A wave of experiments is probing the root of quantum weirdness
nature.com
nature.com
There's a longstanding interpretation that the wave-particle duality is actually caused by (e.g. electrons) being particles riding invisible waves. This interpretation (Bohmian mechanics) has been largely ignored as "valid but uninteresting."
A key reason why this isn't historically that appealing is that the state of the "invisible waves" in the neighborhood of a single particle is mathematically dependent on the instantaneous state of every other particle in the universe.
If you assume the universe is a simulation, then the programmer would be a freshman computer science student who unnecessarily made stepping forward in time quadratic!
The oil-droplet experiments are an accidental existence proof that you can get behavior similar to quantum behavior in particle+wave systems without the quadratic global update rule.
Is it enough? There's still tons of open questions, and possibly (likely) yet another dead end.
So you aren't really going to disprove only the Bohm picture, because it makes the exact same claims as the more common Shrödinger picture.
my understanding of 'natural' physics is as a relation between particle(s) and every other particle in the universe
and our physics calculations trying to understand and predict those natural events wave away those relations valued insignificant to the desired probability threshold?
contrived but applicable example, "assume you are on a frictionless plane with zero wind resistance"
or in one of the most amazing results of applied physics in recent news :
"Fred Jansen, Rosetta's mission manager at ESA, said officials predicted a 70 to 75 percent probability of a successful landing by Philae before the mission's launch in 2004. But that number assumed the comet was a rounded body, not the oddly-shaped world found by Rosetta."
The key word in the parent comment is instantaneous. This means that pilot-wave theory is not compatible with relativity, if I understand correctly.
Perhaps unrelated, but they have already shown that entangled particles propagate state at the speed of light. So we probably wont have any Ender's game ansible communication devices any time soon.
(Again, I am an interested layman, not a scientist, so this comment may be nonsense.)
But if you want any information to travel, you'll need to use a mechanism named "feed-forward", which is limited by the speed of light.
When I read articles that are using words like "spooky" and "weird" as terms of art, and using Schrödinger's cat as a way to clarify a topic, I get nothing out of it. And I'd like to be able to explain to my mom what this stuff is.
Aside, the terms "spooky" and "weird" are used to describe phenomena that "have no classical analogue." Physicists don't agree on what Schrödinger's cat means. I find that it muddles more than it clarifies.
They're kinna mathy, but a lot easier to understand than similar lectures from physicists (because the background knowledge is much greater)
And goes into greater depth in the Douglas Robb Memorial Lectures series: http://vega.org.uk/video/subseries/8
If you want to go all the way down the rabbit hole there's an exhaustive list of Feynman videos here :) http://www.richard-feynman.net/videos.htm
I read this book in high-school and learned about as much as I did in 4 undergrad physics courses about quantum mechanics. There's no mathematics in this book, so it doesn't teach you how to calculate anything (for this, a physics degree helps), but the principles are presented very nicely.
http://www.askamathematician.com/2011/11/q-according-to-the-...
http://www.askamathematician.com/2010/10/q-copenhagen-or-man...
http://www.askamathematician.com/2013/08/q-are-there-example...
http://www.askamathematician.com/2011/11/entanglement-omnibu...
http://www.askamathematician.com/2010/06/q-how-it-is-that-be...
† The Nature article characterises the Many-Worlds Interpretation like this:
"In the many-worlds picture, the wavefunction governs the evolution of reality so profoundly that whenever a quantum measurement is made, the Universe splits into parallel copies."
The first of the links above explains that this is a mischaracterisation.
Check http://www.scottaaronson.com/democritus/ and see if it works for you.
Otherwise, you are in the realm of popularizers like John Gribbin, who I found entertaining but not very enlightening.
How would you isolate an experiment from the potentially-wave-function-collapsing influence of human consciousness, and yet still produce a usable contribution to science?
There are serious philosophical issues with the idea of an observer, conscious or otherwise, as a useful concept.
Entanglement isn't really the issue, because it doesn't solve the problem. What does it mean to be entangled with a complex state in a state of some form of consciousness?
How much consciousness is needed to make a difference? Why should adult human consciousness be the benchmark, and not semi-consciousness, or distraction, or unconsciousness, or toddler-level pre-verbal awareness, or jellyfish consciousness, or LSD-induced hallucination?
If consciousness is necessary, why doesn't reality stop working when we fall asleep? Why do plants live in a consistent physical reality even though they don't know what a Hamiltonian is?
If physics had code smells, this idea of consciousness might not pass the sniff test.
Of course it's possible it's still the right answer. But if it is, it's interesting there's no useful explanation of anything in the concept yet. Nor is there any formalism to support it. (Obviously there's a formalism for wave function collapse. But so far as I know, there's nothing in the math that says "And these variables are where the observer works his/her/its magic.")
Really it's just something that might be true, maybe, because we have no idea what's going on and it's as good a guess as any other.
The photon is in the state it's in because of the result, which means that, after that the photon enters your eye, your brain is also in the state it's in because of the result. But you could say the same of a dog brain, or a cow brain, or PC with a webcam for that matter. "Consciousness" has nothing to do with it.
Sir Roger Penrose said many times that our current models of Physics are not including Consciousness and that is a big issue. He and Hameroff are working in an interesting line of research that is trying heretically to do just that, model Consciousness pushing the current statu quo https://en.m.wikipedia.org/wiki/Orch-OR
Here is a interview of Hameroff talking about why Consciousness is not an epiphenomenon (as the experiments with paramesiums shows) and is far more than computation: http://youtu.be/YpUVot-4GPM
For instance say you're performing some slit experiment, directly after you launch the particle there is still a very broad spectrum of possible positions / states, which are all heavily correlated since states that differ only by the position of 1 particle are in some sense "close". However if the particle hits something then suddenly there can be a very large number of particles that have different positions, depending on where the initial particle hit, hence the difference between those states increases immensely, causing them to become decoherent. Hence, from the perspective of the resulting states, there is only a very small region where it could have hit, anything else becomes remotely unlikely.
This interpretation has some rather interesting issues when you try to interpret what consciousness is, but it's the most consistent one I've found so far.
According to the Many-Worlds Interpretation, it doesn't. Both the thing being observed and the observer exist in many states simultaneously (a superposition of states). Before the observation, those states were independent; the act of observation causes the observer and observed to become entangled, so each state of the observer corelates to a single state of the thing observed. From the observer's points of view, there appears to have been a collapse; but the result of the "collapse" will be different for each of the observer's states.
(Caveat: I am not a physicist, and it's possible the above is not even wrong.)
Though this being HN: Think of it like the edge of the bitcoin block chain two new blocks are can be in an unintended state, but over time the longest one wins.
* Not that this a useful model, but it's much closer than the often repeated voodoo mysticism people spout.
It doesn't. Classical behavior is an emergent property of any large system of mutually entangled particles. For macroscopic systems classical behavior is a damn good approximation, but it's only an approximation. See:
http://www.flownet.com/ron/QM.pdf
Or the movie version:
it becomes much clearer (at least to me) once "observation" is replaced with "interaction" because the former is really not possible without at least a quantum of the latter.
The explanation for the appearance of collapse lies in the phenomenon of decoherence, which basically says that subsystems tend to quickly evolve into something resembling an eigenstate. This evolution must necessarily occur on an incredibly short timescale. It might be possible to design an experiment that would test the assumption that collapse is instantaneous.
I think the best definition of "collapse" is that it is the moment in time in which a particular system can no longer be described (to good approximation) as the direct product of two subsystems (see http://en.wikipedia.org/wiki/Separable_state). The concept of a "good approximation" is of course subjective, but it can always be objectively metricized (totally made that word up) by using some kind of error term.
Epigrammatically, collapse is not so much a physical process as it is a characterization of the capability to represent a quantum state in a specific mathematical form.
(Of course, this doesn't preclude you from categorizing physical processes as "collapse events"; it just means that collapse isn't a fundamental phenomenon so much as it is an emergent one. Kind of like quasiparticles.)
So what about the randomness? I think it's better to refer to it as unpredictability. The difference is subtle but crucial. True randomness (assuming it exists) is the result of absolute indeterminism. On the other hand, if eigenstate selection is merely "unpredictable", then that implies collapse is in fact a deterministic process (specifically e^(-iHt) applied to Ψ over some time interval that we've decided to call a "measurement"); however, we're unable to extract enough information from the environment to make exact predictions because we ourselves constitute the required missing information. In other words, the information necessary for absolute predictive capability is trapped in the subsystem constituting the measuring environment, and it becomes lost when that subsystem becomes entangled with the subsystem being measured. And there's not really any way to prevent that from occurring, because entanglement must occur in order to learn anything about a system.
This even applies classically. The only difference is that classical entanglement occurs between localized physical boundaries instead of between subspace boundaries in an abstract Hilbert space.
To somewhat reify this, assume (for the sake of argument) that a classical description of physics is enough to describe a human. Then perform a large MD simulation of all the atoms inside a physics lab, including those of a physicist. The evolution of this simulated system is provably deterministic. Yet the physicist appears to have free will, and it appears like he is deciding which measurements to perform on his environment. But he's just an arbitrary collection of atoms that we've labeled "human", and he obeys the same time-transformation rules that the unlabeled atoms in the system obey. Mathematically, it's simply impossible for him to predict everything that occurs within the virtual system -- not because of indeterminism -- but because he isn't so much "choosing" what to measure as he is "appearing to choose". There's a limit to the amount of information any system can obtain about itself (well, maybe there's some fractals that are exceptions, but generally speaking, it holds true.)
That said, experiment is always the ultimate arbitrator of truth, and I wonder if there might yet be some clever way to tell whether our universe is simply unpredictable instead of random, despite the possibility that both potential mechanisms might impose the same limits on predictive capability (in fact, Colbeck and Renner recently proved that QM is already maximally predictive, independent of whatever underlying mechanism governs eigenstate selection -- see http://www.nature.com/ncomms/journal/v2/n8/abs/ncomms1416.ht...)
I don't know why it is so hard for this description - or paradigm - to proliferate to the masses and various pop writers. Writers so often are tying human consciousness to QM experimentation as if it were something special. The fact of the matter is: in each QM experiment the only things really interacting with the experiment are the atoms of the measurement apparatuses, sensors, and whatnot. In the case of the double slit experiment, we could have them "interpreted" automatically - and say, kill a cat if an interference pattern is created and not kill it if one is not made. Making the discussion about consciousness is a distraction from the core issues.
The results should be the same, but it is a different interpretation.
A friend of mine modeled soliton interactions. When one soliton passes through another, information can be exchanged such that colliding solitons contain bits of each other when they move apart. No matter how far apart these solitons get, the soliton "children" still "chat" with their "parents". One soliton can contain multiple elements of other solitons, all of them interacting at a distance. Their behavior can mimic "spooky action at a distance". Also, solitons can have wave like behavior or particle like behavior depending on how they are observed.
Also, check out this fascinating debate about these matters on Scott Aaronson's blog. Link is http://www.scottaaronson.com/blog/?p=1255
Brady and Anderson have many posts in this debate, and IMHO, wind up winning.
It's looking more and more like physics took a wrong turn with the Copenhagen interpretation of quantum mechanics.
Brady and Anderson's point is that it's not a qubit until you can calculate with it. And their theory suggests it will get exponentially harder for each qubit above 4 (I think), which throws out all of the interesting quantum algorithms.
I also felt Brady and Anderson silenced every objection. After one or more of their rebuttals, they were no longer challenged. The most recent post about Feynman is also interesting.
In any event, it is a fascinating blog post.