Quantum Circuit Simulator: Qubits, Gates & Entanglement (2D)

This 2D companion trades the 3D original's decorative spinning-orb "quantum computer" for the mechanic its title actually promises: a real exact-statevector circuit simulator. A register of 1-4 qubits starts in the |0…0⟩ ground state; applying H, X, Y, Z, S, T or CNOT gates multiplies the underlying complex amplitude vector by the matching 2×2 (or controlled) unitary, and the probability histogram redraws itself from the genuine Born-rule probabilities |ψᵢ|² read off that vector — nothing here is a pre-scripted animation. A one-click "Bell pair" button (H then CNOT) shows the qubit-0 entanglement entropy jump from 0 to 1 bit, the textbook signature of true quantum correlation, and "Measure" samples and collapses the state exactly as a physical measurement would.