trentmkelly/LessWrong-43k huggingface dataset:
On Being Decoherent
by Eliezer Yudkowsky — 2008-04-27T04:59:02.000Z

Previously in series: The So-Called Heisenberg Uncertainty Principle

"A human researcher only sees a particle in one place at one time." At least that's what everyone goes around repeating to themselves. Personally, I'd say that when a human researcher looks at a quantum computer, they quite clearly see particles not behaving like they're in one place at a time. In fact, you have never in your life seen a particle "in one place at a time" because they aren't.

Nonetheless, when you construct a big measuring instrument that is sensitive to a particle's location—say, the measuring instrument's behavior depends on whether a particle is to the left or right of some dividing line—then you, the human researcher, see the screen flashing "LEFT", or "RIGHT", but not a mixture like "LIGFT".

As you might have guessed from reading about decoherence and Heisenberg, this is because we ourselves are governed by the laws of quantum mechanics and subject to decoherence.

The standpoint of the Feynman path integral suggests viewing the evolution of a quantum system as a sum over histories, an integral over ways the system "could" behave—though the quantum evolution of each history still depends on things like the second derivative of that component of the amplitude distribution; it's not a sum over classical histories. And "could" does not mean possibility in the logical sense; all the amplitude flows are real events...

Nonetheless, a human being can try to grasp a quantum system by imagining all the ways that something could happen, and then adding up all the little arrows that flow to identical outcomes. That gets you something of the flavor of the real quantum physics, of amplitude flows between volumes of configuration space.

Now apply this mode of visualization to a sensor measuring an atom—say, a sensor measuring whether an atom is to the left or right of a dividing line.

Which is to say: The sensor and the atom undergo some physical interaction in which the final state of the sensor depends heavily on whether the atom is to the left or right of a dividing line. (I am reusing some previous diagrams, so this is not an exact depiction; but you should be able to use your own imagination at this point.)

You may recognize this as the entangling interaction described in "Decoherence". A quantum system that starts ...
Where Experience Confuses Physicists
by Eliezer Yudkowsky — 2008-04-26T05:05:01.000Z

Continuation of: Where Physics Meets Experience

When we last met our heroes, the Ebborians, they were discussing the known phenomenon in which the entire planet of Ebbore and all its people splits down its fourth-dimensional thickness into two sheets, just like an individual Ebborian brain-sheet splitting along its third dimension.

And Po'mi has just asked:

"Why should the subjective probability of finding ourselves in a side of the split world, be exactly proportional to the square of the thickness of that side?"

When the initial hubbub quiets down, the respected Nharglane of Ebbore asks: "Po'mi, what is it exactly that you found?"

"Using instruments of the type we are all familiar with," Po'mi explains, "I determined when a splitting of the world was about to take place, and in what proportions the world would split. I found that I could not predict exactly which world I would find myself in—"

"Of course not," interrupts De'da, "you found yourself in both worlds, every time -"

"—but I could predict probabilistically which world I would find myself in. Out of all the times the world was about to split 2:1, into a side of two-thirds width and a side of one-third width, I found myself on the thicker side around 4 times out of 5, and on the thinner side around 1 time out of 5. When the world was about to split 3:1, I found myself on the thicker side 9 times out of 10, and on the thinner side 1 time out of 10."

"Are you very sure of this?" asks Nharglane. "How much data did you gather?"

Po'mi offers an overwhelming mountain of experimental evidence.

"I guess that settles that," mutters Nharglane.

"So you see," Po'mi says, "you were right after all, Yu'el, not to eliminate 'subjective probability' from your worldview. For if we do not have a 4/5 subjective anticipation of continuing into the thicker side of a 2:1 split, then how could we even describe this rule?"

"A good question," says De'da. "There ought to be some way of phrasing your discovery, which eliminates this problematic concept of 'subjective continuation'..."

The inimitable Ha'ro speaks up: "You might say that we find ourselves in a world in which the remembered splits obey the squared-thickness rule, to within the limits of statistical expectation."

De'da smiles. "Yes, excellent! That describes the evidence in terms of recorded exp...
Criminal retribution
by KatjaGrace — 2008-04-25T15:39:00.000Z

The US houses the highest proportion of its people in prison of any country, as Adam Liptak discusses thought provokingly. As expected, this appears to reduce the crime rates.

How much suffering should the guilty endure for a given reduction in suffering of the innocent? I think a 1:1 ratio maximum- that is, it doesn’t matter who suffers. Suffering should be minimised, even if that means the innocent suffer instead of the guilty. Punishment should only be to prevent greater suffering.

***

Liptak also draws attention to the relationship between more democratic appointment of judges in the US and harsher punishment, as people demand fierce retribution. I suspect demand for escalating punishment is a result of fear and angry desire for revenge, rather than widespread consideration of mechanism design for minimising harm, or anything mildly reasoned. I don’t think society should be allowed to inflict harm on its members arbitrarily like this. Should judge appointment be less democratic then?

Perhaps, but this decision can (and should?) only be reached through other democratic decision making. This is the same problem as arises everywhere. The public, through democracy, interferes with people where it has no right to, but the extent to which citizens should be able to interfere with one another through democracy hasn’t been agreed, and so must rely on democratic negotiation.
Where Physics Meets Experience
by Eliezer Yudkowsky — 2008-04-25T04:58:11.000Z

Followup to: Decoherence, Where Philosophy Meets Science

Once upon a time, there was an alien species, whose planet hovered in the void of a universe with laws almost like our own. They would have been alien to us, but of course they did not think of themselves as alien. They communicated via rapid flashes of light, rather than sound. We'll call them the Ebborians.

Ebborians reproduce by fission, an adult dividing into two new individuals. They share genetic material, but not through sexual recombination; Ebborian adults swap genetic material with each other. They have two eyes, four legs, and two hands, letting a fissioned Ebborian survive long enough to regrow.

Human DNA is built in a double helix; unzipping the helix a little at a time produces two stretches of single strands of DNA. Each single strand attracts complementary bases, producing a new double strand. At the end of the operation, a DNA double helix has turned into two double helices. Hence earthly life.

Ebborians fission their brains, as well as their bodies, by a process something like how human DNA divides.

Imagine an Ebborian brain as a flat sheet of paper, computing in a way that is more electrical than chemical—charges flowing down conductive pathways.

When it's time for an Ebborian to fission, the brain-paper splits down its thickness into two sheets of paper. Each new sheet is capable of conducting electricity on its own. Indeed, the Ebborian(s) stays conscious throughout the whole fissioning process. Over time, the brain-paper grows thick enough to fission again.

Electricity flows through Ebborian brains faster than human neurons fire. But the Ebborian brain is constrained by its two-dimensionality. An Ebborian brain-paper must split down its thickness while retaining the integrity of its program. Ebborian evolution took the cheap way out: the brain-paper computes in a purely two-dimensional way. The Ebborians have much faster neuron-equivalents, but they are far less interconnected.

On the whole, Ebborians think faster than humans and remember less. They are less susceptible to habit; they recompute what we would cache. They would be incredulous at the idea that a human neuron might be connected to a thousand neighbors, and equally incredulous at the idea that our axons and dendrit...
Which Basis Is More Fundamental?
by Eliezer Yudkowsky — 2008-04-24T04:17:47.000Z

Followup to: The So-Called Heisenberg Uncertainty Principle

For decades, quantum physics was vehemently asserted to be nothing but a convenience of calculation. The equations were not to be interpreted as describing reality, though they made good predictions for reasons that it was mere philosophy to question. This being the case, any quantity you could define seemed as fundamentally real as any other quantity, which is to say, not real at all.

Physicists have invented, for convenience of calculation, something called a momentum basis of quantum mechanics. Instead of having a complex amplitude distribution over the positions of particles, you had a complex amplitude distribution over their momenta.

The "momentum basis" contains all the information that is in the "position basis", and the "position basis" contains all the information that is in the "momentum basis". Physicists use the word "basis" for both, suggesting that they are on the same footing: that positions are no better than momenta, or vice versa.

But, in my humble opinion, the two representations are not on an equal footing when it comes to being "fundamental".

Physics in the position basis can be computed locally. To determine the instantaneous change of amplitude at a configuration, you only need to look at its infinitesimal neighborhood.

The momentum basis cannot be computed locally. Quantum evolution depends on potential energy. Potential energy depends on how far apart things are from each other, like how high an apple is off the ground. To figure out how far apart things are from each other, you have to look at the entire momentum basis to recover the positions.

The "momentum basis" is in some ways like a description of the chessboard in which you have quantities like "the queen's position minus the rook's position" and "the queen's position plus the rook's position". You can get back a description of the entire chessboard—but the rules of the game are much harder to phrase. Each rule has to take into account many more facts, and there's no longer an elegant local structure to the board.

Now the above analogy is not really fair, because the momentum basis is not that inelegant. The momentum basis is the Fourier transform of the position basis, and symmetrically, the position basis is the Fourier transform of the momentum basis. ...
The So-Called Heisenberg Uncertainty Principle
by Eliezer Yudkowsky — 2008-04-23T06:36:26.000Z

Previously in series: Decoherence

As touched upon earlier, Heisenberg's "Uncertainty Principle" is horribly misnamed.

Amplitude distributions in configuration space evolve over time. When you specify an amplitude distribution over joint positions, you are also necessarily specifying how the distribution will evolve. If there are blobs of position, you know where the blobs are going.

In classical physics, where a particle is, is a separate fact from how fast it is going. In quantum physics this is not true. If you perfectly know the amplitude distribution on position, you necessarily know the evolution of any blobs of position over time.

So there is a theorem which should have been called the Heisenberg Certainty Principle, or the Heisenberg Necessary Determination Principle; but what does this theorem actually say?

At left is an image I previously used to illustrate a possible amplitude distribution over positions of a 1-dimensional particle.

Suppose that, instead, the amplitude distribution is actually a perfect helix. (I.e., the amplitude at each point has a constant modulus, but the complex phase changes linearly with the position.) And neglect the effect of potential energy on the system evolution; i.e., this is a particle out in intergalactic space, so it's not near any gravity wells or charged particles.

If you started with an amplitude distribution that looked like a perfect spiral helix, the laws of quantum evolution would make the helix seem to rotate / move forward at a constant rate. Like a corkscrew turning at a constant rate.

This is what a physicist views as a single particular momentum.

And you'll note that a "single particular momentum" corresponds to an amplitude distribution that is fully spread out—there's no bulges in any particular position.

Let me emphasize that I have not just described a real situation you could find a particle in.

The physicist's notion of "a single particular momentum" is a mathematical tool for analyzing quantum amplitude distributions.

The evolution of the amplitude distribution involves things like taking the second derivative in space and multiplying by i to get (one component of) the first derivative in time. Which turns out to give rise to a wave mechanics—blobs that can propagate themselves across space, over time.

One of the basic tools in wave mechanics is taking ap...
Decoherence
by Eliezer Yudkowsky — 2008-04-22T06:41:04.000Z

Previously in series: Feynman Paths

To understand the quantum process called "decoherence", we first need to look at how the special case of quantum independence can be destroyed—how the evolution of a quantum system can produce entanglement where there was formerly independence.

Quantum independence, as you'll recall, is a special case of amplitude distributions that approximately factorize—amplitude distributions that can be treated as a product of sub-distributions over subspaces.

Reluctant tourists visiting quantum universes think as if the absence of a rectangular plaid pattern is some kind of special ghostly link between particles. Hence the unfortunate term, "quantum entanglement".

The evolution of a quantum system can produce entanglement where there was formerly independence—turn a rectangular plaid pattern into something else. Quantum independence, being a special case, is easily lost.

Let's pretend for a moment that we're looking at a classical system, which will make it easier to see what kind of physical process leads to entanglement.

At right is a system in which a positively charged light thingy is on a track, far above a negatively charged heavy thingy on a track.

At the beginning, the two thingies are far enough apart that they're not significantly interacting.

But then we lower the top track, bringing the two thingies into the range where they can easily attract each other. (Opposite charges attract.)

So the light thingy on top rolls toward the heavy thingy on the bottom. (And the heavy thingy on the bottom rolls a little toward the top thingy, just like an apple attracts the Earth as it falls.)

Now switch to the Feynman path integral view. That is, imagine the evolution of a quantum system as a sum over all the paths through configuration space the initial conditions could take.

Suppose the bottom heavy thingy and the top thingy started out in a state of quantum independence, so that we can view the amplitude distribution over the whole system as the product of a "bottom thingy distribution" and a "top thingy distribution".

The bottom thingy distribution starts with bulges in three places—which, in the Feynman path view, we might think of as three possible starting configurations from which amplitude will flow.

When we lower the top track, the light thingy on top is attracted toward the hea...
Three Dialogues on Identity
by Eliezer Yudkowsky — 2008-04-21T06:13:54.000Z

Followup to: Identity Isn't In Specific Atoms

It is widely said that some primitive tribe or other once feared that photographs could steal their souls.

Ha ha! How embarrassing. Silly tribespeople.

I shall now present three imaginary conversations along such lines—the common theme being frustration.

The first conversation:

Foolishly leaving the world of air-conditioning, you traveled to the Godforsaken Outback, and of course, got lost in the woods. A more primitive tribe than yours, the Hu'wha, saved your butt. Although the Hu'wha have told you how to reach an outpost of Internet access, that is, civilization, you've stayed with them a while longer; you've become their friend, and they yours.

One custom of the Hu'wha does seem strange to you, coming as you do from a more civilized culture: They don't hold with lies, even small ones. They consider a lie as an infringement upon the soul of the listener. They have a saying, "It is better to die than to be lied to." Though this is a very strange and primitive custom, you have come to respect it.

Late one night, the shaman calls you to his tent. His face is grave. "I have heard the most disturbing news," he says, "from the Tribe That Lives Across The Water. They say that your people, the People of the Net, have a most terrible custom: they paint images of others, and thereby steal their souls, for a person cannot be in two places at once. It is even said that you have weapons called 'cameras', for doing this automatically; and that the cameras of your folk can be very small, or disguised as other things."

"Um," you say, "I think you may be laboring under certain basic misconceptions. Cameras are not weapons; they make images, but they don't steal souls."

The grey-bearded shaman smiles, and shakes his head. "Young fellow, I am the shaman of the Hu'wha, and I hold the tradition passed down from my father through many generations; the true and original wisdom granted by the gods to the first shaman. I think I know what steals a soul and what does not, young fellow! Even to you it should be obvious."

And you think: Foolish mortal, how little you understand the power of Science. But this is beyond the conception of this man who thinks himself above you, and so you say nothing.

"I understand," the shaman says, "that your people m...
Zombies: The Movie
by Eliezer Yudkowsky — 2008-04-20T05:53:14.000Z

FADE IN around a serious-looking group of uniformed military officers. At the head of the table, a senior, heavy-set man, GENERAL FRED, speaks.

GENERAL FRED: The reports are confirmed. New York has been overrun... by zombies.

COLONEL TODD: Again? But we just had a zombie invasion 28 days ago!

GENERAL FRED: These zombies... are different. They're... philosophical zombies.

CAPTAIN MUDD: Are they filled with rage, causing them to bite people?

COLONEL TODD: Do they lose all capacity for reason?

GENERAL FRED: No. They behave... exactly like we do... except that they're not conscious.

(Silence grips the table.)

COLONEL TODD: Dear God.

GENERAL FRED moves over to a computerized display.

GENERAL FRED: This is New York City, two weeks ago.

The display shows crowds bustling through the streets, people eating in restaurants, a garbage truck hauling away trash.

GENERAL FRED: This... is New York City... now.

The display changes, showing a crowded subway train, a group of students laughing in a park, and a couple holding hands in the sunlight.

COLONEL TODD: It's worse than I imagined.

CAPTAIN MUDD: How can you tell, exactly?

COLONEL TODD: I've never seen anything so brutally ordinary.

A lab-coated SCIENTIST stands up at the foot of the table.

SCIENTIST: The zombie disease eliminates consciousness without changing the brain in any way. We've been trying to understand how the disease is transmitted. Our conclusion is that, since the disease attacks dual properties of ordinary matter, it must, itself, operate outside our universe. We're dealing with an epiphenomenal virus.

GENERAL FRED: Are you sure?

SCIENTIST: As sure as we can be in the total absence of evidence.

GENERAL FRED: All right. Compile a report on every epiphenomenon ever observed. What, where, and who. I want a list of everything that hasn't happened in the last fifty years.

CAPTAIN MUDD: If the virus is epiphenomenal, how do we know it exists?

SCIENTIST: The same way we know we're conscious.

CAPTAIN MUDD: Oh, okay.

GENERAL FRED: Have the doctors made any progress on finding an epiphenomenal cure?

SCIENTIST: They've tried every placebo in the book. No dice. Everything they do has an effect.

GENERAL FRED: Have you brought in a homeopa...
Identity Isn't In Specific Atoms
by Eliezer Yudkowsky — 2008-04-19T04:55:50.000Z

Continuation of: No Individual Particles
Followup to: The Generalized Anti-Zombie Principle

Suppose I take two atoms of helium-4 in a balloon, and swap their locations via teleportation. I don't move them through the intervening space; I just click my fingers and cause them to swap places. Afterward, the balloon looks just the same, but two of the helium atoms have exchanged positions.

Now, did that scenario seem to make sense? Can you imagine it happening?

If you looked at that and said, "The operation of swapping two helium-4 atoms produces an identical configuration—not a similar configuration, an identical configuration, the same mathematical object—and particles have no individual identities per se—so what you just said is physical nonsense," then you're starting to get quantum mechanics.

If you furthermore had any thoughts about a particular "helium atom" being a factor in a subspace of an amplitude distribution that happens to factorize that way, so that it makes no sense to talk about swapping two identical multiplicative factors, when only the combined amplitude distribution is real, then you're seriously starting to get quantum mechanics.

If you thought about two similar billiard balls changing places inside a balloon, but nobody on the outside being able to notice a difference, then... oh, hell, I don't know, go back to the beginning of the series and try rereading the whole thing over the course of one day. If that still doesn't work, read an actual book on quantum mechanics. Feynman's QED is a great place to start—though not a good place to finish, and it's not written from a pure realist perspective.

But if you did "get" quantum physics, then, as promised, we have now come to the connection between the truth of quantum mechanics, the lies of human intuitions, and the Generalized Anti-Zombie Principle.

Stirling Westrup previously commented, on the GAZP post:

I found the previous articles on Zombies somewhat tedious... Still, now I'm glad I read through it all as I can see why you were so careful to lay down the foundations you did.

The question of what changes one can make to the brain while maintaining 'identity' has been been discussed many times on the Extropians list, and seldom with any sort of constructive results.

Today's article has already far exceeded the signal to noise ratio of

...