In an exciting scientific step that re-asks old questions about the limits and possibilities of the quantum world, a team of Japanese physicists at the University of Tokyo announced the achievement of an achievement that specialists had long considered almost impossible, as the team was able to subject a nanoparticle to a process of “quantum compression” that exceeds the theoretical limit, which scientists believed was impenetrable in quantum physics.
The team published its experiment and its results in a recent study in the journal Science, demonstrating a new technique that opens a wide door to understanding how relatively large particles, not just atoms and electrons, can also exhibit quantum behavior, at a time when most scientists believed that such phenomena disappear in larger objects.
Kiyotaka Aikawa, associate professor in the Department of Physics at the University of Tokyo, Japan, and corresponding researcher in the study, said in exclusive statements to Al Jazeera Net: “Quantum physics has succeeded in microscopic particles such as atoms, but many larger objects, such as those that can be seen with the naked eye or under ordinary microscopes, do not exhibit quantum mechanical behaviors. Indeed, almost nothing is understood about quantum mechanics at all.” Larger scales.
Quantum pressure
Aikawa explains quantum pressure, explaining that it is “a process that aims to reduce the vibration of motion below the vibration of the minimum energy state. This does not happen in our daily life, because any body is always exposed to tremors caused by thermal fluctuations.”
In other words, even in the most static conditions, objects do not stop vibrating due to their thermal energy in our classical world that we see around us. But in the infinitesimal quantum world, it is possible to “compress” or reduce these oscillations in a way that makes the system more stable than anything classical physics can provide.
Scientists wanted to test quantum pressure on nanoparticles larger than atoms to see the effect of reducing their vibrations to bring them to a more stable state. Therefore, the researchers suspended a small nanoparticle in the air using a light field, like “light tweezers,” with the aim of completely isolating the particle from most sources of interference, such as mechanical vibrations and electrical and thermal fluctuations.
They then used extremely precise measurement and control techniques to cool the particle’s motion and reduce its vibration to near the minimum allowed by quantum mechanics (the lowest energy state). They then applied the “quantum compression” protocol to redistribute these vibrations so that they were reduced in one of the dimensions of motion.
The result was amazing, as the researchers were able to reduce the vibrations to below the level of natural vibration, thus exceeding what is known as the physical 3 decibel limit, which is a barrier between our classical world and the quantum world, and which physicists have long considered difficult to penetrate.
This achievement proved that even particles larger than atoms can exhibit clear quantum behavior, and opens the door to the development of high-precision quantum sensors. It is also one of the important steps that follows the achievements of John Clarke, Michel Devoret, and John Martinez from the University of California, USA, who will receive the Nobel Prize in Physics for the year 2025.
These scientists received the award in recognition of their pioneering discovery that showed that strange quantum effects are not limited to atoms and tiny particles, but can be achieved in a man-made device that can be carried by hand, thereby confirming that the boundaries between quantum and everyday life are thinner than we thought.
From atom to nano
Since the scientist Werner Heisenberg developed his famous uncertainty principle, this principle has been the cornerstone of understanding quantum mechanics. The Heisenberg Uncertainty Principle simply means that you cannot know everything about a quantum particle with complete accuracy at the same time, that is, you cannot measure the particle’s position and momentum (i.e., its speed and direction of movement) with absolute accuracy together.
If you try to reduce the error in position, the error in momentum will increase, and vice versa. The reason is not due to a weakness in the devices or measurements, but rather it is a basic law of nature in the quantum world, so when the behavior of matter agrees with the principle of uncertainty, we are faced with confirmation of quantum behavior.
This is what scientists in the University of Tokyo experiment tried to test to ensure that breaking the 3 decibel barrier is not an exception, but rather clear evidence of quantum behavior. “We believe that our results are consistent with the Heisenberg Uncertainty Principle,” Aikawa says. “In doing so, our results confirm that this principle is also valid when studying the motion of nanoparticles.”
In order to achieve Aikawa’s conclusions, the researchers compressed the quantum vibrations of a nanoparticle that does not follow the rules of the quantum world such as Heisenberg’s principle, and succeeded in reducing the vibrations in one dimension of motion, at the expense of increasing the vibrations in the other dimension.
Imagine that you have a balloon filled with water and it is vibrating from its center in all directions. If you try to squeeze this balloon from the top and bottom to reduce its oscillations in this kinetic dimension, its oscillations will increase to the right and left, for example. This behavior is entirely consistent with Heisenberg’s principle, because it shows that a reduction in uncertainty in one property is necessarily offset by an increase in another. Thus, their results confirmed that the principle also applies to relatively large nanoscale objects, and not just to tiny particles such as electrons and atoms.
The team did not expect to achieve quantum compression like this. “Since no one knows if there is a fundamental process that prevents quantum compression, we were surprised by our results,” Aikawa says. “In our opinion, it has only recently become realistic to test quantum mechanics at macroscopic scales. In this respect, our results differ from other recent physics discoveries.”
Challenges and applications
Reaching this result was not easy. Aikawa explains that the experiment faced complex technical challenges. “There are several key aspects. The system is very sensitive to any kind of fluctuations, which forced us to reduce many processes that might disturb the particle’s motion. Specifically, we had to reduce the angular motions of the particle, electrical effects, as well as the vibrations of the experimental system itself.”
This statement reflects the degree of precision required, as the nanoparticle used in the experiment – a body much larger than atoms – reacts to the slightest disruption in the surrounding environment. Therefore, isolating the experiment from any external vibrations that might spoil the results was necessary.
“Exceeding the 3-decibel limit means that our system is considered a good quantum system, and could be useful for various other studies and applications such as accelerometers,” Aikawa adds. Hence, this result is not only an experimental victory, but carries with it practical promises that could change the future of sensing technologies.
It is worth noting that accelerometers are devices used in smartphones, cars, airplanes, and even satellites. “Current devices are limited by thermal fluctuations,” Aikawa explains of accelerometers. “But the suspended system is free of these fluctuations, and our results show that sensitivity can be improved via a compression protocol (devised by the researchers). Quantum accelerometer sensors such as atomic interferometers already exist.”
He adds: “Currently, we cannot say for sure whether nanoparticle-based sensors are better than atomic interferometers. This is an issue that must be answered in the coming years.” This proposal opens the door to a new scientific race between two types of quantum technologies: sensors based on atoms, and others that will rely on nanoparticles.