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Free quantum computing lessons

Free quantum computing lessons: from bits and qubits to superposition, entanglement and interference, then on to Grover’s algorithm, the quantum Fourier transform and phase estimation.

2 courses · 12 lessons · no installation; every lesson comes with a quantum circuit that runs in your browser

Beginner course

Qubits, superposition, measurement, entanglement and interference with no physics or maths background, ending with your first quantum algorithm.

Beginner · 6 lessons · about 58 minutes in total

  1. 1. Bits and qubits: the smallest piece of information · 8 min
    Why do computers work with 0 and 1, how does a qubit differ from a bit, and what are real qubits made of? A first lesson that needs no physics at all.
  2. 2. Superposition: a mixture of 0 and 1 · 10 min
    Put a qubit into superposition with a Hadamard gate, measure it 1000 times and see the randomness for yourself. What superposition means, and what it doesn’t.
  3. 3. Measurement: from quantum to classical · 8 min
    What does measurement do to a qubit, why are quantum programs run thousands of times, and why can’t quantum information be copied?
  4. 4. Entanglement: linked qubits · 10 min
    Entangle two qubits with a CNOT gate: random on their own but always in agreement together. The phenomenon Einstein called “spooky action at a distance”.
  5. 5. Interference: the hidden power of quantum computers · 10 min
    Amplitudes reinforce or cancel each other like waves. See how two H gates wipe out randomness and learn the secret of quantum algorithms.
  6. 6. Your first algorithm: Grover search · 12 min
    Build and run, step by step, Grover’s algorithm, which finds the marked option among four in a single step. How big is the quantum speed-up, and what doesn’t it speed up?

Intermediate course: quantum algorithms

From phase and the Bloch sphere to Deutsch–Jozsa, Bernstein–Vazirani, Grover, the quantum Fourier transform and phase estimation.

Intermediate · 6 lessons · about 62 minutes in total

  1. 1. Phase and the Bloch sphere: the invisible dial · 10 min
    Phase, invisible in measurements, is the real raw material of quantum algorithms. Picture a single qubit with the Bloch sphere and see what the Z, S and T gates do.
  2. 2. Deutsch–Jozsa: a certain answer in one query · 10 min
    The first quantum algorithm to decide with certainty, in a single query, whether a function is constant or balanced. Meet phase kickback and oracles.
  3. 3. Bernstein–Vazirani: find the hidden string in one go · 8 min
    The algorithm that reads a bit string hidden inside a function in a single query instead of the n queries needed classically. See step by step how the oracle is built.
  4. 4. Grover in depth: oracle and diffusion · 10 min
    Take apart the two pieces of Grover’s algorithm: the oracle that marks the answer and the diffusion that amplifies it. Change the oracle and find a different answer.
  5. 5. The quantum Fourier transform: catching the period · 12 min
    Build the quantum Fourier transform at the heart of Shor’s algorithm with two qubits. See how a periodic state turns into peaks that reveal the period.
  6. 6. Phase estimation: measure a gate’s secret · 12 min
    Combine phase kickback and the inverse Fourier transform to measure the phase a gate adds. A shared building block of Shor’s algorithm and quantum chemistry.