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