Quarantine

by Greg Egan

  In the elevator, she says, 'Well, at least now I know that I'm if.'

  'Sorry?'

  'Not the control. Didn't you know? In the mornings, another volunteer has been doing exactly the same thing -counting ions from the same Stern-Gerlach machine. It was a double-blind experiment; one of us had a placebo mod, one of us had the genuine article . . . and only the computers knew who had what - until now. Poor woman. If I'd gone through all of that for nothing, I'm sure I'd be furious.' She laughs. 'Maybe that's what tipped the balance; maybe that's why I'm not the control.' I give her a puzzled look; she smiles in a way that makes it clear that she's joking, but the point of the joke escapes me.

  We alight on the thirtieth floor; Po-kwai says she's too tired to eat. As always, I search the apartment methodically. She sighs. 'Tell me: even assuming that some rival of ASR found out about the project - and managed to get access to the files showing which volunteers had the genuine mod - do you honestly believe they'd go to all the trouble of trying to kidnap one of us?'

  BDI went to all the trouble of kidnapping Laura - for the sake of the very same talent that Po-kwai now possesses. But talk of BDI is forbidden, and Po-kwai knows nothing about Laura; from comments she's made, it's clear that she assumes - or was told -that the mod was designed on a computer, from scratch.

  I shrug. 'I'm sure they'd much rather get their hands on the mod's specifications, but -'

  'Exactly! That would take a thousand times less work than grabbing someone and scanning them -'

  '- but you can be sure that the specifications aren't exactly unprotected, so it would be crazy to make the

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  alternative more tempting. I don't think you should be worried - but I don't think any of the security here is wasted. It's hard to say how far a competitor might go. I have no idea what the commercial value of this thing might be in the long term . . . but just imagine how much you could make in a casino in just one night.'

  She laughs. 'Do you know how many atoms there are in a pair of dice? You're asking me to scale up today's result by roughly twenty-three orders of magnitude.'

  'What about electronic devices? Poker machines?'

  She shakes her head, amused. 'Not in a million years.'

  What about picking locks? Maybe that's out of the question, maybe it took Laura thirty years to learn how to perform feats like that. This prototype mod is unlikely to include anything but the primary skill, leaving out all of Laura's experience in applying it . . . but Po-kwai still deserves to know the truth about the talent she's received - and surely the more she knows, the more she's likely to achieve. How can it be in the Ensemble's best interests to keep her in the dark about the mod's origins, and potential? Maybe I have no right to question that decision . . . but I can't pretend that it makes sense to me.

  She slumps down on the couch, and stretches, then glares at me reproachfully. 'We've just made the scientific breakthrough of the century, and you're talking about poker machines?'

  'I'm sorry; gambling is the first thing that came to mind. I can't say I've given much thought to the nobler applications of telekinesis.'

  She winces. 'Telekinesis!' Then adds, reluctantly, 'Well . . . yeah, I suppose that's exactly what the media will call it - if we ever get to drop all this security bullshit and publish the results.'

  'So what should they call it?'

  'Oh ... neural linear decomposition of the state vector, followed by phase-shifting and preferential reinforcement of selected eigenstates.' She laughs. 'You're right: we'd better think of something catchier, or the whole thing will end up being grossly misreported.'

  Her description is meaningless to me, but -' "Eigenstates"? They're something in quantum mechanics, aren't they?' She nods. 'That's right.'

  For a second, I think she's about to elaborate, but she doesn't; she just yawns. I'm certain, though, that she'd happily explain everything (or as much as she knows); all I'd have to do is ask: how does this mod actually work? What's the mechanism, what's the trick? What's the secret at the heart of the Ensemble? Just what is it that I'm living for?

  She says, 'Nick, I'm pretty tired -'

  Of course. Good night, then. I'll see you tomorrow.'

  'Good night.'

  I sit in the anteroom, dutifully staring at the door in front of me -

  - and catch myself, at three fifty-two, listening to the interminable chirping of synthetic insects . . . mildly, but undeniably, irritated by the sound.

  I try to sink back into stake-out mode; instead, I find myself growing bored, and then uneasy. I run P3's diagnostics, for the twentieth time in a week.

  [no faults detected.]

  What's happening to me?

  It's not a disease - it can't be; all my mods claim they're intact, and even if their self-checking systems had themselves become corrupted, random damage to the neurons involved is hardly likely to have caused exactly the right changes to generate false reports of good health.

  What if the damage isn't random? What if an enemy of ASR is infecting the security staff with nanomachines? But if that's so, then their tactics are absurd. Why would they slowly degrade our mods, giving us days in which to ponder the symptoms? It would make infinitely more sense to build latent puppet mods, which could wait in silence, subjectively undetectable, until they were all activated at some predetermined moment.

  What, then?

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  Karen appears in front of me. I try to banish her, without success. She just stands there; silent, frowning slightly, apparently as much at a loss to explain her presence as I am. I plead with her: 'I'm primed. You know how much you hate to see me primed.' This argument doesn't move her, and no wonder; clearly, I'm not primed - whatever P3 might think.

  What use is a bodyguard whose optimization mods no longer function? Who suffers uncontrollable hallucinations.

  I close my eyes, calm myself. It's simple: tomorrow, I'll go to ASR's occupational health unit, explain the symptoms and let the experts sort it out. Whatever's wrong with me, they'll know how to fix it.

  The prospect of having my skull inventoried by strangers is humiliating, but that's just too bad. I'll have to explain about Karen . . . and the loyalty mod? I'll fudge that, somehow; they don't have to know all the details. What matters in the end is serving the Ensemble, and I can't do that if I'm falling apart.

  I open my eyes. Karen hasn't moved.

  I say, 'Well, if you're going to hang around, what do you want to do? Stand guard with me?'

  'No.'

  'What, then?'

  She reaches down and touches my cheek. I take hold of her other hand - more starkly aware than usual of the mod contriving to restrain me from putting my fingers through her non-existent flesh. I slide my thumb across the back of her hand, pausing on the familiar shape of each knuckle.

  Ί do miss you. You know that.'

  She doesn't reply.

  There has to be a way to get her back. Maybe I can learn to keep her from blaspheming against the Ensemble; learn to control her more tightly - without entirely destroying the illusion of her autonomy. Or . . . maybe I can have her modified, constrained -give her a 'loyalty mod' of her own. Why didn't I think of that before? Mods can be adapted. Anything is possible.

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  I look up and meet her eyes. The calm, untroubled love that she engenders seems to waver slightly, like an image reflected in a mirror-smooth lake, subtly distorted by some hidden current in the depths. A chill of anticipation hits me; I feel no forbidden emotion - no grief, no guilt, no anger. But the mere thought that this mod might fail, too - that everything it rules out, everything from which it shields me, might become possible again - leaves me momentarily light-headed with fear.

  I let go of her hand, and she -

  She fills the room.

  She spreads, smears, replicates, like some holographic paintbox gimmick gone wild. I leap to my feet, knocking over the chair, as the space around me grows thick with ever more copies of her illusory body. I shie
ld my face, but I can still feel her brushing against me on all sides. A droning rises up from all directions, garbled and incoherent, but unmistakably her voice.

  I cry out -

  - and she vanishes, completely.

  In the abrupt silence, memory echoes the last moments of sound - and I realize that my own cry almost masked another voice.

  Po-kwai.

  I enter the apartment, weapon drawn. Advertising signs in the mock windows' cityscape - holograms of holograms - light the way. P2 claims it can't localize the shout - that the data is ambiguous - but I suffer the bizarre conviction that / know it came from the bedroom. Obvious first call, anyway. The door is ajar; I kick it wide open. Po-kwai, standing in a far corner of the room, spins round, startled. I freeze for a moment, trying to read her face, hoping for a signal - a flick of the eyes giving away the intruder's location - but she merely looks alarmed, and baffled, by my presence. I step into the room.

  'You're alone?'

  She nods, and then manages a nervous, angry laugh. 'What are you doing? Trying to frighten me to death?' 'Didn't you call out?'

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  She scowls, and seems about to deny this vehemently -but then she catches herself, and looks about the room, as :f suddenly unable to account for her surroundings. Ί :hink ... I must have had a nightmare. Maybe I yelled in my sleep. I don't know.' She puts a hand to her mouth. I'm sorry. You must have thought -'

  It's all right.' I holster the gun; it's clearly making her uneasy.

  'Nick, I'm sorry.'

  'Don't be; there's no harm done. I'm sorry that I startled you.' With the pressure off, I have time to observe: I'm primed again, P3 is functioning normally. Which is good news - but as inexplicable as everything else.

  She shakes her head, still apologetic. Ί don't even remember getting out of bed.' 'Do you sleepwalk?'

  'Never. Maybe I had such a shock, in the dream, that I leapt out of bed, shouting. . . but only really woke once I was on my feet. I honestly can't remember.'

  I glance at the bed; it doesn't look much like she 'leapt' out of it. I don't argue, though; if she sleepwalks, that's worth knowing, but there's nothing to be gained by embarrassing her if she doesn't want to admit it.

  'Yeah. Well - sorry about the intrusion. I'd better let you get some sleep.'

  She nods.

  Back in the anteroom, I can hear her moving restlessly about the apartment. I sit and wait for P3 to fail, for Karen to appear and go berserk again, but nothing happens. Hoping that the glitch has miraculously vanished is just wishful thinking; the truth is, for all I know it might recur at any time - and I'd rather confront the doctors as a babbling wreck, smothered by the ghost of my dead wife, than have them probe me superficially and offer the same bland reassurances as the mods themselves: no faults

  detected.

  Ten minutes later, Po-kwai emerges. 'Would you mind - if I sat out here for a while?'

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  Of course not.'

  'It's too late to go back to sleep, it's too early to eat breakfast; I don't know what to do with myself.'

  She brings out a second chair and sits, bent forward, still visibly agitated.

  I say, 'Maybe I should get you a doctor.'

  'Don't be silly.'

  'Tranquillizers -'

  Wo/ I'm fine. I'm just not used to armed guards bursting into my room waving guns, that's all.' I start to apologize, but she silences me. 'I'm not complaining. I'm glad you're doing your job. It's just that I'm - finally -coming to terms with the fact that your job is necessary. They were perfectly frank at the interview, they explained precisely what the security arrangements would be; it's entirely my fault if I shrugged it off as paranoia.'

  'But what's changed your mind? Me, overreacting? I'm sorry; I should have handled things more calmly. But you have no reason to feel besieged; the chances are that nobody outside of ASR even knows that the project exists.'

  'Yeah. It's just. . . now that I know I'm not the control, now that the thing is actually working . . . and if I think about how much R&D investment I now . . . embody . . .' She shakes her head. Ί got into this for the physics -1 thought I'd be more of a collaborator, not just a guinea pig. Leung treats me like an idiot. Tse is an idiot. Lui treats me like some kind of fragile minor deity; I don't know what his problem is. And nothing's going to be published for years. This ought to be on the front screen of Nature tomorrow: role of the observer in qm confirmed - and modified!'

  'Role of the - ?'

  'Observer. In quantum mechanics.' She looks at me as if I'd said something blatantly disingenuous, and then it dawns on her: 'They haven't even told you, have they?' She makes a noise of disgust and disbelief. 'Oh, yeah. Nick's just a bodyguard, just a minor flunkey - why should anyone bother to let him know what he's risking his life for?'

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  I shake my head. 'I'm not risking my life. And if I don't need to know, maybe it's better -' 'Oh, crap!' Ί mean it.'

  P3 keeps me calm - but I can observe, dispassionately, a kind of spiritual vertigo building up inside me. / don't want to hear the Ensemble's secrets; I don't want to hear the final, worldly, explanation; I don't want to pierce the veil.

  Primed, though, it's a remote and insubstantial panic; it doesn't belong to me. Primed, I'm content with a literal-minded obedience - and I've had no instructions to maintain my reverential ignorance. The quasi-mystical trappings with which I've embellished the Ensemble don't come from the loyalty mod itself, and the zombie boy scout has no need for them.

  In any case, I have no choice. Po-kwai says firmly, 'Just listen. The technicalities are messy, but the essentials are simple. Have you heard of the quantum measurement problem?'

  'No.'

  'What about Schrodinger's Cat?' 'Of course.'

  'Well, Schrodinger's Cat is an illustration of the quantum measurement problem. Quantum mechanics describes microscopic systems - subatomic particles, atoms, molecules - with a mathematical formalism called the wave function. From the wave function, you can predict the probabilities of getting various results when you make measurements on the system.

  'For example: suppose you have a silver ion, prepared in a certain way, passing through a magnetic field and then striking a fluorescent screen. Quantum mechanics predicts that half the time, you'll see a flash on the screen as if the ion veered upwards in the magnetic field, and half the time you'll see a flash as if it veered downwards. That can be explained by the ion having a spin, which makes it interact with the field; it gets pushed either up or down, depending on the way its spin is pointing,

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  relative to the field. So by observing the flashes on the screen, you're measuring the ion's spin.

  Or suppose you have a radioactive atom with a half-life of one hour. Point a particle detector at it which is wired up to a device which breaks a bottle of poison gas and kills a cat, if the atom decays. Enclose the whole set-up in an opaque box; wait an hour, and then look inside. If you do the experiment again and again -with a fresh atom and a fresh cat each time - quantum mechanics predicts that half the time, you'll find the cat dead, and half the time you'll find it alive. By seeing which it is, you'll have measured whether or not the atom has decayed.'

  'So . . . where's the problem?'

  'The problem is: before you make a measurement in either of these cases, the wave function doesn't tell you what the outcome is going to be; it just tells you that there's a fifty-fifty chance either way. But once you've made the measurement, a second measurement on the same system will always give the same result; if the cat was dead the first time you looked, it will still be dead if you look again. In terms of the wave function, the act of making the measurement has, somehow, changed it from a mixture of two waves, representing the two possibilities, to a "pure" wave - called an eigenstate - representing just one. That's what's called "the collapse of the wave function".

  'But why should a measurement be special? Why should it collapse the wave function? Why should some measuring d
evice - itself made up of individual atoms, all of which are presumably obeying the very same quantum mechanical laws as the system being measured - cause a mixture of possibilities to collapse into one? If you treat the measuring device as just another part of the system, Schrodinger's equation predicts that the device itself should end up in a mixture of states - and so should anything that interacts with it. The bottle of poison gas should end up described by a wave function which is a mixture of a broken state and an unbroken state - and the cat should end up as a mixture of a dead state and a living

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  state. So why do we always see the cat in one pure state, dead or alive?'

  'Maybe the whole theory's simply wrong.'

  'No, it's not as easy as that. Quantum mechanics is the most successful scientific theory ever - if you take for granted the collapse of the wave function. If the entire theory was wrong, there'd be no such thing as microelectronics, lasers, Optronics, nanomachines, ninety per cent of the chemicals and pharmaceuticals industry . . . Quantum mechanics meets every experimental test that anyone's ever performed - so long as you assume that there's this special process called "measurement" - which obeys totally different laws from the ones that operate the rest of the time.

  'So, the aim of studying the quantum measurement problem is to pin down exactly what a "measurement" is, and why it's special. When does the wave function collapse? When the particle detector is triggered? When the bottle is broken? When the cat dies? When someone looks in the box?

  'One view is to shrug and say: quantum mechanics correctly predicts the probabilities of the final, visible results - and what more can you ask for? Atoms are only revealed through their effects on scientific instruments, so if quantum mechanics lets you calculate, precisely, what percentage of the time you'll get various instrument readings - or positions of flashes of light, or cat mortalities - you have a complete theory.

  'Other people have tried to show that the wave function ought to collapse when the system reaches a critical size -or a critical energy, or a critical degree of complexity -and that any useful measuring device would be well over the threshold. People have invoked thermodynamic effects, quantum gravity, hypothetical nonlinearities in the equations ... all kinds of things. None of which has ever quite explained the facts.