feat: implement grovers search

main.py

@@ -9,28 +9,73 @@ using matplotlib.
 from itertools import product
 
 import matplotlib.pyplot as plt
+import numpy as np
 from matplotlib.axes import Axes
 from qiskit import QuantumCircuit
 from qiskit_aer import AerSimulator
 
 
-def grover_search(n: int) -> QuantumCircuit:
+def x(qc: QuantumCircuit, target_state: str) -> None:
+    for i, bit in enumerate(reversed(target_state)):
+        if bit == "0":
+            qc.x(i)
+
+
+def ccz(qc: QuantumCircuit, n: int) -> None:
+    """Multi-controlled Z (for 3 qubits, this is a CCZ)"""
+    if n == 1:
+        qc.z(0)
+    elif n == 2:
+        qc.cz(0, 1)
+    else:
+        qc.h(n - 1)
+        qc.mcx(list(range(n - 1)), n - 1)  # multi-controlled X (Toffoli for 3 qubits)
+        qc.h(n - 1)
+
+
+def oracule(qc: QuantumCircuit, target_state: str) -> None:
+    n = len(target_state)
+
+    x(qc, target_state)
+
+    ccz(qc, n)
+
+    # Undo the X gates
+    x(qc, target_state)
+
+
+def diffusion(qc: QuantumCircuit, n: int) -> None:
+    """Apply the Grovers diffusion operator"""
+
+    qc.h(range(n))
+    qc.x(range(n))
+
+    ccz(qc, n)
+
+    qc.x(range(n))
+    qc.h(range(n))
+
+
+def grover_search(n: int, target_state: str) -> QuantumCircuit:
     qc = QuantumCircuit(n, n)
 
     qc.h(range(n))
 
+    num_states = 2**n
+
+    iterations = int(np.floor(np.pi / 4 * np.sqrt(num_states)))
+    for _ in range(iterations):
+        oracule(qc, target_state)
+        diffusion(qc, n)
+
     qc.measure(range(n), range(n))
     return qc
 
 
 def plot_counts(ax: Axes, counts: dict[str, int], target_state: str) -> None:
-    """Create and display a bar chart for the measurement results.
+    """Create and display a bar chart for the measurement results."""
 
-    Parameters:
-      counts       - A dictionary mapping output states to counts.
-      target_state - The target state used in the Grover circuit.
-    """
-    # Sort the states (optional: you can sort by state or by count)
+    # Sort the states
     states = list(counts.keys())
     frequencies = [counts[s] for s in states]
 
@@ -52,7 +97,7 @@ def main() -> None:
     plt.ion()
 
     for state in states:
-        qc = grover_search(n_qubits)
+        qc = grover_search(n_qubits, state)
 
         print(qc.draw("text"))
 
@@ -68,7 +113,6 @@ def main() -> None:
         plot_counts(ax, sorted_counts, state)
         plt.pause(1)
 
-    # plt.ioff()  # Do not close automatically
     plt.show()