Apply as_sweep for iswap_gauge, spin_inversion_gauge, sqrt_iswap_gauge (

#6911)

cirq-core/cirq/transformers/gauge_compiling/gauge_compiling.py

@@ -118,6 +118,7 @@ class SameGateGauge(Gauge):
         default=(), converter=lambda g: (g,) if isinstance(g, ops.Gate) else tuple(g)
     )
     swap_qubits: bool = False
+    support_sweep: bool = False
 
     def sample(self, gate: ops.Gate, prng: np.random.Generator) -> ConstantGauge:
         return ConstantGauge(
@@ -127,6 +128,7 @@ def sample(self, gate: ops.Gate, prng: np.random.Generator) -> ConstantGauge:
             post_q0=self.post_q0,
             post_q1=self.post_q1,
             swap_qubits=self.swap_qubits,
+            support_sweep=self.support_sweep,
         )
 
 
@@ -332,6 +334,13 @@ def _parameterize(num_qubits: int, symbol_id: int) -> Dict[str, sympy.Symbol]:
 def _gate_sequence_to_phxz_params(
     gates: Tuple[ops.Gate, ...], xza_by_symbols: Dict[str, sympy.Symbol]
 ) -> Dict[str, float]:
+    identity_gate_in_phxz = {
+        str(xza_by_symbols["x_exponent"]): 0.0,
+        str(xza_by_symbols["z_exponent"]): 0.0,
+        str(xza_by_symbols["axis_phase_exponent"]): 0.0,
+    }
+    if not gates:
+        return identity_gate_in_phxz
     for gate in gates:
         if not has_unitary(gate) or gate.num_qubits() != 1:
             raise ValueError(
@@ -347,11 +356,7 @@ def _gate_sequence_to_phxz_params(
         or ops.I
     )
     if phxz is ops.I:  # Identity gate
-        return {
-            str(xza_by_symbols["x_exponent"]): 0.0,
-            str(xza_by_symbols["z_exponent"]): 0.0,
-            str(xza_by_symbols["axis_phase_exponent"]): 0.0,
-        }
+        return identity_gate_in_phxz
     # Check the gate type, needs to be a PhasedXZ gate.
     if not isinstance(phxz, ops.PhasedXZGate):
         raise ValueError("Failed to convert the gate sequence to a PhasedXZ gate.")

cirq-core/cirq/transformers/gauge_compiling/iswap_gauge.py

@@ -56,6 +56,7 @@ def _rz(self, theta, sgn: int) -> ConstantGauge:
             pre_q1=n_rz if flip_diangonal else rz,
             post_q0=rz if flip_diangonal else n_rz,
             post_q1=n_rz,
+            support_sweep=True,
         )
 
     def sample(self, gate: ops.Gate, prng: np.random.Generator) -> ConstantGauge:
@@ -88,7 +89,12 @@ def _xy_gauge(self, a: float, b: float) -> ConstantGauge:
         xy_a = self._xy(a)
         xy_b = self._xy(b)
         return ConstantGauge(
-            two_qubit_gate=ops.ISWAP, pre_q0=xy_a, pre_q1=xy_b, post_q0=xy_b, post_q1=xy_a
+            two_qubit_gate=ops.ISWAP,
+            pre_q0=xy_a,
+            pre_q1=xy_b,
+            post_q0=xy_b,
+            post_q1=xy_a,
+            support_sweep=True,
         )
 
     def sample(self, gate: ops.Gate, prng: np.random.Generator) -> ConstantGauge:

cirq-core/cirq/transformers/gauge_compiling/iswap_gauge_test.py

@@ -21,3 +21,4 @@
 class TestISWAPGauge(GaugeTester):
     two_qubit_gate = cirq.ISWAP
     gauge_transformer = ISWAPGaugeTransformer
+    sweep_must_pass = True

cirq-core/cirq/transformers/gauge_compiling/spin_inversion_gauge.py

@@ -23,8 +23,8 @@
 
 SpinInversionGaugeSelector = GaugeSelector(
     gauges=[
-        SameGateGauge(pre_q0=ops.X, post_q0=ops.X, pre_q1=ops.X, post_q1=ops.X),
-        SameGateGauge(),
+        SameGateGauge(pre_q0=ops.X, post_q0=ops.X, pre_q1=ops.X, post_q1=ops.X, support_sweep=True),
+        SameGateGauge(support_sweep=True),
     ]
 )
 

cirq-core/cirq/transformers/gauge_compiling/spin_inversion_gauge_test.py

@@ -20,18 +20,22 @@
 class TestSpinInversionGauge_0(GaugeTester):
     two_qubit_gate = cirq.ZZ
     gauge_transformer = SpinInversionGaugeTransformer
+    sweep_must_pass = True
 
 
 class TestSpinInversionGauge_1(GaugeTester):
     two_qubit_gate = cirq.ZZ**0.1
     gauge_transformer = SpinInversionGaugeTransformer
+    sweep_must_pass = True
 
 
 class TestSpinInversionGauge_2(GaugeTester):
     two_qubit_gate = cirq.ZZ**-1
     gauge_transformer = SpinInversionGaugeTransformer
+    sweep_must_pass = True
 
 
 class TestSpinInversionGauge_3(GaugeTester):
     two_qubit_gate = cirq.ZZ**0.3
     gauge_transformer = SpinInversionGaugeTransformer
+    sweep_must_pass = True

cirq-core/cirq/transformers/gauge_compiling/sqrt_iswap_gauge.py

@@ -49,7 +49,12 @@ def _rz(self, theta: float) -> ConstantGauge:
         rz = ops.rz(theta)
         n_rz = ops.rz(-theta)
         return ConstantGauge(
-            two_qubit_gate=ops.SQRT_ISWAP, pre_q0=rz, pre_q1=rz, post_q0=n_rz, post_q1=n_rz
+            two_qubit_gate=ops.SQRT_ISWAP,
+            pre_q0=rz,
+            pre_q1=rz,
+            post_q0=n_rz,
+            post_q1=n_rz,
+            support_sweep=True,
         )
 
     def sample(self, gate: ops.Gate, prng: np.random.Generator) -> ConstantGauge:
@@ -80,7 +85,12 @@ def _xy(self, theta: float) -> ops.PhasedXZGate:
     def _xy_gauge(self, theta: float) -> ConstantGauge:
         xy = self._xy(theta)
         return ConstantGauge(
-            two_qubit_gate=ops.SQRT_ISWAP, pre_q0=xy, pre_q1=xy, post_q0=xy, post_q1=xy
+            two_qubit_gate=ops.SQRT_ISWAP,
+            pre_q0=xy,
+            pre_q1=xy,
+            post_q0=xy,
+            post_q1=xy,
+            support_sweep=True,
         )
 
     def sample(self, gate: ops.Gate, prng: np.random.Generator) -> ConstantGauge:

cirq-core/cirq/transformers/gauge_compiling/sqrt_iswap_gauge_test.py

@@ -20,3 +20,4 @@
 class TestSqrtISWAPGauge(GaugeTester):
     two_qubit_gate = cirq.SQRT_ISWAP
     gauge_transformer = SqrtISWAPGaugeTransformer
+    sweep_must_pass = True