circuit: add givens, fix for 3qb

jcmgray · Sep 10, 2023 · 6f24494 · 6f24494
1 parent f95252e
commit 6f24494
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Showing 3 changed files with 44 additions and 1 deletion.
diff --git a/quimb/tensor/circuit.py b/quimb/tensor/circuit.py
@@ -561,6 +561,31 @@ def fsimg_param_gen(params):
 register_param_gate("FSIMG", fsimg_param_gen, 2)
 
 
+def givens_param_gen(params):
+    theta = params[0]
+
+    with backend_like(theta):
+        # get a real backend zero
+        zero = 0.0 * theta
+
+        a = do("complex", do("cos", theta), zero)
+        b = do("complex", do("sin", theta), zero)
+
+        # get a complex backend zero and backend one
+        zero = do("complex", zero, zero)
+        one = zero + 1.0
+
+        data = (
+            (((one, zero), (zero, zero)), ((zero, a), (-b, zero))),
+            (((zero, b), (a, zero)), ((zero, zero), (zero, one))),
+        )
+
+        return recursive_stack(data)
+
+
+register_param_gate("GIVENS", givens_param_gen, num_qubits=2)
+
+
 def rxx_param_gen(params):
     r"""Parametrized two qubit XX-rotation.
 
@@ -1394,6 +1419,19 @@ def fsimg(
             **kwargs,
         )
 
+    def givens(
+        self, theta, i, j, gate_round=None, parametrize=False, **kwargs
+    ):
+        self.apply_gate(
+            "GIVENS",
+            theta,
+            i,
+            j,
+            gate_round=gate_round,
+            parametrize=parametrize,
+            **kwargs,
+        )
+
     def rxx(self, theta, i, j, gate_round=None, parametrize=False, **kwargs):
         self.apply_gate(
             "RXX",

diff --git a/quimb/tensor/tensor_core.py b/quimb/tensor/tensor_core.py
@@ -3493,8 +3493,12 @@ def tensor_network_gate_inds(
                          f"indices {inds} with dimensions {dims}.")
 
     basic = (contract in _BASIC_GATE_CONTRACT)
-    if (not basic) and (ng == 1):
+    if (
         # if single ind, gate splitting methods are same as lazy
+        ((not basic) and (ng == 1)) or
+        # or for 3+ sites, treat auto as no splitting
+        ((contract == "auto-split-gate") and (ng > 2))
+    ):
         basic = True
         contract = False
 

diff --git a/tests/test_tensor/test_optimizers.py b/tests/test_tensor/test_optimizers.py
@@ -238,6 +238,7 @@ def test_every_parametrized_gate(backend):
     circ.cu3(*qu.randn(3), 1, 0, parametrize=True, tags=['OPTIMIZE'])
     circ.fsim(*qu.randn(2), 0, 1, parametrize=True, tags=['OPTIMIZE'])
     circ.fsimg(*qu.randn(5), 1, 0, parametrize=True, tags=['OPTIMIZE'])
+    circ.givens(*qu.randn(1), 0, 1, parametrize=True, tags=['OPTIMIZE'])
     circ.su4(*qu.randn(15), 0, 1, parametrize=True, tags=['OPTIMIZE'])
     psi = circ.psi