I first started thinking about retro-causality back at Brandeis in 1961 when I read David Inglis's Rev Mod Phys paper on the Tau-Theta puzzle from a remark on the EPR effect. I had seen it previously when I read David Bohm's "Quantum Theory" at Cornell in the summer of 1958 when I was Robert Wilson's apprentice at the Synchrotron helping it take it apart and running it at night when it was not in pieces. They had a shower there and I would sing Gilbert and Sullivan loudly.
Photos from the 1958 Princess Ida with me as Prince Hilarion opposite Jeremy Bernstein's sister Alice, with Ronnie Peierls in the chorus - see if you can find him.
Reading Inglis it suddenly dawned on me that there seemed to be a faster than light effect here, that there had to be. I had not yet understood the real intent of Einstein in 1935 that indeed there had to be such an effect in order not to violate Heisenberg's uncertainty principle. The problem was that Sylvan Schweber discouraged me to think along those lines. I suppose he thought it was too philosophical, yet at the same time he was trying to get David Bohm to come to Brandeis.
From: Jack Sarfatti
Date: January 25, 2007 1:57:33 PM PST
Subject: Re: Cramer's Upcoming Retrocausality Experiment Back From The Future - new twist 4
"To use this setup to send a signal, it needs to work without a coincidence circuit. Inspired by Raymond Jensen at Notre Dame University, Cramer then proposed passing each beam through a double slit, not only to give the experimenter the choice of measuring photons as waves or particles, but also to help track photon pairs. The double slits should filter out most unentangled photons and either block or let pass both members of an entangled pair, at least in theory. So a photon arriving at one detector should have its twin appear at the other. As before, the way you measure one should affect the other. Jensen suggested that such a setup might let you send a signal from one detector to another instantaneously -- a highly controversial claim, since it would seem to demonstrate faster-than-light travel."
"Shape of photon" is really the shape of its landscape quantum potential Q or mode function or "wave packet." In a laser pulse each photon has identical shape - the shape of the macro pulse itself. This is same as a Bose-Einstein condensate - all the photons in the pulse are in the same "single particle wave packet" (equivalent to a Q) i.e. collapse in phase space what we call macroquantum ODLRO "more is different".
However, even in the incoherent micro-quantum "ensemble" without macroquantum ODLRO all the quanta in the experiment must be prepared in same way.
"One can imagine the photons as bulletlike cylinders fired at the
target, Howell says, only each cylinder is two-to-three
millimeters in diameter and up to a meter long. As the cylinders
pass through the stencil, the parts that hit the opaque material
are absorbed and no longer represent locations at which the photon
can potentially be measured."
'It's just like when you put Play-Doh through one of those
stencils,' Howell says. Like the Play-Doh, each pulse that passes
through the stencil does carry the whole "UR" shape, but, as with
the two-slit diffraction pattern, one photon does not produce the
whole image on being detected.
Howell says the experiment is the first demonstration that optical buffering, or delaying of light, can reliably transmit two-dimensional information in this case an image. The kind of information sent down optical fibers is normally encoded along the length of the pulse, he says.
On Jan 25, 2007, at 2:50 AM, AB wrote from Moscow:
I belive that the core of a photon may apparently be bullet like a string, but I do not believe that information on the image may be encoded in one photon. I can suppose that this photon excites many other weak photons on the bound of the stencil image, which may produce this image on target.
Let me clarify this and try to be more precise. Of course any single photon detection is a localized point like event and all information on the shape of the wave function. I am using Bohm's pilot wave theory here. Of course it's more complicated for the photon, let's use an electron instead to make it as simple as possible.
The electron really is an extended hard massy ball like in Newton - to the first approximation. It is equivalent to a "string".
Think of it as your Kerr vacuum solution "geon" except Lp* ~ 10^-17 cm not 10^-33 cm
e.g. Abdus Salam's "f-gravity" sort of picture with Wheeler's "Mass without mass" etc.
The electron has a definite classical path rolling like a stone on the landscape of its quantum potential Q made from its wave function PSI. The quantum potential Q encodes the "message" we want to send using entanglement.
The particle here is a test particle without direct back-reaction changing the landscape it rolls on in a self-organizing way - in the orthodox approximation of "no cloning," i.e. "signal locality" in spite of nonlocal entanglement.
Of course we need a large statistical sample of particles all on the same landscape with chaotic initial conditions that populate all final possible positions on the landscape's basins of attraction where the detection is made. This is similar to the chaotic inflation of Susskind's cosmic landscape whose minima contain actual universes. As Above, So Below.
So each quantum particle does not encode the image in the EXPLICATE ORDER (detected as a point), but it does in the IMPLICATE ORDER of the WAVY Quantum Potential Q.
An entangled pair state electrons a & b does not factorize.
In terms of a basis set of modes, one possible class of entangled states is
(1a) Psi(a,b) = Sum over k psi(a)kpsi(b)k
We can write this same thing in the equivalent Q representation
(1b) Q(a,b) = Sum over k Qk(a)Qk(b)e^i@k
including the relative phases @k that for our initial arbitrary choice of convenience has all @k = 0.
Where the complex mode functions psi(...)k and their corresponding real Qk landscapes are the same shape, but have widely separated supports in the actual nonlocal measurement. This special unnormalized form is maximally entangled assuming equal probabilities to measure each k-mode. However, the real experiment with delayed choice UR Stencil will not in general measure those modes. The UR Stencil is a filter that will change the above initial entangled state into
(2a) Psi(a,b) = Sum over k A(k)psi(a)kpsi(b)k
(2b) Q(a,b) = Sum over k A(k)Qk(a)Qk(b)e^i@k
where A(k) are a set of complex UR stencil modulation coefficients defining the shape of the nonlocal signal violating the no-cloning theorem.
In this case, we have a counter-factual, if we did a different experiment other than the one we do here, we would get a different definite result. In particular if we measure the k-modes, then the von-Neumann projection postulate of what Antony Valentini calls the "sub-quantal heat death" of the "boring universe" (Matt Visser's term) gives the Born probability spectrum
(3) P(k) = |A(k)|^2
However, this may do if we assume that the above states are nonlocal in time as well as space.
Let A(k) be inserted by delayed choice (in the relative future of the detection of receiver photon "b") in the path of sender photon "a" in a large ensemble of pairs emitted in an intense pulse where each pair in the ensemble obeys (1). Assume the result is (2). Execute Stapp's algorithim, i.e. integrate over all the orthogonal Q modes. The result in the past is an incoherent mixture of modes each with quantum potential landscape Qk(b). The Born probability of each mode in the past is then precisely (3) using von Neumann's rule. The nonlocal signal is |A(k)|^2 that is the image (b) in
That is, even using von Neumann's rule, if the future delayed choice filter (AKA stencil) is imaged by the twin photons in the entangled pairs then we are home free. We do not seem to need a coincidence circuit. The no-cloning theorem is possibly wrong. In any case this is what the popular descriptions of Dopfer's experiment seem to suggest and what seems to be in Cramer's mind at least subliminally or implicitly. R Srikanth seems to have a similar idea. Hepburn & Peacock also set the stage that the unitary operators U generated by Hamiltonians H may not be local. Whether or not they are is purely empirical.
If any of this is true then as I said in my archive paper http://arxiv.org/abs/gr-qc/0602022 Lenny Susskind needs to go back to the drawing board. Information can leak out of the black hole much faster than the Hawking radiation. We can even see beyond the deSitter observer horizons.
Now the Dopfer experiment + the recent UR experiment seem to say that we can control the collapse at the sender a with a stencil so that for k = UR
Q(a,b) collapses controllably to Qur(a)Qur(b) =
Now this step violates von Neumann's "projection postulate", but it obtains in a NEW total experimental arrangement not conceived by von Neumann.
This would be a post-quantum theory beyond 20th century quantum theory.
Signal locality is based on premise of uncontrollable collapse - here we have a new set of conditions. Ultimately it's an empirical issue.
Signal nonlocality violating the no-cloning theorem says you can use entanglement as a stand-alone C^3 system without needing any coincidence circuits that prevent real faster than light and retro-causal back from the future local decoding of the "UR" message.
They are saying local fringes on both sides without a coincidence circuit on both sides when delayed movable detector is close to lens, and no fringes on both sides when that movable detector is far from the detector. This is close to the setup I had in Gary Zukav's Dancing Wu Li Masters in 1979 before the little creep deleted it in later editions. If the pulses are intense enough, you do not have to wait. You get a lot of photons identically prepared in a short time. That objection you raised is not crucial, though it probably won't work for other reasons.
My new suggestion is to replace the delayed double slit by different shaped stencils at different times - provided only that Cramer's original version works as he thinks it might, but probably won't.
This would seem to contradict pair correlation interferometry experiments where you only see the fringes indirectly in the correlation data output from the coincidence circuit. See math below.
So now we have this new extraordinary "Dopfer" claim:
"Birgit Dopfer found that photons that were 'entangled', or linked by their properties such as momentum, showed the same wave-or-particle behavior as one another. ... The double slits should filter out most unentangled photons and either block or let pass both members of an entangled pair, at least in theory."
And also on the "coincidence circuit":
To use this setup to send a signal, it needs to work without a coincidence circuit. Inspired by Raymond Jensen at Notre Dame University, Cramer then proposed passing each beam through a double slit, not only to give the experimenter the choice of measuring photons as waves or particles, but also to help track photon pairs. The double slits should filter out most unentangled photons and either block or let pass both members of an entangled pair, at least in theory. So a photon arriving at one detector should have its twin appear at the other. As before, the way you measure one should affect the other. Jensen suggested that such a setup might let you send a signal from one detector to another instantaneously -- a highly controversial claim, since it would seem to demonstrate faster-than-light travel.
Patrick Barry wrote this piece for the New Scientist, where it first appeared. Contact us at firstname.lastname@example.org.
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