Adding feature to pass MPS parameters in quimb

src/qibotn/backends/quimb.py

@@ -16,9 +16,11 @@ class QuimbBackend(NumpyBackend):
 
             mps_enabled_value = runcard.get("MPS_enabled")
             if mps_enabled_value is True:
-                self.MPS_enabled = True
+                self.mps_opts = {"method": "svd", "cutoff": 1e-6, "cutoff_mod": "abs"}
             elif mps_enabled_value is False:
-                self.MPS_enabled = False
+                self.mps_opts = False
+            elif isinstance(mps_enabled_value, dict):
+                self.mps_opts = mps_enabled_value
             else:
                 raise TypeError("MPS_enabled has an unexpected type")
 
@@ -74,7 +76,7 @@ class QuimbBackend(NumpyBackend):
             )
 
         state = eval.dense_vector_tn_qu(
-            circuit.to_qasm(), initial_state, is_mps=self.MPS_enabled, backend="numpy"
+            circuit.to_qasm(), initial_state, self.mps_opts, backend="numpy"
         )
 
         if return_array:

src/qibotn/eval_qu.py

@@ -10,7 +10,7 @@ def init_state_tn(nqubits, init_state_sv):
     return qtn.tensor_1d.MatrixProductState.from_dense(init_state_sv, dims)
 
 
-def dense_vector_tn_qu(qasm: str, initial_state, is_mps, backend="numpy"):
+def dense_vector_tn_qu(qasm: str, initial_state, mps_opts, backend="numpy"):
     """Evaluate QASM with Quimb.
 
     backend (quimb): numpy, cupy, jax. Passed to ``opt_einsum``.
@@ -20,14 +20,9 @@ def dense_vector_tn_qu(qasm: str, initial_state, is_mps, backend="numpy"):
         nqubits = int(np.log2(len(initial_state)))
         initial_state = init_state_tn(nqubits, initial_state)
 
-    if is_mps:
-        gate_opt = {}
-        gate_opt["method"] = "svd"
-        gate_opt["cutoff"] = 1e-6
-        gate_opt["cutoff_mode"] = "abs"
-
+    if mps_opts:
         circ_quimb = qtn.circuit.CircuitMPS.from_openqasm2_str(
-            qasm, psi0=initial_state, gate_opts=gate_opt
+            qasm, psi0=initial_state, gate_opts=mps_opts
         )
 
     else:

tests/test_quimb_backend.py

@@ -50,6 +50,15 @@ def test_eval(nqubits: int, tolerance: float, is_mps: bool):
     qasm_circ = qibo_circ.to_qasm()
 
     # Test quimb
+    if is_mps:
+        gate_opt = {}
+        gate_opt["method"] = "svd"
+        gate_opt["cutoff"] = 1e-6
+        gate_opt["cutoff_mode"] = "abs"
+        result_tn = qibotn.eval_qu.dense_vector_tn_qu(
+            qasm_circ, init_state_tn, gate_opt, backend=config.quimb.backend
+        ).flatten()
+    else:
         result_tn = qibotn.eval_qu.dense_vector_tn_qu(
             qasm_circ, init_state_tn, is_mps, backend=config.quimb.backend
         ).flatten()