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Quantum vs. classical computers Leave a comment

Nearly every digital device so far, from ENIAC in 1945 to Apple’s iPhone 11 in 2019, is a classical computer. Their electronics rely on logic circuits to do things like add two numbers and on memory cells to store the results.

Quantum computers are entirely different, reliant instead on the mind-bending rules of physics that govern ultrasmall objects like atoms.

Where classical computers store and process data as individual bits, each a 1 or a 0, quantum computers use a different foundation, called a qubit. Each qubit can store a combination of different states of 1 and 0 at the same time through a phenomenon called superposition. Told you it was weird.

Not only that, but multiple qubits can be ganged together through another quantum phenomenon called entanglement. That lets a quantum computer explore a vast number of possible solutions to a problem at the same time.

Google quantum computer
Google quantum computer looks nothing like a conventional machine. When running, all this complexity is hidden away and refrigerated to near absolute zero.Google

Exponential speedups

In principle, a quantum computer’s performance grows exponentially: add one more qubit, and you’ve doubled the number of solutions you can examine in one fell swoop. For that reason, quantum computing engineers are working to increase the number of qubits in their machines.

“We expect that their computational power will continue to grow at a double-exponential rate,” the Google researchers said in their paper. That’s even faster than the single exponential improvement charted for classical computer chips by Moore’s Law.

Google’s machine had 54 qubits, though one wasn’t working right, so only 53 were available. That happens to match the number in IBM’s most powerful quantum computer.

But qubit count isn’t everything. Unavoidable instabilities cause qubits to lose their data. To counteract that problem, researchers are also working on error correction techniques to let a calculation sidestep those problems.

Cracking your encrypted communications? Not yet

One quantum computing ability, mathematically proved with an idea called Shor’s algorithm, is cracking some of today’s encryption technology.

However, that will require vastly larger quantum computers and new technology breakthroughs to deal with error correction.

“Realizing the full promise of quantum computing (using Shor’s algorithm for factoring, for example) still requires technical leaps,” the researchers said in their paper.

And at the same time, the US government and others are working on “post-quantum” cryptography methods to withstand quantum computing cracking abilities.

So for now at least, quantum computing, while radically different, isn’t blowing up the tech industry.

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