Nobel Prize-winning researchers in physics have proven that the universe does not physically exist in a single place.
Currently, quantum informatics is among the most active directions in the field of physics.
It brings together Einstein's General Theory of Relativity
and quantum mechanics through the still-mysterious behavior of black holes.
It also deals with the construction and operation of quantum sensors,
which are increasingly being used to study everything from earthquakes to dark matter.
It also often elucidates the perplexing nature of quantum entanglement,
a phenomenon that is essential to modern materials science and underlies quantum computing.
CONSCIOUSNESS
"What makes a computer a 'quantum' one?" - Nicole Junger Halpern,
a physicist at the National Institute of Standards and Technology, asks rhetorically.
"One of the most common answers is entanglement, and the main reason we understand entanglement
is because of the tremendous contributions of Bell and three 2022 Nobel Prize winners.
Without understanding entanglement, quantum computers probably wouldn't have been created. "
Complex experiments with entangled light have revealed a profound mystery underlying reality.
One of the most disturbing discoveries of the last 50 years is that the universe is not locally real.
The term "real" means that objects have rigid properties that are not affected by observation.
That is, the red apple can remain so even when no one is looking at it.
"local" means that this apple can only be affected by its immediate surroundings,
and any measurable influence or causes, according to the normal rules of physics,
cannot travel faster than the speed of light.
Research at the limits of quantum physics has shown that these two things cannot be true at the same time.
It shows that objects are not only affected by their environment
but also that they may not have certain properties before they are measured,
which of course is deeply at odds with our everyday experience.
As Albert Einstein once said to a friend: "Do you really think the moon isn't there when you're not looking at it?".
A phrase from the writer Douglas Adams shared that the rejection of local realism made many people angry
and was generally considered a bad move, and the three scholars John Clauser, Allen Aspect,
and Anton Zeilinger get the blame for it!
In 2022, they jointly take the Nobel Prize in Physics "for experiments with entangled photons
demonstrating the violation of Bell's inequalities and pioneering the science of quantum information".
This award was highly anticipated by their colleagues,
who said it was an extremely well-deserved recognition for upending reality as we know it.
From the 1940s until recently, research on quantum fundamentals was often dismissed as a philosophy or even nonsense.
Many scientific journals refused to publish articles on the subject,
and academic positions that allowed for this kind of research were almost impossible to fill.
In 1985, Sandu Popescu's mentor warned him against doing a Ph.D. on the subject, telling him:
"If you do, you'll have fun for five years and then you'll be out of a job".
Nowadays, quantum informatics is among the most dynamic subfields in all of physics.
Among other things, it clarifies the often confusing nature of quantum entanglement,
which is an essential element of modern materials science and underlies quantum computing.
The main problem with quantum mechanics has never been its accuracy since it worked great from the beginning
when physicists developed it in the early 1900s.
What Einstein, Boris Podolsky, and Nathan Rosen had a problem with was the influence of the theory on reality.
Their analysis, called EPR, is based on an imaginary experiment to show how quantum mechanics can break down
under certain conditions and defy our beliefs about reality.
The Nobel Prize-winning experiments showed, however, that two particles,
regardless of the distance between them, can remain entangled in the quantum realm.
This contradicts local realism and Einstein's theory of relativity.
In theory, two particles could be at different ends of the observable universe and still be entangled.
A concept known as "non-locality".
"Alain Aspect, John Clauser, and Anton Zeilinger conducted ground-breaking experiments using entangled quantum states
in which two particles behave as a single entity even when separated," the Nobel Prize review said.
"Their results cleared the way for new technologies based on quantum information."
The 2022 Nobel Prize in Physics was actually awarded for an experiment dating back to 1972
and numerous subsequent ones that showed that the local realism view of the universe was wrong.
"It clarified what quantum mechanics really means," said Professor Thors Hans Hanson,
a member of the Nobel Committee for Physics, in connection with the award.
The scientists' findings actually show that the universe cannot be locally real because particles do not have
certain properties of spinning up or down before they are observed or measured.
Therefore, the simple act of observing a particle changes its state, which contradicts the rules of local realism.
In other words, the universe is "real," but only when we observe it.
"Experiments, starting with Clauser's earliest and continuing onward, show that these conclusions are not just philosophical,
but real - and like other real things, potentially useful," says Charles Bennett,
a prominent quantum researcher at IBM, before Scientific American.
How does it all begin?
In 1967, a graduate student named John Clauser at Columbia University,
who was investigating the possibility of proving hidden variable theories,
happened upon a library copy of Bell's paper.
When Clauser wrote to Bell two years later and asked if anyone had already conducted the test,
this was one of the first responses Bell received regarding his paper.
With the encouragement of Alexander Bell, three years later,
Clauser and scientist Stuart Friedman conducted the first Bell test.
Clauser had permission from his advisers but did not receive much funding.
In his experiment, everything had to be adjusted by hand, photons were sent in opposite directions,
then their state was assessed by detectors.
Clauser concluded that the results were strong evidence against hidden variables.
However, the result was not entirely conclusive, as there were some "loopholes" in the experiment
that could have allowed the influence of hidden variables to go unnoticed.
The most worrisome of these is the locality hole: if the photon source or detectors were able to exchange information,
the measured correlations could originate from hidden variables.
In 1976, Alain Aspect, a French optician, proposed a way to achieve this ultrafast switching.
His group's results, published in 1982, only confirmed Clauser's results: local hidden variables seem very unlikely.
"Maybe nature isn't as strange as quantum mechanics," Bell wrote in response to Aspect's test.
Gaps remained, however, and Bell died in 1990 without witnessing their closure.
It was Austrian physicist Anton Zeilinger who was passionate about filling in the gaps,
and in 1997 he and his team conducted a Bell test over a distance of almost half a kilometer,
which was unprecedented at the time.
Finally, in 2013, Zeilinger's group tackled several gaps simultaneously.
In retrospect, Bell's gapless experiment was a giant systematic engineering project.
One of the requirements for creating an experiment that closes the many loopholes is to find a perfectly straight,
free 60-meter tunnel with access to fiber optic cables.
The underground of Vienna's Hofburg Palace turned out to be the perfect location.
The results of the test, published in 2015, coincided with similar tests by two other groups,
which also found quantum mechanics to be as flawless as ever.
However, there is still one last loophole that needs to be closed.
Any physical connection between the components in the past, no matter how long ago,
can compromise the accuracy of the Bell test.
For example, if Alice and Bob shook hands before Alice left in a spaceship, then they have a shared history.
It is unlikely that a local theory of hidden variables can take advantage of this omission, but it is still possible.
In 2016, a team including Kaiser and Zeilinger conducted a space test of Bell.
They used telescopes located in the Canary Islands, and their random choice of detector settings is taken from stars
that are far enough apart in the sky that light from one does not reach the other for hundreds of years,
thus warranting a large time difference in their shared cosmic past.
Yet, even then, quantum mechanics triumphed.
It is difficult to get the public, as well as skeptical physicists, to understand the significance of Bell's test,
since the accuracy of quantum mechanics is already accepted.
The precision of quantum mechanics cannot rule out the possibility of local hidden variables; only Bell's tests can do that.
Kaiser adds that the motivation for Bell himself and the Nobel Prize winners to work on this topic was actually the question
"Could the universe work this way?".
Bell's tests help physicists shake off the human subjective point of view in their work.
In fact, the scientific community has concluded that Bell tests are a very practical way to observe reality.
What does it all mean?
Quantum physics claims that the universe is random and that the state of particles, such as electrons or protons,
can only be predicted using a probability distribution due to their non-deterministic nature.
In other words, we can predict how particles will behave once they are observed, only within a given probability.
This theoretical probability distribution is called a "wave function",
which contains information such as the position and momentum of the particle.
Here, however, it gets even more complicated - the very act of measuring or observing the particle -
- collapses that wave function into a given state of the particle,
which we can then observe - a phenomenon known as "particle-wave duality".
In theory, this is what makes the universe random.
But scientists still don't understand why and how the wave function collapses -
this collapse is called the "problem of measurement".
So what, for example, does the particle look like before it is observed?
We cannot know, because before the observation the particle is in a state of "quantum superposition".
This means that it is in infinitely many different states at the same time.
You're probably totally confused by now. Don't worry because, in the end, all you need to know is that at the quantum level,
nothing is as it seems and that the discoveries of John Clauser,
Anton Zeilinger, and Alain Aspect shook the world of science, turning reality on its head.
"The growing investments in quantum technology now being made around the world are based on scientific foundations
that stem from the pioneering work of Bell, Clauser, Aspect, and Zeilinger," said John Preskill,
lead scientist in quantum information at Caltech. institute, before Scientific American.
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