Энди Вейр: Randomize

“I have no complaints,” she said.

“You deserve more. And we are trying to have a baby. We need more room. And for that, we need more money. But still, if we get caught, we could spend a long time in jail—”

“That won’t happen,” she said.

“We haven’t really had a chance to go over how this whole thing works. Can you be certain we won’t be caught?”

“No. But in the absence of evidence, why would anyone suspect us?” She stood from the table and walked to her work area in the tiny living room. Her QuanaTech 707 hummed gently. A cursor blinked on the monitor, awaiting instructions. Two long-term storage units sat connected to the computer.

He craned his neck to watch her. “How hard is this to set up?”

“It’s trivial.” She executed a program on the console. In less than a second, it was done. “That’s it. Every qbit on my storage unit is now entangled with a qbit on the unit you’re taking to the Babylon.”

“You’re sure there’s no way they’ll know the qbits are entangled?”

“It’s physically impossible to know if a qbit is entangled.”

“And how exactly does entanglement let us cheat at keno? This quantum stuff has always confused me.”

Sumi’s parents had done their best. Her absurdly high intelligence had been clear as soon as she learned how to speak. They’d put her in the best schools for gifted children, but she still found them dull. They went deeply into debt to hire tutors just to keep up with how fast she learned.

Soon she would be able to repay them. And build the life she and Prashant wanted. The American dream.

Her parents knew they’d never find her a man as smart as she was. So they focused on “smart enough not to be left behind.” Prashant was brilliant in his own ways. It was a wonderful match.

“Quantum physics is a confusing, nonintuitive thing,” she said. “The rules that govern the universe at the small scale are nothing like what we expect. Suffice it to say that two qbits can be set up such that if you randomize one, the other will become the same value. Once you set them up like this, they are ‘entangled,’ and it doesn’t matter how long you wait before using them or how far apart and unconnected they are at the time. Once they’re entangled, they are guaranteed to be the same when randomized.”

He pointed to the storage units. “So we have two copies of some data?”

“No, don’t think of it as data. Think of these storage units as two piles of dice, but the dice are magically linked, so if you roll a die and roll its counterpart in the other pile, they are guaranteed to have the same result.”

“That doesn’t make any sense.”

“Quantum physics doesn’t make any sense,” she said. “Please don’t try to think about it too much. It can be very distressing.”

“Once they’re entangled, they are guaranteed to be the same when randomized.”

He fidgeted in his chair. “Their storage unit and our storage unit are linked. So they’ll basically be talking to each other across the country. But didn’t you tell me once that quantum entanglement can’t be used for communication?”

She typed on the keyboard and ran a quick self-test. “I did, yes. And it’s true. But we’re using a loophole,” she said. “Two parties can’t communicate via quantum measurements. But they can both observe their respective results and act accordingly.”

“That seems like communication.”

“Not quite. Think of an intersection with stoplights. The stoplights are, functionally, entangled. If I see that one light is green, I know the other light is red.”

“With you so far,” he said.

“Let’s say two cars approach at cross-directions. One driver sees a red light, and the other sees green. The drivers don’t talk to each other or communicate in any way. But they each observe their own lights, which lets them know what to do and what the other driver will do. There was no communication, just an agreement in advance on what red and green lights mean.”

“Okay, so do we have an ‘agreement in advance’ with the casino on what these qbits mean?”

“We do.” She returned to the kitchenette and stirred the kheer. “The Babylon Casino has a keno computer from 2002. Old but reliable—just what casinos like. The manufacturer has excellent documentation online, so I know exactly how the random qbit values will be made into random numbers. Running that operation on our own qbits will give us those same random numbers. That algorithm is the ‘agreement in advance.’”

“Why not entangle all the qbits and not just the long-term storage ones?”

She tasted the kheer. Just right. “Entanglement isn’t permanent. Those magic dice I was talking about? They only work once. After that roll, the spell is broken, and they have nothing to do with each other. If you roll them again, there will be no magic. Just two random numbers. So you get one roll—just one—where you know how the other die will be affected.”

“I see,” Prashant said. “So I assume the normal function of the 707 reuses qbits over and over?”

She served a generous portion of kheer into a bowl. Prashant loved sweet food and always wanted more than he claimed. “Yes. The casino’s keno machine would exhaust our supply of entangled qbits in seconds. So the trick is making them use the long-term memory as RAM and striking right at that moment.”

Prashant pushed his plate aside to make room for the bowl. “How do we do that?”

“The 707 does a coherence self-check once a week. When you install the system, make sure those settings are set to do the self-check this Sunday night at 11:58 p.m.”

She adjusted her sari. American clothes certainly looked nice on Americans, but she preferred traditional clothing. “The self-check takes about five minutes. During that time, if the system is asked to do qbit operations, it uses the qbits in the long-term storage unit because the normal RAM is busy. The Babylon does keno draws every fifteen minutes—there’ll be a draw at precisely midnight on Sunday. That’s when we strike. We only have one attempt, though. The long-term memory has 512 qbits, and a keno draw is twenty eight-bit numbers.”

Prashant raised a finger. “Twenty numbers would only be 160 qbits. So we have, like, three tries before it eats all 512.”

She shook her head. “The numbers each have to be unique, and they’re all in the range of one through eighty. There will be a lot of duplicates drawn. The computer will have to generate random numbers until twenty unique numbers are drawn.”

“Ah.”

“Once the system hits the end of the long-term memory, it’ll loop around, re-randomizing, and reusing the already-measured qbits. We’ll have no information on any of that.” She sighed. “This all would be much simpler if I could modify the computer itself before you install it.”

“We’d never get away with it,” said Prashant. “There’s a factory seal over every entry point, and the OS is on a ROM. Same with the long-term memory module. It was easy enough to sneak it here for you to prepare it, but if we try to open it or modify the hardware, the casino will know when they look over the system.”

She set the kheer in front of him, along with a fresh spoon. “Are you sure they would even notice?”

He nodded. “Pretty sure. I spoke to the Babylon’s IT manager on the phone. He’s… very diligent. He’s extremely thorough.”

“Then this is the only way,” she said. “Fortunately, the long-term memory comes pre-superpositioned. The system will skip the Hadamard operation on first use.”