The Quantum Supercomputers of the Future Will Be the Dumbest Computers Ever Created, and the Best

Right now, we can do quantum computations at a very small scale. We’ve been able to create entangled systems of up to eight qubits, which in the scale of practical computing is infinitesimal. But in the grand scheme, is pretty amazing. Remember that in quantum computing you’re able to process vast amounts of information because the computer is allowed to occupy a vast number of states at once. If you have n qubits, they can be in up to 2^n states at once.

With some custom quantum algorithms, you should be able to do some pretty mind-boggling things with that. Meanwhile, a classical computer can only be in one of those states at a time. The catch, however, is that it’s really, really hard to get enough qubits entangled to make good practical computing use. Hence, we’re still fighting upward from eight. Mostly likely, quantum computing will all be done in centralised centers for the simple reason that the process of making and maintaining one makes our current computers look like wheelbarrows.

This is actually how Alan Turing imagined in 1946 the computing of the future, at some big computing center that people would be linked to (neatly foreshadowing the internet in the process). The idea of a desktop computer, though realized and ignored, was still pretty much a non-idea. In the the case of quantum computers, however, it doesn’t seem to be a lack of imagination or big thinking keeping quantum computers off our desks and laps; a quantum system is a fragile and extremely complicated beast. “Realizing quantum devices that are practically applicable is a highly-complex task,” Stefanie Barz, a quantum information researcher at the University of Vienna, tells Motherboard. “So, the challenges in realizing quantum computers lead to the conclusion that in the future only a few specialized facilities around the world might be able to operate those devices.”

Barz has just published a paper about the security potential of a cloud quantum computing system in which different remote users plug into central quantum computers, send their calculations over, get them computed, and get results. It’s a system that would seem to carry a whole lot of risk. After all, first in line for quantum computers are code breakers. The whole idea behind public-key cryptography is that some calculations out there are just too hard for a classical computer to compute. A quantum computer is a doorway to code breaking like nothing else concieved of and would probably do a whole lot to change the cryptography landscape.

So, if you’re dealing in code breaking being performed at remote computing centers, a secure channel is kinda vital. And the system outlined by Barz’ new paper looks perfectly secure. Perfectly. How? The computer doesn’t even know what it’s computing. You send information, a computer computes it, and the computer doesn’t learn anything new. It’s weird and the quirks of quantum mechanics make it possible.

In the first step, you send the quantum computer the information to be processed in an encrypted form. Rather than unencrypt that information, the computer performs measurements on it. “In the blind scheme, the qubits are in a ‘blind’ state’ — a state known only to the user,” says Barz. “These qubits are sent to the quantum computer who entangles the qubits according to a standard scheme. The blind computation is also measurement-based: The user tailors measurement instructions to the particular state of each qubit and sends them to the quantum server. Without knowing the initial state of the qubits, these measurement instructions seem to be random; thus the server cannot interpret the instructions. Even if the quantum computer or an eavesdropper tries to read the qubits, they gain no useful information.”

In the end, the computer comes up with meaningful results from encrypted information. But those results are only meaningful to the user. The machine is kept dumb — yet more powerful than any other computer conceived ever.

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• At The Dawn Of The Quantum Internet And True Privacy
• Science Creeps Even Closer To Quantum Computing

Reach this writer at michaelb@motherboard.tv.