Exotic Photon Trajectories in Quantum Mechanics

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Jim and Randy discuss strange trajectories observed in triple slit experiments with metallic plates. Photons seem to pass through one slit, come back through the middle slit, and out the third due to their interactions with surface plasmons. There are implications in this experiment about the way in which wavefunctions need to be interpreted in non-relativistic quantum mechanics.

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Notes:

1. The paper we read for this program: Exotic looped trajectories of photons in three-slit interference by Magaña-Loaiza, et al. [arXiv]

2. Our subreddit.

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The following post was made to the arXiv_plue subreddit about this paper:

This paper discusses deviations from the predictions of the Born rule (the interpretation of the probability of an observation being the norm of the convolution of the wave functions of the initial and final states) that are observed when the interference effects of a triple slit experiment are examined. By using a three slit experiment rather than a two slit experiment, the authors follow the procedure of Sinha, et al., that showed a null result in 2010. This procedure looks at all seven combinations of the three slits (in a random order), subtracting the three slit interference pattern from the interference patterns of the other six combinations. The combination of the six double and single slit interference patterns should exactly match the the triple slit interference pattern if the Born rule held.

In 2010, they found that the Born rule held, to one part in 100.

This paper (published in Nature Communications) uses surface plasmons on a gold barrier to "enhance the electromagnetic near-fields" near the slits in a way that increases the likelihood of trajectories that cause violations of the Born rule. These trajectories snake and backtrack through the triple slit apparatus.

The comparisons between the single, double, and triple slit interference patterns indicate evidence for these snaking trajectories. Whether this really indicates evidence that the Born rule fails, I'm not sure.

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A Gravitational Arrow of Time

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Recorded: 2017/01/28 Published: 2017/07/16

Jim and Randy discuss a cosmological theory that purports to find an explanation for the arrow of time in gravitational theory based on the shape and distribution of matter and how it evolves.

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Notes:

1. The paper we read for this program: Identification of a Gravitational Arrow of Time by Barbour, Kowslowski, and Mercati.

2. Mentioned in this episode: The Physical Basis for the Arrow of Time by H. Dieter Zeh.

3. Mentioned in this episode: Gravity From the Ground Up, B. Shutz.

4. [Update] It came to me in the shower: the word I was looking for is "eschatological."

5. Our subreddit.

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Photonic Molecules and Optical Circuits

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Recorded: 2017/01/21 Published: 2017/07/16

Randy tells Jim about photonic molecules, pairs of photons that create bound states like molecules do through a force mediated through an ultracold gas and similar ideas in optical circuits. They also discuss application of the same for quantum computing.

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Notes:

1. The papers we read for this program:

Firstenberg, O., Peyronel, T., Liang, Q.-Y., Gorshkov, A., Lukin, M. and Vuletic, V., "Attractive Photons in a Quantum Nonlinear Medium." Nature 502, 71 (2013)

2. My reservations about this episode. Probably just above this one.

3. Our subreddit.

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Requirements for Gravitational Theories

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Recoded: 2017/01/15 Published: 2017/06/30

In this episode Jim and Randy talk about how to evaluate alternative gravity theories. What sort of things do we want them to explain, what experiments do they have to predict, and what theoretical requirements do they have to meet. This is in some ways a continuation of Episode 9 - f(R) Theories of Gravity, but the discussion is relevant to all attempts to amend gravitational theory.

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Notes:

1. "f(R) Theories of Gravity, by Thomas Sotiriou and Valerio Faraoni". The basis for this discussion and the last program's, as well.

2. The list Randy refers to in the episode. Probably just above this one. 3. Our subreddit.

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List of Requirements for Gravitational Theories

Here it is without fanfare. If you have any questions about any part of it, please comment in the comments:


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To be theoretically consistent and compatible with experiment, a theory of gravitation must:
(1) Predict correct cosmological dynamics
a. Big bang nucleosynthesis
(2) Produce the correct evolution of cosmological perturbations
a. Cosmic microwave background
b. Large scale structure
(3) Have the correct weak-field limits
a. Reproduces Newtonian Mechanics
b. Predicts post-Newtonian experiments in weak field
c. Produces stable solutions
i. Matter-side instabilities (Dolgov-Kawasaki)
1. Ground states should be highly symmetric
ii. Gravity-side instabilities
1. Stable de Sitter solutions
iii. Stability of the first loop in quantum gravity
iv. Stability in the face of inhomogeneous but isotropic perturbations
v. Black hole nucleation
(4) Not contain any ghost fields
(5) Admit a well-posed Cauchy problem
(6) Reasonable theory of gravity waves

f(R) Theories of Gravity

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Recorded: 2016/12/17 Published: 2017/06/02

Jim and Randy discuss gravitational theories that modify general relativity by changing the action using a polynomial dependence on the Ricci scalar. Although not physically motivated, some of these theories produce effects similar to those of dark matter, dark energy, and cosmological constants.

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Notes:

1. "f(R) Theories of Gravity, by Thomas Sotiriou and Valerio Faraoni". The basis for this discussion and the next program's, as well.

2. Our subreddit.

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Vacuum Fluctuations and the Casimir Effect

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Recorded: 2016/12/10 Published: 2017/04/27

What are the latest theoretical and experimental developments with the Casimir effect, and are vacuum fluctuations physical, or simply a convenient model for calculating the effects of quantum noise in the fields of matter? On this episode of Physics Frontiers, we explore some of the surprising discoveries that physicists have made unraveling the strange dynamics of mechanical components so small that they can’t even be seen through an optical microscope. And along the way we consider some of the fundamental mysteries of quantum field theory, as applied physics enters the realm of nanotechnology…and approaches exotic new possibilities like quantum levitation.

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Notes:

(1) Materials Perspective on Casimir and van der Waals Interactions by Woods, et al., the basis for this discussion.

(2) Our Subreddit

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