Textbook in PDF format This book introduces quantum mechanics from an algebraic-geometrical point of view. This puts quantum mechanics quite firmly on top of three mathematical legs: linear algebra, calculus, and geometry. Thanks to the new geometrical picture, physics follows naturally from math. Not only that: quantum mechanics is well-embedded in science and technology. For example, the book uses quantum mechanics to develop quantum algorithms, including quantum FFT and Shor's factoring algorithm in cryptography. After introducing quantum mechanics from scratch, the discussion follows to entropy with a focus on entanglement entropy. Moreover, the algebraic study of angular momentum and energy helps analyse spin and polarization alike. Next, the book introduces algorithms in cryptography, where quantum algorithms are particularly relevant. Finally, Feynman diagrams are also introduced from an algebraic perspective. The book ends with examples of how practical algorithms are programmed on the computer