Saturday, December 17, 2016

QC progresses, except for market and qubits

AAAS Science mag has an article (2 DECEMBER 2016 • VOL 354 ISSUE 6316 p 1091) about the many companies pour 100s of millions of dollars into quantum computer research, promising results real soon now:
One thing is certain: Building a quantum computer has gone from a far-off dream of a few university scientists to an immediate goal for some of the world’s biggest companies.
Here is the explanation of QC, which Scott Aaronson would hate:
QUBITS OUTMUSCLE classical computer bits thanks to two uniquely quantum effects: superposition and entanglement. Superposition allows a qubit to have a value of not just 0 or 1, but both states at the same time, enabling simultaneous computation.

Entanglement enables one qubit to share its state with others separated in space, creating a sort of super-superposition, whereby processing capability doubles with every qubit. An algorithm using, say, five entangled qubits can effectively do 25, or 32, computations at once, whereas a classical computer would have to do those 32 computations in succession. As few as 300 fully entangled qubits could, theoretically, sustain more parallel computations than there are atoms in the universe.
This is the way most ppl explain, but Aaronson complains that it is wrong. He says that it leads ppl to overestimate what quantum computers can do.

Buried in all the hype is a couple of admissions:
They say they have a mutual interest in publicizing their advances, not least so that potential customers can think about how they could use a quantum computer. “We all need a market,” Monroe says.

What’s more, nobody knows enough about quantum computing yet to go it alone with a single qubit type. Every approach needs refining before quantum computers can be scaled up.
In other words, there is no market for quantum computers, and the researchers have not even created one scalable qubit.

Update: I was also amused to see the article claim that 50 qubits may be needed to demonstrate quantum supremacy, and Google is claiming that it will soon get 49 qubits. My guess is that Google secretly realizes that it is not getting quantum supremacy.

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