Thanks Art Wagner - also related article on optomechanics in latest Physics Today
Proposal to demonstrate the non-locality of Bohmian mechanics with entangled
Boris Braverman1, 2 and Christoph Simon2
1Department of Physics, MIT-Harvard Center for Ultracold Atoms, and Research Laboratory of Electronics,
Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
2Institute for Quantum Information Science and Department of Physics and Astronomy,
University of Calgary, Calgary T2N 1N4, Alberta, Canada
Bohmian mechanics reproduces all statistical predictions of quantum mechanics, which ensures that entanglement cannot be used for superluminal signaling. However, individual Bohmian particles can experience superluminal influences. We propose to illustrate this point using a double double slit setup with path-entangled photons. The Bohmian velocity field for one of the photons can be measured using a recently demonstrated weak-measurement technique. The found velocities strongly depend on the value of a phase shift that is applied to the other photon, potentially at spacelike separation.

Nonlocal Interferometry Using Macroscopic Coherent States and Weak Nonlinearities

B. T. Kirby, J. D. Franson
(Submitted on 23 Jul 2012)
A straightforward method for performing nonlocal interferometry using macroscopic coherent states is described. The required entanglement can be generated using weak nonlinearities while Bell's inequality can be violated using single photons as a probe. A large number of photons can be absorbed with only a small reduction in the visibility of the nonlocal interference, which may be of practical use in quantum communications in addition to being of fundamental interest.
Comments:    4 pages, 5 figures
Subjects:    Quantum Physics (quant-ph)
Cite as:    arXiv:1207.5487v1 [quant-ph]
Submission history
From: James Franson [view email] [v1] Mon, 23 Jul 2012 19:12:18 GMT (238kb)
On Jul 28, 2012, at 1:41 PM, art wagner <This email address is being protected from spambots. You need JavaScript enabled to view it.> wrote:
Keith wrote:

Jack's idea is interesting b/c he's using standard quantum theory and exploring a corner case--distinguishable but non-orthogonal states which have interesting properties. Using the standard formalism, you find a modulation term that seems to be under the control of Alice, the sender. I get slightly different results depending on the specifics of how the signaling scheme is defined, but I so see a modulation term. The coherent states are subtle and so there could still be errors in what I've done, but there does seem to be something going on to me.

Jack Sarfatti • Yes, Keith, that is correct. You can force the effect to vanish by adhoc normalization, but that is a contradiction in the formalism. If the Born probability rule applies using normalized density operators and measurement projection operators should not require an adhoc second normalization. Since the coherent states are eigenstates of a non-Hermitian operator the usual conditions for the Born probability may not apply. This is an empirical question since forcing the second normalization is circular reasoning assuming what must be tested for by experiment. It's the orthogonality of base eigenstates of Hermitian operators that is assumed for the Born probability axiom to work.

21 minutes ago

Jack Sarfatti • Keith, relevant to this is P.W. Anderson's "phase rigidity" of spontaneous broken symmetry order parameters. The Glauber coherent states are such order parameters for a spontaneous broken global U1 gauge group corresponding to number-phase complementarity. The Glauber states have been generalized to any Lie Group G not just U1. It's this phase rigidity that is the cause of the violation of the Born probability rule in my opinion. However, one may also need a topological obstruction of some kind to get the phase rigidity. In superfluids it's the quantized vortices from the nonlinear term in the Landau-Ginzburg equation that replaces the Schrodinger eq (effective c-number IR field theory) that are the obstructions.

1 second ago