Quantum Physics Lecture Notes

Overview of Quantum Physics

The world is often straightforward: objects are either in one state or another (e.g., a car is at rest or moving, a cat is either dead or alive).
However, at the fundamental level, particles exist in multiple states simultaneously, a concept known as superposition.

Quantum: Derived from Latin, meaning "how much"; it refers to the minimum amount of some physical entity.
Quantum physics deals with the most elementary particles:
- Electrons in atoms
- Protons in the nucleus
- Quarks that compose protons
- Photons, which are perceived as light.

Classical Physics: Based on Newton's laws; deals with macroscopic phenomena (e.g., motion of objects, mechanics of engines).
Limitations of classical physics became evident in the early 1900s with the photoelectric effect:
- Normal physics predicted electron emission based on brightness, but it was actually determined by the color of light.
- Albert Einstein utilized Max Planck's equation (energy in small packets called quanta) to explain this phenomenon.

Quantum Tunneling: Particles can pass through energy barriers without sufficient energy, which is crucial for processes like nuclear fusion in stars.
The quantum world operates on probabilities rather than certainties.
Probabilities and Multiple Realities:
- Position of an electron described in terms of probabilities across a range.
- Each possible position of a particle can be seen as existing in different realities.

Representations in movies, such as the Marvel Universe:
- Doctor Strange: Explores the concept of multiple realities.
- Endgame: Addresses the Grandfather Paradox and time travel, suggesting that changes in the past have probabilistic outcomes.

Quantum computing: Aims to perform complex tasks beyond classical computers' capabilities.
Improved communication systems for safety and privacy.
Nuclear reactors and astrophysics heavily rely on quantum studies.

Quantum physics is integral to understanding the universe’s building blocks and is increasingly important in various fields of science and technology.