FrediFizzx wrote:Here we go again; an experiment that claims to have detected spatial separation of a neutron and its magnetic moment (spin).
http://www.nature.com/ncomms/2014/14072 ... s5492.html
"Observation of a quantum Cheshire Cat in a matter-wave interferometer experiment"
From the abstract, "The experimental results suggest that the system behaves as if the neutrons go through one beam path, while their magnetic moment travels along the other."
What the heck are we to call a neutron that has no spin? It certainly can't be a fermion.
I would make a side bet that the electron or the photon cannot be separated from its spin in this way, but who knows: they all (electron, photons, protons, neutrons, and more) create the same probability density patterns when they strike a detector far afield from the slits. That fact is an underlying unity which cuts across spin type and particle type and interaction type and even whether a particle is elementary or composite, and is on the road to something very deep about nature.
In condensed matter physics, spin–charge separation is an unusual behavior of electrons in some materials in which they 'split' into three independent particles, the spinon, orbiton and the chargon (or its antiparticle, the holon). The electron can always be theoretically considered as a bound state of the three, with the spinon carrying the spin of the electron, the orbiton carrying the orbital degree of freedom and the chargon carrying the charge, but in certain conditions they can become deconfined and behave as independent particles.
Ben6993 wrote:EXTRACT from:
http://en.wikipedia.org/wiki/Spin%E2%80 ... separation:In condensed matter physics, spin–charge separation is an unusual behavior of electrons in some materials in which they 'split' into three independent particles, the spinon, orbiton and the chargon (or its antiparticle, the holon). The electron can always be theoretically considered as a bound state of the three, with the spinon carrying the spin of the electron, the orbiton carrying the orbital degree of freedom and the chargon carrying the charge, but in certain conditions they can become deconfined and behave as independent particles.
Yablon wrote:Fred,
Wow! Just the type of thing you and I were talking about to maintain locality in the double slit experiment. Keep in mind, the proton spin crisis (which applies as well to neutrons) says that the spin 1/2 is distributed mostly into the gluon plasma, and that only about 30% of the overall spin sticks with the quarks. So the spin is already somewhat "transportable."
If this experiment proves to be accurate (and that is an if), then it will either compound the proton spin crisis, or provide a clue to resolve that problem.
I would make a side bet that the electron or the photon cannot be separated from its spin in this way, but who knows: they all (electron, photons, protons, neutrons, and more) create the same probability density patterns when they strike a detector far afield from the slits. That fact is an underlying unity which cuts across spin type and particle type and interaction type and even whether a particle is elementary or composite, and is on the road to something very deep about nature.
FrediFizzx wrote:Here we go again; an experiment that claims to have detected spatial separation of a neutron and its magnetic moment (spin).
http://www.nature.com/ncomms/2014/14072 ... s5492.html
"Observation of a quantum Cheshire Cat in a matter-wave interferometer experiment"
From the abstract, "The experimental results suggest that the system behaves as if the neutrons go through one beam path, while their magnetic moment travels along the other."
What the heck are we to call a neutron that has no spin? It certainly can't be a fermion.
FrediFizzx wrote:Yablon wrote:Fred,
Hmm... I never heard of the proton "spin crisis". I thought is was proton momentum that was 1/2 from gluon plasma. Anyways, I figure this is a related trick that Nature is doing similar to "entanglement". Well... actually we are just tricking ourselves; not Nature really tricking us. Just a matter of figuring out the "trick" if the experiment is correct.
Joy Christian wrote:The claim by the authors is based on a fundamental misconception of what is meant by "spin." Contrary to the indoctrination we are subjected to in our quantum mechanical textbooks, "spin" is not a "property" of a particle, but a reflection of its relationship with the rest of the universe (see Ref.[3] of this paper). Thus a fermion, for example, is an "anchored" particle (anchored to the rest of the universe), and a boson is a "free" particle (unanchored to the rest of the universe).
Yablon wrote:Joy Christian wrote:The claim by the authors is based on a fundamental misconception of what is meant by "spin." Contrary to the indoctrination we are subjected to in our quantum mechanical textbooks, "spin" is not a "property" of a particle, but a reflection of its relationship with the rest of the universe (see Ref.[3] of this paper). Thus a fermion, for example, is an "anchored" particle (anchored to the rest of the universe), and a boson is a "free" particle (unanchored to the rest of the universe).
This is great discussion. There are a lot of things here which I intuitively feel are connected.
This "anchoring" notion that Joy introduces immediately feels like entanglement, but it also seems to drag the Fermion Exclusion Principle into the mix. We take it for granted that no two fermions in a given "system" (whatever defines a system) can occupy the same state. And we may envision this as if the seats in a theater can only hold one person each and no two seats are exactly alike. But we often end the discourse right there, and do not inquire how it is that electron B knows, simply because there is already an election A, that it cannot also be an electron A. And isn't entanglement really based on the fact that we are deeming Alice and Bob's particles to be part of a "system," thus subjecting them to exclusion, thus finding that they must be in exclusive states?
So either either exclusion is at the root of all of this entanglement stuff, or all this entanglement stuff is at the root of exclusion.
Joy Christian wrote:Jay,
Conceptually it is very important to distinguish between the "orientation entanglement" and "quantum entanglement." Orientation entanglement is a straightforward classical notion, whereas quantum entanglement is riddled with magic and mystery. What I am referring to above with "anchoring" is what is known as orientation entanglement (see, for example, the discussion on the pages 1148 to 1150 of Gravitation by Misner, Thorne, and Wheeler). On the face of it, quantum entanglement is a very different concept. The fundamental property of quantum entanglement is non-factorizability, which translates into non-locality in Bell's framework.
Now a parallelized 3-sphere---which happens to be diffeomorphic to the spinor or fermionic group SU(2)---is a quintessential mathematical expression of the orientation entanglement. But the 3-sphere is also one of the well known solutions of Einstein's field equations of GR, which is a purely classical (and local) field theory (cf. the discussion in this paper). What is more, in my work I have shown that the quantum correlation predicted by the emblematic (or simplest) quantum entanglement (i.e., the EPRB or singlet state) is exactly that between the points of a parallelized 3-sphere: E(a, b) = -a.b (cf. the discussion on this page).
Thus, at the root of all is the orientation entanglement, not quantum entanglement. In my view, the so-called quantum entanglement is simply an illusion.
Joy Christian wrote:. . . What I am referring to above with "anchoring" is what is known as orientation entanglement (see, for example, the discussion on the pages 1148 to 1150 of Gravitation by Misner, Thorne, and Wheeler). . .
Yablon wrote:Joy Christian wrote:. . . What I am referring to above with "anchoring" is what is known as orientation entanglement (see, for example, the discussion on the pages 1148 to 1150 of Gravitation by Misner, Thorne, and Wheeler). . .
So, before we even get to the parallelized 3-sphere -- which I may ask about next -- are you saying that the crux of your argument based on 1148 to 1150 of MTW, is this?
From a singlet state, prepare a pair of electrons in the same place at the same time, one with spin up and one with spin down. So these two electrons have entanglements with the physical space which differ from one another by 2pi. But via their entanglements with the same space, these are necessarily entangled with one another. That is, A anchored to space, and B anchored to the same space, means A is anchored to B. Then, it is just a question of evolving these anchors as time passes and the particles are separated, which is to say, we are simply studying the time evolution of 1148 to 1150 of MTW for two particles which start out together in opposite versions.
Is this on the fairway?
I have two earlier blog posts that you might like. First is at http://jayryablon.wordpress.com/2008/02 ... -fermions/, and it references my first published paper from 1988, at http://jayryablon.files.wordpress.com/2 ... tiplet.pdf. This 1988 paper summarized a very large set of materials I had pulled together in 1986, discussed and available at
http://jayryablon.wordpress.com/2012/04 ... ification/. It was by writing these 200 or so pages, that I taught myself Dirac theory and particle theory and the basics of
Yang-Mills and Lie Groups, but of course, assimilated this all in my own particular way and saw a preon model in the middle of it all.
FrediFizzx wrote:Here we go again; an experiment that claims to have detected spatial separation of a neutron and its magnetic moment (spin).
http://www.nature.com/ncomms/2014/14072 ... s5492.html
Denkmayr et al wrote:A surprising effect originating from pre- and post-selection of a system is the ability to 'separate' the location of a system from one of it's properties'
In our experiment, the? neutron plays the role of the cat, and the cat's grin is represented by the? neutron's spin component along the z-direction. The? system is initially prepared so that after entering the beam splitter its quantum state is given by ...
In order to observe the quantum Cheshire Cat, after we preselect the ensemble, we will next perform weak measurements of the neutrons’ population in a given path on the one hand and of the value of the spin in a given path on the other.... Whenever the postselection succeeds, that is, when a Cheshire Cat is created, a minimally disturbing measurement will find the Cat in the upper beam path, while its grin will be found in the lower one.
minkwe wrote:If anyone knows what "the neutron's population" means, they should help me understand it. It seems, what they did was measure the position of one set of neutrons in one arm, the spin of a similar but different set of neutrons in another arm, and then after confusingly mixing up "ensemble", "the", "a", "its", claim that they separated "the neutron's" spin from it's position. Sad indeed.
FrediFizzx wrote:minkwe wrote:If anyone knows what "the neutron's population" means, they should help me understand it. It seems, what they did was measure the position of one set of neutrons in one arm, the spin of a similar but different set of neutrons in another arm, and then after confusingly mixing up "ensemble", "the", "a", "its", claim that they separated "the neutron's" spin from it's position. Sad indeed.
And they never show what effect the absorber has for the H detector. Yep, sad indeed.
Contrary to the indoctrination we are subjected to in our quantum mechanical textbooks, "spin" is not a "property" of a particle, but a reflection of its relationship with the rest of the universe (see Ref.[3] of this paper). Thus a fermion, for example, is an "anchored" particle (anchored to the rest of the universe), and a boson is a "free" particle (unanchored to the rest of the universe).
Ben6993 wrote:The -cosθ value indicates that the measured spin is not always equal to the chiral spin, else the value would always be -1.
minkwe wrote:What do you mean by "measured spin"? I think sometimes we are misled by oversimplification of what is possible in experiments. Try to imagine how you would go about measuring the spin, and then let me know if the result you get out of your measurement is still what you called "spin" to begin with.
Ben6993 wrote:One can put a hypothetical, infinitesimal R3 box around an electron and in that box the chiral spin would be evident, hypothetically.
One can put a hypothetical flat infinitesimal R3 box around the electron at various points in its flight so that all the R3 boxes record the same chiral spin, each relative to its own box. All the boxes are aligned alike in the wider R3 space, but in the S3 space, the alignement would be different. So, under S3, the electron spin is actually changing during flight to an observer outside all the infinitesimal boxes. That would fit in with the electron not having a fixed measurable spin property. I think, though, that if an electron in an infinitesimal R3 box has a chirality of either + or -, then that is a property of the electron alone. It is just that an observer not in that infinitesimal boxhas a hard time knowing its chiral spin if the spin is variable in S3. So in R3 the electron chiral spin is constant (plus the mystical random choice on detection) but in S3 the spin is changing according to formula with no need for any mysticism on detection.
Ben6993 wrote:Yet I still like to think of the electron having its own chirality, or call it a self-observed constant spin state determined by its structure.
Ben6993 wrote:I am not sure about the relevance here of anchoring as both electron and photon have spin, but one is anchored and the other isn't.
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