Natural selection acts on the quantum world

Objective reality may owe its existence to a 'darwinian' process that advertises certain quantum states.

A team of US physicists has proved a theorem that explains how our objective, common reality emerges from the subtle and sensitive quantum world.

If, as quantum mechanics says, observing the world tends to change it, how is it that we can agree on anything at all? Why doesn't each person leave a slightly different version of the world for the next person to find?

Because, say the researchers, certain special states of a system are promoted above others by a quantum form of natural selection, which they call quantum darwinism. Information about these states proliferates and gets imprinted on the environment. So observers coming along and looking at the environment in order to get a picture of the world tend to see the same 'preferred' states.

If it wasn't for quantum darwinism, the researchers suggest in Physical Review Letters [Ollivier H., Poulin D. & Zurek W. H. Phys. Rev. Lett., 93. 220401], the world would be very unpredictable: different people might see very different versions of it. Life itself would then be hard to conduct, because we would not be able to obtain reliable information about our surroundings... it would typically conflict with what others were experiencing.

The difficulty arises because directly finding out something about a quantum system by making a measurement inevitably disturbs it. "After a measurement," say Wojciech Zurek and his colleagues at Los Alamos National Laboratory in New Mexico, "the state will be what the observer finds out it is, but not, in general, what it was before."

Because, as Zurek says, "the Universe is quantum to the core," this property seems to undermine the notion of an objective reality. In this type of situation, every tourist who gazed at Buckingham Palace would change the arrangement of the building's windows, say, merely by the act of looking, so that subsequent tourists would see something slightly different.

Yet that clearly isn't what happens. This sensitivity to observation at the quantum level (which Albert Einstein famously compared to God constructing the quantum world by throwing dice to decide its state) seems to go away at the everyday, macroscopic level. "God plays dice on a quantum level quite willingly," says Zurek, "but, somehow, when the bets become macroscopic he is more reluctant to gamble." How does that happen?

The Los Alamos team define a property of a system as 'objective', if that property is simultaneously evident to many observers who can find out about it without knowing exactly what they are looking for and without agreeing in advance how they'll look for it.

Physicists agree that the macroscopic or classical world (which seems to have a single, 'objective' state) emerges from the quantum world of many possible states through a phenomenon called decoherence, according to which interactions between the quantum states of the system of interest and its environment serve to 'collapse' those states into a single outcome. But this process of decoherence still isn't fully understood.

"Decoherence selects out of the quantum 'mush' states that are stable, that can withstand the scrutiny of the environment without getting perturbed," says Zurek. These special states are called 'pointer states', and although they are still quantum states, they turn out to look like classical ones. For example, objects in pointer states seem to occupy a well-defined position, rather than being smeared out in space.

The traditional approach to decoherence, says Zurek, was based on the idea that the perturbation of a quantum system by the environment eliminates all but the stable pointer states, which an observer can then probe directly. But he and his colleagues point out that we typically find out about a system indirectly, that is, we look at the system's effect on some small part of its environment. For example, when we look at a tree, in effect we measure the effect of the leaves and branches on the visible sunlight that is bouncing off them.

But it was not obvious that this kind of indirect measurement would reveal the robust, decoherence-resistant pointer states. If it does not, the robustness of these states won't help you to construct an objective reality.

Now, Zurek and colleagues have proved a mathematical theorem that shows the pointer states do actually coincide with the states probed by indirect measurements of a system's environment. "The environment is modified so that it contains an imprint of the pointer state," he says.

Yet this process alone, which the researchers call 'environment-induced superselection' or einselection [Zurek W. H. Arxiv, Preprint, link at footnote 2 in original article], isn't enough to guarantee an objective reality. It is not sufficient for a pointer state merely to make its imprint on the environment: there must be many such imprints, so that many different observers can see the same thing.

Happily, this tends to happen automatically, because each individual's observation is based on only a tiny part of the environmental imprint. For example, we're never in danger of 'using up' all the photons bouncing off a tree, no matter how many people we assemble to look at it.

This multiplicity of imprints of the pointer states happens precisely because those states are robust: making one imprint does not preclude making another. This is a Darwin-like selection process. "One might say that pointer states are most 'fit'," says Zurek. "They survive monitoring by the environment to leave 'descendants' that inherit their properties."

"Our work shows that the environment is not just finding out the state of the system and keeping it to itself", he adds. "Rather, it is advertising it throughout the environment, so that many observers can find it out simultaneously and independently."

I'm using sawdust and water as analogies of photons moving as waves. It is still an open question as to the SIZE of photons. Since photons of light travel all the way across the universe without HITTING each other they must be true points, unlike electrons, protons, neutrons, molecular gases. If they DID have appreciable size/volumes you wouldn't be able to see distant objects like the moon or faraway quasars/galaxies, things would just "fuzz out". As to matter(fermions-electrons, protons, neutrons), the waves are given by DeBroglie's formula : h/mv or the quantum area divided by the momentum of the object(collection of fermions), and the speed of the wave crest is given as U=c^2/v. This means matter waves are far too tiny in wavelength to see with your eyes(that see in the 4000 to 7700 angstrom range)but requires that they travel FASTER than light(Einstein's c limit). This threw the relativists into a tizzy : nothing can travel faster than 3 x 10^8km/sec. So they came up with this hokey explanation : PHASE matter waves travel at up to 9 x 10^16km/sec, coming from +infinity to -infinity, but cancel everywhere(destructive wave interference)except at the GROUP that wave-defines your blinking eyelid at less than c, to satisfy wave-particle complementarity. Pure NONSENSE! What they didn't consider is to ask : is c^2 a LINE or an AREA? As line in momentum you get 9 x 10^16km/sec of fermions GLOBALLY and 0 km/sec(v=0)LOCALLY; like completely at rest on a speeding jet. So you go from a line statement : mv(momentum)to mv^2/2(area statement)for mass. Anyway, merry CHRISTMAS, we'll continue on the other side of santa's visit..

This loss of information happened at The Fall. When G-D kicked Adam & Eve out of the garden, He removed H~s protection of all the majickal, non-localized quantum states, eventually leaving only cold, cruel, Darwinian objectivity to survive.
In short: Objectivity is all Satan's fault.
But now, if we let G*D into our hearts, He'll extend H-s protection back to all those fragile quantum states while you pray to H^m. This is why prayer produces miracles.

You've got it exactly backwards! Without the suppression of all of those non-local states, we wouldn't have an objective world at all. All of the bewildering multiplicity of quantum possibilities would be equally real, making stable, steady reality an impossibility.

So be careful in blaming Satan for objectivity...you might be assigning him credit rather than blame!

Merry Christmas ...

Speaking of photons, hopefully you will be able to help me understand an aspect of special relativity that I have been puzzling over related to red shift.

Since a photon travels at the speed of light it never ages. It's identical today to the point when it was originally emitted, even if it originated back near the time of the Big Bang. All it's energy on it's journey through spacetime is expended on its motion through the familiar 3 dimensions, so it never advances through the 4th dimension: time.

Am I right so far?

If so, then how does an individual photon arrive at a detector on earth today with a different frequency than when it was originally emitted? The explanations I have read attribute this to the expansion of the universe and the relative motion of the photon and observer.

But I also thought that the relative motion between a photon and an observer were always the constant c, so how does the expansion of the universe change this? Or do we have to invoke general relativity, or am I just very confused?

Physicist, I've always enjoyed your informative postings, your participation in the 1998 March for Justice, and your efforts in defending Don Adams.

I always thought that the quantum states were properties associated with materials invovled. For example, the green in the leaves of a tree arise from the absorption of light of a frequency whose energy matches the quantum transition from a ground state to an excited state in chlorophyll.

Chlorophyll is a molecule containing many atoms which all have different "excitation states" available to emit (reflect) light. Thus, all light is absorbed and many wavelenghts (mainly in the green spectrum) are emitted.

One molecule of chlorophyll is like every other and has the same transition state.

Actually, there oare two types of chlorophyll molecules but that is beside the point. There are many transistion states with those with energies corresponding to the greens emitting while the other frequencies of light are not (at least for the most part) emitted but the absorbed energy (exitation) is converted into molecular re-actions.

The only change would be slight variations in its chemical environent that can casue the energy for the transition to shift slightly higher or lower, hence casuing a broadening of the wavelength window responsible for the observed color.

Again, it is a molecule and has many transition states resulting in many frequencies being emitted (reflected). You are partially correct in that bringing atoms and/or molecules in close proximity results in additional transition states (frequencies).

"I donno about this one..."

I had doubts because it reads, at first, like New Age mystic commentary.

But, Phys Rev Letters and Nature are serious.
Big Time editing and peer review here. So it should be read carefully.

The point to look for is:
What new experiment or observation is the basis for the headline?

What new experiment or observation is the basis for the headline?

I can't see it. But this whole topic seems related to an article which sparked a lively thread a few months ago:
Deriving Dimensions: Emergence of a 4D World From Causal Quantum Gravity.

QM gives me a brain ache, so I can't focus on it just now. Maybe tomorrow.

And a merry christmas to you too. Here then is another christmas present, IF you can"unwrap"it : By Lorentz Transformations I assume you mean : M = Mo/(1-v^2/c2)^1/2 or T = To/(1-v^2/c^2)^1/2 These are of course just cosine functions between 0 deg and 90 deg(infinity). They refer to Einstein's Relativistic Rocket wherein the rocket shrinks to zero in the forward(polar)direction and expands in equatorial area to infinity as the rocket approaches c in velocity. Mass thus expands to infinity and time stops. Much theoretical and experimental work has shown this to be true. Now, how? Easy explanation : an electrical circuit can have 3 things going on simultaneously : resistance, capacitance, inductance. So, throw(accelerate)a baseball. You feel a back drag/resistance that you call "inertia". Its actually deceleration that you feel/sense as under-running matter waves, or, you've increased the Particle velocity(Pv)but you haven't also increased the complementary matter wave energy(Ws), so accel is Pv>Ws(and deceleration PvWs or Pv

Chlorophyll is a poor example because of its complexity and the multiple transitions that occur in the visible. My point was that each of these transitions involves changes between specific quantum states and that a continuum of states does not exist for a specific transition in a molecule. Chlorophyll, as you mentioned, has multiple transitions, but these each have a different, specific origin. Only a few of the atoms in chlorophyll are directly involved in transitions in the visible, and some arise from the conjugated system around the central iron atom. All things being constant, the same molecule will have the same transition energy involved with aborption for a specific transition.

Also, using color is also poor example because of the complexities involved in the biological perception of color. I say this because in vision, the observer is as critical as the source and the object observed. Light observation also involves quantum transitions in the photosensitive chemicals in the photoreceptors of the retina. The same apparent color can be produced by the proper balance of stimulation of the three tristimulus functions of the eye, even though completely different wavelengths of light may be involved. That's an interesting phenomenon in cheap fluorescent lights. They are really a mix of a red and a green emission bands that are balanced in such a way that they look bright white to thenhuman eye.

>It's also interesting that there are two commentaries (one Polish and one in something like "Physics Today") that review these games but get the math wrong

Yes, this kind, of thing
pops up in many contexts . . .
In fact, in his book

speculating on
optics in art history,
David Hockney shows

manuscript excerpts
going back hundreds of years
where concepts are clear,

but the "practical"
examples cited are flawed.
Theory is, dumb folk

get tripped up by the
nuts and bolts, whereas smart folk
can extrapolate

everything they need
from a clear presentation
of concepts alone.

So, knowledge gets out
to people who can use it
but not to poseurs. . .

(When I think about
how much money I've wasted
trying to get my

oscillators to
become entrained by or to
become synchronized

with lottery draws,
I have to admit knowledge
colors me poseur . . .)

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