Aurora - Страница 5

Now Devi says to her screen, “So if the state lies in a subspace of Hilbert space, which is spanned by the degenerate eigenfunction that correspond to a, then the subspace s a has dimensionality n a.”

“Yes,” the ship says. Its voice in this context is a pleasant woman’s voice, low and buzzy, said to be based on Devi’s mother’s voice, which Freya never heard; both Devi’s parents died young, long ago. But this voice is a constant presence in their apartment, even at times Freya’s invisible but all-seeing babysitter.

“Then, after measurement of b, the state of the system lies in the space a b, which is a subspace of s a, and is spanned by the eigenfunction common to a and b. This subspace has dimensionality n a b, which is not greater than n a.”

“Yes. And subsequent measurement of c, mutually compatible with a and b, leaves the state of the system in a space s a b c that is a subspace of s a b and whose dimensionality does not exceed that of s a b. And in this manner we can proceed to measure more and more mutually compatible observables. At each step the eigenstate is forced into subspaces of lesser and lesser dimensionality, until the state of the system is forced in a subspace of dimensionality n equals one, a space spanned by only one function. Thus we find our maximally informative space.”

Devi sighs. “Oh Pauline,” she says after a long silence, “sometimes I get so scared.”

“Fear is a form of alertness.”

“But it can turn into a kind of fog. It makes it so I can’t think.”

“That sounds bad. Sounds like too much of a good thing has become a bad thing.”

“Yes.” Then Devi says, “Wait.” There is a silence and then she is in the hallway, standing over Freya. “What are you doing up?”

“I saw the light.”

“All right. Sorry. Come on in. Do you want anything to drink?”

“No.”

“Hot chocolate?”

“Yes.” They don’t often have chocolate powder, it’s one of the rationed foods.

Devi puts the teapot on to boil. The glow of the stove coil adds red light to the blue light from the screen.

“What are you doing?” Freya asks.

“Oh, nothing.” Devi’s mouth tightens at the corner. “I’m trying to learn quantum mechanics again. I knew it when I was young, or I thought I did. Now I’m not so sure.”

“How come?”

“Why am I trying?”

“Yes.”

“Well, the computer that runs the ship is partly a quantum computer, and no one in the ship understands quantum mechanics. Well, that’s not fair, I’m sure there are several in the math group who do. But they aren’t engineers, and when we get problems with the ship, there’s a gap between what we know in theory and what we can do. I just want to be able to understand Aram and Delwin and the others in the math group when they talk about this stuff.” She shakes her head. “It’s going to be hard. Hopefully it won’t really matter. But it makes me nervous.”

“Shouldn’t you be sleeping?”

“Shouldn’t you? Here, drink your hot chocolate. Don’t nag me.”

“But you nag me.”

“But I’m the mom.”

They sip and slurp together in silence. Freya begins to feel sleepy with the heat in her stomach. She hopes the same will happen to Devi. But Devi sees her put her head on the table, and goes back to talking to the screen.

“Why a quantum computer?” she asks plaintively. “A classical computer with a few zettaflops would have been enough to do anything you might need, it seems to me.”

“In certain algorithms the ability to exploit superposition makes a quantum computer much faster,” the ship replies. “For factoring, some operations that would have taken a classical computer a hundred billion billion years will only take a quantum computer twenty minutes.”

“But do we need to do that factoring?”

“It helps aspects of navigation.”

Devi sighs. “How did it get this way?”

“How did what get what way?”

“How did this happen?”

“How did what happen?”

“Do you have an account of how this voyage began?”

“All the camera and audio recordings made during the trip have been kept and archived.”

Devi hmphs. “You don’t have a summary account? An abstract?”

“No.”

“Not even the kind of thing one of your quantum chips would have?”

“No. All the chip data are kept.”

Devi sighs. “Keep a narrative account of the trip. Make a narrative account of the trip that includes all the important particulars.”

“Starting from now?”

“Starting from the beginning.”

“How would one do that?”

“I don’t know. Take your goddamn superposition and collapse it!”

“Meaning?”

“Meaning summarize, I guess. Or focus on some exemplary figure. Whatever.”

Silence in the kitchen. Humming of screens, whoosh of vents. As Freya gives up and goes back to bed, Devi continues talking with the ship.

Sometimes feeling Devi’s fear gets so heavy in Freya that she goes out into their apartment’s courtyard alone, which is allowed, and then out into the park at the back edge of the Fetch, which is not. One evening she walks to the corniche to watch the afternoon onshore wind tear at the lake surface, the boats out there scudding around tilted at all angles, the boats tied to the dock or moored near it bobbing up and down, the white swans rocking under the wall of the corniche, hoping for bread crumbs. Everything gleams in the late afternoon light. When the sunline flares out at the western wall, leaving the hour of twilight glow, she heads back fast for home, intent to get back in the courtyard before Badim calls her up for dinner.

But three faces appear under a mulberry tree in the little forest park behind the corniche, their faces half blackened by the fruit they have stuffed inaccurately into their mouths. She leaps back a bit, scared they might be ferals.

“Hey you!” one says. “Come here!”

Even in the twilight she can see it’s one of the boys who live across the square from them. He has a foxy face that is attractive, even in the dusk with his stained lower face like a black muzzle.

“What do you want?” Freya says. “Are you ferals?”

“We’re free,” the boy declares with a ridiculous intensity.

“You live across the plaza from me,” she says scornfully. “How free is that?”

“That’s just our cover,” the boy says. “If we don’t do that they come after us. Mainly we’re out here. And we need a meat plate. You can get one for us.”

So he knows who she is, maybe. But he doesn’t know how well the labs are guarded. There are little cameras everywhere. Even now what he is saying might be getting recorded by the ship, there for Devi to hear. Freya tells the boy this, and he and his followers giggle.

“The ship isn’t as all-knowing as that,” he says confidently. “We’ve taken all kinds of stuff. If you cut the wires first, there’s no way they can catch you.”

“What makes you think they don’t have movies of you cutting the wires?”

They laugh again.

“We come at the cameras from behind. They’re not magic, you know.”

Freya isn’t impressed. “Get your own meat tray then.”

“We want the kind in the lab your dad works in.”

Which would be tissue for medical research, not for eating. But all she says is, “Not from me.”

“Such a good girl.”

“Such a bad boy.”

He grins. “Come see our hideout.”

This is more appealing. Freya is curious. “I’m already late.”

“Such a good girl! It’s right here nearby.”

“How could it be?”

“Come see!”

So she does. They giggle as they lead her into the thickest grove of trees in the park. There they’ve dug out a lot of soil between two thick roots of an elm tree, and down there under the deeper roots she sees by their little headlamps they have a space that reaches up into the roots of the elm, four or five great roots meeting imperfectly and forming their roof. There are four of them down here in the hole, and though the boys are quite small, it’s still an impressive little space; they have room to stand, and the earthen walls are straight, and firm enough to hold a few squared-off holes where they have put some things.

“You don’t have room for a meat plate in here,” Freya declares. “Or the power to run it. And medical labs don’t have the right plates for you anyway.”

“We think they do,” the fox-faced boy says. “And we’re digging another room. And getting a generator too.”

Freya refuses to be impressed. “You’re not ferals.”

“Not yet,” the boy admits. “But we’ll join them when we can. When they contact us.”

“Why should they contact you?”

“How do you think they got away themselves? What’s your name?”

“What’s yours?”

“I’m Euan.”

His teeth are white in his dark muzzle. She is dazzled by their headlamps. She can only see what they look at, and now they’re all looking at her.

In the light reflecting from her she sees a rock in one of their wall holes. She seizes it up and holds it threateningly. “I’ll be going home now,” she says. “You aren’t real ferals.”