Decomposes operations into an FSimGate near theta=pi/2, phi=0.

This decomposition is guaranteed to use exactly four of the given FSim gates. It works by decomposing into two B gates and then decomposing each B gate into two of the given FSim gate.

This decomposition only works for FSim gates with a theta (iswap angle) between 3/8π and 5/8π (i.e. within 22.5° of maximum strength) and a phi (cphase angle) between -π/4 and +π/4 (i.e. within 45° of minimum strength).

interaction The two qubit operation to synthesize. This can either be a cirq object (such as a gate, operation, or circuit) or a raw numpy array specifying the 4x4 unitary matrix.
fsim_gate The only two qubit gate that is permitted to appear in the output. Must satisfy 3/8π < phi < 5/8π and abs(theta) < pi/4.
qubits The qubits that the resulting operations should apply the desired interaction to. If not set then defaults to either the qubits of the given interaction (if it is a cirq.Operation) or else to cirq.LineQubit.range(2).

A list of operations implementing the desired two qubit unitary. The list will include four operations of the given fsim gate, various single qubit operations, and a global phase operation.

ValueError If the fsim_gate has invalid angles or is parameterized, or if the supplied target to synthesize acts on more than two qubits.