with human minds. The Exordium chamber was a device for coupling one or more augmented brains to a coherent quantum system: a bar of magnetically suspended rubidium that was being continually pumped into cycles of quantum coherence and collapse. During each episode of coherence the bar was in a state of superposition with infinite counterparts of itself, and it was at this moment that a neural coupling was attempted. The act itself always forced the bar to collapse down to one macroscopic state, but the collapse was not instantaneous. There was a moment when some of the bar’s coherence bled back into the linked minds, putting them into weak superposition with their own parallel-world counterparts. In that moment, Galiana hoped that there might be some perceptible change in the experienced consciousness state of the participant. Her theories, however, did not say what that change might be. It was, in the end, nothing like she had expected. Galiana had never spoken to Felka about her detailed impressions, but Felka had learned enough to know that her own experience must have been broadly similar. When the experiment began, with the subject or subjects lying on couches in the chamber, their heads swallowed in the gaping white maws of high-resolution neural interfacing trawls, there was a presentiment, like the aura that warned of an impending epileptic seizure. Then there would come a sensation that Felka had never been adequately able to describe outside of the experiment. All she could say was that her thoughts suddenly became plural, as if behind every thought she detected the faint choral echo of others that almost perfectly shadowed it. She did not sense an infinity of such thoughts, but she did sense, faintly, that they receded into something , diverging at the same time. She was, in that moment, in touch with counterparts of herself. Then something far stranger would begin to happen. Impressions would gather and solidify, like the phantoms that take shape after hours of sensory deprivation. She became aware of something stretching ahead of her, into a dimension she could not quite visualise but which nonetheless conveyed a tremendous sense of distance and remoteness. Her mind would grasp at the vague sensory clues and throw some kind of familiar framework over them. She would see a long white corridor stretching towards infinity, washed out in bleak colourless light, and she would know, without being able to articulate quite how she knew, that what she was seeing was a corridor into the future. Numerous pale doors or apertures, each of which opened into some more remote future epoch, lined the corridor. Galiana had never intended to open a door into that corridor, but it seemed that she had made it possible. Felka sensed that the corridor could not be traversed; one could only stand at its end and listen for messages that came down it. And there would be messages. Like the corridor itself they were filtered through her own perceptions. It was impossible to say from how far in the future they had come, or what exactly the future that had sent them looked like. Was it even possible for a particular future to communicate with the past without causing paradoxes? In trying to answer this, Felka had come across the nearly forgotten work of a physicist named Deutsch, a man who had published his thoughts two hundred years before Galiana’s experiments. Deutsch had argued that the way to view time was not as a flowing river but as a series of static snapshots stacked together to form space-times in which the flow of time was only a subjective illusion. Deutsch’s picture explicitly permitted past-directed time travel with the preservation of free will and yet without paradoxes. The catch was that a particular ‘future’ could only communicate with the ‘past’ of another universe. Wherever these messages were coming from, they were not from Galiana’s future. They might be from one that was very close to it, but it would never be one she could reach. No matter. The exact nature of the future was less important than the content of the messages themselves. Felka had never learned the precise content of the messages Galiana had received, but she could guess. They had probably been along the same lines as the ones that came through during Felka’s brief period of participation. They would be instructions for making things, clues or signposts that pointed them in the right direction rather than detailed blueprints. Or there would be edicts or warnings. But by the time those distant transmissions had reached the participants in the Exordium experiments, they had been reduced to half-heard echoes, corrupted like Chinese whispers, intermingled and threaded with dozens of intervening messages. It was as if there was only one open conduit between the present and the future, with a finite bandwidth. Every message sent reduced the potential capacity for future messages. But it was not the actual content of the messages that was alarming, rather the thing that Felka had glimpsed behind them. She had sensed a mind. ‘We touched something,’ she told Remontoire. ‘Or rather something touched us . It reached down the corridor and grazed against our minds, coming through at the same time as we received the instructions.’ ‘And that was the evil thing?’ I can’t think of any other way to describe it. Merely encountering it, merely sharing its thoughts for an instant, drove most of us insane, or left us dead.‘ She looked at their reflections in the glass wall. ’But I survived.‘ ‘You were lucky.’ ‘No. It wasn’t luck. Not entirely. Just that I recognised the thing, so the shock of encountering it wasn’t so absolute. And because it recognised me, too. It withdrew as soon it touched my mind, and concentrated on the others.’ ‘What was it?’ Remontoire asked. ‘If you recognised it…’ ‘I wish I hadn’t. I’ve had to live with that moment of recognition ever since, and it hasn’t been easy.’ ‘So what was it?’ he persisted. ‘I think it was Galiana,’ Felka said. ‘I think it was her mind.’ ‘In the future?’ ‘In a future. Not ours, or at least not precisely.’ Remontoire smiled uneasily. ‘Galiana’s dead. We both know that. How could her mind have spoken to you from the future, even if it was a slightly different one from ours? It can’t have been that different.’ ‘I don’t know. I wonder. And I keep wondering how she became like that.’ ‘And that’s why you left?’ ‘You’d have done the same thing.’ Felka watched the mouse take a wrong turning; not the one she had hoped it would take. ‘You’re angry with me, aren’t you? You feel that I betrayed her.’ ‘Irrespective of what you’ve just told me, yes. I suppose I do.’ His tone had softened. ‘I don’t blame you. But I had to do it, Remontoire. I had to do it once. I don’t regret that at all, even though I wish I hadn’t learned what I did.’ Remontoire whispered, ‘And Clavain… does he know any of this?’ ‘Of course not. It would kill him.’ There was a rap of knuckle against wood. Clavain pushed his way into the space, glancing at the maze before speaking. ‘Talking about me behind my back again,
