Phased GHZ

GHZ states are used as phase sensors because a relative phase on the cat state is collectively visible. Prepare a cat state that already carries a chosen phase between its two branches.

Objective

prepare_phased_ghz(num_qubits, phi) returns a circuit preparing (|0...0> + e^(i phi)|1...1>)/sqrt(2).

Constraints

• No initialize / state_preparation shortcuts.

Entry Point

Checks

• Exports prepare_phased_ghz(num_qubits, phi).
• Matches the phased cat state for 1, 2, 3 and 5 qubits.