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The Nobel Prize in Physics for the year 2025 was recently awarded to three physicists, John Clarke, Michel Devoret, and John Martinis, for their discoveries in the field of Quantum tunneling. We know that this is not the first time the Nobel Prize has been awarded for work related to Quantum tunneling. Such is the importance of this branch of Quantum mechanics that in 1973 and 1986, Nobel Prizes were awarded for research works related to quantum tunneling.
Quantum tunneling is a special feature associated with quantum particles. Quantum mechanics established that a quantum particle, like an electron, exhibits wave properties as well, and this feature is termed wave-particle duality. An important feature of quantum mechanics is that it talks only about the probability of an outcome and not about a fixed outcome. It states that a quantum particle, like an electron, can behave like a particle and also as a wave, and it can have superpositions simultaneously. It has great implications in science that even though the exact reason for such behavior of quantum particles is not known yet, their applications are widely used in many areas like quantum computing, sophisticated electronic machinery, and appliances. Quantum tunneling effect was predicted in the early 20th century.
The Schrodinger equation is a fundamental wave function equation predicting the probability of the position of an electron over time. The world of quantum particles is further governed by the exclusion principle, the uncertainty principle, and quantum entanglement. (explained in the first article)
Wave-particle duality and superposition make the probability of an electron appearing in a position possible even when separated by a barrier, even if the electron does not have enough energy to overcome the barrier. For simple understanding, let us imagine a person standing in front of a tall wall. To reach the other side of the wall, he has to have enough energy to climb the wall and reach the other side. Imagine the person not having enough energy, could leak through the wall and reach the other side, without climbing the wall. This is what is possible for an electron in the quantum world through quantum tunneling, due to its wave nature.. It may be noted that the particle does not dig a tunnel to appear at the other side of the barrier. Because of its wave function, it has a small probability of being there at the other end of the barrier, and that is why it appears there. The probability of tunneling through a barrier decreases exponentially with the barrier height and width, and the mass of the particle. Tunneling is observed in physical phenomena like nuclear fusion and radioactive decay of atomic nuclei. Applications of tunneling are used in tunnel diodes, quantum computing, flash memory, etc.
The Nobel Laureates of the year 2025 proved that Quantum tunneling is possible outside the quantum world, that is, macroscopic quantum tunneling (MQT). Even though quantum tunneling was already well known, it was confined at micro level only. They were the first to experimentally demonstrate quantum tunneling at the macro level. This is regarded as a historical achievement capable of bringing dramatic discoveries/inventions in the future. They used two superconductors separated by a thin insulating barrier (Josephson Junction) and observed that the current at a certain energy level passed across the thin insulator. This proved that, under the right conditions, tunneling is possible not only at the quantum level but also at the macroscopic level.
The quantum world is governed by probabilistic rules. The classical world we live in is more deterministic and predictable. The significance of MQT is that a phenomenon which was hitherto possible only in the quantum world is made possible in the classical world. MQT, in future, may open doors to the discovery of many things which hereto were regarded as impossible. Maybe, one day, teleporting objects will be possible?
It will be interesting to know if physics is offering any other such opportunity to travel through a shortcut.
We know space is vast beyond our imagination. If a person wants to travel across our home galaxy, the Milky Way, that is, from one end to the other end of Milky Way, the journey will take more than one hundred thousand light-years. Remember, light takes only eight minutes to reach from sun. In this context just imagine how big is our home galaxy, the Milky Way. There are billions of such galaxies in universe. Our nearest neighbor galaxy, Andromeda, is 2.5 million light years away. Also remember that nothing can travel at a speed higher than that of light. So inter-galatic travel is practically impossible, unless we find some shortcut. Luckily, Eistein’s general relativity talk about possibility of shortcut to travel across space, namely a Wormhole.
A wormhole is a hypothetical theory proposed by the solution of the field equations of the general theory of relativity, applicable to space-time. It has not been proven yet. An extremely massive object can bend space-time so much as to create a bridge between the distant regions. A traveler entering through one edge (mouth) would come out through the other edge (mouth), far away in space (may be even in another galaxy), and even in another time, pointing to the theoretical possibility of time travel. But, for two mouths not to collapse due to gravity, exotic energy (negative energy) and matter are required, which have not been discovered yet. A wormhole could theoretically allow travel between two mouths faster than light by going the normal way through normal space.
Similarity with quantum tunneling is that a wormhole is also a shortcut to travel. Unlike quantum tunneling, where a quantum particle travels across a thin energy barrier, the Wormhole theoretically predicts the possibility of travel across a vast space through the shortcut. Like quantum tunneling, wormholes also require special conditions to travel across vast space. It’s not like a quantum particle crossing the energy barrier because of its wave nature. It’s about curving space and time, making travel across space faster, in theory.
For a simple understanding of a wormhole, imagine space as a sheet of two-dimensional A4-sized paper. Mark points at the center of each edge so that when you fold the paper, one mark comes over the other. To travel from one mark to the other mark in the normal course, you need to travel the entire length of the A4 sheet. If the sheet is folded, to make one mark over the other, it requires very small effort to travel from one mark to the other, as the space between them is considerably reduced. (Two marks on the edges of the paper are the mouths, and the space between the marks is the throat mentioned above.)
Recollect the scene in the movie Interstellar, where the crew travels through a wormhole near planet Saturn to reach another galaxy.
Renowned physicists like Einstein and Rosen believed that wormholes and quantum entanglement might be two sides of the same coin, as the entangled particles may be connected by narrow wormholes.
Jarard Thomas
10/10/2025
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