In recent decades, Quantum Physics Curiosities have been gaining more and more strength. Several innovative materials and techniques, such as the production of electrical energy through the photovoltaic effect and the emergence of LED panels, result from the study of a wide variety of quantum phenomena.
The quantum world is totally different from the macroscopic world. On subatomic scales, the laws of Physics work in a non-deterministic way, that is, things may or may not happen according to a probability distribution.
Although it is not completely understood, it is known that Quantum Theory is very precise. Thus, most of its predictions, even the oldest ones, have been experimentally proven with the arrival of new technologies.
The quantum world holds some strangeness. How about getting to know some of them?
Curiosity #1 – Quantum superposition
One of the strangest properties of Quantum Mechanics is certainly quantum superposition. This property makes it possible for a quantum particle to be simultaneously in two or more possible states . However, this will only occur if the state of that particle has not yet been determined.
For example, if there were a quantum door, it could be open , closed , or open and closed at the same time. This last possibility, however, would only exist if you could not observe, or even touch, this door. If you interacted in any way with this “quantum gate”, the superposition would simply cease to exist. In this way, nature would collapse the state of the door into the two possibilities of the classical situation: open or closed .
→ Schrödinger’s Cat
Because he did not understand or accept the idea of quantum superposition, one of the most influential physicists in Quantum Mechanics, Erwin Schrödinger, proposed a paradox that became known as “Schrödinger ‘s cat ”.
In this thought experiment, the physicist suggested that we imagine a cat locked in a box perfectly isolated from the external environment. Inside this box, in addition to the cat, there would be a radioactive atom, which could or could not undergo decay and emit radiation, depending on the quantum probabilities by which it was governed. Next to this atom, there would be a mechanism that would release a poison capable of killing the cat.
The proposal is simple: if the cat is locked inside the box, according to superposition, can we say that it is simultaneously alive and dead ? And if we open the box, would one of these states collapse?
This situation elaborated by Schrödinger, however, presents some conceptual errors and does not meet the precepts of quantum superposition; therefore, it is a paradoxical experiment. In this case, for quantum superposition to arise, there would need to be no transfer of information between the inside and outside of the box, which would only be possible in an ideal situation.
Curiosity #2 – Wave-particle duality
Wave-particle duality arises from quantum superposition. Every quantum particle, such as protons, neutrons and electrons, can behave sometimes like a particle, sometimes like a wave . For this to happen, it is enough that we do not know how to determine its nature.
If it is possible to detect the particle or wave frequency, nature will be in charge of choosing the most likely state for that situation. This is why, in some phenomena, electrons behave like waves and, in others, like particles.
Curiosity #3 – Quantum measurements
Did you know that when you measure the position of a quantum particle, you end up determining where it should be? Since everything in the quantum world has a probability of happening, a quantum particle can be anywhere in space. That’s right: anywhere!
Before being observed, the particle had many open possibilities, each with its own probability. When you try to locate it, however, you make it stop existing right there, in that position. From then on, only one of the possible positions is chosen.
At this point, you may be wondering how the quantum particle “knows” that it has been observed. It’s simple: in order for us to observe it, we need to illuminate this particle. To do this, it is necessary to emit at least one photon in its direction, which is later recovered, providing information about the whereabouts of this particle.
The conclusion we can draw from quantum measurements is that they fundamentally depend on who makes the measurement and how it is made. The reason for this, however, is unknown.
Curiosity #4 – Quantum entanglement
Without a doubt, quantum entanglement is one of the most curious phenomena in Quantum Mechanics. The state of a quantum particle is determined by a complex mathematical entity called a wave function. In some cases, it is possible to make two quantum particles share the same wave function, starting to behave as if they were a single particle.
Some experiments have been done to test quantum entanglement. In one of them, a set of entangled photons was separated into two parts. Half of them collided with a frame that had an image of a cat, and the others were reflected by a mirror before reaching the frame and subsequently sent to a nearby detector.
To the researchers’ astonishment, the image captured by the detector showed the cat in the picture that had been hit by the first photons. This happened because the first group of photons interacted with the image, capturing its color, absorption, reflection and polarization information. As these photons were intertwined with the others, information was transmitted instantly between them.
The experiment in question was carried out by a team of five scientists led by Brazilian scientist Gabriela Barreto Lemos , at the University of Vienna, Austria.
Apparently, entangled particles are capable of sharing information with each other instantly, regardless of the physical separation between them.