- The Mott Problem https://en.wikipedia.org/wiki/Mott_problem
- Feynman describes "measurement" as form of copying quantum information from one system to another. https://www.youtube.com/watch?v=AyejXtZrGb0 , and https://www.youtube.com/watch?v=hWTbtXgqYMo
- Stanford article on Many Worlds Interpretation (or MWI) http://plato.stanford.edu/entries/qm-manyworlds/
- A publication (very advanced) on the classical trajectories of fundamental particles. http://arxiv.org/pdf/1209.2665v1.pdf
(It is strongly suggested. Look over only the beginning and ending sections of the MWI article at stanford. Don't bother reading the whole thing. The Feynman lecture was broken up at a really bad section which straddles part 3 and part 4. For brevity, watch the end of part 3 and the beginning of part 4.)
In this thread I will be investigating the consequences an outlandish claim about the nature of the universe. In a nutshell, the claim goes :
All particles in the universe are as large as the universe. However, we experience particles as tiny, located points because the speed of light induces a spacetime lag between them.
That claim is so absurd that it feels like it should be abandoned without a second glance. However, as this article progresses, we will see that its consequences will (ironically) dovetail nicely with how quantum mechanics describes fundamental particles. In all situations where you say "Well this claim can't be true because..." eventually explain some known aspect of quantum weirdness.
This article is not introductory physics. It is not for the untrained. The motivation is to produce a theory for entangled photons, whose entanglement is dependent on the destruction of the "which-way" information in the lab.
If two photons are sent through mirrors in an optics lab, and a partially-silvered mirror sends them into an unknown path, it is said that the "which-way" information of the photon has been destroyed. The formalism of quantum mechanics then dictates the two photons are entangled. This phenomenon is also observed in the famous double-slit. Lacking the "which slit" information, the photon acts as if it took both slits and "interfered with itself". This is as much spoon-fed explanations as I will provide. It is expected that the reader will be familiar with the materials linked.
From modern formulations of quantum information theory, we get a coherent picture of how the universe around us never destroys any information. The "unexpected" correlations in the boxes described by Feynman can be explained mechanistically by a universe that never lets us poor humans destroy any information. Nor does the universe allow us to change the total number of bits of information in the universe. (see Esalen lectures above) Because we humans live our daily lives in a macroscopic world where things are forgotten, lost, destroyed and so on, our intuitions are (temporarily) confused by this. Our attempts to duplicate a quantum state exactly will be foiled by the universe. ("No Cloning theorem"). Our attempts to broadcast a quantum state exactly will be foiled by the universe. ("No broadcast theorem"). The universe is not malicious, its just that it never forgets anything (..it never "loses information").
So the information the quantum state of an isolated particle is largely resolved ; laid to rest. Isolated immobile particles contain 'information' in them like Feynman's three boxes do. See part 4 of the lecture vid starting around minute 13:00.
The remaining problem (hopefully addressed by this article) is that mere information-in-box picture does not help at all in resolving the fact that a particle also contains "which-way" information about its location in space and time. The entanglement seen in the "Feynman boxes" also extends to direction a photon was sent through an optics lab. Worse, the photon could be sent down long distances, whole city blocks, and still exhibit both entanglement as well as "self interference".
We could comfortably sleep at night if the weird quantum stuff was isolated snugly into the nucleus of tiny atoms. With the funny stuff inside boxes, we could keep the weirdness at arms length. But if entangled photons are sent down city blocks, or transmitted across water to a distant lab, we can no longer rely on those comforting illusions.
The essential sentence from the stanford article on MWI reads :
The Schrödinger equation itself does not explain why we experience definite results in quantum measurements.
This is a neat summary of the whole drama swirling around various interpretations of quantum mechanics. When the Schroedinger equation is extended to "city blocks" where photons travel, or don't travel, or go both ways, the problem rears its head in a more dramatic way.
The idea that we should give up on the photon ever having any position in space is not new. It was first posited seriously by a physicist named Nevill Francis Mott in the 1920s. It was then reiterated again more formally in Matrix Mechanics. From the PDF above, page 3 :
As a consequence, Matrix Mechanics appears as an abstract algebraic formalism where any visualized or intuitive description of a microscopic object is abandoned.
The emphasis was added by me. Mott knew that when a nucleus decayed and emitted a particle , that the Schroedinger equation was describing a spherical wave with the mother nucleus at the center. But in real physical bubble chambers, that never happens. The emitted particle always chooses a particular direction, and then traces out a straight line. In the presence of magnetic fields, the particle will trace a curved path. In all cases the observed trajectory is 'classical' -- as if the particle were exactly like a very tiny object moving in space.
The formalism contains no "tiny balls moving in space" (remember we abandoned all intuitive descriptions), and yet this is what is always observed in the lab. I believe a resolution can be obtained. I first propose an equivalence between emitted alphas exhibiting classical trajectories, and photons containing which-way information as a "kind of" quantum state. In other words, the phenomenon underlying classical trajectories emerging from alphas is the same phenomenon that erases the decoherence of photons whose which-way information is resolved by measurement. A simple example is placing a detector on a slit, which immediately removes the interference pattern.
Now that the "which-way" is a quantum state, it should be emphasized that we cannot rely on the stuff-in-boxes picture, nor will my theory ever resolve into it. Instead whenever a photon chooses a particular pathway, or an alpha moves in a classical trajectory, that position/state is not intrinsic to the alpha or the photon itself. To understand my theory, imagine that the position of a particle in spacetime is not "inside" the particle itself. Abandon such notions, as difficult as that might be right now.
Instead the quantum state which we have formerly named the "position" of a particle or the "trajectory" of a photon is stored in an ensemble of perceiving physical systems separated from that position in spacetime. But the separation is not intrinsic to quantum mechanics. Instead it is induced by the fact that observers are causally lagged from those positions by the speed of light. For all intents and purposes, we perceive a "particle at a place" but this is not actually happening. The particle is everywhere. It's not crazy because the Schroedinger equation says this exactly.
I empathize that the reader may be recoiling in horror from this idea. But look at how this theory fairs against what we actually observe in experiment. When the "ensemble of causally separated observing systems" is not storing the "position-state" of a photon, the photon will go through both slits. If the causally-separated-ensemble does something to leak the position-state (i.e. grad student places a detector) the photon's position/state is resolved for that ensemble. That's precisely what physically happens!
Analogously, the ultra-cooled alcohol in a bubble chamber acts as the causally-separated-ensemble for the alpha. The speed of light acts as a universal lag for quantum-state copying , and the alcohol atoms perceive a universe where the alpha is moving like a microscopic thing at a location. Formerly we believed this happens because the alpha particle intrinsically "carries around its own location". That's backwards. All particles are the size of the universe, and only appear as particles-at-a-place because the ensemble-of-measurers all have the same speed of light in their reference frames. That's why they all see the same thing -- not because they are all getting copies of the reality of the location of the (alleged) actual location that is actually out there.
I will be extending and summarizing this article later on. Time permitting, and depending on levels of interest in this thread.