"What should they be made out of?"

"Two different substances." She handed him her datapad. Its screen showed two chemical formulas. "Can you synthesize them?"

He squinted at the display. "Sure-nothing difficult about them. You're certain they're solid at room temperature?"

Heather's eyes went wide. She'd read all the papers on the chemicals ten years ago, when they'd first been synthesized, but hadn't really thought about them much since. "I have no idea."

"This one will be," he said, pointing at the top formula. "That one . . . well, we'll see. Are these formulas from the alien messages?"

Heather nodded. "From the first eleven pages. People have synthesized these compounds before, of course, but no one ever figured out what they were for."

Komensky made an impressed face. "Interesting."

She nodded. "I want the zero bits to be made of one of these substances, and the one bits made of the other."

"You want one painted onto the other?"

"Painted? No, no, I thought you'd build them out of the two materials."

Komensky frowned again. "I don't know. That formula looks to me like it'll be a liquid, but it might dry into a hard crust. See those oxygens and hydrogens? They could evaporate out as water, leaving a solid behind."

"Oh. Well, then, yes-and that answers the big question I'd been unable to solve."

"Which is?"

"Well, I was trying to figure out which substance represented the one bits and which one represented the zero bits. The ones are 'on' bits, so the paint must represent the ones; it must go on the-the-"

" 'The substrate' we call it in materials science."

"The substrate, yes." A pause. "How hard would it be to do that?"

"Well, again, it comes back to how big you want the tiles."

"I don't know. They're not all the same size, but even the biggest shouldn't be more than a few centimeters-I want to fit them together."

"Fit them?"

"Yeah, you know-lay them side by side. See, if you arrange each group of fifty-nine tiles properly, they form a perfect square-there's only one layout that'll do that."

"Why not just build the big panels instead of the individual tiles?"

"I don't know-the tiling itself might be significant. I don't want to make any a.s.sumptions."

"Like the 'on' bits go 'on' the substrate?" His tone was one of gentle teasing.

Heather shrugged. "It's as good a guess as any."

He nodded, conceding the point. "So twenty-eight hundred tiles make up how many bigger squares?"

"Forty-eight."

"And what are you going to do with the resulting squares?"

"a.s.semble them into cubes-and then a.s.semble those cubes into an unfolded tesseract."

"Really? Wow."

"Yes."

"Well, do you want the finished thing big enough so that you can crawl inside of one of the cubes?"

"No, that won't be-"

She stopped dead.

No scale specified. Nowhere in any of the messages did there seem to be anything suggesting a size for the construct.

Make it any size, the aliens seemed to be saying.

Make it your your size. size.

"Yes, yes-that would be perfect! Big enough to go inside."

"Well, okay-sure. We can build the substrate tiles, no problem. How thick should they be?"

"I don't know. As thin as possible, I guess."

"I can make them one molecule thick if that's what you want."

"Oh, not that that thin. They'll have to hold together. A millimeter or two, maybe." thin. They'll have to hold together. A millimeter or two, maybe."

"No problem. We've got a machine all set up to turn out plastic building panels for the School of Architecture; I could modify it easily enough to turn out the tiles you need. Do you want them to have smooth edges or would you like a tongue-and-groove arrangement, so they can snap together?"

"You mean so they form a big solid piece?"

Komensky nodded.

"That would be great."

"What about the painting on of the other chemical?"

"I figured I'd have to do that by hand," said Heather.

"Well, you could, could, but we've got programmable microsprayers that can do it for you, a.s.suming the substance has a low enough viscosity. We use the sprayers to paint patterns onto the panels we make for the architecture students-you know, little outlines of bricks, or little dots to represent rivets, stuff like that." but we've got programmable microsprayers that can do it for you, a.s.suming the substance has a low enough viscosity. We use the sprayers to paint patterns onto the panels we make for the architecture students-you know, little outlines of bricks, or little dots to represent rivets, stuff like that."

"That'd be perfect. How soon can you do it?"

"Well, during the school year, we're usually pretty backed up. But in summer, we've got lots of free time. We can get at it right away. We've still got a couple of grad students hanging around; I'll have one of them look into manufacturing those chemicals. As I say, at first glance they look simple enough, but we won't know for sure until we actually try to synthesize them." A pause. "Who's going to pay for this?"

"What'll it cost?" asked Heather.

"Oh, not much. Robots are so cheap these days, we no longer amortize their cost over manufacturing runs like we used to. Maybe five hundred dollars for the material."

Heather nodded. She'd find some way to explain it to her department head later, once he got back from vacation. "That's fine. Charge it to Psych; I'll sign the requisition."

"I'll e-mail you the paperwork."

"Terrific. Thank you. Thank you very very much." much."

"You're very welcome." He smiled and held her with his eyes.

14.

There was a bleep at Kyle's office door. He pushed the b.u.t.ton that caused it to slide open. A middle-aged Asian woman in an expensive-looking gray suit was standing in the curving corridor, the atrium with its tumbling tapestries visible behind her.

"Dr. Graves?" she said.

"Yes?"

"Brian Kyle Graves?"

"That's right."

"I wish to talk to you, please."

Kyle rose and motioned for her to come in.

"My name is Chikamatsu. I wish to speak to you about your research."

Kyle indicated another chair. Chikamatsu took it, and Kyle sat back down.

"I understand you have had some success with quantum computing."

"Not as much as I'd like. I ended up with egg on my face a couple of weeks ago."

"So I heard." Kyle's eyebrows went up. "I represent a consortium that would like to contract for your services." She p.r.o.nounced consortium "consorsheeum."

"Oh?"

"Yes. We believe you are close to a breakthrough."

"Not judging by my current results."

"A minor problem, I am sure. You are trying to use Dembinski fields to inhibit decoherence, are you not? They are notoriously tricky."

Kyle's eyebrows climbed again. "That they are."

"We have monitored your progress with interest. You are doubtless very close to a solution. And if you do find a solution, my consortium may be prepared to invest heavily in your procedure, a.s.suming, of course, that you can convince me that your system works."

"Well, it will either work or it won't."

Chikamatsu nodded. "Doubtless so, but we will need to be sure. You would have to factor a number for us. And, of course, I would have to provide the number-just to be sure it is not some trick, you understand."

Kyle narrowed his eyes. "What exactly is the nature of your consortium?" He preferred the hard-T p.r.o.nunciation himself, but matched Chikamatsu's usage.

"We are an international group," she said. "Venture capitalists." She had a small cylindrical leather purse, with metal end caps. She opened it, removed a memory wafer, and proffered it to Kyle. "The number we wish factored is on this wafer."

Kyle took the wafer but didn't look at it. "How many digits in the number?"

"Five hundred and twelve."

"Even if I can work out the current bugs with my system, it'll be a while before I can do that."

"Why?"

"Well, for two reasons. The first is a practical one. Democritus-that's the name of our prototype-is hardware constrained to factor numbers exactly three hundred digits long, no more, no less. Even if I could get it to work properly, I can't do numbers of any other length-the quantum registers have to be carefully jiggered for the precise total number of digits."

Chikamatsu looked disappointed. "And the other reason?"

Kyle raised his eyebrows. "The other reason, Ms. Chikamatsu, is that I'm not a criminal."

"I-I beg your pardon?"

He flipped the memory wafer over and over in his hand as he spoke. "There's only one practical application for factoring large numbers-and that's cracking encryption schemes. I don't know whose data you're trying to access, but I'm no hacker. Find yourself another boy."

"It is just a randomly generated number," said Chikamatsu.

"Oh, come on. If you'd asked me to factor a number whose length fell within a range-between five hundred and six hundred digits, say-and if you hadn't shown up with your number all picked out, I might have believed you. But it's pretty d.a.m.ned obvious you're trying to crack somebody's code."

Kyle went to hand back the wafer, but now its other side was facing up. As he looked down at it, he saw its label, with a single word written on it in pen: Huneker.

"Huneker!" said Kyle. "Not Joshua Huneker?"

Chikamatsu reached out to retrieve the wafer. "Who?" she said, sounding innocent but looking visibly fl.u.s.tered.

Kyle clenched his fist, covering the wafer. "What the h.e.l.l are you playing at?" he said. "What's this got to do with Huneker?"

Chikamatsu lowered her gaze. "I did not think you would know the name."

"My wife was involved with him when she and I met."

Chikamatsu's almond-shaped eyes went wide. "Really?"