This is an undergraduate-level introduction to the theory of quantum computing and information. We'll cover the rules of quantum mechanics (qubits, unitary transformations, density matrices, measurements); quantum gates and circuits; entanglement; the Bell inequality; protocols for teleportation, quantum key distribution, and other tasks; basic quantum algorithms such as Shor's and Grover's; basic quantum complexity theory; basic quantum error correction; decoherence and the measurement problem; and the challenges of building scalable quantum computers. Previous exposure to quantum mechanics is not required.