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Learn quantum mechanics by playing with it

That is a real qubit beside this text — or just below it on a phone. Spin it, hit it with a gate, measure it.

Try it — this is the first lesson

P(0) 100%·P(1) 0%

This is one qubit. The arrow is its state. Press a gate — every move is the real rotation, not an animation.

Build your first circuit →Explore the visualizations
  • 40 visualizations
  • All 16 qubits free, no account needed
  • 0 dependencies to run

Four ways in

What’s inside

Interactive Visualizations

40 hands-on simulations, from the double-slit experiment to the surface code. Drag the sliders, break your intuition.

Circuit Simulator

Build quantum circuits with drag-and-drop gates, run thousands of shots, and export real OpenQASM 3.

AI Tutor

Ask anything. The tutor runs circuits to show you the answer instead of just asserting it.

AI Workbench

18 tools that produce a result, not a lesson: verified circuits, trained decoders, routed circuits, mitigated readouts and agent-run experiments — on the same engines.

Learning paths

Where do you want quantum to take you?

Pick a goal and follow a roadmap built from everything here — milestone by milestone, with your progress tracked, until you are there.

Compare all paths

A path through it

Start here

Each one builds on the last. Start with the experiment that broke classical physics, finish with the algorithm that reads a phase out of a quantum register.

  1. The Double-Slit ExperimentBeginnerFire electrons one at a time and watch stripes appear that no particle should make.
  2. Superposition & MeasurementBeginnerBuild a quantum state gate by gate, then find out what measuring it actually destroys.
  3. The Bloch SphereBeginnerEvery possible state of a single qubit, as one point on a globe you can spin.
  4. The Stern-Gerlach ExperimentBeginnerMeasure a beam sideways and it forgets which way was up — put it back through the first magnet and half of it comes out down.
  5. Particle in a BoxBeginnerTrap a particle between two walls and only certain energies survive — then lower the walls and watch it leak out through them.
  6. The Photoelectric EffectBeginnerTurn the lamp up as far as you like. Below a certain colour, not one electron comes out.
  7. Blackbody RadiationBeginnerThe classical curve does not overshoot slightly — it goes to infinity, and fixing that took quantising light itself.
  8. EntanglementIntermediateTwo qubits whose answers always match — without either one carrying the answer.
  9. Quantum TunnelingIntermediateA particle without the energy to climb the wall, appearing on the other side anyway.
  10. Grover's SearchIntermediateFind one item in a million with a thousand guesses — by making the wrong answers cancel.
  11. DecoherenceIntermediateWatch a qubit forget — the arrow retracts into the sphere and takes the phase with it.
  12. The Bell TestIntermediateRace a hidden-variable universe against a real one and watch it stall at exactly 2.
  13. Quantum TeleportationIntermediateA state crosses the room without the qubit — and still waits on two ordinary bits sent the slow way.
  14. Superdense CodingIntermediateTwo classical bits down a single qubit. Take the entangled pair away and exactly one of them vanishes.
  15. The Quantum Harmonic OscillatorIntermediateA ladder of evenly spaced rungs, and one packet that swings like a marble in a bowl without ever spreading.
  16. Wave Packets and ScatteringIntermediateDraw a landscape, fire a packet at it, and watch some of it bounce off a barrier it had plenty of energy to cross.
  17. Models of the Hydrogen AtomIntermediateBohr’s orbits and Schrödinger’s clouds predict the same spectrum — and disagree about everything else.
  18. The Mach-Zehnder InterferometerIntermediateTwo beams, each carrying half the light, meeting at a detector that never clicks — until you lengthen one path by half a wavelength.
  19. Deutsch–Jozsa: The First Quantum SpeedupIntermediateOne call to a black box settles a question that can cost a classical computer half a million.
  20. Spin PrecessionIntermediatePut a magnetic field on the Bloch sphere and the arrow starts to turn — the same physics as an MRI scanner and as every RX gate.
  21. Uncertainty as a Fourier Trade-offIntermediateSqueeze a packet in position and its momentum spreads to compensate — watch the Gaussian land exactly on the ħ/2 floor that nothing beats.
  22. How a Laser WorksIntermediatePump atoms up faster than they fall and one stray photon becomes a beam of identical copies — take one level away and it never can.
  23. Alpha Decay: Tunneling with a Half-lifeIntermediateUranium’s four-billion-year half-life is one number: the chance, per knock, that an alpha particle is simply on the other side of a wall it cannot climb.
  24. Davisson–Germer: Electron DiffractionIntermediateFire electrons at a nickel crystal and a peak appears at 54 V and 50° — exactly where a 0.167 nm wave would put it. The experiment that proved de Broglie.
  25. Quantum Key DistributionIntermediateLet Eve intercept the photons and watch a quarter of the key go wrong — she cannot listen more quietly, and 11% is where Alice and Bob stop trusting it.
  26. Quantum Fourier TransformAdvancedThe transform at the heart of Shor’s algorithm, with every phase laid bare.
  27. VQE and the Barren PlateauAdvancedA classical optimiser hunts a ground-state energy across a landscape that goes flat as the qubit count grows.
  28. Shor's Algorithm: Period FindingAdvancedThe one quantum step inside factoring — finding a hidden period, not the factors themselves.
  29. The Surface CodeAdvancedWhy one error-corrected qubit costs a hundred real ones, and what happens when you skimp on distance.
  30. Decoder Duel: Lookup vs LearnedAdvancedA neural decoder trains in your browser and chases majority vote — which, on this code, is provably unbeatable.
  31. The Quantum EraserAdvancedErase which-path information after the photon has already been detected, and find the interference waiting in the bookkeeping.
  32. Quantum Phase EstimationAdvancedAn eigenvalue nobody can measure, written into spare qubits as a phase and read back as a number.
  33. Band StructureAdvancedSwitch a row of atoms on under a free electron and whole ranges of energy become forbidden — then count electrons to see which solids conduct.
  34. Fermions and BosonsAdvancedPut two particles in one well and swap them. A minus sign you cannot see carves a hole where they would meet — and stacks the periodic table.
  35. Tomography and No-CloningAdvancedLearn an unknown state from thousands of copies measured three ways — and try to build the copier that would make it cheap.
  36. Mixed States and the Density MatrixAdvancedThe arrow inside the sphere, as a matrix: purity is its length, a mixture is not a superposition, and half of a Bell pair is the most mixed a qubit gets.
  37. Wavefunctions in Three DimensionsAdvancedBox, oscillator, rotor and hydrogen as the probability clouds they are — no edge, no isosurface, and a plane you can drag through the nodes.
  38. Phase Space and the Wigner FunctionAdvancedA quantum state as a landscape over position and momentum — and a single photon digs it below zero, where no probability can go.
  39. Majorana StarsAdvancedThe Bloch sphere for bigger spins: 2j points instead of one — rotate them and they turn together, squeeze them and they fly apart.
  40. The HHL AlgorithmAdvancedSolve Ax = b without ever computing x — phase estimation reads out an eigenvalue, and a controlled rotation divides by it.

Why not just use IBM, Brilliant, or a MOOC?

The combination nobody else offers

IBM Quantum has real hardware and a huge community, but no guided tutoring. Brilliant teaches beautifully, with an in-browser simulator, but has no free-form circuit editor, no OpenQASM export and no path to hardware. University courses give you rigor and a credential, at a multi-week pace. Qubit16 is the one place that combines Brilliant’s visual, interactive teaching with an exact statevector simulator that runs in your browser — no upload, no queue — and is verified against Qiskit and PennyLane in our test suite; the AI tutor checks its answers with Qiskit/Aer, and every circuit exports as OpenQASM that loads straight into Qiskit. Add a live AI tutor that can see what you built, and a spaced-repetition review queue that brings quiz questions back right before you’d forget them, instead of leaving retention to chance. Free to start, zero install, and every line of progress stays in your browser — no account required to begin.

See the full comparison →Why this exists

For learners

Everything free for your first 30 days

Create an account and every Pro feature — the live AI tutor, the full advanced track, and real quantum hardware where this deployment has provider credentials configured — is included, no card, nothing to cancel. The foundations course and all 40 visualizations stay free forever, with or without an account.

Create a free account

For educators and institutions

Run a course on a real quantum lab

Seats, classes and assignments built from the same lessons, challenges and exams; completion tracking your students opt into; CSV export; an embeddable circuit widget for your own pages. Nothing to install in any lab.

See what educators get →