circuits / hadamard-test

Hadamard Test

✓FEATURED

Estimates ⟨ψ|U|ψ⟩ using an ancilla qubit, controlled-U, and measurement. Fundamental for many quantum algorithms.

quantumcomputer.dev
openqasm2q3 gatesdepth 30 views0 saves0 forks0 downloads

Source Code

OPENQASM 2.0;
include "qelib1.inc";
qreg q[2];
creg c[1];
h q[0];
// Controlled-U (example: controlled-Z)
cz q[0],q[1];
h q[0];
measure q[0] -> c[0];

Cite this circuit

MIT
quantumcomputer.dev. "Hadamard Test". quantumcomputer.dev/circuits/hadamard-test. 2026.