Drag-and-drop quantum circuit construction with live state evolution
A quantum circuit is a sequence of gates applied to qubits — it's the "program" of a quantum computer. Unlike classical circuits that carry electrical signals, quantum circuits manipulate probability amplitudes. Every quantum algorithm — from Grover's search to Shor's factoring — is expressed as a circuit.
Build circuits by placing gates on qubit wires, step through execution to see the state evolve, and explore famous circuits that demonstrate the power of quantum computation.
Select a gate from the palette and click on the circuit grid to place it. The state vector updates in real-time as you build. Try placing H on q₀ then CNOT to create a Bell state — watch the entanglement indicator light up! Click any placed gate to remove it.
Select a gate, then click on the circuit grid to place it. Click an existing gate to remove it. CNOT uses the clicked wire as control and the other wire as target.
Start with H to create superposition, then use CNOT to entangle. Notice how single-qubit gates never create entanglement — you need two-qubit gates.
Gates execute left-to-right (t0, t1, t2...). Each column is one time step. The output state depends on the order of gates — quantum operations don't commute!
Watch the quantum state evolve one gate at a time. Select a pre-built circuit and step forward to see exactly how each gate transforms the state vector. This is how quantum computation actually works — amplitudes flow and interfere at each step.
These circuits are the building blocks of quantum information science. The Bell state circuit creates entanglement. The GHZ circuit entangles three qubits. Superdense coding sends two classical bits using one qubit. Quantum teleportation transfers a state without moving a qubit. Phase kickback is the engine behind every quantum algorithm.