Learn by doing
Quantum Playground
Real quantum computing, simulated exactly in your browser. No installation, no account — just qubits.
Everything on this page runs client-side on an exact state-vector simulator. Refresh-proof randomness included.
01 · One qubit
Single-Qubit Lab
Apply gates and watch the state move on the Bloch sphere. Then measure it — and watch the superposition collapse.
Drag the sphere to rotate it
State
|ψ⟩ = 1.000 |0⟩
Measurement probabilities
x 0.00 · y 0.00 · z 1.00
Gates
Applied gates
02 · 1–3 qubits
Circuit Composer
Build a circuit by placing gates on the wires, then run it and read the statistics. For a two-qubit gate, pick the gate and tap its two qubits in the same column.
First qubit picked (control for CNOT) — now tap the second wire in the same column. Esc to cancel.
Measurement outcomes
Press Run to sample the circuit.
— dash = expected count from the exact distribution
Exact probabilities
Bitstrings read top wire → leftmost bit.
Per-qubit Bloch vectors
q0 · |r| 1.00
q1 · |r| 1.00
q2 · |r| 1.00
Entanglement shrinks the arrows: a maximally entangled qubit sits at the very center of its sphere.
03 · Quantum Internet
BB84 — Quantum Key Distribution
Alice sends Bob single photons, each carrying a random bit in a random basis. Anyone who intercepts them leaves fingerprints in the statistics — security guaranteed by the laws of physics, not by math being hard.
- Alice encodes random bits in random bases — + (rectilinear) or × (diagonal) — and sends the photons.
- Bob measures each photon in a random basis. When his basis matches Alice’s, his bit is guaranteed to equal hers.
- They publicly compare bases and keep only the matching rounds (sifting). Any errors in the sifted bits expose an eavesdropper.
Press “Exchange photons” to start the protocol.
✓ bases match — bit kept· bases differ — discarded error in a sifted bit
Sifted
—
Errors
—
QBER
—
Sifted key (Bob)
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