Algorithmic Assertions - Craig Gidney's Computer Science Blog

The mundane uses of quantum computers

22 Apr 2023

A spark plug pauses, waiting for its moment. A ship turns, adjusting to the current. A card opens, and plays a happy tune.

When I picture computers, what comes to mind is a laptop, or a data center, or maybe a phone. But most of the computers in the world aren't like that. They're hidden away, solving some mundane problem, like telling your microwave how long it takes to pop corn. They're microcontrollers, gluing the right input to the right output via the right function. Cars, boats, planes, ovens, stoves, grills, heaters, washers, dryers, humidifiers, drills, microphones, speakers, guitars, radios, flashlights, pregnancy tests, greeting cards... you name it, there's a version with a microcontroller in it. Because a huge variety of physical tasks can be cheaply solved by translating them into information, manipulating that information with a computer, then translating back. Computation used this way is like duct tape, a tool for linking everything to anything.

Well... almost anything.

To the best of our knowledge, our world is quantum mechanical. Objects have properties (position, charge, mass, spin, everything) that, at a fundamental level, are described using quantum information. Which is different from normal information, and can't be handled by normal computers. In fact, in the entire history of humanity, we've never had a way to reliably store quantum information, or transmit quantum information, or manipulate quantum information. We can glimpse it, poke it, predict it, but we've never truly held it.

Quantum computers fix that. They can store quantum information. Transmit it. Manipulate it. Truly hold it.

Typical summaries of quantum computers evoke the image of a golden chandelier falling on cryptography while solving chemistry problems. But I suspect most quantum computers in the world won't be like that. I think, like normal computers, most quantum computers will be solving "mundane" problems. Attaching one thing to another. Collecting and combining and synthesizing. When I picture a world steeped in quantum computation, what I see is...

Telescopes applying perfect software mirrors to transduced light, because it's cheaper than polishing glass. Quants pumping Bell inequalities out of the financial system. An Einstein-certified /dev/random. Elitzur-Vaidman microscopes counterfactually probing at sensitive samples. First year philosophy students grumbling about having to run loophole free violations of local realism. Unmeasured snapshots of the night sky, stored like tissue samples for unforeseen uses by future generations. A world finally grasping its foundations with ease!

Headlines focus on the computer part of quantum computers. Factoring. Simulating. Whatever. But maybe that will just be a sideshow to the mundane uses of quantum computers. To linking physical systems together, by operating on their quantum information.

PS: Okay, fine, I admit it, "mundane" isn't quite the right word to use here. But you get what I mean!

PPS: This post is highly speculative. Transducers cheaper than polishing glass? That's ridiculously amazingly astoundingly better than we can do today. It's like going from the analytical engine to a modern computer (i.e. going from gears to finfets). Similarly, there might not be any Bell inequalities in the financial system in the first place!

PPPS: I'd like to thank Adam Zalcman and Abe Asfaw and Matt McEwen and Kunal Arya for giving feedback on this post. This post doesn't necessarily represent their opinions, nor the opinions of my employer.