Fredkin Gate (CSWAP) | Controlled-SWAP Conservative Logic
Quick Technical Answer:
The Fredkin gate (Controlled-SWAP or CSWAP) is a 3-qubit gate that exchanges the states of two target qubits if and only if the control qubit is |1⟩. It is conservative, meaning it strictly preserves the total number of 1s (Hamming weight).
Formula / Unitary:
CSWAP|1, t_1, t_2\rangle = |1, t_2, t_1\rangle, \quad CSWAP|0, t_1, t_2\rangle = |0, t_1, t_2\rangle
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Frequently Asked Questions
Where is the Fredkin gate utilized?
The Fredkin gate is essential in quantum optical computing, error detection networks, and the SWAP-test circuit used to measure state overlap |⟨ψ|φ⟩|² in quantum machine learning.