def exitGate(self, ctx: QuilParser.GateContext):
gate_name = ctx.name().getText()
params = list(map(_param, ctx.param()))
qubits = list(map(_qubit, ctx.qubit()))
# The Gate.controlled() method *prepends* the CONTROLLED modifier to the gate. But the
# parser works from the outside-in. Therefore the controlled qubits would be in reverse
# order. We reverse here to fix that.
modifiers = [mod.getText() for mod in ctx.modifier()][::-1]
control_qubits = qubits[0:len(list(filter(lambda str: str == "CONTROLLED", modifiers)))][::-1]
target_qubits = qubits[len(control_qubits):]
if gate_name in QUANTUM_GATES:
if params:
gate = QUANTUM_GATES[gate_name](*params, *target_qubits)
else:
gate = QUANTUM_GATES[gate_name](*target_qubits)
else:
gate = Gate(gate_name, params, target_qubits)
for modifier in modifiers:
if modifier == "CONTROLLED":
gate.controlled(control_qubits.pop(0))
elif modifier == "DAGGER":
gate.dagger()
else:
raise ValueError(f"Unsupported gate modifier {modifier}.")
self.result.append(gate)
def exitGate(self, ctx: QuilParser.GateContext):
gate_name = ctx.name().getText()
modifiers = [mod.getText() for mod in ctx.modifier()]
params = list(map(_param, ctx.param()))
qubits = list(map(_qubit, ctx.qubit()))
# The parsed string 'DAGGER CONTROLLED X 0 1' gives
# modifiers ['DAGGER', 'CONTROLLED']
# qubits ['0', '1']
#
# We will build such gates by applying modifiers from right to left,
# e.g. X 1 -> CONTROLLED X 0 1 -> DAGGER CONTROLLED X 0 1
# Some gate modifiers increase the arity of the base gate.
# The new qubit arguments prefix the old ones.
modifier_qubits = []
for m in modifiers:
if m in ["CONTROLLED", "FORKED"]:
modifier_qubits.append(qubits[len(modifier_qubits)])
base_qubits = qubits[len(modifier_qubits):]
# Each FORKED doubles the number of parameters,
# e.g. FORKED RX(0.5, 1.5) 0 1 has two.
forked_offset = len(params) >> modifiers.count("FORKED")
base_params = params[:forked_offset]
if gate_name in QUANTUM_GATES:
if base_params:
gate = QUANTUM_GATES[gate_name](*base_params, *base_qubits)
else:
gate = QUANTUM_GATES[gate_name](*base_qubits)
else:
gate = Gate(gate_name, base_params, base_qubits)
# Track the last param used (for FORKED)
for modifier in modifiers[::-1]:
if modifier == "CONTROLLED":
gate.controlled(modifier_qubits.pop())
elif modifier == "DAGGER":
gate.dagger()
elif modifier == 'FORKED':
gate.forked(modifier_qubits.pop(),
params[forked_offset:(2 * forked_offset)])
forked_offset *= 2
else:
raise ValueError(f"Unsupported gate modifier {modifier}.")
self.result.append(gate)
