Optimizer failure

[glanzz]

Description of the issue
The optimize_for_target_gateset crashes when trying to optimize XXPowGate with larger global shift value. The optimizer crashes with division by zero error.

How to reproduce the issue

import cirq as c
qubits = c.LineQubit.range(4)
circuit = c.Circuit()
circuit.append(c.rz(-0.0171*np.pi)(qubits[0]))
circuit.append(c.CNOT(qubits[3], qubits[1]))
circuit.append(c.MSGate(rads=-0.01*np.pi)(qubits[0], qubits[1]))
circuit.append(c.Y(qubits[0]))
circuit.append(c.CSWAP(qubits[2], qubits[0], qubits[3]))
circuit.append(c.Ry(rads=0.014*np.pi)(qubits[2]))
circuit.append(c.Z(qubits[3]))
circuit.append(c.ISWAP(qubits[0], qubits[2]))
circuit.append(c.XX(qubits[1], qubits[3]))
circuit.append(c.XXPowGate(exponent=0.26, global_shift=100000)(qubits[2], qubits[3]))
circuit.append(c.ISWAP(qubits[0], qubits[2]))
circuit.append(c.Ry(rads=-0.042*np.pi)(qubits[3]))



print(circuit)
optimized = c.optimize_for_target_gateset(circuit, gateset = cg.SycamoreTargetGateset())
print(optimized)

                                                      ┌───────┐
0: ───Rz(-0.017π)───MS(-0.01π)───Y───×─────────────────iSwap────────────────iSwap─────────
                    │                │                 │                    │
1: ───X─────────────MS(-0.01π)───────┼─────────────────┼────XX──────────────┼─────────────
      │                              │                 │    │               │
2: ───┼──────────────────────────────@───Ry(0.014π)────iSwap┼─────XX────────iSwap─────────
      │                              │                      │     │
3: ───@──────────────────────────────×───Z──────────────────XX────XX^0.26───Ry(-0.042π)───
                                                      └───────┘
Traceback (most recent call last):
  File "/Users/xxx/xxx/cirq_diverging_sycamore.py", line 36, in <module>
    optimized = c.optimize_for_target_gateset(circuit, gateset = cg.SycamoreTargetGateset())
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/xxx/xxx/cirqenv/lib/python3.11/site-packages/cirq/transformers/transformer_api.py", line 379, in func_with_logging
    return _transform_and_log(
           ^^^^^^^^^^^^^^^^^^^
  File "/Users/xxx/xxx/cirqenv/lib/python3.11/site-packages/cirq/transformers/transformer_api.py", line 438, in _transform_and_log
    transformed_circuit = _run_transformer_on_circuit(
                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/xxx/xxx/cirqenv/lib/python3.11/site-packages/cirq/transformers/transformer_api.py", line 424, in _run_transformer_on_circuit
    return func(mutable_circuit if mutable_circuit else circuit, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/xxx/xxx/cirqenv/lib/python3.11/site-packages/cirq/transformers/optimize_for_target_gateset.py", line 150, in optimize_for_target_gateset
    circuit = transformer(circuit, context=context)
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/xxx/xxx/cirqenv/lib/python3.11/site-packages/cirq/transformers/target_gatesets/compilation_target_gateset.py", line 71, in transformer_with_kwargs
    return transformer(circuit, context=context, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/xxx/xxx/cirqenv/lib/python3.11/site-packages/cirq/transformers/transformer_api.py", line 379, in func_with_logging
    return _transform_and_log(
           ^^^^^^^^^^^^^^^^^^^
  File "/Users/xxx/xxx/cirqenv/lib/python3.11/site-packages/cirq/transformers/transformer_api.py", line 438, in _transform_and_log
    transformed_circuit = _run_transformer_on_circuit(
                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/xxx/xxx/cirqenv/lib/python3.11/site-packages/cirq/transformers/transformer_api.py", line 424, in _run_transformer_on_circuit
    return func(mutable_circuit if mutable_circuit else circuit, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/xxx/xxx/cirqenv/lib/python3.11/site-packages/cirq_google/transformers/target_gatesets/sycamore_gateset.py", line 75, in merge_swap_rzz_and_2q_unitaries
    circuit = cirq.merge_operations_to_circuit_op(
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/xxx/xxx/cirqenv/lib/python3.11/site-packages/cirq/transformers/transformer_primitives.py", line 566, in merge_operations_to_circuit_op
    return merge_operations(circuit, merge_func, tags_to_ignore=tags_to_ignore, deep=deep)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/xxx/xxx/cirqenv/lib/python3.11/site-packages/cirq/transformers/transformer_primitives.py", line 505, in merge_operations
    merged_circuit.add_op_to_moment(moment_idx, op)
  File "/Users/xxx/xxx/cirqenv/lib/python3.11/site-packages/cirq/transformers/transformer_primitives.py", line 345, in add_op_to_moment
    self.ops_by_index[moment_index][op] = 0
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^
  File "/Users/xxx/xxx/cirqenv/lib/python3.11/site-packages/cirq/_compat.py", line 104, in wrapped_no_args
    result = func(self)
             ^^^^^^^^^^
  File "/Users/xxx/xxx/cirqenv/lib/python3.11/site-packages/cirq/value/value_equality_attr.py", line 90, in _value_equality_hash
    return hash((self._value_equality_values_cls_(), self._value_equality_values_()))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/xxx/xxx/cirqenv/lib/python3.11/site-packages/cirq/_compat.py", line 104, in wrapped_no_args
    result = func(self)
             ^^^^^^^^^^
  File "/Users/xxx/xxx/cirqenv/lib/python3.11/site-packages/cirq/value/value_equality_attr.py", line 90, in _value_equality_hash
    return hash((self._value_equality_values_cls_(), self._value_equality_values_()))
                                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/xxx/xxx/cirqenv/lib/python3.11/site-packages/cirq/_compat.py", line 104, in wrapped_no_args
    result = func(self)
             ^^^^^^^^^^
  File "/Users/xxx/xxx/cirqenv/lib/python3.11/site-packages/cirq/_compat.py", line 104, in wrapped_no_args
    result = func(self)
             ^^^^^^^^^^
  File "/Users/xxx/xxx/cirqenv/lib/python3.11/site-packages/cirq/ops/eigen_gate.py", line 319, in _value_equality_values_
    return self._canonical_exponent, self._global_shift
           ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/xxx/xxx/cirqenv/lib/python3.11/site-packages/cirq/ops/eigen_gate.py", line 311, in _canonical_exponent
    period = self._period()
             ^^^^^^^^^^^^^^
  File "/Users/xxx/xxx/cirqenv/lib/python3.11/site-packages/cirq/ops/eigen_gate.py", line 300, in _period
    return _approximate_common_period(real_periods)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/xxx/xxx/cirqenv/lib/python3.11/site-packages/cirq/ops/eigen_gate.py", line 443, in _approximate_common_period
    common = float(_common_rational_period(approx_rational_periods))
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/xxx/xxx/cirqenv/lib/python3.11/site-packages/cirq/ops/eigen_gate.py", line 461, in _common_rational_period
    int_common_period = _lcm(int_periods)
                        ^^^^^^^^^^^^^^^^^
  File "/Users/xxx/xxx/cirqenv/lib/python3.11/site-packages/cirq/ops/eigen_gate.py", line 402, in _lcm
    t = t * r // math.gcd(t, r)
        ~~~~~~^^~~~~~~~~~~~~~~~
ZeroDivisionError: integer division or modulo by zero

Cirq version: 1.4.1

[NoureldinYosri]

A global_shift=100000 doesn't make sense. global_shift represents global phase as $e^{i \pi t}$ where $t$ is the global_shift so global_shift should be $\in [0, 2)$. We probably need to add input validation for this.

---

As for the circuit in question:

import cirq as c
qubits = c.LineQubit.range(4)
circuit = c.Circuit()
circuit.append(c.rz(-0.0171*np.pi)(qubits[0]))
circuit.append(c.CNOT(qubits[3], qubits[1]))
circuit.append(c.MSGate(rads=-0.01*np.pi)(qubits[0], qubits[1]))
circuit.append(c.Y(qubits[0]))
circuit.append(c.CSWAP(qubits[2], qubits[0], qubits[3]))
circuit.append(c.Ry(rads=0.014*np.pi)(qubits[2]))
circuit.append(c.Z(qubits[3]))
circuit.append(c.ISWAP(qubits[0], qubits[2]))
circuit.append(c.XX(qubits[1], qubits[3]))
circuit.append(c.XXPowGate(exponent=0.26, global_shift=100000%2)(qubits[2], qubits[3]))
circuit.append(c.ISWAP(qubits[0], qubits[2]))
circuit.append(c.Ry(rads=-0.042*np.pi)(qubits[3]))



# print(circuit)
optimized = c.optimize_for_target_gateset(circuit, gateset = cg.SycamoreTargetGateset())
print(optimized)

0: ─────────────────────────────────────────────────────────PhXZ(a=0.0217,x=0.198,z=-0.435)─────SYC───────────────────────────────────SYC───PhXZ(a=-0.0502,x=0.398,z=-0.0656)───SYC───PhXZ(a=0.0677,x=1,z=0)───────SYC───PhXZ(a=-0.491,x=0.373,z=0.672)───SYC───PhXZ(a=0.0677,x=1,z=0)───────SYC───PhXZ(a=0.883,x=0.435,z=0.779)──────────────────────────────────────────────────────────────────────────────────────────────────────────────────PhXZ(a=0,x=0.586,z=0.0833)────────SYC────────────────SYC───PhXZ(a=-0.0833,x=0.586,z=0.583)────────────────────────────────────────────PhXZ(a=0,x=0.586,z=0.0833)─────SYC────────────────SYC───PhXZ(a=-0.0833,x=0.586,z=0.583)────────────────────────────────────────────PhXZ(a=0.5,x=0.5,z=0.917)───────SYC───Rx(0.477π)───SYC───PhXZ(a=0.75,x=0.5,z=0.75)──────────────────────────────────PhXZ(a=0.568,x=0.586,z=0)──────────SYC───PhXZ(a=0.0677,x=1,z=0)───────SYC───PhXZ(a=-0.815,x=0.891,z=0.0223)───────────────────────────────────────PhXZ(a=-0.273,x=0.289,z=0)──────SYC───PhX(-0.358)────────SYC───PhX(0.968)^0.691───SYC───PhXZ(a=0.1,x=1,z=0)──────────────────────────────────────────────────PhXZ(a=-0.273,x=0.289,z=0)──────SYC───PhX(-0.358)────────SYC───PhX(0.968)^0.691───SYC───PhXZ(a=0.1,x=1,z=0)─────────────
                                                                                                │                                     │                                         │                                  │                                      │                                  │                                                                                                                                                                                      │                  │                                                                                                               │                  │                                                                                                                │                  │                                                                                                   │                                  │                                                                                                           │                        │                        │                                                                                                          │                        │                        │
1: ───PhXZ(a=0.5,x=0.5,z=0.917)────SYC───Rx(0.477π)───SYC───PhXZ(a=0.264,x=4.44e-16,z=-0.514)───SYC───PhXZ(a=-1.11e-16,x=0.979,z=0)───SYC───PhXZ(a=0.0689,x=0.5,z=-0.569)───────┼──────────────────────────────────┼──────────────────────────────────────┼──────────────────────────────────┼──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┼──────────────────┼───────────────────────────────────────────────────────────────────────────────────────────────────────────────┼──────────────────┼────────────────────────────────────────────────────────────────────────────────────────────────────────────────┼──────────────────┼───────────────────────────────────────────────────────────────────────────────────────────────────┼──────────────────────────────────┼───────────────────────────────────────────────────────────────────────────PhXZ(a=-1,x=1,z=0)──────────────┼────────────────────────┼────────────────────────┼──────────────────────────────────────────────────────────────────────────────────────────────────────────┼────────────────────────┼────────────────────────┼─────────────────────────────────────
                                   │                  │                                                                                                                         │                                  │                                      │                                  │                                                                                                                                                                                      │                  │                                                                                                               │                  │                                                                                                                │                  │                                                                                                   │                                  │                                                                                                           │                        │                        │                                                                                                          │                        │                        │
2: ────────────────────────────────┼──────────────────┼─────────────────────────────────────────────────────────────────────────────────────PhXZ(a=-1,x=0.5,z=0.71)─────────────SYC───PhXZ(a=-0.515,x=0.523,z=0)───SYC───PhXZ(a=-0.0745,x=0.5,z=-0.216)───SYC───PhXZ(a=-0.515,x=0.523,z=0)───SYC───PhXZ(a=0.993,x=0.586,z=-0.426)───SYC───PhXZ(a=0.0677,x=1,z=0)───────SYC───PhXZ(a=-0.647,x=0.633,z=0.802)───SYC───────────────────────────SYC───PhXZ(a=-0.401,x=0.319,z=-0.404)───SYC───Rx(0.477π)───SYC───PhXZ(a=-0.0429,x=0.109,z=0.827)───SYC───PhXZ(a=0.0677,x=1,z=0)───────SYC───PhXZ(a=0.776,x=0.199,z=0.99)───SYC───Rx(0.477π)───SYC───PhXZ(a=-0.0429,x=0.109,z=0.827)───SYC───PhXZ(a=0.0677,x=1,z=0)───────SYC───PhXZ(a=0.383,x=0.502,z=0.635)───SYC────────────────SYC───PhXZ(a=-0.667,x=0.477,z=-0.667)───SYC────────────────SYC───PhXZ(a=-0.0833,x=0.0863,z=0.293)───SYC───PhXZ(a=-0.515,x=0.523,z=0)───SYC───PhXZ(a=-0.161,x=0.5,z=0.744)──────SYC───────────────────────────SYC───PhXZ(a=-0.0833,x=0.6,z=0.583)───SYC───PhX(0.849)^0.975───SYC──────────────────────SYC───PhXZ(a=0.946,x=0.666,z=-0.361)───SYC───────────────────────────SYC───PhXZ(a=0.432,x=0.519,z=0.355)───SYC───PhX(0.849)^0.975───SYC──────────────────────SYC───PhXZ(a=0.916,x=0.148,z=0.845)───
                                   │                  │                                                                                                                                                                                                                                                                             │                                  │                                      │                             │                                                                                                  │                                  │                                                                                               │                                  │                                                                                                │                  │                                                                                                                   │                             │                                                                                                                              │                             │
3: ───PhXZ(a=0,x=0.586,z=0.0833)───SYC────────────────SYC───PhXZ(a=-0.0833,x=0.586,z=0.583)────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────PhXZ(a=0.355,x=1,z=0)────────────SYC───PhXZ(a=-0.515,x=0.523,z=0)───SYC───PhXZ(a=0.926,x=0.5,z=0.991)──────SYC───PhXZ(a=0,x=0.189,z=0)───SYC──────────────────────────────────────────────────────────────PhXZ(a=-0.5,x=0.5,z=-0.29)────────SYC───PhXZ(a=-0.515,x=0.523,z=0)───SYC───PhXZ(a=0.426,x=0.5,z=0.824)─────────────────────────────PhXZ(a=0.5,x=0.5,z=-0.29)─────────SYC───PhXZ(a=-0.515,x=0.523,z=0)───SYC───PhXZ(a=-0.574,x=0.5,z=0.824)─────────────────────────────PhXZ(a=0.5,x=0.5,z=0.917)─────────SYC───Rx(0.477π)───SYC───PhXZ(a=0.75,x=0.5,z=0.75)───────────────────────────────────────────────────PhXZ(a=-0.5,x=0.5,z=-0.0833)──────SYC───PhXZ(a=0,x=0.477,z=0)───SYC───PhXZ(a=0.375,x=1,z=0)───────────────────────────────────────────────────────────────────PhXZ(a=-0.5,x=0.5,z=0.893)───────SYC───PhXZ(a=0,x=0.202,z=0)───SYC───PhXZ(a=0.226,x=0.458,z=0.274)───────────────────────────────────────────────────────────────────────────────────────────

And even with a non zero global_shift it works. For example when global_shift=0.1 we get

0: ─────────────────────────────────────────────────────────PhXZ(a=0.0217,x=0.198,z=-0.435)─────SYC───────────────────────────────────SYC───PhXZ(a=-0.0502,x=0.398,z=-0.0656)───SYC───PhXZ(a=0.0677,x=1,z=0)───────SYC───PhXZ(a=-0.491,x=0.373,z=0.672)───SYC───PhXZ(a=0.0677,x=1,z=0)───────SYC───PhXZ(a=0.883,x=0.435,z=0.779)──────────────────────────────────────────────────────────────────────────────────────────────────────────────────PhXZ(a=0,x=0.586,z=0.0833)────────SYC────────────────SYC───PhXZ(a=-0.0833,x=0.586,z=0.583)────────────────────────────────────────────PhXZ(a=0,x=0.586,z=0.0833)─────SYC────────────────SYC───PhXZ(a=-0.0833,x=0.586,z=0.583)────────────────────────────────────────────PhXZ(a=0.5,x=0.5,z=0.917)───────SYC───Rx(0.477π)───SYC───PhXZ(a=0.75,x=0.5,z=0.75)──────────────────────────────────PhXZ(a=0.568,x=0.586,z=0)──────────SYC───PhXZ(a=0.0677,x=1,z=0)───────SYC───PhXZ(a=-0.815,x=0.891,z=0.0223)───────────────────────────────────────PhXZ(a=-0.273,x=0.289,z=0)──────SYC───PhX(-0.358)────────SYC───PhX(0.968)^0.691───SYC───PhXZ(a=0.1,x=1,z=0)──────────────────────────────────────────────────PhXZ(a=-0.273,x=0.289,z=0)──────SYC───PhX(-0.358)────────SYC───PhX(0.968)^0.691───SYC───PhXZ(a=0.1,x=1,z=0)─────────────
                                                                                                │                                     │                                         │                                  │                                      │                                  │                                                                                                                                                                                      │                  │                                                                                                               │                  │                                                                                                                │                  │                                                                                                   │                                  │                                                                                                           │                        │                        │                                                                                                          │                        │                        │
1: ───PhXZ(a=0.5,x=0.5,z=0.917)────SYC───Rx(0.477π)───SYC───PhXZ(a=0.264,x=4.44e-16,z=-0.514)───SYC───PhXZ(a=-1.11e-16,x=0.979,z=0)───SYC───PhXZ(a=0.0689,x=0.5,z=-0.569)───────┼──────────────────────────────────┼──────────────────────────────────────┼──────────────────────────────────┼──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┼──────────────────┼───────────────────────────────────────────────────────────────────────────────────────────────────────────────┼──────────────────┼────────────────────────────────────────────────────────────────────────────────────────────────────────────────┼──────────────────┼───────────────────────────────────────────────────────────────────────────────────────────────────┼──────────────────────────────────┼───────────────────────────────────────────────────────────────────────────PhXZ(a=-1,x=1,z=0)──────────────┼────────────────────────┼────────────────────────┼──────────────────────────────────────────────────────────────────────────────────────────────────────────┼────────────────────────┼────────────────────────┼─────────────────────────────────────
                                   │                  │                                                                                                                         │                                  │                                      │                                  │                                                                                                                                                                                      │                  │                                                                                                               │                  │                                                                                                                │                  │                                                                                                   │                                  │                                                                                                           │                        │                        │                                                                                                          │                        │                        │
2: ────────────────────────────────┼──────────────────┼─────────────────────────────────────────────────────────────────────────────────────PhXZ(a=-1,x=0.5,z=0.71)─────────────SYC───PhXZ(a=-0.515,x=0.523,z=0)───SYC───PhXZ(a=-0.0745,x=0.5,z=-0.216)───SYC───PhXZ(a=-0.515,x=0.523,z=0)───SYC───PhXZ(a=0.993,x=0.586,z=-0.426)───SYC───PhXZ(a=0.0677,x=1,z=0)───────SYC───PhXZ(a=-0.647,x=0.633,z=0.802)───SYC───────────────────────────SYC───PhXZ(a=-0.401,x=0.319,z=-0.404)───SYC───Rx(0.477π)───SYC───PhXZ(a=-0.0429,x=0.109,z=0.827)───SYC───PhXZ(a=0.0677,x=1,z=0)───────SYC───PhXZ(a=0.776,x=0.199,z=0.99)───SYC───Rx(0.477π)───SYC───PhXZ(a=-0.0429,x=0.109,z=0.827)───SYC───PhXZ(a=0.0677,x=1,z=0)───────SYC───PhXZ(a=0.383,x=0.502,z=0.635)───SYC────────────────SYC───PhXZ(a=-0.667,x=0.477,z=-0.667)───SYC────────────────SYC───PhXZ(a=-0.0833,x=0.0863,z=0.293)───SYC───PhXZ(a=-0.515,x=0.523,z=0)───SYC───PhXZ(a=-0.161,x=0.5,z=0.744)──────SYC───────────────────────────SYC───PhXZ(a=-0.0833,x=0.6,z=0.583)───SYC───PhX(0.849)^0.975───SYC──────────────────────SYC───PhXZ(a=0.946,x=0.666,z=-0.361)───SYC───────────────────────────SYC───PhXZ(a=0.432,x=0.519,z=0.355)───SYC───PhX(0.849)^0.975───SYC──────────────────────SYC───PhXZ(a=0.916,x=0.148,z=0.845)───
                                   │                  │                                                                                                                                                                                                                                                                             │                                  │                                      │                             │                                                                                                  │                                  │                                                                                               │                                  │                                                                                                │                  │                                                                                                                   │                             │                                                                                                                              │                             │
3: ───PhXZ(a=0,x=0.586,z=0.0833)───SYC────────────────SYC───PhXZ(a=-0.0833,x=0.586,z=0.583)────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────PhXZ(a=0.355,x=1,z=0)────────────SYC───PhXZ(a=-0.515,x=0.523,z=0)───SYC───PhXZ(a=0.926,x=0.5,z=0.991)──────SYC───PhXZ(a=0,x=0.189,z=0)───SYC──────────────────────────────────────────────────────────────PhXZ(a=-0.5,x=0.5,z=-0.29)────────SYC───PhXZ(a=-0.515,x=0.523,z=0)───SYC───PhXZ(a=0.426,x=0.5,z=0.824)─────────────────────────────PhXZ(a=0.5,x=0.5,z=-0.29)─────────SYC───PhXZ(a=-0.515,x=0.523,z=0)───SYC───PhXZ(a=-0.574,x=0.5,z=0.824)─────────────────────────────PhXZ(a=0.5,x=0.5,z=0.917)─────────SYC───Rx(0.477π)───SYC───PhXZ(a=0.75,x=0.5,z=0.75)───────────────────────────────────────────────────PhXZ(a=-0.5,x=0.5,z=-0.0833)──────SYC───PhXZ(a=0,x=0.477,z=0)───SYC───PhXZ(a=0.375,x=1,z=0)───────────────────────────────────────────────────────────────────PhXZ(a=-0.5,x=0.5,z=0.893)───────SYC───PhXZ(a=0,x=0.202,z=0)───SYC───PhXZ(a=0.226,x=0.458,z=0.274)───────────────────────────────────────────────────────────────────────────────────────────

[glanzz]

Even though the value is not practical the gate did accept the value and it failed later at the optimization stage. A human error with such value is still possible and its effects are realized later. Printing the circuit does not show that value so debugging the source of issue could be hard for a developer.

[mhucka]

Discussed during bit.ly/cirq-cynq today (2024-10-16): it should do either numeric validation, or or adjust the shift. (Note that the global shift could be symbolic.)