Plans & Prospects 2023

Quantum entanglement
and reality
You probably already know that, at subatomic scales, we enter the strange world
of quantum physics, governed by counterintuitive laws very far from the classical
mechanics of the human-scale world. But did you know that quantum physics provides
our most complete description of reality, and that we can even observe quantum
effects in living creatures? Professor Vlatko Vedral, a Governing Body Fellow, brings us
up to speed on his research into the “ultimate logic of everything”.
Vlatko Vedral
Vlatko Vedral (BSc, PhD, Imperial
College) is a Professor of Quantum
Information at Oxford. He has
published over 400 research papers
on various topics in quantum physics
and quantum computing and is
one of the Clarivate Highly Cited
Researchers. He has given numerous
invited plenary and public talks during
his career. These include a specialised
talk at a Solvay meeting (2010) and a
popular one at the International Safe
Scientifique (2007). He was awarded
the Royal Society Wolfson Research
Merit Award in 2007, the World
Scientific Medal and Prize in 2009,
the Marko Jaric Award in 2010 and
was elected a Fellow of the Institute
of Physics in 2017 and a member of
the European Academy of Sciences in
2020. He is a consultant to the World
Economic Forum on the Future of
Computation. Vlatko is the author
of 4 textbooks and 2 popular books
(Decoding Reality and From Micro to
Macro). He gives regular interviews to
the media and is actively engaged in
popularisation of physics in pieces for
New Scientist, Scientific American and
major UK and overseas newspapers.
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Isaac Newton, who discovered what
we now call classical physics, thought
that everything is made up of particles.
However, various aspects of light
could not be explained if light was
also made up of particles. Ultimately,
James Clerk Maxwell - standing on the
shoulders of Huygens, Young, Faraday
and many others - proved that light is
actually an electromagnetic wave. At
that point the world (still classical) was
understood to be made up of two kinds
of entities, particles (constituents of
matter) and waves (things making up the
electromagnetic field).
Then came Albert Einstein who
(seemingly, but not really) reverted back
to Newton and said that light is, after all,
made up of particles (photons), though
he did admit that they can also behave
like waves (which is how we can account
for the interference of light). This was
the beginning of quantum physics.
Finally, Louis de Broglie hypothesized
that material quantum objects (such as
electrons) can also behave like waves.
This led to a unification (everything
is a wave and a particle) and inspired
Bohr to talk about complementarity,
namely the fact that all entities can
manifest their particle-like or wave-like
nature depending on how we “look at”
(experiment with) them. This is at the
heart of the famous wave-particle duality
of quantum systems.
So, then, what is the right ontology
when it comes to reality? Is the world
made of particles or waves or things
that sometimes behave like particles or
waves? According to quantum physics,
everything is actually made up of waves.
But these are quantum waves (or
q-waves for short), meaning that the
entities that are doing the waving are
what Paul Dirac called q –numbers (as
opposed to the ordinary c-numbers, “c”
being classical). This picture emerged
through the work of Heisenberg, Mott,
Schrödinger and Everett (all standing on
the shoulders of William Hamilton).
Let me explain why everything is a
q-wave and why this presents us with
the best picture of reality at present.
First there was a problem. If particles are
waves, the key phenomenon to explain
in the 1920s was the observation of the
alpha-particle decay in a cloud chamber.
This experiment seemed to present a
paradox for quantum physics.
An alpha-particle is a Helium nucleus
(two protons and two neutrons) and
it sometimes gets ejected in a nuclear
decay of a larger nucleus. A cloud
chamber was a great invention to
observe such particles (worthy of several
Nobel Prizes), though nowadays you can
make one in 15 minutes in your own
house with everyday kitchen utensils
(there are many YouTube videos on
this). The idea, as the name suggests, is
to have a particle travel through a gas
that can readily be ionized by collisions
with the particle. As the particle collides
with the gas molecules, it ionizes