arXiv2026
We present a conceptually clear introduction to quantum theory, deriving the theory from scratch from the point of view of quantum information, with focus on developing intuition and dispelling misconceptions. Different subsets of these lectures were taught to a wide variety of audiences, including exceptional high-school students in the International Summer School for Young Physicists (ISSYP) at Perimeter Institute, 2nd-year physics undergraduates at the University of Toronto, and 4th-year physics and math undergraduate and graduate students at Brock University. The lectures are completely self-contained, including all the necessary mathematical background: complex numbers, linear algebra, and probability theory. They cover topics such as the axioms of quantum theory, qubits, superposition, entanglement, the uncertainty principle, unitary transformations and evolution, quantum gates, projective measurements, Bell's theorem, interpretations of quantum mechanics, the no-cloning theorem, quantum teleportation, quantum algorithms, density operators, mixed states, von Neumann entropy, the Bloch sphere, quantum decoherence, Hamiltonians, the Schrödinger equation, canonical quantization, quantum harmonic oscillators, wavefunctions, and much more. The lectures also contain 111 proof-based problems and 51 computational exercises.