Merge pull request #125 from CQCL/feature/mainonly

Feature/mainonly

.github/pull_request_template.md

@@ -8,6 +8,7 @@ Please mention any github issues addressed by this PR.
 
 # Checklist
 
+- [ ] I have run the tests on a device with GPUs.
 - [ ] I have performed a self-review of my code.
 - [ ] I have commented hard-to-understand parts of my code.
 - [ ] I have made corresponding changes to the public API documentation.

.github/workflows/build_and_test.yml

@@ -4,10 +4,9 @@ on:
   pull_request:
     branches:
       - main
-      - develop
   push:
     branches:
-      - develop
+      - main
       - 'wheel/**'
       - 'runci/**'
   release:

.github/workflows/check-examples.yml

@@ -3,7 +3,6 @@ name: check examples
 on:
   pull_request:
     branches:
-      - develop
       - main
   schedule:
     # 04:00 every Saturday morning

.github/workflows/issue-to-project.yml

@@ -0,0 +1,16 @@
+name: Add issues to project
+
+on:
+  issues:
+    types:
+      - opened
+
+jobs:
+  add-to-project:
+    name: Add issue to project
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/[email protected]
+        with:
+          project-url: https://github.com/orgs/CQCL-DEV/projects/19
+          github-token: ${{ secrets.ADD_TO_PROJECT_PAT }}

.github/workflows/lint.yml

@@ -4,10 +4,9 @@ on:
   pull_request:
     branches:
       - main
-      - develop
   push:
     branches:
-      - develop
+      - main
       - 'wheel/**'
       - 'runci/**'
 
@@ -31,4 +30,4 @@ jobs:
         black --check .
     - name: Run pylint
       run: |
-        pylint --recursive=y --ignore=ttn_tutorial.py,mps_tutorial.py */
+        pylint --recursive=y --ignore=ttn_tutorial.py,mps_tutorial.py */

README.md

@@ -51,7 +51,7 @@ pip install -e .
 ## Contributing
 
 Pull requests are welcome. To make a PR, first fork the repo, make your proposed
-changes on the `develop` branch, and open a PR from your fork. If it passes
+changes on the `main` branch, and open a PR from your fork. If it passes
 tests and is accepted after review, it will be merged in.
 
 ### Code style

docs/changelog.rst

@@ -1,6 +1,15 @@
 Changelog
 ~~~~~~~~~
 
+Unreleased
+----------
+
+* New feature: ``add_qubit`` to add fresh qubits at specified positions in an ``MPS``.
+* New feature: added an option to ``measure`` to toggle destructive measurement on/off. Currently only supported for ``MPS``.
+* New feature: a seed can now be provided to ``Config`` objects, providing reproducibility across ``StructuredState`` simulations.
+* New feature: ``apply_unitary`` both for ``MPS`` and ``TTN`` to apply an arbitrary unitary matrix, rather than a ``pytket.Command``.
+* New feature: ``apply_qubit_relabelling`` both for ``MPS`` and ``TTN`` to change the name of their qubits. This is now used within ``simulate`` to take into account the action of implicit SWAPs in pytket circuits (no additional SWAP gates are applied).
+
 0.6.1 (April 2024)
 ------------------
 

docs/modules/structured_state.rst

@@ -18,15 +18,17 @@ Simulation
 
 .. autoclass:: pytket.extensions.cutensornet.structured_state.CuTensorNetHandle
 
+    .. automethod:: destroy
+
 
 Classes
 ~~~~~~~
 
 .. autoclass:: pytket.extensions.cutensornet.structured_state.StructuredState()
 
-    .. automethod:: __init__
     .. automethod:: is_valid
     .. automethod:: apply_gate
+    .. automethod:: apply_unitary
     .. automethod:: apply_scalar
     .. automethod:: vdot
     .. automethod:: sample
@@ -49,10 +51,12 @@ Classes
 .. autoclass:: pytket.extensions.cutensornet.structured_state.MPSxGate()
 
     .. automethod:: __init__
+    .. automethod:: add_qubit
 
 .. autoclass:: pytket.extensions.cutensornet.structured_state.MPSxMPO()
 
     .. automethod:: __init__
+    .. automethod:: add_qubit
 
 
 Miscellaneous

lint-requirements.txt

@@ -1,2 +1,2 @@
 black~=24.4
-pylint~=3.1
+pylint~=3.2

pytket/extensions/cutensornet/general.py

@@ -18,7 +18,7 @@
 def set_logger(
     logger_name: str,
     level: int = logging.WARNING,
-    fmt: str = "[%(asctime)s] %(name)s (%(levelname)s) - %(message)s",
+    fmt: str = "[%(asctime)s.%(msecs)03d] %(name)s (%(levelname)s) - %(message)s",
 ) -> Logger:
     """Initialises and configures a logger object.
 

pytket/extensions/cutensornet/structured_state/general.py

@@ -64,12 +64,20 @@ def __init__(self, device_id: Optional[int] = None):
 
         self.handle = cutn.create()
 
+    def destroy(self) -> None:
+        """Destroys the memory handle, releasing memory.
+
+        Only call this method if you are initialising a ``CuTensorNetHandle`` outside
+        a ``with CuTensorNetHandle() as libhandle`` statement.
+        """
+        cutn.destroy(self.handle)
+        self._is_destroyed = True
+
     def __enter__(self) -> CuTensorNetHandle:
         return self
 
     def __exit__(self, exc_type: Any, exc_value: Any, exc_tb: Any) -> None:
-        cutn.destroy(self.handle)
-        self._is_destroyed = True
+        self.destroy()
 
 
 class Config:
@@ -79,6 +87,7 @@ def __init__(
         self,
         chi: Optional[int] = None,
         truncation_fidelity: Optional[float] = None,
+        seed: Optional[int] = None,
         float_precision: Type[Any] = np.float64,
         value_of_zero: float = 1e-16,
         leaf_size: int = 8,
@@ -102,6 +111,11 @@ def __init__(
                 ``|<psi|phi>|^2 >= trucantion_fidelity``, where ``|psi>`` and ``|phi>``
                 are the states before and after truncation (both normalised).
                 If not provided, it will default to its maximum value 1.
+            seed: Seed for the random number generator. Setting a seed provides
+                reproducibility across simulations using ``StructuredState``, in the
+                sense that they will produce the same sequence of measurement outcomes.
+                Crucially, consecutive samples taken from the same ``StructuredState``
+                can still be different from each other.
             float_precision: The floating point precision used in tensor calculations;
                 choose from ``numpy`` types: ``np.float64`` or ``np.float32``.
                 Complex numbers are represented using two of such
@@ -176,6 +190,8 @@ def __init__(
                 UserWarning,
             )
 
+        self.seed = seed
+
         if leaf_size >= 65:  # Imposed to avoid bond ID collisions
             # More than 20 qubits is already unreasonable for a leaf anyway
             raise ValueError("Maximum allowed leaf_size is 65.")
@@ -191,6 +207,7 @@ def copy(self) -> Config:
         return Config(
             chi=self.chi,
             truncation_fidelity=self.truncation_fidelity,
+            seed=self.seed,
             float_precision=self._real_t,  # type: ignore
             value_of_zero=self.zero,
             leaf_size=self.leaf_size,
@@ -224,7 +241,35 @@ def apply_gate(self, gate: Command) -> StructuredState:
 
         Raises:
             RuntimeError: If the ``CuTensorNetHandle`` is out of scope.
-            RuntimeError: If gate is not supported.
+            ValueError: If the command introduced is not a unitary gate.
+            ValueError: If gate acts on more than 2 qubits.
+        """
+        raise NotImplementedError(f"Method not implemented in {type(self).__name__}.")
+
+    @abstractmethod
+    def apply_unitary(
+        self, unitary: cp.ndarray, qubits: list[Qubit]
+    ) -> StructuredState:
+        """Applies the unitary to the specified qubits of the StructuredState.
+
+        Note:
+            It is assumed that the matrix provided by the user is unitary. If this is
+            not the case, the program will still run, but its behaviour is undefined.
+
+        Args:
+            unitary: The matrix to be applied as a CuPy ndarray. It should either be
+                a 2x2 matrix if acting on one qubit or a 4x4 matrix if acting on two.
+            qubits: The qubits the unitary acts on. Only one qubit and two qubit
+                unitaries are supported.
+
+        Returns:
+            ``self``, to allow for method chaining.
+
+        Raises:
+            RuntimeError: If the ``CuTensorNetHandle`` is out of scope.
+            ValueError: If the number of qubits provided is not one or two.
+            ValueError: If the size of the matrix does not match with the number of
+                qubits provided.
         """
         raise NotImplementedError(f"Method not implemented in {type(self).__name__}.")
 
@@ -240,6 +285,24 @@ def apply_scalar(self, scalar: complex) -> StructuredState:
         """
         raise NotImplementedError(f"Method not implemented in {type(self).__name__}.")
 
+    @abstractmethod
+    def apply_qubit_relabelling(self, qubit_map: dict[Qubit, Qubit]) -> StructuredState:
+        """Relabels each qubit ``q`` as ``qubit_map[q]``.
+
+        This does not apply any SWAP gate, nor it changes the internal structure of the
+        state. It simply changes the label of the physical bonds of the tensor network.
+
+        Args:
+            qubit_map: Dictionary mapping each qubit to its new label.
+
+        Returns:
+            ``self``, to allow for method chaining.
+
+        Raises:
+            ValueError: If any of the keys in ``qubit_map`` are not qubits in the state.
+        """
+        raise NotImplementedError(f"Method not implemented in {type(self).__name__}.")
+
     @abstractmethod
     def vdot(self, other: StructuredState) -> complex:
         """Obtain the inner product of the two states: ``<self|other>``.
@@ -276,17 +339,18 @@ def sample(self) -> dict[Qubit, int]:
         raise NotImplementedError(f"Method not implemented in {type(self).__name__}.")
 
     @abstractmethod
-    def measure(self, qubits: set[Qubit]) -> dict[Qubit, int]:
-        """Applies a Z measurement on ``qubits``, updates the state and returns outcome.
+    def measure(self, qubits: set[Qubit], destructive: bool = True) -> dict[Qubit, int]:
+        """Applies a Z measurement on each of the ``qubits``.
 
         Notes:
-            After applying this function, ``self`` will contain the projected
-            state over the non-measured qubits.
-
-            The resulting state has been normalised.
+            After applying this function, ``self`` will contain the normalised
+            projected state.
 
         Args:
             qubits: The subset of qubits to be measured.
+            destructive: If ``True``, the resulting state will not contain the
+                measured qubits. If ``False``, these qubits will appear on the
+                state corresponding to the measurement outcome. Defaults to ``True``.
 
         Returns:
             A dictionary mapping the given ``qubits`` to their measurement outcome,