A course on quantum physics for everyone, which will lead you by hand as clearly as possible from the abc of quantum mechanics to the most recent experiments and its philosophical implications. This course does not only introduce you to the basics of quantum theory, but covers also with a simple and non academic approach topics and several experiments that usually are discussed only among specialists. We review the standard concepts like the wave-particle duality, Heisenberg`s uncertainty principle, Schrödinger`s cat, the vacuum zero-point energy and virtual particles, among several others. Then we deepen the subject analysing quantum entanglement, the so called "EPR paradox" which question our naive understanding of the meaning of reality and locality, together with other effects and ground braking discoveries of the last century physics. Another, more advanced section, and that is usually not explained to the popular audience in an accurate but clear and understandable way, is what I call the "quantum philosophy experiments", like the "which way", "quantum erasure", "delayed choice", "interaction free" and "quantum teleportation" experiments.
This course is unique in the sense that, after delivering a historic introduction and the foundations, getting rid of typical popular misunderstandings, it discusses also several topics which go to the essence of the quantum phenomena, making it available for the first time in an easy understandable way to everyone. It is for those who always wanted to understand the principles of quantum physics, but are not physicist. Especially the part on quantum philosophy experiments may be interesting for physicists too who want to deepen the conceptual foundations and the philosophy of QM. For those who always have been attracted by the fascinating and weird quantum world, but found only advanced level university courses, or superficial popular science hypes where you couldn't discriminate between serious sensical and nonsensical stuff and between scientific and pseudo-scientific theories. For those who searched for a course that explains the basics of quantum mechanics, but that does not presuppose a technical preparation, and yet furnishes the most rigorous account as far an (almost) non mathematical exposition allows for.
By covering the basics of quantum theory, from its birth about a century ago until today's modern research, its aim is to deliver the material necessary so that you will be able by yourself to distinguish between mere speculative (and more or less extravagant) interpretations in fashion, and the real experimental facts.
Note: students from schools or colleges will get a free bonus. Send an email to email@example.com from your school/department mail account and you will get the coupon.
The historical point of departure of quantum theory was Planck's derivation of the black body radiation which assumed energy to be quantized. Previously it was thought that energy is a continuous phenomenon. Its quantization was a conceptual revolution that can be compared to a sort of "Copernican revolution".
The photoelectric effect comes as a further validation of the fact that enery appears always quantized. Bohr, inspired by these results, advances his famous "planetary model" of the atom.
PS: Please note a msitake in the video. Niels Bohr was Danish, not Dutch!
Bohr's atom model seemed to receive experimental validation by Frank-Hertz's experiment which definitely demonstrated that atoms absorb energy in quantized amounts of energy. The Compton scattering of photons and pair production of matter and anti-matter particles showed that electromagnetic radiation has a corpuscular nature.
A brief introductory description on waves and the concept of interference. A concept of paramount importance to understand quantum mechanical phenomena.
Some mathematical aspects about waves, interference and complex numbers. This brief formal overview is necessary to understand QM, espcially from section III on.
Bragg diffraction and the de Broglie hypothesis pave the way for understanding better the wave-particle duality problem.
Are photons and electrons particles or waves? If they are both, when do they show upn as one or the other aspect? The wave-particle duality illustrated by Young's double slit experiment will shed some light on this.
Heisenberg's uncertainty principle is explained and some of its frequent misinterpretations illustrated.
The concept of the wavefunction in quantum mechanics is explained. We will address the question if the wavefunction is a mere mathematical object or if it represents a real physical entity.
The description of the quantum world in terms of a probabilistic interpretation led to a mathematical formalism which is quite different than that used in classical physics. Classical states and dynamical variables are replaced by state vectors and operators, the "observables". The resulting formalism led to Schrödinger's equation which became the base for a successful understaning of atomic physics.
Angular momentum and spin are physical quantities which we intuitively ascribe to rotating objects. Do they apply in the same way for elementary point particles?
The Stern-Gerlach experiment was decisive in demonstrating the impossibility to know the particles's spin values along two directions at the same time.
Can particles spin clockwise AND anti-clockwise at the same time? In the microscopic quantum world it is a normal state of affairs.
Can a cat be dead AND alive at the same time? Quantum mechanics seems to suggest this, however at a closer inspection the paradox can be solved.
In analogy to Heisenberg's uncertainty over position and impulse, likewise it is impossible to determine with absolute precision the energy has at a definite time. There are however fundamental differences between the two uncertainties.
Can a particle jump through a classically forbidden barrier? Quantum mechanics allows to tunnel through a potential barrier even if it has not the classical allowed energy to do that.
Is "empty" space really empty? According to quantum physics there can't exist no such thing. We will take a look at the vacuum zero-point energy, the concept of virtual particles and the Casimir effect.
Enstein and Bohr did not agree on how to interpret quantum physics. Einstein tried to disprove it with thought experiments and Bohr pointed out its fallacies. The Copenhagen interpretation of quantum mechanics took shape.
Two identical elementary particles are no longer distinguishable after interaction. They will form a unique indistinguishable whole.
In quantum theory particles can be entangled with each others also light years away and apparently "feel" instantly the state of the other. How should this be correctly interpreted?
A. Einstein, B. Podolsky and N. Rosen proposed a thought experiment that was supposed to show how it is possible to circumvent the commutation relations of QM and why it has to be considered therefore an incomplete theory. Were they right?
Some quantum phenomena seem to imply an action at a distance faster than light. Instant correlation between particles also light years apart are possible. Does this allow for faster than light transmission of information?
It looks like that quantum mechanics describes a non-local reality, where apparently faster than light interactions might occur. In what sense should we interpret this? What experiments could help us to discriminate between different interpretations?
What does it really mean that particles interact? What is a field and what kind of particles are the "material" particles and those responsible as force carriers? This lecture sets the stage to understand better the distinction between bosons and fermions.
The universe is made by two types of particles: bosons and fermions. In this lecture we review the basic properties of them and how they behave differently in quantum mechanics.
The Pauli exclusion principle, one of the most fundamental principles of quantum physics, is explained, and its consequences or the behavior of matter in extreme conditions like in White Dwarfs or neutron stars analysed.
Why is matter stable? Why do electrons not fall into the atomic nucleus?
This is a long lecture and for advanced students only. It is however not compulsory or necessary to understand the rest of the course material. It is nevertheless a fascinating effect which shows how quantum objects do (apparently?) not need to be in direct contact with a magnetic field to be influenced by its presence.
The Quantum Zeno effect is a strange quantum property of the quantum world whereby, the time evolution of a quantum system can be suppressed by frequent measurements.
Why do particles, which are not subjected to external forces, move along a straight line? Richard's Feynman path integral formulation of quantum mechanics furnishes an unexpected answer.
With the advent of laser and optical technologies it is nowadays possible to perform experiments which were impossible at the times of Einstein or Schrödinger. The Mach-Zehnder interferometer is a typical device that is used to test the foundation of quantum mechanics and is worth a closer look.
The "which way" experiments are particular experimental setups that trace the whereabouts of a particle without perturbing it along the path, and which show that the mere information of the particle's path is sufficient to destroy interference.
IMPORTANT NOTICE: ERRATA
Please consider that the second polarzation-rotator should be placed after the first polarization-rotator and before the second beam splitter (i.e., NOT after the second beam splitter and D1, as shown in the lecture's slide). I apologize for this mistake and will fix this with a new video as soon as I can, but meanwhile keep this in mind!
It is information about the path a particles travels along which makes the wavefunction collapse. But is it due to a perturbation of it or is it a general (information theoretic) law of nature? By using twice the same device which furnishes this information, but erasing it at the second stage of measurement we get the answer.
Is it possible to measure the presence of an object without interacting with it? Does meausurement always imply interaction and perturbation of the measured object?
Can we deceive nature by delaying the choice if we want to observe the wave or particle nature of a photon flying through the double slit experiment?
The Scully-Englert-Walther experiments contains several of the typical quantum philosophy experiment: it is a quantum eraser and which-way experiment that shows the wave-particle duality for atoms. It is important for understanding how the principle of complementarity is fundamental and seems to have temporal retro-causal effects.
Quantum teleportation is a bizarre quantum effect that reminds scifi transportation systems like that of the "beaming" of objects in Star Trek's film. This is still not possible for macroscopic objects, but it has been shown experimentally to be possible with single particles or atoms.
I graduated in physics at the university of Padua (near Venice), and later obtained a Ph.D in physics at the university of Trento. Later worked as a PostDoc researcher in universities in Italy, France and more recently in Germany, where I'm actually living. I'm striving for a new pedagogical paradigm for higher education and working on a project to establish a Free Progress University.