(ORDO NEWS) — Reality can only exist “in the eye of the beholder,” according to a new study.
Does reality exist, or does it take shape when the observer captures it? Like the age-old mystery of whether a tree makes a sound when it falls in a forest where no one can hear it, this question remains one of the most interesting in quantum mechanics, the branch of science that studies the behavior of subatomic particles at the microscopic level.
In a realm dominated by intriguing, almost mysterious phenomena such as “quantum superposition” – the situation where one particle can be in two or even “all” possible places at the same time – some experts argue that reality exists outside of your consciousness, and you are nothing can’t do to change it.
Others insist that “quantum reality” can be a kind of plasticine that you shape into various shapes by your own actions. Now scientists at the ABC Federal University (UFABC) in São Paulo, Brazil are adding fuel to the speculation that reality can only exist “in the eye of the beholder”.
In their new study, published in the journal Communications Physics, Brazilian scientists tried to test the “principle of complementarity” proposed by the famous Danish physicist Niels Bohr in 1928.
It states that objects have certain pairs of complementary properties that cannot be observed or measured simultaneously, like energy and duration, or position and momentum.
For example, no matter how you set up the experiment with a pair of electrons, there is no way you can study the position of both quantities at the same time: the test will illustrate the position of the first electron, but obscure the position of the second particle (complementary particle) at the same time.
“God Doesn’t Play Dice”
To understand how this principle of complementarity is related to objective reality, we need to plunge into history, about a century ago.
The legendary argument took place in Brussels in 1927 between Bohr and the famous German-born theoretical physicist Albert Einstein during the Fifth Solvay Conference (the most important annual international conference in physics and chemistry).
In the presence of 77 other brilliant scientists gathered in the Austrian capital to discuss the emerging field of quantum theory, Einstein insisted that quantum states have their own reality, independent of how the scientist manipulates them.
Bohr, meanwhile, championed the idea that quantum systems could only have their own reality after a scientist established an experimental model.
“God does not play dice,” said Einstein.
“A system behaves like a wave or a particle depending on the context, but you can’t predict what it will do,” Bohr argued, pointing to the concept of wave-particle duality, which says that matter can look like a wave at one point in time. , and at another point in time as a particle, an idea first put forward by the French physicist Louis de Broglie in 1924.
“Principle of Complementarity”
After the end of the Solvay Conference in 1927, it did not take long for Bohr to publicly formulate his principle of complementarity. Over the next few decades, Bohr’s controversial notion will be tested and re-examined to the smallest detail.
One of those who experimented with the complementarity principle was the American theoretical physicist John Archibald Wheeler.
In 1978, Wheeler attempted to rethink Thomas Young’s 1801 experiment on the properties of light using a double slit. In the double slit experiment, light is directed onto a wall with two parallel slits.
As light passes through each slit, it is diffracted on the far side of the partition and superimposed on light from the other slit, interfering with each other.
This means that there are no more straight lines: the pattern that appears at the end of the experiment is an interference pattern, which means that light moves in waves. Essentially, light has the nature of a particle and a wave, and the two natures are inseparable.
Wheeler had his apparatus switch between the “wave measuring apparatus” and the “particle measuring apparatus” after the light had already passed through most of the apparatus.
In other words, he made a delayed choice between whether the light had already propagated as a wave or as a particle, and found that even after the delayed choice, the complementarity principle was not violated.
However, in more recent studies that attempted to apply the principle of quantum superposition to the delayed choice experiment, the two possibilities were seen to coexist (much like two waves on the surface of a lake can overlap).
This indicates a hybrid behavior of wavelike and particles in the same apparatus, which contradicts the principle of complementarity.
Brazilian scientists also decided to conduct an experiment to create a quantum-controlled reality.
“In the experiment, we used nuclear magnetic resonance techniques similar to those used in medical imaging,” said Roberto M. Serra, researcher in quantum information science and technology at UFABC, who led the experiment.
Particles such as protons, neutrons, and electrons have nuclear spin, which is a magnetic property analogous to the orientation of a compass needle.
“We manipulated the nuclear spins of various atoms in a molecule using electromagnetic radiation. In this setup, we have created a new interference device for the nuclear spin of the proton to explore its wave and partial reality in the quantum domain,” explains Serra.
“This new setup produced exactly the same observed statistics as previous delayed-choice quantum experiments,” Pedro Ruas Dieguez, now a postdoctoral fellow at the International Center for Theory of Quantum Technology (ICTQT) in Poland, who took part in the study, tells Popular Mechanics.
“However, in the new configuration, we were able to relate the result of the experiment to the behavior of waves and particles in a way that confirms Bohr’s complementarity principle,” continues Dieguez.
The main conclusion from the study, published in April 2022, is that the physical reality in the quantum world consists of mutually exclusive entities, which, nevertheless, do not contradict, but complement each other.
This is an exciting result, experts say. “Brazilian researchers have developed a mathematical framework and a corresponding experimental configuration that allows testing quantum theory, in particular, understanding the nature of complementarity by examining the physical realism of the system,” said Stephen Haller, associate professor of physics at Fordham University.
This study highlights a long-standing adage by legendary American quantum physicist and Nobel laureate Richard Feynman: “If you think you understand quantum mechanics, you don’t understand quantum mechanics,” Holler says.
“We still have a lot to learn about the theory, and researchers continue to make strides in understanding even the basic principles, which is especially important as we enter an era where quantum devices and computing are starting to proliferate.”
Dieguez is delighted. “The fact that a material particle can behave like a wave and light can behave like a particle, depending on the context, is still one of the most intriguing and beautiful mysteries of quantum physics,” he says.
Paradoxically, this “weirdness” inherent in quantum mechanics can be very useful: “The more we unravel quantum mechanics, the more we can offer revolutionary quantum technologies that surpass their classical counterparts, including quantum computers, quantum cryptography, quantum sensors and quantum thermal devices ” says Serra.
That reality can only be in the eye of the beholder is a very unusual aspect of physical reality in the quantum realm, and the mystery itself shows no signs of being solved, both researchers agree.
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