The Year's Best Science Fiction, Vol. 20

Back in my office, I summoned up a schematic of the device I called the Qusp: the quantum singleton processor. The Qusp would employ all the techniques designed to shield the latest generation of quantum computers from entanglement with their environment, but it would use them to a very different end. A quantum computer was shielded so it could perform a multitude of parallel calculations, without each one spawning a separate history of its own, in which only one answer was accessible. The Qusp would perform just a single calculation at a time, but on its way to the unique result it would be able to pass safely through superpositions that included any number of alternatives, without those alternatives being made real. Cut off from the outside world during each computational Step, it would keep its temporary quantum ambivalence as private and inconsequential as a daydream, never being forced to act out every possibility it dared to entertain.

The Qusp would still need to interact with its environment whenever it gathered data about the world, and that interaction would inevitably split it into different versions. If you attached a camera to the Qusp and pointed it at an ordinary object-a rock, a plant, a bird-that object could hardly be expected to possess a single classical history, and so neither would the combined system of Qusp plus rock, Qusp plus plant, Qusp plus bird.

The Qusp itself, though, would never initiate the split. In a given set of circumstances, it would only ever produce a single response. An AI running on the Qusp could make its decisions as whimsically, or with as much weighty deliberation as it liked, but for each distinct scenario it confronted, in the end it would only make one choice, only follow one course of action.

I closed the file, and the image vanished from my retinas. For all the work I’d put into the design, I’d made no effort to build the thing. I’d been using it as little more than a talisman: whenever I found myself picturing my life as a tranquil dwelling built over a slaughter house, I’d summon up the Qusp as a symbol of hope. It was proof of a possibility, and a possibility was all it took. Nothing in the laws of physics could prevent a small portion of humanity’s descendants from escaping their ancestors’ dissipation.

Yet I’d shied away from any attempt to see that promise fulfilled, firsthand. In part, I’d been afraid of delving too deeply and uncovering a flaw in the Qusp’s design, robbing myself of the one crutch that kept me standing when the horror swept over me. It had also been a matter of guilt: I’d been the one granted happiness, so many times, that it had seemed unconscionable to aspire to that state yet again. I’d knocked so many of my hapless cousins out of the ring, it was time I threw a fight and let the prize go to my opponent instead.

That last excuse was idiotic. The stronger my determination to build the Qusp, the more branches there would be in which it was real. Weakening my resolve was not an act of charity, surrendering the benefits to someone else; it merely impoverished every future version of me, and everyone they touched.

I did have a third excuse. It was time I dealt with that one, too.

I called Francine.

“Are you free for lunch?” I asked. She hesitated; there was always work she could be doing. “To discuss the Cauchy-Riemann equations?” I suggested.

She smiled. It was our code, when the request was a special one. “All right. One o’clock?”

I nodded. “I’ll see you then.”

Francine was 20 minutes late, but that was less of a wait than I was used to. She’d been appointed deputy head of the mathematics department 18 months before, and she still had some teaching duties as well as all the new administrative work. Over the last eight years, I’d had a dozen short-term contracts with various bodies-government departments, corporations, NGOs-before finally ending up as a very lowly member of the physics department at our alma mater. I did envy her the prestige and security of her job, but I’d been happy with most of the work I’d done, even if it had been too scattered between disciplines to contribute to anything like a traditional career path.

I’d bought Francine a plate of cheese-and-salad sandwiches, and she attacked them hungrily as soon as she sat down. I said, “I’ve got ten minutes at the most, haven’t I?”

She covered her mouth with her hand and replied defensively, “It could have waited until tonight, couldn’t it?”

“Sometimes I can’t put things off. I have to act while I still have the courage.”

At this ominous prelude she chewed more slowly. “You did the second stage of Olivia’s experiment this morning, didn’t you?”

“Yeah.” I’d discussed the whole procedure with her before I volunteered.

“So I take it you didn’t lose consciousness, when your neurons became marginally more classical than usual?” She sipped chocolate milk through a straw.

“No. Apparently no one ever loses anything. That’s not official yet, but-”