Update measurement.py

quantum/measurement.py

@@ -1 +1,54 @@
-print("Hello World")
+from __future__ import annotations
+from dataclasses import dataclass
+import random
+
+@dataclass
+class Qubit:
+    """
+    Represents a single qubit that can be measured in the computational basis.
+
+    Attributes
+    ----------
+    alpha : complex
+        Amplitude for the |0> state.
+    beta : complex
+        Amplitude for the |1> state.
+    """
+    alpha: complex
+    beta: complex
+
+    def measure(self) -> int:
+        """
+        Measure this qubit and collapse it to either |0> or |1>.
+
+        The probability of obtaining 0 is |alpha|^2 and the probability of obtaining 1 is |beta|^2.
+        After measurement, the qubit collapses to the observed basis state.
+
+        Returns
+        -------
+        int
+            0 if the outcome is |0>, 1 if the outcome is |1>.
+        """
+        p_zero = abs(self.alpha)**2
+        rnd = random.random()
+        if rnd < p_zero:
+            # Collapse to |0>
+            self.alpha, self.beta = 1+0j, 0+0j
+            return 0
+        else:
+            # Collapse to |1>
+            self.alpha, self.beta = 0+0j, 1+0j
+            return 1
+
+
+if __name__ == "__main__":
+    # Demonstration: measure a qubit multiple times
+    import math
+    # Normalized state |psi> = sqrt(0.36)|0> + sqrt(0.64)|1>
+    amp0 = math.sqrt(0.36)
+    amp1 = math.sqrt(0.64)
+    q = Qubit(alpha=amp0, beta=amp1)
+    print("Measuring the qubit five times (state is reset each time):")
+    for _ in range(5):
+        q2 = Qubit(alpha=amp0, beta=amp1)
+        print(q2.measure())