My story starts
almost half a century ago in a school in South East London.
Fig 1.
Gold Leaf Electroscope
used
in Photoelectric Effect

On an October morning my physics teacher, Mr Poole, decided that it was time to demonstrate the wave–particle duality of light [1].
With two demonstrations, the 1887, Heinrich Hertz, Photoelectric Effect experiment [2] and the 1801, Thomas Young, DoubleSlit experiment [3], we were first shown how light in the form of photons could liberate electrons from a metal plate and then how light in the form of waves could interact, producing an interference pattern.
Fig
2. Interference Pattern from Sodium Vapour Lamp via two slits

This early and limited glimpse
into the strange world of quantum physics [4],
provided me with a “world model” [5] that I was
comfortable with and one which I did not question in my early career as a
Microwave Systems Engineer.
As time moved on I progressed through roles such as Project Engineer, Internet Systems Developer and Research Programme Manager, finally almost 50 years later I found myself supporting a small number of very bright PhD students in their research. It was only then that the early world model I had created in my mind seemed insufficient.
Fig 3. A scanning tunneling microscopy image of
singlewalled carbon nanotube

I had met with one of my PhD students and we were discussing the interaction of electric fields in adjacent carbon nanotubes [6], within a wire composed of the tubes [7].
I quickly realised that I needed a better understanding of quantum mechanics [8].
I quickly realised that I needed a better understanding of quantum mechanics [8].
Fig 4. Allan Adams, MIT 
I read several texts on the subject but still did not really understand enough. So I looked to the open course material at MIT and specifically some video lectures by Allan Adams on Quantum Mechanics [9].
Suddenly it all began to fall into place and I felt confident again, that is until I watched Allan talk about an experiment carried out at the Hitachi Central Research Laboratory, by Akira Tonomura (1987).
Akira Tonomura recreated the
famous DoubleSlit experiment, but with individual particles (electrons) [10]. His conclusion was brief and its true
significance was only to be realized later, he said, "We realized a
twoslit interference experiment, once regarded as a pure thought experiment
with no hope of precise execution, with a combination of both electroncounting
and magnifying techniques. The resultant buildup of the interference pattern
is exactly as predicted by quantum mechanics". (Subsequently this has also
been shown with a light source producing small numbers of photons, which in
effect pass though the slits individually) [11].
How could individual
electrons passing through one or other of the two slits form an interference
pattern, what were they interacting with? I was frankly shaken.
Fig 5. Interference pattern from single particles 
My nice comfortable model of particles and waves had suddenly been ripped apart. I was quite honestly I bit miffed, why had I not heard about this?
One of my colleagues at college explained that one of the challenges of quantum physics is that the electrons are particles and waves simultaneously. The particles can never produce such interference patterns on their own, they need to somehow gain the information that the “wave function” [12] provides, so all any other explanation is doing is replacing the wave function by something that does the same thing. (NB: The Schrödinger equation [13] determines how wave functions evolve over time)
However that said, apparently while I had been away being an Engineer, several arguments, some a little more complex and implausible than others, have been developed to explain how individual particles can produce an interference pattern in the experiment.
I consulted Google.
On one end of the spectrum
was the idea that the particle changes into a wave, passes through both slits,
and then changes back into a particle, which is subject to interference with
itself, this seemed to be in quantum mechanical terms sort of reasonable [14], but I read on.
Fig 6. Mathematical plot of a Lorentzian wormhole (EinsteinRosen bridge) 
At the other end of the spectrum
of thought was the argument that the electron is somehow connected to other
electrons in SpaceTime [15], by something like
an “EinsteinRosen bridge” [16] and although
they do not pass through the slits at exactly the same time they still
experience the effects of interaction, this being known as Quantum Entanglement
[17].
From Wikipedia  Quantum
entanglement is a physical phenomenon that occurs when pairs or groups of
particles are generated or interact in ways such that the quantum state of each
particle cannot be described independently of the others, even when the
particles are separated by a large distance—instead, a quantum state must be
described for the system as a whole.
I had certainly heard of this, but only in terms of quantum computing [18].
But on reading further I
found that this explanation might help in understanding why when an attempt is
made to “observe” what is happening at each slit in the single particle
experiment, the interference pattern ceases. However a physicist friend at
college recommended I read, “Origin of quantummechanical complementarity
probed by a `whichway' experiment in an atom interferometer, by S. Durr, T.
Nonn & G. Rempe [19].
In this experiment when a
`whichway' detector is employed to determine the particle's path, the
interference pattern is destroyed. However the atom’s momentum is far too small
to explain the disappearance in terms of Heisenberg's uncertainty principle [20]. (one standard explanation for the effect).
Fig 7. A cat, with its mirror reflection

Apparently Quantum entanglement theory tells us (Wikipedia), “it appears that one particle of an entangled pair "knows" what measurement has been performed on the other, and with what outcome, even though there is no known means for such information to be communicated between the particles, which at the time of measurement may be separated by arbitrarily large distances”.
Reading all this I envisioned Schrödinger's cat [21], with a twin.
Having read various papers
on the subject and consulted some physicist friends I was sort of comfortable
again, but at the same time took some solace in the fact that both Einstein and
Schrödinger were dissatisfied with the concept of entanglement [22], because it seemed to violate the speed limit on
the transmission of light. I found the following quote
from Niels Bohr, which made me feel a little better.
If quantum mechanics hasn’t profoundly shocked you, you haven’t
understood it yet [23].
And I might have left it
there but for an early arrival for lunch last week.
My college has an excellent
collection of science periodicals, so having arrived 30 minutes early, I decided
to catch up on the latest copy of Nature [24].
The title of one of the
articles caught my attention, Cosmic test backs 'quantum spookiness' (2^{nd}
February 2017) [25]. The article explained the
latest attempts, using light that had taken 600 years to reach us, to prove
quantum entanglement. I discovered that this type of experiment is known as a
“Bell Test Experiment” [26] after John Bell,
whose experiments are designed to demonstrate the real world existence of
certain theoretical consequences of the phenomenon of entanglement in quantum
mechanics.
I consulted Google again.
An earlier Nature article
looked worth a read, “The quantum source of spacetime” (16^{th}
November 2015) [27]. The article explained that
Mark Van Raamsdonk [28] had decided to tackle
one of the deepest mysteries in physics: the relationship between quantum
mechanics and gravity, he explains his theories in, “Building up spacetime with
quantum entanglement”, (31^{st} March 2010) [29]
Fig 8. Tadpole Galaxy PS1  NASA

Even though I had been away
from the subject for a long time I certainly knew that there was really only
one great challenge facing physicists today – a unified theory of everything [30] – a single theory which brings together the very
large and the very small – quantum mechanics and gravity. I knew that the
successful unification of quantum mechanics and gravity had eluded physicists
for nearly a century.
I discovered that as well as
Mark Van Raamsdonk, a second researcher, Leonard Susskind [31], had written some key research on the subject,
“Cool horizons for entangled black holes” [32],
in which he says, “General relativity contains solutions in which two distant
black holes are connected through the interior via a wormhole, or
EinsteinRosen bridge. These solutions can be interpreted as maximally
entangled states of two black holes that form a complex Einstein–Podolsky–Rosen
(EPR) pair [33]. We suggest that similar
bridges might be present for more general entangled states”.
So, apparently, the way
around the problem with information travelling faster than the speed of light,
in relation to entangled particles at a distance [34],
is to speculate that a nanoscale wormhole [35]
might exist between entangled particles? [36]
Are we any closer to a unified theory?
I really don’t know, but certainly there are some really big questions being asked and they are both opening up new lines of thought and questioning existing assumptions, which must be good.
But what I find truly amazing is that Einstein knew there was more to do. He believed quantum mechanics was correct, but desperately wanted to find a way to "complete" quantum mechanics so it made sense [37], something I would support!
Oh, and the cat is alive and well and living in Finland.

My sincere thanks to my son for proof reading this article, my daughter for her ideas and comments and my friends and colleagues in Physics for their comments and for pointing me at some quite amazing research papers.
 WaveParticle Duality  http://hyperphysics.phyastr.gsu.edu/hbase/mod1.html
 Photoelectric Effect  https://en.wikipedia.org/wiki/Photoelectric_effect
 The Double Slit Experiment  https://en.wikipedia.org/wiki/Doubleslit_experiment
 Quantum Physics  https://www.khanacademy.org/science/physics/quantumphysics
 Mental Models  https://en.wikipedia.org/wiki/Mental_model
 Advances in the science and technology of carbon nanotubes and their composites: a review, Erik T. Thostensona, Zhifeng Renb, TsuWei Choua  https://wwwprod.bc.edu/content/dam/files/schools/cas_sites/physics/pdf/Ren/p85.pdf
 Electrical Properties of Carbon Nanotube Based Fibers and Their Future Use in Electrical Wiring, Agnieszka LekawaRaus, Jeff Patmore, Lukasz Kurzepa, John Bulmer & Krzysztof Koziol http://onlinelibrary.wiley.com/doi/10.1002/adfm.201303716/full
 Quantum Mechanics  https://en.wikipedia.org/wiki/Quantum_mechanics
 Allan Adams on Quantum Mechanics  https://ocw.mit.edu/courses/physics/804quantumphysicsispring2013/lecturevideos/
 Demonstration of singleelectron buildup of an interference pattern, A. Tonomura, J. Endo, T. Matsuda, and T. KawasakiH. Ezawa  http://aapt.scitation.org/doi/abs/10.1119/1.16104
 Researchers observe single photons in twoslit interferometer experiment https://phys.org/news/201106quantumphysicsphotonstwoslitinterferometer.html
 Wave Function  https://en.wikipedia.org/wiki/Wave_function
 The Schrödinger equation  https://en.wikipedia.org/wiki/Schr%C3%B6dinger_equation
 Do atoms going through a double slit ‘know’ if they are being observed?  http://physicsworld.com/cws/article/news/2015/may/26/doatomsgoingthroughadoubleslitknowiftheyarebeingobserved
 SpaceTime  https://en.wikipedia.org/wiki/Spacetime
 EinsteinRosen Bridge  https://en.wikipedia.org/wiki/Wormhole
 Quantum Entanglement  https://en.wikipedia.org/wiki/Quantum_entanglement
 Quantum Computing – https://en.wikipedia.org/wiki/Quantum_computing
 Origin of quantummechanical complementarity probed by a `whichway' experiment in an atom interferometer, by S. Durr, T. Nonn & G. Rempe  http://www.nature.com/nature/journal/v395/n6697/full/395033a0.html
 Heisenberg's uncertainty principle  https://en.wikipedia.org/wiki/Uncertainty_principle
 Schrödinger's cat https://en.wikipedia.org/wiki/Schrödinger's_cat
 Both Einstein and Schrödinger were dissatisfied with the concept of entanglement https://en.wikipedia.org/wiki/Quantum_entanglement
 If quantum mechanics hasn’t profoundly shocked you, you haven’t understood it yet  https://www.brainyquote.com/quotes/quotes/n/nielsbohr164546.html
 Nature  http://www.nature.com
 Nature, Cosmic test backs 'quantum spookiness' (2nd February 2017)  http://www.nature.com/news/cosmictestbacksquantumspookiness1.21401
 Bell Test experiments  https://en.wikipedia.org/wiki/Bell_test_experiments
 Nature  The quantum source of spacetime  http://www.nature.com/news/thequantumsourceofspacetime1.18797
 Mark Van Raamsdonk  http://www.phas.ubc.ca/~mav/vanraamsdonk.html
 Building up spacetime with quantum entanglement  https://arxiv.org/abs/1005.3035
 Will we ever have a theory of everything?  http://www.bbc.co.uk/earth/story/20150409canscienceeverexplaineverything
 Leonard Susskind  https://en.wikipedia.org/wiki/Leonard_Susskind
 Cool horizons for entangled black holes, Juan Maldacena and Leonard Susskind – https://arxiv.org/abs/1306.0533
 Einstein–Podolsky–Rosen (EPR) https://en.wikipedia.org/wiki/EPR_paradox
 Cosmic Test Bolsters Einstein's “Spooky Action at a Distance” https://www.scientificamerican.com/article/cosmictestbolsterseinsteinsldquospookyactionatadistancerdquo/
 Wormhole  https://en.wikipedia.org/wiki/Wormhole
 Creation of entanglement simultaneously gives rise to a wormhole  https://phys.org/news/201312creationentanglementsimultaneouslywormhole.html
 Quantum mechanics so it makes sense  https://phys.org/news/201406einsteinquantummechanicshedtoday.html
Figures:
Fig 2. Double slit
experiment, with sodium vapour lamp – Wikimedia  https://commons.wikimedia.org/wiki/File:Young%27s_twoslit_experiment_and_Lloyd%27s_mirror.png
Fig 3. A scanning tunneling
microscopy image of singlewalled carbon nanotube – Wikipedia  https://en.wikipedia.org/wiki/Carbon_nanotube
Fig 4. Allan Adams MIT
Lectures on Quantum Mechanics  MIT  https://ocw.mit.edu/courses/physics/804quantumphysicsispring2013/lecturevideos/
Fig 5. Interference pattern
from single particles – Thierry Dugnolle  Wikimedia  https://commons.wikimedia.org/wiki/File:Waveparticle_duality.gif
Fig 6. Mathematical plot of a Lorentzian wormhole (EinsteinRosen bridge)  Wikipedia  https://en.wikipedia.org/wiki/Wormhole
Fig 7. A cat and its
reflection – image owned by author.
Fig 8. Tadpole Galaxy PS1 –
NASA  . https://apod.nasa.gov/apod/image/1211/TadpoleGalaxyPS1V9snyder.jpg
No comments:
Post a Comment