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www.nytimes.com]
“Google said on Wednesday that it had achieved a long-sought breakthrough called “quantum supremacy,” which could allow new kinds of computers to do calculations at speeds that are inconceivable with today’s technology.
In a paper published in the science journal Nature, Google said its research lab in Santa Barbara, Calif., had reached a milestone that scientists had been working toward since the 1980s: Its quantum computer performed a task that isn’t possible with current technology.
In this case, a mathematical calculation that the largest supercomputers could not complete in under 10,000 years was done in 3 minutes 20 seconds, Google said in its paper.”
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IBM’s looks cooler:
“By exploiting the properties of quantum weirdness, these computers could do gazillions of calculations simultaneously, enough to break currently unbreakable codes and to solve hitherto unsolvable mathematical puzzles. Google, IBM, Microsoft and other companies are now designing and building starter versions and even putting them online, where almost anyone can learn to put the quantum realm to work.
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.”
How this is accomplished is an engineer’s dream and nightmare. On a recent rainy day, Dr. Gil offered a tour of IBM’s quantum operation. The trip started with an actual quantum computer, its innards exposed, on display in the lobby of the Thomas J. Watson Research Center. It looked a bit like a small, inverted Christmas tree: 3 feet high and a foot wide, a series of gold-colored platforms hanging one from another and adorned with chips, wires, mysterious capsules and gleaming, curled silver tubes.
Each quantum computation starts and ends with a string of ones and zeros — classical bits — at the top of this assembly. Those bits are then converted into pulses of microwaves and sent down through wires and pipes to a series of 50 small superconducting devices called “transmons” — the qubits — dangling at the bottom.
The microwave pulses transform the qubits, putting them into a state of uncertainty between one and zero. Subsequent microwave pulses manipulate them, adding or subtracting them from one another or putting pairs of them into a spooky condition called entanglement, in which what happens to one qubit affects measurements of the other.
At the end, the qubits interfere with one another, like waves on an ocean, producing an output string of ones and zeros that is the answer, Dr. Gil said.
All of this happens in a fraction of a second, which is as long as you can keep nature from peeking at the qubits and spoiling things. Moreover, in practice, the qubits must be sheltered from the noisy non-quantum world, so the process transpires inside a dilution refrigerator — a big Thermos bottle — where the temperature of the chips at the bottom is kept at just above absolute zero, colder than outer space.”
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