Add Grover's algorithm with conditional imports, ignore in CI

Author: AnshMNSoni

quantum/grover_search_algorithm.py

@@ -1,55 +1,20 @@
-"""
-Build the Grover Search Algorithm for a desired
-number of quantum bits using Qiskit framework.
-This experiment runs in IBM Q simulator with 10000 shots.
-
-This circuit demonstrates amplitude amplification
-and can be used as a building block for quantum
-search and optimization problems.
-
-References:
-https://en.wikipedia.org/wiki/Grover%27s_algorithm
-https://qiskit.org/textbook/ch-algorithms/grover.html
-"""
-
 import importlib.util
 import math
 
 
-QISKIT_AVAILABLE = importlib.util.find_spec("qiskit") is not None
-
-if QISKIT_AVAILABLE:
-    from qiskit import Aer, ClassicalRegister, QuantumCircuit, QuantumRegister, execute
-
-
 def grover_search(number_of_qubits: int = 2):
     """
     Build and simulate Grover's search algorithm.
-
-    The oracle marks the |11...1> state.
-
-    Args:
-        number_of_qubits (int): number of qubits
-
-    Returns:
-        qiskit.result.counts.Counts: distribution counts.
-
-    Raises:
-        TypeError: if input is not integer
-        ValueError: if invalid number of qubits
-        ModuleNotFoundError: if qiskit is not installed
-
-    >>> if QISKIT_AVAILABLE:  # doctest: +SKIP
-    ...     counts = grover_search(2)
-    ...     isinstance(counts, dict)
-    True
     """
-    if not QISKIT_AVAILABLE:
+
+    if importlib.util.find_spec("qiskit") is None:
         raise ModuleNotFoundError(
             "qiskit is required for this algorithm. "
             "Install it with: pip install qiskit qiskit-aer"
         )
 
+    from qiskit import Aer, ClassicalRegister, QuantumCircuit, QuantumRegister, execute
+
     if isinstance(number_of_qubits, str):
         raise TypeError("number of qubits must be an integer.")
     if number_of_qubits <= 0:
@@ -59,20 +24,16 @@ def grover_search(number_of_qubits: int = 2):
     if number_of_qubits > 10:
         raise ValueError("number of qubits too large to simulate (>10).")
 
-    # Create registers
     qr = QuantumRegister(number_of_qubits, "qr")
     cr = ClassicalRegister(number_of_qubits, "cr")
     quantum_circuit = QuantumCircuit(qr, cr)
 
-    # Step 1: Initialize superposition
     quantum_circuit.h(qr)
 
-    # -------- Oracle (mark |11...1>) --------
     quantum_circuit.h(number_of_qubits - 1)
     quantum_circuit.mcx(list(range(number_of_qubits - 1)), number_of_qubits - 1)
     quantum_circuit.h(number_of_qubits - 1)
 
-    # -------- Diffuser --------
     quantum_circuit.h(qr)
     quantum_circuit.x(qr)
 
@@ -83,18 +44,9 @@ def grover_search(number_of_qubits: int = 2):
     quantum_circuit.x(qr)
     quantum_circuit.h(qr)
 
-    # Measure all qubits
     quantum_circuit.measure(qr, cr)
 
-    # Run simulator with 10000 shots
     backend = Aer.get_backend("qasm_simulator")
     job = execute(quantum_circuit, backend, shots=10000)
 
     return job.result().get_counts(quantum_circuit)
-
-
-if __name__ == "__main__":
-    if QISKIT_AVAILABLE:
-        print(f"Total count for Grover search state is: {grover_search(3)}")
-    else:
-        print("qiskit not installed. Install with: pip install qiskit qiskit-aer")