merge master

pennylane_lightning/core/_version.py

@@ -16,4 +16,4 @@
    Version number (major.minor.patch[-label])
 """
 
-__version__ = "0.36.0-rc1"
+__version__ = "0.36.0-dev46"

pennylane_lightning/lightning_tensor/__init__.py

@@ -0,0 +1,18 @@
+# Copyright 2018-2024 Xanadu Quantum Technologies Inc.
+
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+
+#     http://www.apache.org/licenses/LICENSE-2.0
+
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""PennyLane lightning_tensor package."""
+
+from pennylane_lightning.core import __version__
+
+from .lightning_tensor import LightningTensor

pennylane_lightning/lightning_tensor/backends/quimb/_mps.py

@@ -0,0 +1,100 @@
+# Copyright 2018-2024 Xanadu Quantum Technologies Inc.
+
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+
+#     http://www.apache.org/licenses/LICENSE-2.0
+
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""
+Class implementation for the Quimb MPS interface for simulating quantum circuits while keeping the state always in MPS form.
+"""
+
+import numpy as np
+import pennylane as qml
+import quimb.tensor as qtn
+from pennylane.wires import Wires
+
+_operations = frozenset({})  # pragma: no cover
+# The set of supported operations.
+
+_observables = frozenset({})  # pragma: no cover
+# The set of supported observables.
+
+
+def stopping_condition(op: qml.operation.Operator) -> bool:
+    """A function that determines if an operation is supported by ``lightning.tensor`` for this interface."""
+    return op.name in _operations  # pragma: no cover
+
+
+def accepted_observables(obs: qml.operation.Operator) -> bool:
+    """A function that determines if an observable is supported by ``lightning.tensor`` for this interface."""
+    return obs.name in _observables  # pragma: no cover
+
+
+class QuimbMPS:
+    """Quimb MPS class.
+
+    Used internally by the `LightningTensor` device.
+    Interfaces with `quimb` for MPS manipulation, and provides methods to execute quantum circuits.
+
+    Args:
+        num_wires (int): the number of wires in the circuit.
+        interf_opts (dict): dictionary containing the interface options.
+        dtype (np.dtype): the complex type used for the MPS.
+    """
+
+    def __init__(self, num_wires, interf_opts, dtype=np.complex128):
+
+        if dtype not in [np.complex64, np.complex128]:  # pragma: no cover
+            raise TypeError(f"Unsupported complex type: {dtype}")
+
+        self._wires = Wires(range(num_wires))
+        self._dtype = dtype
+
+        self._init_state_ops = {
+            "binary": "0" * max(1, len(self._wires)),
+            "dtype": self._dtype.__name__,
+            "tags": [str(l) for l in self._wires.labels],
+        }
+
+        self._gate_opts = {
+            "contract": "swap+split",
+            "parametrize": None,
+            "cutoff": interf_opts["cutoff"],
+            "max_bond": interf_opts["max_bond_dim"],
+        }
+
+        self._expval_opts = {
+            "dtype": self._dtype.__name__,
+            "simplify_sequence": "ADCRS",
+            "simplify_atol": 0.0,
+        }
+
+        self._circuitMPS = qtn.CircuitMPS(psi0=self._initial_mps())
+
+    @property
+    def state(self):
+        """Current MPS handled by the interface."""
+        return self._circuitMPS.psi
+
+    def state_to_array(self) -> np.ndarray:
+        """Contract the MPS into a dense array."""
+        return self._circuitMPS.to_dense()
+
+    def _initial_mps(self) -> qtn.MatrixProductState:
+        r"""
+        Returns an initial state to :math:`\ket{0}`.
+
+        Internally, it uses `quimb`'s `MPS_computational_state` method.
+
+        Returns:
+            MatrixProductState: The initial MPS of a circuit.
+        """
+
+        return qtn.MPS_computational_state(**self._init_state_ops)