def decompose_two_qubit_interaction_into_four_fsim_gates_via_b(
interaction: Union['cirq.Operation', 'cirq.Gate', np.ndarray, Any],
*,
fsim_gate: Union['cirq.FSimGate', 'cirq.ISwapPowGate'],
qubits: Sequence['cirq.Qid'] = None) -> 'cirq.Circuit':
circuit = decompose_two_qubit_interaction_into_four_fsim_gates(
interaction, fsim_gate=fsim_gate, qubits=qubits)
merge_single_qubit_gates.MergeSingleQubitGates().optimize_circuit(circuit)
drop_empty_moments.DropEmptyMoments().optimize_circuit(circuit)
return circuit
def decompose_two_qubit_interaction_into_four_fsim_gates_via_b(
interaction: Union['cirq.Operation', 'cirq.Gate', np.ndarray, Any],
*,
fsim_gate: 'cirq.FSimGate',
qubits: Sequence['cirq.Qid'] = None) -> 'cirq.Circuit':
"""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).
Args:
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)`.
Returns:
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.
"""
if not 3 / 8 * np.pi <= fsim_gate.theta <= 5 / 8 * np.pi:
raise ValueError('Must have 3π/8 ≤ fsim_gate.theta ≤ 5π/8')
if abs(fsim_gate.phi) > np.pi / 4:
raise ValueError('Must have abs(fsim_gate.phi) ≤ π/4')
if qubits is None:
if isinstance(interaction, ops.Operation):
qubits = interaction.qubits
else:
qubits = devices.LineQubit.range(2)
if len(qubits) != 2:
raise ValueError(f'Expected a pair of qubits, but got {qubits!r}.')
kak = linalg.kak_decomposition(interaction)
result_using_b_gates = _decompose_two_qubit_interaction_into_two_b_gates(
kak, qubits=qubits)
b_decomposition = _decompose_b_gate_into_two_fsims(fsim_gate=fsim_gate,
qubits=qubits)
result = []
for op in result_using_b_gates:
if isinstance(op.gate, _BGate):
result.extend(b_decomposition)
else:
result.append(op)
circuit = circuits.Circuit(result)
merge_single_qubit_gates.MergeSingleQubitGates().optimize_circuit(circuit)
drop_empty_moments.DropEmptyMoments().optimize_circuit(circuit)
return circuit