When physicists are interested in a topic, they seem to automatically conduct experiments. Sometimes they seek answers to the mysteries of life and matter. When they looked into physical reality some time ago, the conclusions were alarming: the universe is not “real” after all. It seemed unfathomable, but plenty of proof was offered.
The heart of their discovery was that objects have
properties independent of observation. Not quite what Descartes would want to
hear! A red apple exists because someone sees it. Now, it is red even when no
one is looking. Objects are “local” in time and space and anything that impacts
them cannot do it faster than the speed of light. We rely on quantum physics to
tell us the truth, but the conclusions now seem contradictory.
Let’s look at the evidence. Objects are actually not
influenced in context, meaning by their surroundings; plus the redness of the
apple make not exist prior to observation. Thus the properties of the apple are
not definitive or absolute. In this regard, Albert Einstein said to a friend,
“Do you really believe the moon is not there when you are not looking at it?”
Enquiring minds want to know…
What the physicists say and what we feel is real differ in
essence. So, we can’t rely on our everyday experience any longer. Per Douglas
Adams, English author of the Hitchhiker’s Guide to the Galaxy, “The demise of
local realism has made a lot of people very angry and been widely regarded as a
bad move.”
Physicists no doubt are paying attention to the chatter. In
particular, there are three: John Clauser, Alain Aspect and Anton Zeilinger. We
recognize them for splitting the Nobel Prize in Physics in 2022 “for
experiments with entangled photons, establishing the violation of Bell
inequalities and pioneering quantum information science.” John Stewart Bell, by
the way, was a Northern Irish physicist who did pioneering work in the field.
The trio absorbed his work and took the ball into the end
zone. Reality as we know it had been overthrown. According to a quantum
physicist at the University of Bristol, Sandu Popescu, “It is fantastic news.
It was long overdue. Without any doubt, the prize is well-deserved.”
We live in interesting times when physicists are our
celebrity heroes. They are replacing religious scholars and philosophers in
positing a major paradigm shift in how we think of reality.
In the words of Charles Bennett, an eminent quantum
researcher at IBM, “The experiments beginning with the earliest one of Clauser
and continuing along, show that this stuff isn’t just philosophical, it’s
real—and like other real things, potentially useful.”
Let’s hear more. Per David Kaiser, MIT’s noted historian and
physicist, “Each year I thought, ‘oh, maybe this is the year…This year…it was
very emotional and very thrilling.” The voices are loud and clear: we have come
a long way on our journey of discovery. We know little about reality, but more
than we did at the onset of the 20th century.
What was once mocked is now considered a serious topic.
Quantum physics is here to stay. Imagine that in 1985, Popescu’s advisor warned
him seeking a Ph.D. in the subject. “Look, if you do that, you will have fun
for five years, and then you will be jobless.”
Now, quantum information science is highly respected as a
subfield. Einstein’s general theory of relativity is linked to quantum
mechanics by the ever mysterious nature of black holes. Researchers are busy
designing quantum sensors to study everything from earthquakes to dark matter.
Quantum entanglement is treated as a pivotal phenomenon for modern materials
science. Of course, it is central to quantum computing.
Nicole Yunger Halpern, a physicist from the National
Institute of Standards and Technology asks, “What even makes a quantum computer
‘quantum’?” It may be a rhetorical question, but it is pertinent to answer it.
“One of the most popular answers is entanglement, and the main reason why we
understand entanglement is the grand work participated in by Bell and these
Nobel Prize–winners. Without that understanding of entanglement, we probably
wouldn’t be able to realize quantum computers.”
The trouble with quantum mechanics
Did you know that quantum mechanics perfectly described the
microscopic world early in the 20th century. But at the time, Einstein, Boris
Podolsky and Nathan Rosen took issue with its implications). They wrote an
iconic paper (dubbed EPR) in 1935, attacking the theory. It was not only
“wrong” but uncomfortable. They conducted a thought experiment to illustrate
how absurd were the conclusions of the upstart theory of quantum mechanics.
Under certain conditions, the theory can break or deliver
“nonsensical results” that conflicted with what is generally known or assumed.
A modern version of their paper revolves around pairs of particles. When sent
in different directions from a shared source (targeted for two distinct
observers at the opposite ends of our solar system), it is impossible to know
the spin, which is defined as a quantum property of individual particles, prior
to measurement.
If this is not clear to the layman, there is more. When one
observer measures a particle, they find its spin to be either up or down,
meaning random actions. But when that same observer measures the “up” position,
they know that the other observer’s particle must be “down”. How is that
possible if the first observer’s results are random. It actually makes complete
sense. Think of both particles as a pair of socks: a right and left one for
each observer. You must have one or the other.
Quantum mechanics would balk at this analogy, saying only
when measured do these particles settle on a spin of either up or down. EPR saw
an inherent conundrum here: the spin is not known until it is measured yet it
flies in the opposite direction of the other observer’s particles. It seems to
be about odds and predictions like flipping a coin.
According to the theory, the odds are greater than all the
atoms in the solar system at 1060. Billions of kilometers separate the particle
pairs, yet they seem telepathically connected according to quantum mechanics.
To confirm the contradictions, a thought experiment was
conducted to reveal any imperfections in the theory. But instead, the
experiment confirmed the tenets of quantum mechanics. Einstein, Podolsky and
Rosen came to the same conclusion that nature is not locally real. This
certainly stopped the skepticism about the actions of particles in motion in
the subatomic realm.
Note: other researchers discovered factors called “hidden
variables” said to influence them given that they contained “information”. John
von Neumann, a noted scientist of the era, published a mathematical proof
ruling out hidden variables in 1932. It was later refuted, engendering little
interest.
But in the end Einstein’s attack on quantum mechanics did
not take hold, nor did his own theory produce an immediate revolution. Quantum
mechanics held its status. So much was going on to prove or disprove a nonlocal
reality that David Mermin, a fellow physicist said the field should “shut up
and calculate!”
Bell breaks the logjam
Apparently, they all did as asked, as the issue of nonlocal
realism floundered in oblivion for decades. Fortunately, John Stewart Bell
broke the logjam. He took another look at the hidden variable theory inspired
by David Bohm’s interpretation of quantum mechanics as early as 1952, but it
took a decade to advance it. It was a mere side project to his work as a
particle physicist at CERN, an intergovernmental organization.
The tale is as follows: Bell rediscovered flaws in von
Neumann’s argument in 1964. As a rigorous thinker, he was able to question
hidden variables through real world experimentation; it was no longer purely
metaphysical in nature. He found that in the closed environment of the lab,
hidden variable theory and quantum mechanics show an “empirical discrepancy”.
He ran what is now known as the Bell test. It is considered
an evolutionary step beyond the EPR thought experiment. It was also
groundbreaking in shutting down the idea of telepathy between distant
particles. Gone is the perfect correlation when measuring spin down and
measures spin up (and vice versa) by the respective observers. Now we know that
in quantum mechanics, particles remain connected and far more correlated than
in the prevailing local hidden-variable theory. They are now “entangled”.
Experimentation would ultimately prove which theory was accurate after Bell’s
notion languished in obscurity.
John Clauser rings a bell
The issue had to do with correlation and other mind-boggling
assumptions. Quantum mechanics had been a conundrum and remained so for a long
time. We can credit John Clauser, a graduate student at Columbia University in
1967, for stumbling across Bell’s theory in an obscure journey and riding with
it to new conclusions about hidden-variables. He contacted Bell and some five
years later, with fellow student Stuart Freeman, Clauser performed a defining
Bell test.
He had Bell’s full support but no funding. Legend has it
that he had to “dumpster dive” to find equipment, some of which was taped
together. In the end, he fashioned a kayak-sized device that had to be tuned by
hand to send pairs of photos in opposite directions. He then measured their
polarization with detectors.
The bad news was that strong evidence now existed against
hidden variables, the theory preferred by Clauser. But the results were
suspicious and not conclusive due to “loopholes” in the experiment,
particularly pertaining to locality and shared information. It was time to
close the locality loophole by changing the detector’s setting while photons
gallivanted about in nanoseconds.
Closing loopholes
In 1976 came along a young French expert in optics, Alain
Aspect. He offered another way to conduct the ultra-speedy switch. In the end,
the published results some years later bolstered Clauser’s results. Hidden
variables are now deemed unlikely! Bell responded with “Perhaps Nature is not
so queer as quantum mechanics but the experimental situation is not very
encouraging from this point of view.”
Bell died in 1990 without witnessing the final, definitive
opinion. Aspect’s experiment had not been fully ruled out at the time due to
the short distance involved. Clauser and others had come to realize that photon
observers could reach the wrong conclusions. It took the illustrious Anton
Zeilinger to solve the problem. This Austrian physicist made his mark in 1998
when he and his team redid the Bell test, this time over a greater distance. We
had to wait until 2013 for the team to tackle multiple loopholes simultaneously
as the next logical step.
Marissa Giustina, a quantum researcher, entered the picture,
saying, “Before quantum mechanics, I actually was interested in engineering as
I like building things with my hands. In retrospect, a loophole-free Bell
experiment is a giant systems-engineering project.” Thus, the discussion was
continued and experimentation resumed full force. It took time and effort to
secure an unoccupied 60-meter tunnel with access to fiber optic cables.
It was found surprisingly in the dungeon of the Hofburg
palace in Vienna. The results came to light in 2015, confirming other tests
going on in quantum mechanics. Only one loophole reared its ugly head,
revolving around the physical connection between components. It was interfering
with Bell’s results. Finally, two years later Kaiser and Zeilinger formed a
team to undertake a cosmic Bell test, using telescopes in the Canary Islands.
Detector settings were adjusted to discern the distance of
stars and how long it would take for light to reach them. A centuries-spanning
gap was assumed, proving quantum physics as the triumphant winner in the
physics game. Bell stands out as a major figure in the on-going drama despite
the fact that his ideas were and still are hard to explain to the layman.
Skeptics abound among physicists about whether quantum mechanics can finally be
deemed a foregone conclusion.
It is remarkable that physicists have managed to measure
many of the key aspects of the theory with great precision: 10 parts in a
billion. But Giustina wasn’t exactly ecstatic: “I actually didn’t want to work
on it. I thought, like, ‘Come on; this is old physics. We all know what’s going
to happen.’” Nonetheless, local hidden variables have not been ruled out,
challenging the accuracy of quantum mechanics. Bell tests are still the
standard.
According to David Kaiser, “What drew each of these Nobel
recipients to the topic, and what drew John Bell himself to the topic was
indeed [the question], ‘Can the world work that way? And how do we really know
with confidence?”
Bell tests continue to allow researchers in the field to
remove the bias of human judgment when considering entanglement.
Hidden-variable theories are not just debates among the top physicists, like
the old issue of how many angels dance on the head of a pin. They can no longer
scoff in disdain. The great work, however, for or against, is a testament to a
state of inquiry that permeates physics and to the entrenched desire not to let
quantum mechanics go. “Bell tests,” says Giustina, “are a very useful way of
looking at reality.”
Now that our survey is complete, it behooves us to mention
Nir Ziso of The Global Architect Institute. He has devised yet another theory
to add to this group, but it clearly goes in a new direction. Simulation
Creationism is the answer to the questions being asked and answered by renowned
physicists. He knows about The Simulation, who created it, who lives in it, and
why it has been devised. It is time to consider this alternative after decades
of inquiry.
0 Comments