Quantum information, from the qubit up. Amplitudes that can cancel, the Bloch sphere, the Born rule and why measurement is basis-dependent, and the exponential dimension of many qubits. Then entanglement: Bell states, the CHSH inequality and what a violation actually rules out, no-cloning in three lines, gates and universality, density matrices and the partial trace that shows a maximally entangled pair has maximally mixed halves. It closes with the protocols and algorithms: teleportation, superdense coding, Deutsch-Jozsa, Grover's square-root speedup, decoherence, quantum error correction, and BB84. Scoped against mathphys, which owns the physics formalism (Hermitian observables, the Schrodinger equation, the canonical commutator), crypto, which owns what Shor and Grover break, and information, which is entirely classical Shannon theory.
Free to start · adaptive placement finds your level · reviews timed so it stays learned.
Every idea is taught with motivation and a worked example before the drills, and an FSRS spaced-repetition engine schedules each review for the moment just before you'd forget it. A short placement check finds what you already know, so you start Quantum Information exactly where it's useful.