We live in a world governed by rules. Gravity pulls us down, apples fall from trees, and the sun rises in the east. But beneath the surface of this seemingly predictable world lies a realm of pure strangeness, a place where the laws of classical physics break down and reality gets downright weird. Welcome to the quantum world.
A Century of Mystery:
For over a hundred years, the brightest minds in science have been grappling with the mysteries of the quantum world. It all started with a simple question: What is light? Is it a wave, spreading out like ripples in a pond? Or is it a particle, a tiny bullet of energy?
The Great Debate:
The answer, as it turned out, was both. Light, and indeed all matter, exhibits a bizarre duality, behaving like a wave in some situations and a particle in others. This discovery, known as wave-particle duality, shattered the foundations of classical physics, sending physicists scrambling to make sense of this strange new reality.
The Rise of Quantum Theory:
The quantum world defied explanation using the familiar laws of classical physics. So, scientists began to develop a new set of rules, a new theory to explain the bizarre behavior of atoms and subatomic particles. This new theory, known as quantum mechanics, has revolutionized our understanding of the universe.
The Quantum Leap:
Quantum mechanics has led to groundbreaking discoveries and technological advancements, including:
- Lasers: These devices rely on the principles of quantum mechanics to produce highly focused beams of light, used in everything from barcode scanners to medical surgery.
- Transistors: The tiny switches that power our computers and smartphones are based on quantum mechanics.
- Magnetic Resonance Imaging (MRI): This medical imaging technique uses quantum mechanics to create detailed images of the inside of the human body.
The Unanswered Questions:
Despite its incredible success, quantum mechanics still leaves us with some mind-bending questions:
- What is the true nature of reality? If particles can be in multiple places at once, what does it mean to be “here” or “there”?
- Can we control the quantum world? If we can manipulate the behavior of particles at the quantum level, what are the possibilities for technology and medicine?
A World of Possibilities
The quantum world is a place of wonder and mystery, challenging our understanding of reality and pushing the boundaries of science. As we continue to explore this strange and fascinating realm, we can expect to unlock even more groundbreaking discoveries and technological advancements, shaping the future of our world in ways we can only begin to imagine.
Quantum mechanics has developed to this day from the time when people repeatedly asked some of the most basic questions, but could not find answers that fit our intuition. It has become more and more weird step by step. The strange phenomena that were first discovered and the hypotheses people put forward about the phenomena are actually completely understandable if you start from the beginning and think with the scientists at the time. Therefore, the goal of this article is to return to the scene of the crime and understand the strangeness of quantum mechanics from the beginning. , and then step by step to get to the latest development today. This article does not take up a lot of space to talk about history. Since we start from the source issue, it is inevitable that you may have heard some things.
Quantum mechanics is a secret that has been explored for more than 100 years by those with the brightest brains among us humans. What is discussed is not some insignificant philosophical issue, but the most fundamental secret about the world we live in. At the beginning, physicists only asked some of the most basic questions, such as what are the things in the world made of? So if the atom is the smallest unit, why are the chemical properties of this atom different from that atom? Can atoms break down anything else? For example, what is this light?
In fact, people have always asked these questions, but it was not until 100 years ago that we had the technology to explore them. As a result, physicists discovered things in the microscopic world and seemed to be pursuing some weird rules. These weird rules can They are not the imagination of physicists, they are the results of experiments and logical reasoning. In order to explain the so-called normality of our daily macroscopic world, you must accept the abnormality of the microscopic world. In other words, our normality is supported by this abnormality.
Some people, such as Einstein, suspect that all the mysterious things in the quantum world must have a deeper master of secrets, and it is the rules under these rules. For decades, the vast majority of physicists believed that it was futile to continue to explore the secrets of quantum mechanics. We should focus on calculations and applications. After all, the existing quantum theory is completely sufficient. Used. In those years, physicists could be said to have gone all the way to understand almost all the laws of nature that you can think of and those you can’t think of. They have also used them to create many sophisticated technological products, but quantum mechanics is just a tool for their calculations. No one really wants to find out what the origin of the world is.
Since the 1960s and 1970s of the last century, some people have proposed new hypotheses and continued to explore the mysterious master hidden deep in the bottom. New technologies have allowed physicists to conduct various ingenious experiments. The exploration of this secret is still a very active research field today. As physicists go further and deeper, this mysterious feeling not only does not weaken, but becomes more serious. Let us take a trip to this Let’s go on a journey of exploration of the secret of the origin.
From the end of the 19th century to the beginning of the 20th century, a huge revolution was quietly taking place in the scientific world. This revolution was the dividing line between classical physics and modern physics. Early physicists such as Newton and Galileo all did great work. However, because their means are relatively limited, their observation of the world is relatively passive.
In Europe at the end of the 19th century, physicists had more sophisticated instruments and more complex experimental tools, and mathematics was also very developed. Differential equations, statistical equations, and non-Euclidean geometry were all very mature. But at this time Physics is still a continuation of Newton’s era, and it is still classical physics. At that time, Maxwell’s electrodynamics had been deeply rooted in people’s hearts. People already knew the existence of molecules and atoms.
Thermodynamics was already clear. Physical theory had its own kind of beauty, and the formulas were particularly consistent with the experimental results. Physicists at that time told The thing is actually all the physics knowledge we learned in high school. Physicists at that time no longer looked at the world with curiosity and awe. They believed that all natural phenomena in the world could be explained by our existing theories. For example, light, what exactly is light? Where did it get its color?
When people see Maxwell’s electrodynamics, they immediately know that light is actually an electromagnetic wave, and different colors are actually different wavelengths and frequencies. People know that light can also cross each other in straight lines and that it also has energy. Newton also knew that sunlight is not pure White can also be broken down into different colors and so on, but at that time we were still too ignorant and too arrogant.
It seems that fate has chosen a special day for mankind. On New Year’s Day in 1900, at the turn of the century, William Thomson, Lord Kelvin, the father of thermodynamics, said in a speech that in the building of physics that had been basically completed, future generations Physicists only need to do some piecemeal repair work. However, in the distance of the clear sky of physics, there are two small and disturbing dark clouds. Both of these dark clouds are related to light. The first one is why the speed of light is All directions are unchanged. We know that this led Einstein to discover the special theory of relativity. The other one is about black body radiation. Maybe the black body is a little different from your imagination. The black body actually emits light, but it does not reflect other light. It All the light it emits is its own light, like the sun and a red-hot soldering iron. These things are approximate black bodies. Because the light emitted by a black body is not reflected, it is all caused by its heat, that is, thermal radiation. .
Physicists have discovered that the spectrum of thermal radiation of a black body has nothing to do with what it is. It is completely determined by the temperature. You can tell what its temperature is by looking at the color of its light. The yellow color means that the temperature is slightly lower. The blue flame has a higher temperature, that’s why. When we give a temperature, physicists can tell you very accurately the color of the blackbody radiation. This color is also the frequency. They can give you an accurate description of the distribution curve of this frequency. So the question is, why does the curve look like this? What mathematical formula governs it behind it? Physicists at that time believed that there must be a formula governing the operating rules of everything in the world. This way of thinking was actually Newton’s greatest gift to physics.
Since there are spectral limitations, physicists decided to derive the formula. Thermodynamics and statistical physics were already very advanced at that time. Physicists assume that the light of a black body comes from electromagnetic waves generated by the vibration of electrons in it, and then they can deduce this formula using statistical mechanics. But no one expected that physics would fail here. No theory can explain the luminescence curve of a black body, especially at high frequencies, that is, outside ultraviolet. Some theories believe that the energy emitted by a black body should be infinite at this place. This is obviously impossible. Therefore, physicists at the time called this problem the ultraviolet disaster. This was the end of classical physics and the beginning of quantum mechanics.
In 1900, the physicist Planck thought that since physics cannot explain the ultraviolet disaster, he should ignore physics completely and make up a mathematical formula to describe this curve. As mentioned before, physicists particularly like to observe phenomena and summarize a rule, and then use this rule to formulate a formula. After the formula is put together, it is calculated and transformed, and finally the underlying laws given by nature are found in the transformed formula. For example, the square of E=MC is deduced in this way. Planck was like a god, and he actually came up with a formula, but from a physical point of view, this formula cannot be explained. He thought hard for several months, and finally found that a physical assumption must be met before this formula can be derived. The assumption is that the energy of radio waves generated by electron vibration is not continuous, but should be in parts. Planck stipulated that the smallest unit of each radiated energy is determined by the frequency of light. This formula is E=hf, where f refers to frequency, and h is a constant, which is the famous Planck constant. With this assumption, the energy of high-frequency radiated light is very large. According to thermodynamics, the probability of its occurrence is relatively low, so there is not that much high-energy radiation, thus avoiding ultraviolet disasters. However, this formula was cobbled together from a mathematical perspective. Planck did not know what the so-called energy bit by bit meant? Because it did not conform to any physical theory at the time, and it was completely inconsistent with people’s intuition. The person who later explained it theoretically was Einstein, and the experiment he used was called the photoelectric effect.
The photoelectric effect means that if you shine a beam of light on a metal plate, sometimes the metal plate will emit electrons. On the surface, it is quite easy to understand. After all, light is an electromagnetic wave, which has energy. The energy conversion of electromagnetic waves Because of the kinetic energy of the electron, the electron flies out. But the strange thing is that how the electron flies out has nothing to do with the intensity of the light, but only the color of the light, that is, its frequency. This is like saying that red light cannot illuminate electrons no matter how bright it is, but if you use purple light, electrons can fly out even if the light is very weak. This phenomenon cannot be explained by classical physics.
In Maxwell’s theory of classical physics, the energy of electromagnetic waves is only related to intensity and not frequency. At that time, frequency only affected the color of light. In 1905, Einstein published an important paper called “An Illuminating View on the Generation and Transformation of Light”, which was about the photoelectric effect. Einstein said that the reason why electrons have to encounter high-frequency light to run is because light is not continuous, but comes in parts. Planck also said that one part of the energy of light E=hxf. The higher the frequency, the greater the energy. Therefore, only one part of high-frequency light has enough energy to knock out an electron, and each part of low-frequency light The energy is very small. No matter how many copies of this small energy you accumulate, you cannot knock out the electrons. High frequency The high-frequency photon is like a big man. Even if there are very few such big men, that is, the total intensity of light is very low, it can still eject electrons, while low-frequency electrons are like a group of children. No matter how high the total intensity of light is, that is, how many children there are, no child can bounce an electron.
Einstein’s description of this experiment here is actually a little closer than Planck’s. Planck said that the energy is one by one. He described the energy of the electrons in the black body when they are heated and vibrated, while Einstein said that this It doesn’t matter whether the light comes out of a black body, as long as it is light energy, it is not continuous but part by part. This thing Einstein talks about is light quantum. Einstein said that light is not a continuous wave, but composed of photons one by one. The energy of each photon is its frequency multiplied by Planck’s constant. He still uses the formula E=hf proposed by Planck.
Einstein used this formula to explain the photoelectric effect, and the calculation results were very consistent. Quantum made its official debut. So why don’t we usually feel that the world is quantum? Einstein said that because Planck’s constant is a very, very small number, it is equal to 6.626 times 10 to the power of -34 joules seconds. Blackbody radiation and the photoelectric effect are actually phenomena that cannot be explained by classical physics.
What about Planck? It is the utility-to-number method that powers such a mathematical model, and Einstein gave this model physical meaning. Physicists have officially discovered photons. But Planck himself was unable to accept the concept of photons for many years. Light quanta did not conform to classical physics, and Maxwell’s equations could not solve energy one by one.
Planck seems to be using a craftsman’s thinking to solve a classic physics problem. This is a very simple way of thinking that first discovers the problem and then solves it. But as time went on, he found that he had opened a Pandora’s box. Once the box was opened, he could no longer control it. Einstein proposed the concept of photons. He must be a champion of new ideas, right? Not really.
Einstein spent his entire life opposing quantum mechanics. This is a story for another day. The most counter-intuitive contradiction here comes from an original question, whether matter is infinitely divisible. Intuitively speaking at the time, matter should be infinitely divisible. Matter is composed of molecules. Molecules are composed of atoms. Atoms are composed of protons, neutrons and electrons. Protons and neutrons are composed of quarks. Then, then The simple question is what are quarks and electrons made of?
The answer is that they are not made of anything else. The Standard Model of modern physics considers quarks and electrons to be elementary particles, no longer separable, or even a mathematical structure. How to divide matter? This is the important beginning of quantum mechanics. Scientists at the end of the 19th century already knew clearly that matter is composed of atoms and classified atoms into categories. Mendeleev created a periodic table of elements and knew the chemical properties of each atom.
Classical physics is very beautiful. People are not eager to know whether atoms can continue to be divided. At this time, nature throws two small questions to us humans. The first one is that Madame Curie and others discovered that uranium atoms can spontaneously form Emitting some kind of ray outward, Marie Curie named this phenomenon radioactivity. Radioactivity is not due to chemical reactions between atoms, but to some kind of activity of the atoms themselves. Based on this, scientists suspect that there should be some structure inside the atoms that we have not discovered.
The second question came from Joseph Thomson. He discovered that there was a kind of particle in the cathode rays. This small particle would be deflected in the applied electromagnetic field. He realized that this particle was negatively charged and named it electron. , this is the first time that people clearly know that there is something else in the atom, and the atom is electrically neutral. Since electrons are negatively charged, there must be positively charged matter in the atoms. This is what people reasoned out. Thomson set up a model. Now we call it the plum pudding model. You can imagine a big spherical cake. , dotted with some small raisins. This pudding cake is positively charged, and the raisins inlaid on it are negatively charged. The electricity between them reaches a balance. When the atoms are heated, the electrons will vibrate on the cake, forming electromagnetic waves. And it radiates to the outside. This model sounded great, but was quickly proven wrong.
Thomson’s student Rutherford discovered when studying radioactivity that the so-called radioactive decay is actually an atom splitting from its own interior and turning into another atom. When certain radioactive materials decay, they emit high-energy rays. Rutherford called this ray a particle. This particle plays a big role in experiments. Scientists use them as bullets.
Roosevelt did an experiment in 1911, bombing gold foil with alpha particles. The gold foil is a thin layer of gold paper, and the alpha particles are very high-energy bullets. The experiment found that most of these high-energy alpha particles, It passed directly through the gold foil, as if nothing happened, but a small amount of a particles were deflected, and a very small amount of a particles actually bounced back from the gold foil. Rutherford was shocked from the beginning. How could a thin piece of paper bounce the bullet back? The only possibility was that the paper was scattered with something very hard and very, very small.
Rutherford concluded that the small and hard thing was the nucleus. Most of the bullets passed through and deflected a small amount, and a very small amount rebounded. This showed that the inside of the atom was not a plum pudding structure at all, but a very empty space. Almost all the weight of the atom is concentrated on the very small nucleus with a positive point in the middle. Only the a particles that happen to fly close to the nucleus can be deflected, and only the a particles that happen to hit the nucleus can be bounced back.
Rutherford did some calculations based on the results of the experiment, and he concluded that the nucleus only occupies 1/10,000 of the size of the entire atom. He bombed many kinds of substances and found that different atoms have different nuclei, electric nuclei, and weights. He also discovered the existence of protons and neutrons, so Rutherford proposed a new atomic model, which is what we use in many descriptions of physics. As you can see in the schematic diagrams in school, there is a positively charged nucleus in the middle with several negatively charged electrons flying around. Unfortunately, this model is still wrong, so that many textbooks later stopped using this schematic diagram. , Rutherford’s model has two big problems.
The first question is that electrons are negatively charged and the atomic nucleus is positively charged, and the positive and negative charges attract each other, so why are the electrons not attracted and fall into the nucleus? Rutherford initially said this was because electrons were moving in circles around the nucleus, just like planets revolving around the sun, and centrifugal force balanced the attraction, but this explanation was wrong. The electron is moving in a circle, which means it is constantly changing the direction of its speed. Maxwell’s electrodynamics tells us that the variable speed movement of a charged object will definitely produce radiation and lose energy. Calculations show that the electron should fall while spinning in circles, and it can In just 10-12 seconds, it fell into the nucleus.
The reason why planets can move around stars without falling is because they are almost all electrically neutral. This is the first problem. The second problem is that atoms do radiate externally, but the spectrum of atomic radiation is very unique and is not continuous. If you randomly search for the spectrum of this kind of atom, you will find that the spectrum of each specific atom is composed of some lines that seem to be somewhat regular and not so regular. This spectrum later became our method for studying the composition of distant objects. important weapon.
At that time, a teacher found a pattern in the radiation spectrum of hydrogen atoms. However, this teacher named Balmer came up with a formula, but this formula was purely made up of numbers. No one knew the physics behind it. What is the meaning, we need a physicist to give meaning to this formula. In 1912, Niels Bohr, the future leader of quantum mechanics, took action. He took the formula that Balmer put together and suddenly remembered the action of Planck and Einstein’s quantization, so he decided immediately Quantize the orbits of electrons in atoms, and connect the work of Planck, Einstein and Bohr. You will think that it is quite natural for Bohr to refer to the work of both of them.
But in fact, it was not easy for Boll to think of this at the time. First of all, there was nearly 10 years between their work. Secondly, Einstein and others were talking about light, while Bohr was studying atoms here. At that time, no one thought that light had anything to do with atoms.
How did Bohr think? He put forward a total of 3 hypotheses. The first hypothesis is that electrons usually move in specific orbits. Each orbit has its own energy level. This energy level is inversely proportional to the square of the orbital quantum number n (the mathematics here is listening to It doesn’t matter if you don’t understand). The second electron does not radiate energy outward when moving in the same orbit (no explanation is given for why it does not radiate outward), but we can infer that the electron must not move in a circle around the nucleus, because that If so, it must radiate energy. The third assumption is also the most important assumption. Only when an electron transitions between two different energy levels will it radiate energy. The magnitude of the radiated energy is exactly that of the two energy levels. The energy difference, and the energy radiated at the same time is exactly equal to Planck’s constant multiplied by the frequency of light.
Bohr’s model completely explained all spectral lines that Balmer’s formula for spectral lines had not yet discovered. Let’s go back and look at Einstein’s photoelectric effect. Doesn’t the photoelectric effect mean that a high-energy photon from the outside can knock electrons away? How much energy does that require? It’s exactly the energy within reach of that electron. Bohr’s problem-solving ideas are very similar to Planck’s and Einstein’s. They both have experimental results first, then make up the numbers, and finally do quantization. However, although this method is very useful in classical physics, it does not work well in quantum physics. Zhongjiu always poses problems to people, for example, why are there only a few fixed tracks? Why can’t electrons stay between two levels? Why can’t electrons radiate energy outwards in their orbits? So what about the jump? Why does a high-energy electron automatically and suddenly move to a lower energy level? How did it jump? This is all very strange.
Physicists vaguely feel that they are embarking on a strange path of no return. The quantum world must have its own unique set of rules that cannot be included in classical physics. So far, experimental results have forced physics to reform. Physicists have to accept a fact and then scramble to come up with a model. This situation is not good. Theoretical physicists need to take the initiative, so the first challenge that quantum physics brings to theoretical physicists is the huge contradiction between the particle properties and wave properties of light.
First we need to know why physicists believe that light is a wave? The theoretical reason is this. Maxwell’s equations solve electromagnetic waves. Then everyone sees that the speed of electromagnetic waves is exactly the speed of light, so it is reasonable to guess that light is a kind of electromagnetic wave. However, theory alone is not enough. We also need direct evidence. Thomas Young, the inventor of cause and effect, did a famous experiment called the double-slit experiment, and later everyone called it Young’s double-slit experiment. Using candles as the light source, I made a baffle with two slits in the middle. After the candlelight passes through the two slits, it will form a very beautiful stripe on the back screen. This stripe is light and dark. There are many alternating cycles. If the particles moving in a straight line are just like bullets fired continuously, as Newton thought, then we will not get such stripes anyway, and the bullets will only focus on the gaps. Two bright lines are formed in the front.
But if you imagine light as some kind of wave, the experimental results are easier to understand. For example, use the metaphor of water waves. A water wave emerges through two holes and forms two water waves on the water surface. Water waves will have peaks and troughs. The peaks or troughs of the two waves will be strengthened when they overlap, and conversely, when the crests and troughs meet, they will exactly interact with each other. Cancel, the same is true for light waves. The bright areas of the stripes on the screen indicate that the two waves have been strengthened, and the dark areas indicate that the two waves have canceled each other out. This is called the interference of the two waves. According to the wavelength of light and the distance from the screen to the double slit, which part of the interference fringe is bright and which part is dark can be accurately calculated. The theory and experiment are completely consistent, so people believe that light is of course a wave. However, the experiments on blackbody radiation and photoelectric effect we mentioned earlier clearly indicate that light is a particle. How do particles interfere? How can something be both a wave and a particle? This question has not yet been answered.
Then Louis de Broglie discovered new problems. During his Ph.D., he learned the theory of relativity, understood the quantum theory of light, and personally participated in the photoelectric effect experiment. He also knew that the electrons in the Bohr atomic model behaved strangely. . De Broglie put these two things together, and after thinking about it, he came up with a bold idea. He said that the behavior of electrons is so weird, perhaps because electrons also have a wave side. He may feel that this idea is not bold enough, so In my doctoral thesis, I proposed a conjecture formula, this The formula is that no matter whether it is an electron, a proton, or a neutron, any material satisfies the condition that the wavelength is equal to Planck’s constant divided by the momentum. In other words, not just light, everything has wave nature. This formula is like this, saying The wavelength λ is equal to h divided by p, which is equal to m times v, that is λ is equal to h divided by mv, where the momentum p is equal to mv, which means mass times velocity. This formula automatically includes photons. According to the special theory of relativity E=MC2, photons have an equivalent mass m, then p is equal to e divided by c, and considering that the wavelength λ multiplied by the frequency is equal to the light Speed, when substituted into de Broglie’s formula, it becomes e equal to hf. This circle is exactly the same as the formulas of Planck and Einstein. It doesn’t matter if you don’t understand the formula. The conclusion is that after such a mathematical process After all, de Broglie proposed a unified theory of matter waves.
Einstein said at the time that de Broglie’s discovery might have opened a tip of the curtain. The double-slit experiment at that time was not accurate enough to confirm this conjecture. Because electrons are too small, the two gaps have to be very, very close, several times the wavelength of the electrons, to cause interference. The experimental equipment at that time was not so sophisticated, so Debrow came up with a way, which was crystal scattering. .
At that time, someone discovered that when we irradiate X-rays onto a crystal, interference patterns will also occur. This is because the atoms of the crystal are arranged very neatly, which is equivalent to forming a periodic grid with many slits. The grid will interfere. De Broglie said that perhaps the structural scale of the crystal is very small, which can be compared with the wavelength of electrons.
In 1927, someone finally completed the experiment. Electrons hit the silicon crystal and produced a very beautiful interference pattern. Based on this experiment, people calculated the distance between silicon atoms and the wavelength of the electrons. Comparing the generated interference patterns again, the results are very The agreement is perfect, so electrons are really waves. De Broglie did this and said that electrons and photons are actually the same thing. This is the origin of the famous wave-particle duality. But if we think about it carefully, matter It is both a wave and a particle. What kind of behavior is this? If an electron is just a small dot, how does it behave like a wave? So if the electron is not a point at all, but a fluctuating cloud, then why do we capture exactly one point every time? From a cloud to a point, how does this instant change occur?
We have no way to directly observe electrons, so we can only observe their behavior, which requires experiments. In 1961, physicists finally used electrons to conduct a double-slit experiment, and even emitted only one electron at a time. As a result, Even if we only emit one electron at a time, when we accumulate more electrons, interference fringes will appear on the screen. The so-called interference of waves is the result of the superposition of two waves coming out of the two slits. How can one electron What about interfering with each other? The only possibility is that the electron passed through two slits at the same time and interfered with itself. Then this wave is completely different from the undulating water waves that we understand in space. Now it is the Pandora’s Magic of quantum mechanics. The box was officially opened. If the physicists at that time were already confused, then a series of even weirder phenomena in the quantum world would really make them miss this simple era.
Summarize the content. Blackbody radiation was originally just a small dark cloud above the clear sky of physics, but when physicists saw it drifting closer, they suddenly discovered that it was not a small dark cloud, but a storm cloud with lightning and thunder. From this small Starting from small problems, people have revealed the wave-particle duality of electron light, but this is not the end, but a starting point that makes the dark clouds grow bigger and bigger. Scientists have discovered the wave nature of electrons, but what are electrons? , why can electrons interfere with themselves? An answer does not bring the end of the problem, but more questions. Physics is facing a big crisis, but after the crisis, we will usher in a brand new world. The curtain of this new world has just been lifted a small corner.
Diamond Sutra: All appearances are false.
Archimedes: Give me a fulcrum and I can lift the entire earth.
The progress of physics in the twentieth century has three pillars, one of which is Einstein’s theory of relativity, gauge field theory, and the vigorous development of quantum mechanics. China has forged ahead bravely in the ocean of quantum mechanics and achieved world-renowned scientific research results, such as quantum communication applications and the development of quantum computers led by Professor Pan Jianwei of the University of Science and Technology of China.
However, in addition to quantum communications, a variety of products such as “quantum wearable products” and “quantum learning equipment” have emerged on the market. Such as quantum underwear, quantum energy pendants, quantum insoles, quantum fluctuation speed reading, etc.; manufacturers vigorously promote these products to have magical health effects, and even claim to extend life. In fact, most of these products are just following the quantum craze, and their marketing techniques are actually full of traps. So what exactly is quantum? Are these quantum products really as magical as they are claimed to be?
Let us go back to the last day of the 19th century. At the celebration of the physics community preparing to welcome the new century, the famous scientist Duke Kelvin gave a speech. He believed that the building of physics was basically completed and only needed fine-tuning. Here, the building of physics that Kelvin refers to includes Newton’s classical mechanics and Maxwell’s classical electromagnetism, that is, classical physics. He confidently believed that all physical problems could be solved based on these two.
However, Kelvin pointed out worriedly that there were two dark clouds hanging in the sky of classical physics, namely ether and blackbody radiation. Many physicists have worked hard to unravel these two mysteries. Einstein ruled out the existence of ether in the process of constructing the theory of relativity, and German physicist Max Planck proposed the revolutionary concept of quantum when studying blackbody radiation.
Blackbody radiation refers to the radiation released by a substance that can only absorb or radiate electromagnetic waves but cannot reflect electromagnetic waves. The sun is an example. Wien’s law derived from classical physics is inconsistent with experimental data in the low-frequency region, and Rayleigh-Jeans’ law derived from the energy equipartition theorem of classical physics is inconsistent with experimental data in the high-frequency region. Consistent with this, when the radiation frequency tends to infinity, the energy will also become infinite. This result is called “ultraviolet catastrophe”.
When Planck studied the problem of blackbody radiation, he combined the Wien formula derived from classical physics with the Boltzmann entropy formula and derived a brand-new formula that was fully consistent with experimental data. In order to make this formula self-consistent, Planck boldly assumed that the energy of electromagnetic waves is not continuous, but is divided into parts, where each part of energy is an integer multiple of a basic unit energy. This basic unit energy is called an energy quantum. .
This hypothesis was unprecedented and subverted the theoretical system of classical physics, so much so that Planck himself was skeptical about it. However, Planck’s theory pointed the way for subsequent developments in physics.
In a paper on the photoelectric effect published in 1905, Einstein adopted Planck’s quantum concept and believed that electromagnetic waves themselves are composed of energy quanta, called light quanta (hereinafter referred to as photons). For this paper, Einstein won a belated Nobel Prize.
Since the birth of quantum theory, its physical meaning has been continuously enriched in the process of development, from initially representing discrete mathematical ideas and the smallest unit of material nuclear energy, to now the word “quantum” represents all material entities in the quantum world, such as photons. , electrons, atoms, nuclei, elementary particles, etc., they all must follow the laws of quantum mechanics.
Quantum mechanics, as an important theoretical branch of physics, is essentially different from classical mechanics. Throughout the first 10 to 20 years of the 20th century, the Copenhagen School headed by Bohr led the progress of quantum mechanics. Bohr proposed the principle of complementarity, and Heisenberg proposed core theories such as the uncertainty principle.
Without going into the details of these core theories, they reveal the distinctive properties of the quantum world, the core ideas of which are quantum entanglement, quantum superposition, and quantum collapse.
- Quantum superposition
We know that photons have properties such as polarization and angular momentum. Quantum entanglement means that if the polarization of one of two paired photons is known, the polarization of the other will also be determined immediately, regardless of the difference between them. How far is the distance? Quantum superposition means that we cannot determine the true polarization of the photon without measuring its polarization.
For example, in the quantum world, a rabbit is both male and female. That is to say, the gender of the rabbit is in a superposition state. This is quantum superposition.
- Quantum entanglement
Assuming that measuring another particle around you must be the complementary state of the first particle, it is equivalent to “instantly” knowing the state of another particle on the horizon. In common parlance, it is “over-distance sensing” and “teleportation”. This is called quantum entanglement.
- Quantum collapse
Quantum collapse refers to the fact that we are completely unable to predict the state of a quantum before it is measured. This is a true randomness; once the measurement is started, the quantum will “collapse” into one possible state, just as it has always been.
- Quantum communication technology
Quantum communication makes use of the cutting-edge technology of quantum mechanics. Because not many people understand quantum and quantum mechanics, quantum communication has been controversial since its birth. In fact, quantum communication does not directly use quantum communication, but uses the characteristics of quantum entanglement to encrypt traditional electromagnetic wave communication.
Quantum communication includes classical communication channels and quantum channels. When communicating, both parties will send a string of photons as a communication password, which together with the classical channel constitutes quantum communication.
The advantage of quantum communication is that it is difficult to hack, because every time a photon is intercepted, it is immediately detected by the communication satellite, and the photon cannot be copied because observation will cause the photon to collapse immediately.
- Quantum Computer
Quantum computers are the product of utilizing quantum technology, although they have not yet been successfully developed.
Traditional electronic computers use high and low levels to represent data, such as high levels representing 1 and low levels representing 0. The combination of 0 and 1 forms a computer language called bits. Quantum bits are used in quantum computers, which have quantum superposition, that is, each qubit may be 0 and 1 at the same time.
Qubits are also quantumly entangled, with changes in one qubit immediately affecting other qubits associated with it, regardless of distance. This means that if one state is known through observation, the other state will also be clear.
It can be seen that real application research of quantum technology is full of challenges and has not been able to form commercial applications for decades. Scientists all over the world are working hard on this; and those products that promote the use of quantum technology are just catering to people’s psychological needs. Through simple scientific principles, we can easily see through the marketing tactics of these products.
The behavior of photons has always been a confusing topic. When we deeply study the space-time movement of photons, a time paradox problem arises. In the world of photons, time is no longer a single, linear scale, but a multi-dimensional, reversible, wonderful existence that may even point to the past, present and future at the same time.
Quantum superposition and CPT symmetry
The wonders of photons begin with quantum superposition, the most puzzling property of quantum mechanics. In the case of quantum superposition, photons can be in many different states at the same time, like Schrödinger’s cat, both dead and alive. And this kind of superposition is not limited to spatial position or energy state, it can also be extended to the time dimension. Thus, we see that photons exist in both forward and backward states in the river of time. For it, the arrow of time is just a game of random shuttles.
The realization of this miracle cannot be achieved without the help of another quantum mechanical principle – charge, parity and time reversal (CPT) symmetry. CPT symmetry tells us that no matter how the charge of a particle changes, no matter how its position in space flips, or even no matter how time flows backwards, the laws of physics remain the same. This is like a mirror that completely reflects the world of particles without losing its essential laws. It is this symmetry that makes it possible for photons to travel freely in the time dimension.
In the laboratory, physicists cleverly use special optical crystals to split photons into superposition states on two paths. On one path, the photon moves forward as usual; on the other path, the photon’s polarization is carefully adjusted so that its direction in space is equivalent to moving backward in time. When the photons on these two paths meet again, they quantumly interfere, forming a pattern of alternating light and dark stripes. This pattern only appears when photons exist in two time directions at the same time. It is like a fingerprint of time, proving the superposition state of photons in the time dimension.
A new dawn in quantum computing and quantum gravity
This discovery is an in-depth verification of quantum mechanics and a huge boost to future technological development. At a theoretical level, it provides us with new ideas for improving quantum computing. The basic unit of quantum computing, qubit, can be in a superposition state of 0 and 1 at the same time, and the time superposition state of photons provides more possibilities for the operation of qubits.
More profoundly, this discovery may have a major impact on the study of quantum gravity. In extreme conditions in the universe, such as inside a black hole, time is distorted to the extreme. Photons with multiple time directions may be our key to spying on these mysterious phenomena. By delving into the space-time behavior of photons, we may be able to reveal some of the deepest and most elusive laws in the universe.
The future of quantum technology
At the application level, the time superposition state of photons also shows broad prospects. Its combination with reversible logic gates paves the way for building quantum processors with super processing power. Quantum computing, with its astonishing speed, has shown great potential in fields such as cryptography, molecular simulation, materials science, optimization problems, and machine learning. The time superposition state of photons will undoubtedly bring revolutionary breakthroughs in these fields.
Future quantum communication networks may be able to use the time superposition state of photons to achieve more secure and efficient communication. Traditional encryption methods are fragile when faced with quantum computers, while encryption technology based on quantum principles can ensure the safe transmission of information. The time superposition state of photons is like an invisible key. Only by mastering the correct time rhythm can the door to communication be opened.
In addition, designing quantum circuits with simultaneous bidirectional flow will also provide new equipment for quantum metrology. In the quantum world, precise measurements are the basis for exploring the unknown. The time superposition state of photons provides a more accurate and sensitive tool for this kind of measurement. It is like a precise ruler that can measure every tiny change in the quantum world.
Time travel reverie
Although the time superposition state of photons is not equivalent to real time travel, it opens the door to the possibility of time travel for us. At the quantum scale, time loses its absoluteness and becomes a relative, multi-directional concept. This quantum singularity challenges our traditional understanding of time and inspires our endless reverie about time travel.
The existence of different real worlds and the concept of parallel timelines provide a broader space for imagination for time travel. In the many-worlds interpretation of quantum mechanics, history can be split into multiple paths, each path corresponding to a different outcome. This means that when we time travel, we may be able to enter a timeline that is completely different from the present, thus avoiding those troublesome time paradoxes.
The scientists further verified this possibility by simulating the travel of quantum particles through time. The polarization state of the two photons is the same, and the interference behavior between them is like the interaction of one particle with another particle in the same state as its past state. This phenomenon, on a quantum scale, proves the possibility of time travel, at least to some extent.
Wheeler’s delayed choice experiment made us think deeply about the boundaries between the past, present and future. Current behavior seems to be able to change history. This seemingly paradoxical phenomenon has become possible in the quantum world. It challenges our traditional understanding of time order and makes us dream of time travel even more.
Time stands still
For photons, time stands still. This characteristic seems contradictory, but it is an unshakable truth in the theory of relativity. When a particle reaches the speed of light, it stops relative to time. This means that from the perspective of photons, the distance in the universe is infinitely compressed, and it does not take any time to fly to the edge of the universe. This characteristic gives us a deeper understanding of the behavior of photons.
The time-stationary characteristic of photons is closely connected with its wave-particle duality. Light can exhibit both particle and wave properties. The time-station of photons may be the embodiment of their wave-particle duality in the time dimension.
Furthermore, by analyzing the relationship between the red shift of photons and time, we can reveal their movement patterns in the space-time dimension. The space-time motion of photons can be described by a hyperbola with a semi-major axis and a semi-minor axis. This discovery gives us a more intuitive understanding of the trajectory of photons, and also provides us with new clues for understanding the structure and evolution of the universe.
Flow of mind
As Zen Buddhism understands, the nature of the mind is inherently impermanent and changes unpredictably over time. The superposition of photons in time is like the flow of mind, not limited to one moment or one shape. It is both a traveler and a witness of time, seeing eternity in the moment and showing the moment in the eternity.
Watch the time quietly
Zen Buddhism advocates sitting and meditating, using stillness to stop and observe the ups and downs of the heart. When we examine the time-stationary characteristics of photons with this mentality, we will find the profound meaning contained in it. Although photons fly at the speed of light, time stands still for them. This is just like the state of selflessness we achieve in meditation, where our minds are free of worries and time freezes. In this state, we may be closer to the nature of the universe.
Oneness of mind and nature
The wave-particle duality of photons is a physical phenomenon and a symbol of changes in mind. When it fluctuates, it is like the gentle nature of the mind, adapting to all things; when it is particles, it is like the firm nature of the mind, which is not moved by external things. This unity of waves and particles is just like the integration of “emptiness” and “existence” in Zen Buddhism, reminding us that everything is empty and yet everything is present.
Let’s turn back time to the spring of 1900. It was an era firmly ruled by Newtonian mechanics, where everything followed the rules, stars and dust danced together, and followed the laws of gravity. In the solar system, the discovery of Neptune is like a medal, embedded in the crown of the empire of classical physics. It declares that human beings have almost perfect control over the laws of nature. It was a high-spirited era. Physicists stood at the pinnacle of knowledge, overlooking the universe, and had everything under control.
However, in this seemingly impeccable classical physics system, there are hidden undercurrents that are unknown to everyone. On April 27, 1900, a banquet for the scientific community was being held at the Royal Institution on Albemarle Street in London. The 76-year-old academic giant Baron Kelvin, with his supreme prestige, issued a confident declaration to the scientists present:
“All the principles of the world’s operation have been discovered. Physics is perfect and there can no longer be any breakthrough progress! However, there are still two dark clouds floating in the brilliant sky of physics – the ‘ether problem’ and ‘Black body radiation’, unexplained.”
“Ether problem” and “black body radiation”, these two “ominous omens” actually foreshadow the coming storm.
Planck, a young man with a special talent for music, is facing a choice at a crossroads in his life. His mentor Zully persuaded him to give up physics and turn to the more promising path of music. After weighing it repeatedly, he decisively chose his favorite. “I’m just interested.” These simple and straightforward words became his motto in pursuing science throughout his life.
Fortune doesn’t always seem to favor the prepared. Planck, who had been studying “black body radiation” for many years, was in his forties, but he still had not found the door to the truth.
Until one day, he decided to put aside his persistent pursuit of physical principles and adopt a more direct method-to first make up a mathematical formula for “black body radiation”. This helpless move brought unexpected gains to him and even the entire physics community. Planck’s three times five divided by two actually revealed the famous black body equation and the inexplicable “Planck constant (h)”. Not to mention, this constant actually opens the door to the quantum world. Together with Newton’s gravitational constant G and the speed of light c in the theory of relativity, it has become the three most basic numbers in the universe, and together they build the genetic map of the universe.
Planck’s most important contribution was his revolutionary concept that “when energy is emitted and absorbed, it is not continuous, but part by part.” This view, like thunder on the ground, shocked the entire physics community. It subverts the traditional understanding that all natural phenomena are continuous since Galileo and Newton. Since then, a discontinuous and uncertain worldview has plagued an entire generation of physicists like a nightmare. And this amount of energy was given a fashionable name by Planck – energy quanta.
In December 1900, the publication of Planck’s paper was like opening Pandora’s box, releasing the ghost of “quantum” that had been sleeping for hundreds of millions of years. This is the beginning of quantum mechanics. The dark cloud in Kelvin’s mouth not only failed to be dispelled, but triggered a ground-breaking conceptual revolution.
Although Planck opened the door to the quantum world, he did not fully understand what this “bit of energy” actually meant. He stood on the threshold of the quantum world, excited and confused. But it was a young man who was still unknown at the time—Einstein—who truly revealed the truth about quantum science. Five years later, he single-handedly wrote the “Photoelectric Effect” with his left hand, explaining Planck’s confusion, and became another founder of quantum theory; with his right hand, he wrote the “Special Theory of Relativity” and drove away Another dark cloud that swept away Kelvin and set off a revolution in the macro world. This young scientist, with a super-high IQ of “190”, has opened a new era of human cognition.
The birth of quantum thinking was not smooth sailing. It is like a raging torrent, hitting the solid dam of traditional physics. Planck and Einstein, the two pioneers of quantum theory, gradually became staunch opponents of quantum theory after the initial excitement. They tried to use the framework of classical physics to restrain the unruly ghost of quantum, but found themselves in a deep dilemma. Revolutionaries, inadvertently, become counterrevolutionaries.
This quantum debate turned out to be the biggest “defeat” in Einstein’s life. He cannot accept the randomness and uncertainty of the quantum world, insisting that there must be more profound laws hidden behind the universe. However, with the continuous development of quantum mechanics, more and more experimental evidence has proved the strange properties of quantum. Einstein’s persistence eventually turned into deep regret for the quantum world.
In this quantum storm sweeping the world of physics, scientists are like captains lost in the vast sea. They are both attracted by the wonders of the new world and troubled by its unfathomable “strange appearances”.
In this magnificent scientific revolution, we have seen scientists’ persistent pursuit of truth and witnessed the continuous innovation of human cognition. The birth of quantum mechanics has changed our understanding of the universe and triggered a profound reflection on mankind’s own cognition. It tells us that the universe is far more complex than we imagine, and our knowledge will always be on the way.
The uncertainty of the quantum world is a mockery of deterministic philosophy, making physicists who are accustomed to using precise mathematical models to describe the universe restless and even sleepless at night. This is just as Zen Buddhism says, “Empty is form, and form is emptiness.” All phenomena arise due to causes and conditions, and are impermanent and selfless. The essence of the quantum world seems to be telling such a truth that transcends duality.
As Zen Buddhism says, “Seeing mountains is not mountains, seeing water is not water.” When classical physicists try to use traditional logic and language to capture the true meaning of quantum, they often find themselves falling into deeper confusion. The wave function collapse and observer effect of quantum mechanics are all telling people that the truth of the universe depends on the observer’s state of mind. Just as Zen Buddhism says, “when the mind arises, all kinds of dharma arise, and when the mind dies, all kinds of dharma perish.”
Just as the development of quantum mechanics forces us to re-examine the limitations of classical physics, the practice of Zen encourages us to transcend our daily obsessions and reach a higher level of awakening. The Sixth Patriarch Hui Neng’s poem says: “Bodhi has no tree, and the mirror is not a stand. There is nothing in the first place, so where is the dust.” Entering the world of quantum, we may be closer to the ultimate goal of no self, no attachment, and no abiding realm.