybe?


Dario Gil, director of IBM Research, standing in front of the IBM Q System One quantum computer. It is sealed in a cube of black glass to keep in the cold and seal out the universe of noise and interference.

Dear Commons Community,

A paper by Google computer scientists appeared on a NASA website, claiming that a quantum computer had demonstrated “quantum supremacy.”

According to the paper, the device, in three minutes, had performed a highly technical and specialized computation that would have taken a regular computer 10,000 years to work out. The achievement, if real, could presage a revolution in how we think, compute, guard our data and interrogate the most subtle aspects of nature.

But then the paper disappeared, leaving tech enthusiasts wondering.

At the time, Google declined to comment, but then yesterday, google reported its findings in the current edition of Nature published yesterday.

As reported in The New York Times:

“In an email, John Preskill, a physicist at the California Institute of Technology who coined the term “quantum supremacy,” said the Google work was potentially “a truly impressive achievement in experimental physics.”

Mathematicians are still debating what might be accomplished with all this quantum power when it finally grows up. Ordinary computers are good for solving “easy” problems — questions that can be answered in a reasonable amount of time, like navigating the rings of Saturn or predicting the path of a hurricane.

Then there are “hard” problems, whose solutions are difficult to find but, once identified, are easy to verify. Among them is the factoring of large numbers. Many modern encryption schemes, like the widely used RSA cryptographic algorithm, rely on the inability to factor such numbers in a reasonable amount of time.

In 1994 Peter Shor, then at Bell Labs and now at M.I.T., devised an algorithm that a quantum computer (a still-hypothetical device at the time) could use to factor big numbers and thus break most cybersecurity codes now in common use.

In 2012 Dr. Preskill, the Caltech physicist, invented the term “quantum supremacy” to describe the potential of quantum computers to drastically outperform classical ones.

That is what a Google team has been trying to do with a quantum computer called Sycamore. The calculation they are tackling is highly specialized and technical, designed mostly to show that quantum supremacy is possible.

Success would be an inflection point in the march of human knowledge, a baby step toward a radically different future, like the first Wright Brothers flight. But it’s only one step on a long road.

“We need to be very careful about setting expectations,” said Bob Sutor, vice president of Q strategy and ecosystem at IBM, which is competing with Google for a different kind of quantum supremacy. “It’s easy to overhype this stuff.”

Indeed, in a demonstration of just how hazy the quantum future is, and how hotly contested is its ownership, a quartet of scientists from IBM, led by data scientist Edwin Pednault, earlier this week challenged Google’s claim that the calculation would take 10,000 years on a regular computer. In a paper published on the physics website arXiv, and in a blog entry posted to IBM’s research website, they estimated that the task could be accomplished in just two and a half days.

“Because the original meaning of the term ‘quantum supremacy,’ as proposed by John Preskill in 2012, was to describe the point where quantum computers can do things that classical computers can’t, this threshold has not been met,” they wrote in the blog post.

They went on to invite aspiring young scientists who wanted to do quantum computing to log on to one of IBM’s machines: “Go ahead and run your first program on a real quantum computer today.”

Google did not respond to a request for comment.

In conversation, Dr. Gil maintained that the term “quantum supremacy” was misleading and rhetorical overkill: “The reality is, the future of computing will be a hybrid between classical computer of bits, A.I. systems and quantum computing coming together.”

He and his colleagues would rather that we not judge quantum computers by qubits at all. They prefer a new metric, “quantum volume,” which takes into account both the numbers of qubits and the amount of error correction.

Quantum volume is doubling every year, according to IBM, but nobody can say how far this doubling must go before things get interesting.

The ultimate goal of quantum supremacy would be to use qubits to crack encryption codes. But that will take a while. Google’s Sycamore computer has all of 53 qubits to its name, as does a new IBM computer, installed online at the company’s Quantum Computation Center in Poughkeepsie, N.Y. System One, IBM’s black cube from tomorrow, only has 20 qubits.

In contrast, many hundreds of qubits or more may be required to store just one of the huge numbers used in current cryptographic codes. And each of those qubits will need to be protected by many hundreds more, to protect against errors introduced by outside noise and interference.

All told, it could take millions of qubits to break a code using Dr. Shor’s algorithm; patience is required. In the meantime, Dr. Preskill said, “it will be fun to play with them and learn what they can do.”

For laymen, the Times article went on to describe the power of qubits as follows.

“Ordinary computers store data and perform computations as a series of bits that are either 1 or 0. By contrast, a quantum computer uses qubits, which can be 1 and 0 at the same time, at least until they are measured, at which point their states become defined.

Eight bits make a byte; the active working memory of a typical smartphone might employ something like 2 gigabytes, or two times 8 billion bits. That’s a lot of information, but it pales in comparison to the information capacity of only a few dozen qubits.

Because each qubit represents two states at once, the total number of states doubles with each added qubit. One qubit is two possible numbers, two is four possible numbers, three is eight and so forth. It starts slow but gets huge fast.

“Imagine you had 100 perfect qubits,” said Dario Gil, the head of IBM’s research lab in Yorktown Heights, N.Y., in a recent interview. “You would need to devote every atom of planet Earth to store bits to describe that state of that quantum computer. By the time you had 280 perfect qubits, you would need every atom in the universe to store all the zeros and ones.”

If harnessed, quantum computing will revolutionize how we do computing but that future is a way off.


Comments are closed.