*126*

*Read: June 2023*

*Inspiration: *Came across on Amazon’s bestseller list; wanted to gain some basic level of understanding of “quantum physics” and “quantum computing”

## Summary

**Written with the help of ChatGPT, below is a brief summary to understand what is covered in the book.**

“Quantum Physics for Beginners”, published in 2021 author, professor, and scientist Carl Pratt, is a comprehensive introductory guide to the fascinating world of quantum physics. Pratt takes readers on a journey from the foundational concepts of wave theory to the cutting-edge realm of quantum computing. The book provides a simplified explanation of quantum physics, making it accessible to beginners. It explores key topics such as wave-particle duality, quantum superposition, and quantum entanglement. Pratt also delves into the potential applications of quantum physics in various fields, including computing, cryptography, and communication. Overall, “Quantum Physics for Beginners” offers readers a solid foundation in understanding the principles and implications of this groundbreaking scientific field.

## Unedited Notes

*Direct from my original book log, below are my unedited notes (abbreviations and misspellings included) to show how I take notes as I read.*

Quantum physics has nothing in common with classical physics, deals with physical phenomena at microscopic levels, infinitely small objects working with distance shorter than the diameter of an atom, explains how everything works, “quanta” are the smallest unit of any physical entity—atoms, electrons etc are not actually particles but rather quanta of various things (energy, mass), nothing happens in quantum physical world unless observed, traditional theory of light is what learn in school, wave theory of light first presented 1678 by Christiaan Huygens (dutch)—represent light as waves, Thomas Young refine idea a century later, double slit experiment shows light can behave like wave—shoot rays through 2 slits and they interfere with each other like waves in specific predictable pattern known as diffraction pattern, 1845 Faraday present that a magnetic field influenced polarized light and speculate light could be a vibration of the electric and magnetic lines of force (Faraday Law of Induction), James Maxwell of Scotland build on Faraday to explain electricity and magnetism (electromagnetism) and voltage creation (EMF, electromotive force), Maxwell say that changes in electric current can generate a magnetic field and vice versa (Maxwell’s Third Law)—prove waves vs instantaneous signals, unified electricity and magnetism as well as light/heat, ultraviolet catastrophe=using light as a wave, had theory that intensity of blackbody radiation (object that absorbs all radiation without reflecting any) increases with frequency of wave BUT only proved to be true to a certain point—when frequency of light exceeded UV range theory failed as intensity actually dropped (contradicted wave theory), unresolved from 1859 to 1900 when Max Planck develop his Law about quanta to resolve uv catastrophe—basically said magnetic energy exists in form of discrete packets known as quanta (he set a min energy value and said particles could only vibrate with energy values that are multiple of Planck’s Constant, Planck changed view of light as discontinuous not cont, einstein then 1905 introduce particle theory of light building on Planck—said that light travels in discrete packets, light possess Wave-Particle Duality—behaves like both under diff circumstances, Planck is the one who initially posited that energy is quantized not continuous (supported by Eistein’s experiement on Photoelectric Effect), 1924 Louis Victor de Broglie go further to show wave-particle duality applies to all things not just light, Unified Field Theory is holy grail (still unachieved) which attempts to create mathematical proofs for all interactions/relationships in quantum physics (one set of laws), Schrodinger try 1910s UFT but not succeed, however Schrodinger’s Equation caused giant rift between classical physics and quantum—looked to take time out of wave-particle equation, Schrodinger’s Equation is complex partial differential equation but can predict probability of finding a particle at any given point in space, Bohr’s model of electron’s not fully accurated—quantized energy levels right but not capture uncertainty of electron location and velocity as in reality, Schrodinger build on it to form probability based equation for electron location by orbital region, Schrodinger posit that until observed or measured an electron can be thought of as existing in multiples places at once (Schrodinger’s Cat idea that cat in poisonous black box dead and alive at once until box uncovered, not know), act of measurement drives electron to be localized in specific location (“wave function collapse”), quantum superposition is idea can exist in multiple places—measuring one attribute resets another attribute (i.e. exists in both states superimposed until measured), wave-particle duality explains why measurement of an atom/electric can only be an approximation—cannot precisely measure position and momentum, 1905 einstein posit special relativity theory which explain how speed affects mass time and space and that small amounts of mass can be interchangeable with enormous amounts of energy—Schrodinger lacked a speed limit, Dirac’s Quantum Field Theory merged quantum mechanics and theory of relativity and magnetic fied theory, enabled modeling of particle creation/destruction, in quantum world gravity is extremely weak—essentially does not exist for particles (strong nuclear force is 10^41 times stronger), 1915 Einstein posit general relativity theory (expand on special relativity to describe gravity as a geometric property of space and time aka 4D spacetime), Einstein merged special relativity and newton’s law of universal gravitation—holds today as best gravity theory, gravity does have a quantum nature though weak—lead to speculative particle of gravitons (never found in experiments yet, still outstanding in quantum mechanics), String Theory proposes that rather than elemental particles, the smallest building blocks of universe are tiny vibrating strings of energy from which all matter and known forces emenate, attempts to connect all 4 known forces and explain how work vs general theory of relativity and quantum mechanics not being compatible, string theory requires more than 4 dimensions (3 for space and 1 for time), bosonic string theory requires 27 dimensions (“hyperspace”)—tries to explain quantum gravity, today when reference string theory—really mean superstring theory which combines string theory with supersymmetry (SUSY) which relates bosons and fermions, 5 string theories developed then American Edward Witten propose M-Theory to combine them—closest to Theory of Everything, mapped the 5 to one another by certain conditions known as dualities, M-Theory has 11 dimensions and involves one-dimensional strings + P brains (objects with range of dimensions), Quantum Entanglement is idea that when pair/group of particles generated or interact or share spatial proximity in such a way that quantum state of each particle cannot be described indep of state of others (once know one, immediately know other), Quantum Tunneling is about probablistic nature of particles position and momentum—minsicule probability of penetrating a barrier, how protons merge in sun for heat to fuel nuclear fusion, quantum computer leverages superposition of qubits (vs strings of 1s and 0s classical computing), 1 qubit can be in two states, 2 in 4 states and so on, also have entanglement—have 2 qubits and measure 1 then tells us something about second (not independent, info is diff than binary info classically), qubits are artificial atoms created from Josephson Junction and microwave resonator—temp of quantum computer chip must cool to -460 degrees F and use microwaves to flip/interact with qubit state