[feature] Adding support for MPS simulation (#63)

* Adding an MPS simulator

* Adding tests for MPS

* Using non-destructive measurements

* Added a reset method to MPS

* Including MPS as a qsim backend for HybridEngine

* Adding more bindings for initialisation that are needing for the tests

* Allowing users to provide parameters for the MPS simulation from HybridEngine

* Add HybridEngine tests for MPS

Author: PabloAndresCQ

README.md

@@ -99,6 +99,7 @@ Certain simulators from `pecos.simulators` require external packages that are no
 
 - `QuEST` is installed along with the python package `pyquest` when calling `pip install .[all]`. However, it uses 64-bit float point precision by default, and if you wish to make use of 32-bit float point precision you will need to follow the installation instructions provided by the developers [here](https://github.com/rrmeister/pyQuEST/tree/develop).
 - `CuStateVec` requires a Linux machine with an NVIDIA GPU (see requirements [here](https://docs.nvidia.com/cuda/cuquantum/latest/getting_started/getting_started.html#dependencies-custatevec-label)). PECOS' dependencies are specified in the `[cuda]` section of `pyproject.toml`, however, installation via `pip` is not reliable. The recommended method of installation is via `conda`, as discussed [here](https://docs.nvidia.com/cuda/cuquantum/latest/getting_started/getting_started.html#installing-cuquantum). Note that there might be conflicts between `conda` and `venv`; if you intend to use `CuStateVec`, you may follow the installation instructions for PECOS within a `conda` environment without involving the `venv` commands.
+- `MPS` uses `pytket-cutensornet` (see [repository](https://github.com/CQCL/pytket-cutensornet)) and can be installed via `pip install .[cuda]`. This simulators uses NVIDIA GPUs and cuQuantum. Unfortunately, installation of cuQuantum does not currently work via `pip`. Please follow the instructions specified above for `CuStateVec` to install cuQuantum.
 
 ## Uninstall
 

pyproject.toml

@@ -64,6 +64,7 @@ cuda = [
     "cuquantum-python>=24.03.0",
     "custatevec>=1.6.0",
     "cupy>=10.4.0",
+    "pytket-cutensornet>=0.7.0",
 ]
 wasmtime = [
     "wasmtime>=13.0"

python/pecos/engines/hybrid_engine.py

@@ -32,7 +32,12 @@
 
 
 class HybridEngine:
-    """A simulation engine which is capable of running noisy hybrid classical/quantum programs."""
+    """A simulation engine which is capable of running noisy hybrid classical/quantum programs.
+
+    Note:
+        Parameters of the quantum simulator are provided as extra keyword arguments passed
+        down to ``QuantumSimulator`` as the dictionary ``**params``.
+    """
 
     def __init__(
         self,
@@ -41,6 +46,7 @@ def __init__(
         machine: Machine | None = None,
         error_model: ErrorModel | None = None,
         op_processor: OpProcessor | None = None,
+        **params,
     ) -> None:
         self.seed = None
 
@@ -54,7 +60,7 @@ def __init__(
         if self.qsim is None:
             self.qsim = QuantumSimulator()
         elif isinstance(self.qsim, str):
-            self.qsim = QuantumSimulator(self.qsim)
+            self.qsim = QuantumSimulator(self.qsim, **params)
 
         self.machine = machine
         if machine is None:

python/pecos/simulators/__init__.py

@@ -50,5 +50,6 @@
     import cuquantum
 
     from pecos.simulators.custatevec.state import CuStateVec  # wrapper for cuQuantum's cuStateVec
+    from pecos.simulators.mps_pytket import MPS  # MPS implementation from pytket-cutensornet
 except ImportError:
     pass

python/pecos/simulators/mps_pytket/__init__.py

@@ -0,0 +1,13 @@
+# Copyright 2024 The PECOS Developers
+#
+# 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
+#
+#     https://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.
+
+from pecos.simulators.mps_pytket import bindings
+from pecos.simulators.mps_pytket.state import MPS

python/pecos/simulators/mps_pytket/bindings.py

@@ -0,0 +1,74 @@
+# Copyright 2024 The PECOS Developers
+#
+# 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
+#
+#     https://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.
+
+import pecos.simulators.mps_pytket.gates_one_qubit as one_q
+import pecos.simulators.mps_pytket.gates_two_qubit as two_q
+from pecos.simulators.mps_pytket.gates_init import init_one, init_zero
+from pecos.simulators.mps_pytket.gates_meas import meas_z
+
+# Supporting gates from table:
+#   https://github.com/CQCL/phir/blob/main/spec.md#table-ii---quantum-operations
+
+gate_dict = {
+    "Init": init_zero,
+    "Init +Z": init_zero,
+    "Init -Z": init_one,
+    "init |0>": init_zero,
+    "init |1>": init_one,
+    "leak": init_zero,
+    "leak |0>": init_zero,
+    "leak |1>": init_one,
+    "unleak |0>": init_zero,
+    "unleak |1>": init_one,
+    "Measure": meas_z,
+    "measure Z": meas_z,
+    "I": one_q.identity,
+    "X": one_q.X,
+    "Y": one_q.Y,
+    "Z": one_q.Z,
+    "RX": one_q.RX,
+    "RY": one_q.RY,
+    "RZ": one_q.RZ,
+    "R1XY": one_q.R1XY,
+    "RXY1Q": one_q.R1XY,
+    "SX": one_q.SX,
+    "SXdg": one_q.SXdg,
+    "SqrtX": one_q.SX,
+    "SqrtXd": one_q.SXdg,
+    "SY": one_q.SY,
+    "SYdg": one_q.SYdg,
+    "SqrtY": one_q.SY,
+    "SqrtYd": one_q.SYdg,
+    "SZ": one_q.SZ,
+    "SZdg": one_q.SZdg,
+    "SqrtZ": one_q.SZ,
+    "SqrtZd": one_q.SZdg,
+    "H": one_q.H,
+    "F": one_q.F,
+    "Fdg": one_q.Fdg,
+    "T": one_q.T,
+    "Tdg": one_q.Tdg,
+    "CX": two_q.CX,
+    "CY": two_q.CY,
+    "CZ": two_q.CZ,
+    "RXX": two_q.RXX,
+    "RYY": two_q.RYY,
+    "RZZ": two_q.RZZ,
+    "R2XXYYZZ": two_q.R2XXYYZZ,
+    "SXX": two_q.SXX,
+    "SXXdg": two_q.SXXdg,
+    "SYY": two_q.SYY,
+    "SYYdg": two_q.SYYdg,
+    "SZZ": two_q.SZZ,
+    "SqrtZZ": two_q.SZZ,
+    "SZZdg": two_q.SZZdg,
+    "SWAP": two_q.SWAP,
+}

python/pecos/simulators/mps_pytket/gates_init.py

@@ -0,0 +1,41 @@
+# Copyright 2024 The PECOS Developers
+#
+# 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
+#
+#     https://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.
+
+from typing import Any
+
+from pecos.simulators.mps_pytket.gates_meas import meas_z
+from pecos.simulators.mps_pytket.gates_one_qubit import X
+
+
+def init_zero(state, qubit: int, **params: Any) -> None:
+    """Initialise or reset the qubit to state |0>
+
+    Args:
+        state: An instance of MPS
+        qubit: The index of the qubit to be initialised
+    """
+    result = meas_z(state, qubit)
+
+    if result != 0:
+        X(state, qubit)
+
+
+def init_one(state, qubit: int, **params: Any) -> None:
+    """Initialise or reset the qubit to state |1>
+
+    Args:
+        state: An instance of MPS
+        qubit: The index of the qubit to be initialised
+    """
+    result = meas_z(state, qubit)
+
+    if result != 1:
+        X(state, qubit)

python/pecos/simulators/mps_pytket/gates_meas.py

@@ -0,0 +1,36 @@
+# Copyright 2024 The PECOS Developers
+#
+# 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
+#
+#     https://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.
+
+from typing import Any
+
+from pytket import Qubit
+
+
+def meas_z(state, qubit: int, **params: Any) -> int:
+    """Measure in the Z-basis, collapse and normalise.
+
+    Notes:
+        The number of qubits in the state remains the same.
+
+    Args:
+        state: An instance of MPS
+        qubit: The index of the qubit to be measured
+
+    Returns:
+        The outcome of the measurement, either 0 or 1.
+    """
+    if qubit >= state.num_qubits or qubit < 0:
+        msg = f"Qubit {qubit} out of range."
+        raise ValueError(msg)
+
+    result = state.mps.measure({Qubit(qubit)}, destructive=False)
+
+    return result[Qubit(qubit)]