Which one should we learn first for Quantum research? How did Feynman teach at Caltech in 1960s?
When I first heard about the word of Quantum Mechanics, I though it was about new type of atoms in Physics. Because most people said that Quantum has super mysterious behaviour that can be on multiple locations in the earth at the same time. And also it can have infinite dimensional states including a superposition of zero and one at the same time.
Actually, there was no difference for me between science movie like Spider man and Quantum. Because it was difficult to explain how it works but very fun.
However, after studying Feynman’s lecture I’ve been knowing Quantum more and more. I hope this would be helpful to you, too.
So today, I’d like to describe exactly what the meaning of Quantum Mechanics through Richard Feynman’s lecture at Caltech in 1960s.
Firstly, to better understand Feynman introduced Atomic Mechanics.
In view of atomic mechanics, there are two definitions like below.
1) “Quantum mechanics” is not about special material but the description of the behavior of matter and light in all its details and, in particular, of the happenings on an atomic scale.
In this setence, the matter means atomic objects that are electrons, protons, neutrons, photons, and so on.
2) The quantum behavior of atomic objects is the same for all, they are all Particle Waves.
If you remember these two important simple two definitions you can avoid a lot of miscommunications and confusing when you research with your colleagues.
To fully understand the real meaning of the Particle Waves you need to know first about some historically great scientists and their achievement related to atomic behavior. Newton thought that light was made up of particles, but then it was discovered that it behaves like a wave. Later, however, it was found that light did indeed sometimes behave like a particle. Historically, the electron, for example, was thought to behave like a particle, and then it was found that in many respects it behaved like a wave. So it really behaves like neither. Feynman says “It is like neither.”
The gradual accumulation of information about atomic and small-scale behavior during the first quarter of the 20th century, which gave some indications about how small things do behave, produced an increasing confusion which was finally resolved in 1926 and 1927 by Schrödinger, Heisenberg, and Born.
Max Plank
I think the starting point to birth Quantum is Max Plank’s experiment and discovery. Because Science could not explain the wavelength dependence of the curve until Max Planck focused on the problem around 1900.
Max Planck’s earliest work was on the subject of thermodynamics, an interest he acquired from his studies under Kirchhoff, whom he greatly admired. He was an expert in the science of thermodynamics and he used the tools of thermodynamics to try and explain radiation.
However, after several failures he almost gave up.
He made one last attempt. He decided to throw away the ideas of classical science and make a bold assumption: He assumed that the atoms in the black-body could not absorb just any energy but could only absorb or emit energy in packets he called “quanta”.
With this assumption he quickly derived a formula that exactly reproduced the black-body radiation spectrum.
That means that to explain the colors of hot glowing matter, he proposed energy is radiated in very minute and discrete quantized amounts or packets, rather than in a continuous unbroken wave. He was able to determine that the energy of each quanta is equal to the frequency of the radiation multiplied by a universal constant that he derived, now known as Planck’s constant.
We’ve probably heard of “Planck Constant” once in high school.
This constant, expressed in terms of erg-seconds, measures the energy of an individual quantum. An erg(https://en.wikipedia.org/wiki/Erg) is the amount of energy needed to raise a milligram of mass by a distance of 1 centimeter. Planck’s constant, expressed by the variable “h” in equations, is approximately 6.63 x 10(E-27) erg-second.
Planck’s constant has become one of the basic constants of physics. It is used to describe the behavior of particles and waves at the atomic scale.
Erwin Schrödinger
Schrödinger created “Schrödinger equation” that is a linear partial differential equation that governs the wave function of a quantum mechanical system. Conceptually, the Schrodinger equation is the quantum counterpart of Newton’s second law in classical mechanics.
Schrödinger equation is a wave equation in terms of the wave function which predicts analytically and precisely the probability of events or outcome.
The detailed outcome is not strictly determined, but given a large number of events, the Schrodinger equation will predict the distribution of results.
The kinetic and potential energies are transformed into the Hamiltonian (I will talk about Hamiltonian Operator in detal.) which acts upon the wavefunction to generate the evolution of the wavefunction in time and space. The Schrodinger equation gives the quantized energies of the system and gives the form of the wavefunction so that other properties may be calculated.
Werner Heisenberg
He published his work in 1925 in a breakthrough paper, “Quantum theoretical re-interpretation of kinematic and mechanical relations”. In the subsequent series of papers with Max Born and Pascual Jordan, during the same year, this matrix formulation of quantum mechanics was substantially elaborated. He is known for the uncertainty principle, which he published in 1927. Heisenberg was awarded the 1932 Nobel Prize in Physics “for the creation of quantum mechanics”.
Max Born
For his statistical interpretation of quantum mechanics as well as for his lattice theory of crystals Max Born received the Nobelprize in Physics in the year 1954.
His research comprises in addition a wealth of ground breaking studies to describe atomic processes in quantum mechanical terms, key contributions towards the development of the formalism of quantum mechanics (together with his assistants W. Heisenberg and P. Jordan) as well as on modern optics which are documented in “Born und Wolf: Optics”, still a standard textbook even today. The name Max Born represents thus symbolically the research programme of the Max Born Institute which in this sense concentrates on a field between quantum optics, atomic and molecular physics and the physics of condensed matter.
In summary, atomic behavior is so unlike ordinary experience, it is very difficult to get used to, and it seems like mysterious world to everyone whether they are novice or experienced physics scientists. Even the experts do not understand it the way of human experience and of human intuition which can apply to large objects. People know how large objects will act, but things on a very small scale just do not act that way. So Feynman said that we have to learn about them in a sort of abstract or imaginative fashion and not by connection with our direct experience.
That’s it! This is simple introduction and background for studying Quantum. How do you feel? Maybe you are still confusing at the monent. But don’t worry! I’m sure that although we cannot fully understand the theory, you and I can fully utilize and apply Quantum Mechanics to our domain like AI that I’m focusing now.
On the next blog, I’m going to explain bullets and wave experiment to understand a concept of inteference and probability before talking about atomic wave.
Thank you for reading.
Cheers,
Bongsang
