Discover Circuits

Quantum Approximate Counting

Simple amplitude estimation circuit estimating the probability of a marked state.

Hadamard Test

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

SWAP Test

Determines the overlap between two quantum states without measuring them. Ancilla qubit reads |0⟩ if states are identical.

Quantum Phase Estimation (2+1)

Estimates the phase θ in U|ψ⟩ = e^{2πiθ}|ψ⟩ using 2 counting qubits and inverse QFT.

Quantum Fourier Transform (3 qubit)

The 3-qubit Quantum Fourier Transform (QFT), a key subroutine in Shor's algorithm and quantum phase estimation.