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new a59e8b8ba Avoid mutating user backend config (#1076)
a59e8b8ba is described below
commit a59e8b8bac3177c3138dfa6f8cb65ab370827c36
Author: Shivam Mittal <[email protected]>
AuthorDate: Mon Feb 23 10:21:38 2026 +0530
Avoid mutating user backend config (#1076)
---
qumat/qumat.py | 6 +++---
testing/qumat/test_parameter_binding.py | 32 ++++++++++++++++++++++++++++++++
2 files changed, 35 insertions(+), 3 deletions(-)
diff --git a/qumat/qumat.py b/qumat/qumat.py
index ae21ec335..449938666 100644
--- a/qumat/qumat.py
+++ b/qumat/qumat.py
@@ -60,12 +60,12 @@ class QuMat:
"Please provide a dictionary with backend-specific options "
)
- self.backend_config = backend_config
- self.backend_name = backend_config["backend_name"]
+ self.backend_config = backend_config.copy()
+ self.backend_name = self.backend_config["backend_name"]
self.backend_module = import_module(
f".{self.backend_name}_backend", package="qumat"
)
- self.backend = self.backend_module.initialize_backend(backend_config)
+ self.backend =
self.backend_module.initialize_backend(self.backend_config)
self.circuit = None
self.num_qubits = None
self.parameters = {}
diff --git a/testing/qumat/test_parameter_binding.py
b/testing/qumat/test_parameter_binding.py
index b304e8e5c..ae8fdb9e6 100644
--- a/testing/qumat/test_parameter_binding.py
+++ b/testing/qumat/test_parameter_binding.py
@@ -220,3 +220,35 @@ class TestParameterBinding:
# This should raise ValueError
with pytest.raises(ValueError, match="unbound parameters"):
qumat.execute_circuit(parameter_values={"theta0": math.pi})
+
+ @pytest.mark.parametrize("backend_name", TESTING_BACKENDS)
+ def test_execute_circuit_does_not_mutate_backend_config(self,
backend_name):
+ """Test that execute_circuit does not mutate the user's backend_config
across all backends."""
+ backend_config = get_backend_config(backend_name).copy()
+ original_config = backend_config.copy()
+
+ qumat = QuMat(backend_config)
+ qumat.create_empty_circuit(num_qubits=1)
+ qumat.apply_rx_gate(0, "theta")
+ qumat.execute_circuit(parameter_values={"theta": math.pi})
+
+ assert backend_config == original_config, (
+ f"backend_config was mutated in {backend_name}; "
+ "parameter_values or other keys must not be added."
+ )
+
+ @pytest.mark.parametrize("backend_name", TESTING_BACKENDS)
+ def test_get_final_state_vector_does_not_mutate_backend_config(self,
backend_name):
+ """Test that get_final_state_vector does not mutate the user's
backend_config across all backends."""
+ backend_config = get_backend_config(backend_name).copy()
+ original_config = backend_config.copy()
+
+ qumat = QuMat(backend_config)
+ qumat.create_empty_circuit(num_qubits=1)
+ qumat.apply_rx_gate(0, "theta")
+ qumat.bind_parameters({"theta": math.pi / 2})
+ qumat.get_final_state_vector()
+
+ assert backend_config == original_config, (
+ f"backend_config was mutated by get_final_state_vector in
{backend_name}."
+ )
