Day 1
Day 1 | Bit vs Qubit: what is really encoded
Focus: expand state from 0/1 to an amplitude vector.
Start this stageQUANTUM COURSE
Quantum Computing in 21 Days
A 0-to-1 path focused on what you actually need: state, gate, measurement, entanglement, algorithms, and noise. One sharp goal per day, no vague survey mode.
All pages support Chinese/English switch. Learn in sequence for best results.
21 stages
Each page solves one core question with one animation and one focused practice task.
Day 2
Day 2 | Complex amplitudes and probability
Focus: separate amplitude from probability and see phase effects.
Start this stageDay 3
Day 3 | Dirac notation and vector view
Focus: unify |0>, |1>,
Day 4
Day 4 | Single-qubit gates: X, Z, H
Focus: separate bit flip, phase flip, and basis change.
Start this stageDay 5
Day 5 | Phase gates S/T and controlled phase
Focus: programmable phase is central to algorithmic power.
Start this stageDay 6
Day 6 | Measurement and Born rule
Focus: include measurement cost in algorithm design.
Start this stageDay 7
Day 7 | Bloch sphere intuition
Focus: see single-qubit gates as rotations.
Start this stageDay 8
Day 8 | Interference mechanics
Focus: build intuition for spread-then-cancel design.
Start this stageDay 9
Day 9 | Two-qubit states and tensor product
Focus: master the jump from 2D to 4D state space.
Start this stageDay 10
Day 10 | CNOT and entry to entanglement
Focus: inseparable states as source of quantum coordination.
Start this stageDay 11
Day 11 | Bell states and correlations
Focus: make entanglement advantage testable as correlation.
Start this stageDay 12
Day 12 | Density matrix and partial trace
Focus: reason about partially observed quantum systems.
Start this stageDay 13
Day 13 | Circuit thinking from goal to gate sequence
Focus: start from target distribution, then back-solve gates.
Start this stageDay 14
Day 14 | Deutsch algorithm
Focus: parallel amplitude query plus interference readout.
Start this stageDay 15
Day 15 | Deutsch-Jozsa for n-bit promise problems
Focus: structural advantage on promise problems.
Start this stageDay 16
Day 16 | QFT intuition
Focus: treat QFT as a phase decoder.
Start this stageDay 17
Day 17 | Phase estimation basics
Focus: controlled powers plus inverse QFT pipeline.
Start this stageDay 18
Day 18 | Shor skeleton and factoring acceleration
Focus: decompose Shor into period finding plus classical post-process.
Start this stageDay 19
Day 19 | Grover search and quadratic speedup
Focus: geometric meaning of mark-and-diffuse iterations.
Start this stageDay 20
Day 20 | Noise, decoherence, and error intuition
Focus: understand the gap between ideal circuits and hardware.
Start this stageDay 21
Day 21 | From understanding to designing
Focus: turn knowledge into an executable project loop.
Start this stageRecommended learning rhythm
Days 1-7: single-qubit fundamentals
Master state, amplitude, phase and measurement. Without this layer, later algorithms become memorization only.
Days 8-15: interference and circuit thinking
Train the workflow: design target amplitude flow first, then design the gate sequence.
Days 16-21: algorithm skeletons to hardware reality
From QFT and phase estimation to Grover/Shor, then noise and error correction into a project-ready path.