“Now picture a state vector which has equal components when written as superpositions of the old set, or the new.”
In two dimensions, that was easy: north-north-east lay at the same angle to north as it did to north-east, and the same angle to east as it did to north-west. In terms of the quantum mechanics Rasmah was describing, it had equal uncertainty in the two complementary variables: it did not obey a precise dynamic law, but nor did it have any precise law-momentum. It split the difference and compromised, in the most symmetrical way.
Rasmah continued. “These are the states Yann wants to scribe, because if you create one on the border, and then arrange to measure the same kind of state coming back, they yield the highest attainable probability of returning with information about the interior.”
“ The highest attainable probability? That’s a resounding declaration of confidence.” Tchicaya had been hoping for something more reliable. He knew what quantum mechanics was like, but if his own Qusp could pluck certainty from the haze, granting him the ability to make unique decisions, surely Yann could work some similar trick with the vastly more powerful abstract machine behind the border?
Rasmah emerged from her visualization. “I know how that sounds, but it really is the best we can hope for. We’re not arranged in the same way as the far side; we’re stuck in a dynamic-law eigenstate, and that’s always going to make things difficult.”
“Yeah.” Tchicaya was grateful for anything that took them beyond the current, artificial view of definite laws spread across the border, but it was sobering to realize how much stranger things became as the price of that advance. “I shouldn’t be disappointed, but I keep underplaying the problems in my head: sweeping all the hard parts off to one side, where I don’t have to look at them. If I faced the difficulties squarely, I’d probably just turn around and run.”
Rasmah regarded him with a mixture of curiosity and affection. “You really do want to go through the border, don’t you?”
“I think so. What about you?”
“Absolutely. That’s what I came here to do.” She hesitated, then added, “For a while, I thought I must have said something too extreme along those lines, and it put you off. But I don’t think that’s it. So what is it about me that you hate so much?”
Tchicaya shook his head vehemently. “Nothing.”
“But we got halfway,” she said, “and then you changed your mind.” This wasn’t a question. Their bodies had ceased the silent exchange of pheromones, and that in itself would have dampened her feelings toward him, but it must have been clear to her that he was the one who’d halted the process.
“You’re very good company,” Tchicaya said. “But you remind me too much of someone else, and I don’t feel right about that. I don’t want to confuse you with her; that wouldn’t be fair on either of us.” He frowned apologetically. “Am I making any sense?”
Rasmah nodded uncertainly. “The other thing I thought was, maybe you and Yann were still, somehow — ”
“No!” Tchicaya was taken aback. “Where did you hear about that?”
She waved a hand dismissively. “Everyone knows.”
“Actually, I think Yann might have forgotten.”
“But there is no one else, in the present? Just this nameless competitor from the past?”
Not exactly a competitor. And not wholly in the past. But Tchicaya didn’t want to explain any further. “That’s right.”
“Okay.” Rasmah stood, and Tchicaya rose beside her. In part, he was glad that she’d cleared the air, though at the same time he felt a surge of resentment, now that he’d been forced to put his reasons into words. He and Mariama would never be together. Why was he letting her shape his decisions at all?
“You’ll support Yann with this?” he asked.
Rasmah smiled. “Definitely. This is our best hope, and I’m sure I can sell it to the others. Suitably uglified.”
The Blue Room was packed from wall to wall; it hadn’t been so crowded since the Left Hand’s first trial run. The room was near the bottom of its module, and it had already been expanded as far as possible in all horizontal directions; several unobliging neighbors above prevented it from growing upward. As relations had deteriorated, some Yielders and Preservationists had swapped cabins in order to be surrounded by fellow partisans, but the Rindler hadn’t yet reached a state where every module was “owned” by one faction or another.
Yann paced the ceiling, ducking away from the tallest heads and shoulders — making his presence visible, but wisely desisting from trying to claim space that he could not defend with solid elbows. Other acorporeals came and went beside him, and no doubt he was conversing with some who weren’t bothering to display icons. Almost everyone who’d been born acorporeal had now donated their bodies to new arrivals, effectively splitting the Yielders into two distinct communities, more so in some ways than the factions themselves. Tchicaya had mixed feelings about this; their generosity had given many more people a chance to participate in events on the ship, in the only manner that would not have been alien to them. But the acorporeals had been willing to change modes in the first place, so why couldn’t the newcomers make do with software bodies? Maybe he had no right to think that way, having accepted the first such sacrifice himself, but the segregation by birth still depressed him, however well acclimatized to their condition the acorporeals were.
The Left Hand had scribed Yann’s state almost an hour before, and they were still waiting hopefully for an echo. Rasmah had ended up translating Yann’s purely algorithmic account into a kind of sophisticated scattering experiment: they were probing the far side by sending in an elaborately structured pulse that was capable of propagating relatively large distances. At least part of this pulse stood a good chance of bouncing off any structure that lay in its path, and coming back to them bearing an imprint of whatever it encountered.
This made it sound cozily familiar: a cross between radar, particle physics, and tomography. But the “distance” the pulse would travel and the “structures” it might or might not interact with were the raw topological details of an unknown superposition of quantum graphs, not properties of such elaborate near-side constructions as vacuum obeying Euclidean geometry, or the kind of matter that would reflect light or microwaves. Even the pulse itself had no real analogies in the ordinary world: it was not a particle, or a gravitational wave, or any kind of electromagnetic signal. It was a new form of dislocation in the pattern of threads from which all those mundane things were woven.
Rasmah cried out, “We’ve got something!”
People started jostling for a better view of the screen, though the image was being made available directly to everyone in the room. Tchicaya stubbornly stood his ground behind Rasmah for several seconds, then he gave up and let the crowd percolate around him, forcing him back.