What exactly is quantum mechanics?

  Quantum mechanics is confusing and obscure to ordinary people. The theories that are completely beyond the life experience of ordinary people are too difficult to understand. But in the eyes of physicists, it is magical and wonderful. It is a scientific “rich mine” that has fascinated and dedicated generations of scientists.
  In the past hundred years, several quantum-related studies have won Nobel Prizes-integer quantum Hall effect, fractional quantum Hall effect, graphene half-integer quantum Hall effect…
  Among them, the most out of the circle was in 1935 A cat named Schrödinger was born. The famous physicist Schrödinger wanted to ridicule quantum mechanics, but his cat became the most famous spokesperson of quantum mechanics, so that he has been in the scientific circle for decades and has become a science. One of the four great beasts in history. How sacred is this cat that is both alive and dead? How does it endorse quantum mechanics?
  Today, let us uncover its mystery and take a look at the various applications of quantum mechanics in real life.

  A cat in 1935 has been rampant in science circles for decades and has become one of the four great beasts in the history of science. The famous physicist Schrödinger, the famous physicist, wanted to ridicule a quantum mechanics, but his destiny changed people, but his cat became the most deadly spokesperson of quantum mechanics.
  How sacred is this cat that is both alive and dead? Today, let us uncover its mystery.
The magical quantum world

  Before wandering into the magical quantum world, we must start with the world of daily life, that is, the classical world.
  Before the 20th century, our knowledge of the classical world mainly came from Newton. In his most famous academic work “The Mathematical Principles of Natural Philosophy”, he established the classical Newtonian mechanics system, whose core is Newton’s three laws and universal gravitation. law.
  Our daily lives, ranging from the sun, moon and stars, to rivers, lakes, and seas, to firewood, rice, oil and salt, can all be explained by Newton’s theory. Therefore, people believe that this is the ultimate truth that governs the entire universe. In the 20th century, scientists discovered that Newtonian mechanics is only applicable to our macroscopic world, and this theory will not work at all if the scale is extremely small in the microscopic world.
  Therefore, quantum mechanics is a theoretical system about the laws of movement in the microscopic world of matter. It forms the theoretical basis of modern physics together with the theory of relativity, and is widely used in chemistry and other disciplines and many modern technologies.
  So, how did quantum mechanics come about?
  Simply put, human beings accidentally encountered quantum in the process of studying light.
  We know that all matter in the world is made up of atoms. In addition to atoms, there is also a common thing-light. As early as the 19th century, scientists have discovered that light is a wave that travels at the speed of light, and the energy of the light emitted by the thermal radiation of an object is not continuous, but a portion. This characteristic is called “quantum化”. In other words, in the quantum world, physical quantities always have a minimum value, which cannot be directly approached to zero like in the classical world. This great discovery opened the door to the quantum world. Its discoverer, Planck, won the Nobel Prize in Physics in 1918 for this.
  Next, the shiny golden Einstein appeared. He made three major discoveries that shocked the world in 1905—special relativity, Brownian motion and photoelectric effect. The photoelectric effect is the second step taken by human beings on the road to understanding the quantum world, and Einstein won the Nobel Prize in Physics in 1921 for this.

Schrodinger’s cat is dead or alive?

  What is the photoelectric effect? That is, when a photon irradiates a light-sensitive material, its energy can be absorbed by a certain electron in the material. After the electron absorbs the energy of the photon, the kinetic energy immediately increases. If the kinetic energy is increased enough to overcome the gravitational force of the nucleus on it, it can escape from the metal surface in a billionth of a second and become a photoelectron, forming a photocurrent.
  This is a particularly rare physical phenomenon, because the occurrence of this phenomenon depends on the frequency of light. Light above a certain frequency can eject electrons from the metal with just one shot; while light below this frequency, no matter how long it is radiated, electrons cannot be ejected. This is difficult to understand. Because in Newton’s classical mechanics, energy is continuous. For example, if you want to fill a large water tank with water, you can fill the water tank with a large washbasin, one basin and one basin, and you can fill the water tank with small water cups. . But now the photoelectric effect experiment tells us that you can fill the water tank with a large basin, but not with a small water cup.
  Einstein explained that because light itself is not continuous, it is composed of individual particles called photons. The energy of photons depends on the frequency of light. The higher the frequency of light, the greater the energy of photons. If the energy of the photon is small, the energy it transfers to the electron is also small. If the energy is always lower than the minimum energy required for the electron to escape, the electron will always be trapped inside the metal.
  The phenomenon of photoelectric effect shows that the world is no longer linear, but nonlinear. All particles in the microscopic world, including atoms, nuclei, electrons, and photons, are all quantum, and none of them satisfy the laws of Newtonian mechanics. Behind this is a field that humans have never set foot in-the microscopic quantum world.
  In this blue spark of the photoelectric effect, a hurricane in the physical world is coming, transitioning from the macroscopic real world to the microscopic quantum world where past experience is completely inapplicable. “Quantum Demon” is ready to come out.
Schrodinger’s cat is dead or alive?

  A physicist named Laplace once predicted that if we can know the state of motion of all objects at a certain moment, we can know everything that will happen in the future. For example, if you grab a handful of stones and throw them into the sky, as long as you know the height of the stones when they are thrown out, and the speed or momentum of the stones when they are thrown out (the mass of the object multiplied by its speed), you can accurately calculate each stone Where will it end up?
  But Heisenberg discovered that in the microscopic world, it is impossible to measure the position and momentum of an object at the same time. In other words, if your “stone” is only as small as an atom, if you want to accurately measure its position, then its momentum must be inaccurate; on the contrary, if you want to accurately measure its momentum, then its momentum The location must be inaccurate. In short, it is impossible to have both fish and bear paws. And this result is the most important Heisenberg uncertainty principle in quantum mechanics.
  We can use light with a longer wavelength to measure the momentum of a microscopic particle, but cannot measure its position; while using light with a shorter wavelength, we can measure the position of a microscopic particle, but cannot measure its momentum. In other words, it is impossible for us to measure the position and speed of an object in the microcosm at the same time, so we cannot accurately calculate their future movement.
  Now, we can make Schrödinger’s cat appear.
  Schrödinger is one of the founders of quantum mechanics. He discovered the most central equation in quantum mechanics-Schrödinger’s equation, which won the Nobel Prize in Physics in 1933. It is through this equation that physicists have discovered that particles can exist in many places at the same time in the quantum world. The famous “Schrödinger’s Cat” is in the superimposed state of 50% life and 50% death because of this principle.

  All particles in the microscopic world, including atoms, nuclei, electrons, and photons, are all quantum, and none of them satisfy the laws of Newtonian mechanics. Behind this is a field that humans have never set foot in-the microscopic quantum world.