Repo structure (#3)

* refactor: create basic folder structure

* meta: add license

* meta: add basic tooling

* ci: add basic Travis CI configuration

* nb: remove imports from notebook

The notebook still has other issues but those can be resolved later.

* lint: format with ruff

* lint: satisfy pydocstyle

This just adds TODO placeholders in the docstrings but at least gets the
basic structure of them into the right shape.

* lint: satisfy mypy

* lint: satisfy pylint

* lint: satisfy nbqa

.travis.yml

@@ -0,0 +1,44 @@
+language: python
+
+jobs:
+  include:
+    # Lint tests
+    - python: 3.10
+      env: TOXENV=lint
+      script: tox -e $TOXENV
+
+    # Coverage tests
+    - python: 3.10
+      env: TOXENV=coverage
+      script: tox -e $TOXENV
+
+    # Unit tests (py39)
+    - python: 3.9
+      env: TOXENV=py39
+      script: tox -e $TOXENV
+
+    # Unit tests (py310)
+    - python: 3.10
+      env: TOXENV=py310
+      script: tox -e $TOXENV
+
+    # Unit tests (py311)
+    - python: 3.11
+      env: TOXENV=py311
+      script: tox -e $TOXENV
+
+    # Unit tests (py312)
+    - python: 3.12
+      env: TOXENV=py312
+      script: tox -e $TOXENV
+
+    # Notebook tests
+    - python: 3.10
+      before_install:
+        - sudo apt-get update
+      env: TOXENV=notebook
+      script: tox -e $TOXENV
+
+install:
+  - pip install --upgrade pip
+  - pip install tox

LICENSE.txt

@@ -0,0 +1 @@
+IBM Restricted

README.md

@@ -1,4 +1,3 @@
-# IC-POVM
-Informationally complete POVM 
+# POVMs
 
-This is a first try
+A module for the implementation of positive operator-valued measures (POVMs).

test.ipynb → notebooks/test.ipynb

@@ -14,8 +14,6 @@
     "from base_povm import  Povm\n",
     "from single_qubit_povm import SingleQubitPOVM\n",
     "from povm_implementation import ProductPVMSimPOVMImplementation\n",
-    "from test_base_povm import TestBasePovm\n",
-    "\n",
     "from qiskit.quantum_info import random_density_matrix, Operator"
    ]
   },
@@ -421,11 +419,11 @@
     "sqpovm = SingleQubitPOVM.from_vectors()\n",
     "print(sqpovm.check_validity())\n",
     "\n",
-    "sum = np.zeros(4, dtype=complex)\n",
+    "summed = np.zeros(4, dtype=complex)\n",
     "for coef in sqpovm.povm_pauli_decomp:\n",
-    "    sum += coef\n",
+    "    summed += coef\n",
     "\n",
-    "sum"
+    "summed"
    ]
   },
   {
@@ -679,8 +677,6 @@
     }
    ],
    "source": [
-    "import numpy as np\n",
-    "from povm_implementation import ProductPVMSimPOVMImplementation\n",
     "povm_implementation = ProductPVMSimPOVMImplementation(2, np.array([0,0, 1,0.5, 1,1, 1,1,     0,0, 1,0.5, 0.3,0.2, 2,1]))\n",
     "povm_implementation._build_qc().draw()"
    ]
@@ -1165,6 +1161,7 @@
     "    return povm\n",
     "\n",
     "def compare_povms(povm1: Povm, povm2: Povm, tol:float=1e-5) -> bool:\n",
+    "    del tol\n",
     "    povm1 = clean_povm(povm1)\n",
     "    povm2 = clean_povm(povm2)\n",
     "\n",
@@ -1379,7 +1376,7 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Python 3",
+   "display_name": "Python 3 (ipykernel)",
    "language": "python",
    "name": "python3"
   },
@@ -1393,9 +1390,9 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.11.7"
+   "version": "3.11.8"
   }
  },
  "nbformat": 4,
- "nbformat_minor": 2
+ "nbformat_minor": 4
 }

povms/__init__.py

@@ -0,0 +1 @@
+"""TODO."""

base_povm.py → povms/base_povm.py

@@ -1,3 +1,7 @@
+"""TODO."""
+
+from __future__ import annotations
+
 import numpy as np
 
 from qiskit.quantum_info import Operator, DensityMatrix
@@ -6,41 +10,49 @@
 class Povm:
     """Abstract base class that collects all information that any POVM should specifiy."""
 
-    def __init__(self, povm_ops: np.ndarray):
+    def __init__(self, povm_ops: np.ndarray) -> None:
         """Initialize from explicit POVM operators.
 
         Args:
-            povm_operators: np.ndarray that contains the explicit list of POVM operators"""
+            povm_operators: np.ndarray that contains the explicit list of POVM operators.
 
+        Raises:
+            ValueError: TODO.
+        """
         if not (len(povm_ops.shape) == 3 and povm_ops.shape[1] == povm_ops.shape[1]):
-            raise ValueError(
-                f"POVM operators need to be square instead of {povm_ops.shape[1:]}"
-            )
+            raise ValueError(f"POVM operators need to be square instead of {povm_ops.shape[1:]}")
 
-        self.n_outcomes = povm_ops.shape[0]
-        self.dimension = povm_ops.shape[1]
-        self.povm_operators = [Operator(op) for op in povm_ops]
+        self.n_outcomes: int = povm_ops.shape[0]
+        self.dimension: int = povm_ops.shape[1]
+        self.povm_operators: list[Operator] = [Operator(op) for op in povm_ops]
         self.array_ops = None
 
         self.dual_operators = None
         self.frame_superop = None
         self.informationlly_complete = None
 
     def check_validity(self) -> bool:
-        """Checks if POVM axioms are fulfilled."""
+        """Check if POVM axioms are fulfilled.
 
-        summed_op = np.zeros((self.dimension, self.dimension), dtype=complex)
+        Returns:
+            TODO.
 
-        for k in range(len(self)):
+        Raises:
+            ValueError: TODO.
+        """
+        summed_op: np.ndarray = np.zeros((self.dimension, self.dimension), dtype=complex)
 
-            if not np.allclose(self.povm_operators[k].data.conj().T - self.povm_operators[k].data, 0.0, atol=1e-5):
+        for k in range(len(self)):
+            if not np.allclose(
+                self.povm_operators[k].data.conj().T - self.povm_operators[k].data,
+                0.0,
+                atol=1e-5,
+            ):
                 raise ValueError(f"POVM operator {k} is not hermitian.")
 
             for eigval in np.linalg.eigvalsh(self.povm_operators[k].data):
                 if eigval.real < -1e-6 or np.abs(eigval.imag) > 1e-5:
-                    raise ValueError(
-                        f"Negative eigenvalue {eigval} in POVM operator {k}."
-                    )
+                    raise ValueError(f"Negative eigenvalue {eigval} in POVM operator {k}.")
 
             summed_op += self.povm_operators[k].data
 
@@ -49,22 +61,41 @@ def check_validity(self) -> bool:
 
         return True
 
-    def __getitem__(self, index: slice) -> np.ndarray:
+    def __getitem__(self, index: slice) -> Operator:
         """Return a povm operator or a list of povm operators."""
         return self.povm_operators[index]
-
-    def __len__(self):
+
+    def __len__(self) -> int:
+        """TODO."""
         return len(self.povm_operators)
 
     def get_prob(self, rho: DensityMatrix) -> np.ndarray:
-        return np.array([
-            np.real(np.trace(rho.data @ povm_op.data))
-            for povm_op in self.povm_operators])
+        """TODO.
+
+        Args:
+            rho: TODO.
+
+        Returns:
+            TODO.
+        """
+        return np.array(
+            [np.real(np.trace(rho.data @ povm_op.data)) for povm_op in self.povm_operators]
+        )
 
     @classmethod
-    def from_vectors(cls, povm_vectors: np.ndarray):
-        """Initialize a POVM from the bloch vectors |psi> (not normalized!) such that Pi = |psi><psi|."""
-        povm_operators = np.zeros((povm_vectors.shape[0], povm_vectors.shape[1], povm_vectors.shape[1]), dtype=complex)
+    def from_vectors(cls, povm_vectors: np.ndarray) -> Povm:
+        """Initialize a POVM from the bloch vectors |psi> (not normalized!) such that Pi = |psi><psi|.
+
+        Args:
+            povm_vectors: TODO.
+
+        Returns:
+            TODO.
+        """
+        povm_operators: np.ndarray = np.zeros(
+            (povm_vectors.shape[0], povm_vectors.shape[1], povm_vectors.shape[1]),
+            dtype=complex,
+        )
         for i, vec in enumerate(povm_vectors):
             povm_operators[i] = np.outer(vec, vec.conj())
         return cls(povm_operators)