Add support for ECR gate to MPS (#2137)

* Add support for ECR gate

* replace is not to !=

* fix release note

* Fix ecr implementation for stabilizer/extended-stabilizer

qiskit_aer/backends/aer_simulator.py

@@ -745,6 +745,9 @@ def __init__(
             backend_options=backend_options,
         )
 
+        if "basis_gates" in backend_options.items():
+            self._check_basis_gates(backend_options["basis_gates"])
+
     @classmethod
     def _default_options(cls):
         return Options(
@@ -898,11 +901,12 @@ def configuration(self):
         config = copy.copy(self._configuration)
         for key, val in self._options_configuration.items():
             setattr(config, key, val)
+
+        method = getattr(self.options, "method", "automatic")
+
         # Update basis gates based on custom options, config, method,
         # and noise model
-        config.custom_instructions = self._CUSTOM_INSTR[
-            getattr(self.options, "method", "automatic")
-        ]
+        config.custom_instructions = self._CUSTOM_INSTR[method]
         config.basis_gates = self._cached_basis_gates + config.custom_instructions
         return config
 
@@ -933,6 +937,9 @@ def set_option(self, key, value):
                     f" are: {self.available_methods()}"
                 )
             self._set_method_config(value)
+        if key == "basis_gates":
+            self._check_basis_gates(value)
+
         super().set_option(key, value)
         if key in ["method", "noise_model", "basis_gates"]:
             self._cached_basis_gates = self._basis_gates()
@@ -1047,3 +1054,11 @@ def _set_method_config(self, method=None):
 
         self._set_configuration_option("description", description)
         self._set_configuration_option("n_qubits", n_qubits)
+
+    def _check_basis_gates(self, basis_gates):
+        method = getattr(self.options, "method", "automatic")
+        # check if basis_gates contains non-supported gates
+        if method != "automatic":
+            for gate in basis_gates:
+                if gate not in self._BASIS_GATES[method]:
+                    raise AerError(f"Invalid gate {gate} for simulation method {method}.")

qiskit_aer/backends/backend_utils.py

@@ -200,6 +200,7 @@
             "cswap",
             "diagonal",
             "initialize",
+            "ecr",
         ]
     ),
     "stabilizer": sorted(
@@ -246,6 +247,7 @@
             "ccz",
             "delay",
             "pauli",
+            "ecr",
             "rz",
         ]
     ),
@@ -417,6 +419,7 @@
             "delay",
             "pauli",
             "mcx_gray",
+            "ecr",
         ]
     ),
 }

releasenotes/notes/add_ecr_to_mps-0eec56596fc486c7.yaml

@@ -0,0 +1,7 @@
+---
+features:
+  - |
+    `matrix_product_state`, `extended_stabilizer` and `tensor_network` methods
+    now support ecr gate.
+    Add check if `basis_gates` backend option has unsupported gate for
+    the `method`

src/simulators/extended_stabilizer/extended_stabilizer_state.hpp

@@ -46,7 +46,7 @@ const Operations::OpSet StateOpSet(
     // Gates
     {"CX", "u0",  "u1",  "p",   "cx",    "cz",    "swap", "id",
      "x",  "y",   "z",   "h",   "s",     "sdg",   "sx",   "sxdg",
-     "t",  "tdg", "ccx", "ccz", "delay", "pauli", "rz"});
+     "t",  "tdg", "ccx", "ccz", "delay", "pauli", "ecr",  "rz"});
 
 using chpauli_t = CHSimulator::pauli_t;
 using chstate_t = CHSimulator::Runner;
@@ -224,6 +224,7 @@ const stringmap_t<Gates> State::gateset_({
     {"cx", Gates::cx},     // Controlled-X gate (CNOT)
     {"cz", Gates::cz},     // Controlled-Z gate
     {"swap", Gates::swap}, // SWAP gate
+    {"ecr", Gates::ecr},   // ECR Gate
     // Three-qubit gates
     {"ccx", Gates::ccx}, // Controlled-CX gate (Toffoli)
     {"ccz", Gates::ccz}, // Constrolled-CZ gate (H3 Toff H3)
@@ -716,6 +717,14 @@ void State::apply_gate(const Operations::Op &op, RngEngine &rng, uint_t rank) {
   case Gates::pauli:
     apply_pauli(op.qubits, op.string_params[0], rank);
     break;
+  case Gates::ecr:
+    BaseState::qreg_.apply_s(op.qubits[0], rank);
+    BaseState::qreg_.apply_sdag(op.qubits[1], rank);
+    BaseState::qreg_.apply_h(op.qubits[1], rank);
+    BaseState::qreg_.apply_sdag(op.qubits[1], rank);
+    BaseState::qreg_.apply_cx(op.qubits[0], op.qubits[1], rank);
+    BaseState::qreg_.apply_x(op.qubits[0], rank);
+    break;
   case Gates::rz:
     pi2 = (int_t)std::round(std::real(op.params[0]) * 2.0 / M_PI) & 3;
     if (pi2 == 1) {

src/simulators/extended_stabilizer/gates.hpp

@@ -59,6 +59,7 @@ enum class Gates {
   ccx,
   ccz,
   pauli,
+  ecr,
   rz,
 };
 
@@ -87,6 +88,7 @@ const AER::stringmap_t<Gatetypes> gate_types_ = {
     {"cx", Gatetypes::clifford},   // Controlled-X gate (CNOT)
     {"cz", Gatetypes::clifford},   // Controlled-Z gate
     {"swap", Gatetypes::clifford}, // SWAP gate
+    {"ecr", Gatetypes::clifford},  // ECR Gate
     // Three-qubit gates
     {"ccx", Gatetypes::non_clifford}, // Controlled-CX gate (Toffoli)
     {"ccz", Gatetypes::non_clifford}, // Controlled-CZ gate (H3 Toff H3)

src/simulators/matrix_product_state/matrix_product_state.hpp

@@ -75,10 +75,10 @@ const Operations::OpSet StateOpSet(
      OpType::jump,
      OpType::mark},
     // Gates
-    {"id",  "x",    "y",   "z",   "s",     "sdg",   "h",    "t",  "tdg", "p",
-     "u1",  "u2",   "u3",  "u",   "U",     "CX",    "cx",   "cy", "cz",  "cp",
-     "cu1", "swap", "ccx", "sx",  "sxdg",  "r",     "rx",   "ry", "rz",  "rxx",
-     "ryy", "rzz",  "rzx", "csx", "delay", "cswap", "pauli"});
+    {"id",  "x",    "y",   "z",   "s",     "sdg",   "h",     "t",  "tdg", "p",
+     "u1",  "u2",   "u3",  "u",   "U",     "CX",    "cx",    "cy", "cz",  "cp",
+     "cu1", "swap", "ccx", "sx",  "sxdg",  "r",     "rx",    "ry", "rz",  "rxx",
+     "ryy", "rzz",  "rzx", "csx", "delay", "cswap", "pauli", "ecr"});
 
 //=========================================================================
 // Matrix Product State subclass
@@ -296,6 +296,7 @@ const stringmap_t<Gates>
                      {"ryy", Gates::ryy},   // Pauli-YY rotation gate
                      {"rzz", Gates::rzz},   // Pauli-ZZ rotation gate
                      {"rzx", Gates::rzx},   // Pauli-ZX rotation gate
+                     {"ecr", Gates::ecr},   // ECR Gate
                      /* Three-qubit gates */
                      {"ccx", Gates::ccx}, // Controlled-CX gate (Toffoli)
                      {"cswap", Gates::cswap},
@@ -673,6 +674,9 @@ void State::apply_gate(const Operations::Op &op) {
   case Gates::pauli:
     apply_pauli(op.qubits, op.string_params[0]);
     break;
+  case Gates::ecr:
+    qreg_.apply_matrix(op.qubits, Linalg::Matrix::ECR);
+    break;
   default:
     // We shouldn't reach here unless there is a bug in gateset
     throw std::invalid_argument(

src/simulators/matrix_product_state/matrix_product_state_internal.hpp

@@ -58,7 +58,8 @@ enum Gates {
   csx, // two qubit
   ccx,
   cswap, // three qubit
-  pauli
+  pauli,
+  ecr,
 };
 
 // enum class Direction {RIGHT, LEFT};

src/simulators/stabilizer/stabilizer_state.hpp

@@ -383,14 +383,14 @@ void State::apply_gate(const Operations::Op &op) {
     apply_pauli(op.qubits, op.string_params[0]);
     break;
   case Gates::ecr:
-    BaseState::qreg_.append_h(op.qubits[1]);
     BaseState::qreg_.append_s(op.qubits[0]);
-    BaseState::qreg_.append_z(op.qubits[1]); // sdg(1)
-    BaseState::qreg_.append_s(op.qubits[1]); // sdg(1)
+    BaseState::qreg_.append_z(op.qubits[1]);
+    BaseState::qreg_.append_s(op.qubits[1]);
     BaseState::qreg_.append_h(op.qubits[1]);
+    BaseState::qreg_.append_z(op.qubits[1]);
+    BaseState::qreg_.append_s(op.qubits[1]);
     BaseState::qreg_.append_cx(op.qubits[0], op.qubits[1]);
     BaseState::qreg_.append_x(op.qubits[0]);
-    BaseState::qreg_.append_x(op.qubits[1]);
     break;
   case Gates::rz:
     pi2 = (int_t)std::round(std::real(op.params[0]) * 2.0 / M_PI) & 3;

test/terra/backends/aer_simulator/test_cliffords.py

@@ -28,10 +28,6 @@
     "tensor_network",
 ]
 
-SUPPORTED_ECR_METHODS = [
-    "stabilizer",
-]
-
 
 @ddt
 class TestCliffords(SimulatorTestCase):
@@ -249,11 +245,11 @@ def test_pauli_gate_deterministic(self, method, device):
     # ---------------------------------------------------------------------
     # Test ecr gate
     # ---------------------------------------------------------------------
-    @supported_methods(SUPPORTED_ECR_METHODS)
+    @supported_methods(SUPPORTED_METHODS)
     def test_ecr_gate_nondeterministic(self, method, device):
         """Test ecr gate circuits"""
         backend = self.backend(method=method, device=device, seed_simulator=self.SEED)
-        shots = 100
+        shots = 1000
         circuits = ref_2q_clifford.ecr_gate_circuits_nondeterministic(final_measure=True)
         targets = ref_2q_clifford.ecr_gate_counts_nondeterministic(shots)
         result = backend.run(circuits, shots=shots).result()