host.py

# Copyright (c) Microsoft Corporation.
# Licensed under the MIT License.

import numpy as np
import random
from typing import Tuple

import qsharp
from Microsoft.Quantum.Samples.CHSHGame import PlayQuantumStrategy

def get_random_bits(n_bits=1):
    return [
        bool(random.getrandbits(1))
        for _ in range(n_bits)
    ] if n_bits > 1 else bool(random.getrandbits(1))

def referee_single_round() -> bool:
    """
    Play a single round of the CHSH game and referee to see if the quantum
    strategy won the round.
    """
    
    # Generate random inpus for each player.
    alice_input, bob_input = get_random_bits(2)
    
    # Check whether Alice or Bob should go first.
    alice_measures_first = get_random_bits(1)
    
    # Run the Q# program to get the parity of Alice's and Bob's answers.
    output_parity = PlayQuantumStrategy.simulate(
        aliceBit=alice_input,
        bobBit=bob_input,
        aliceMeasuresFirst=alice_measures_first
    )

    # Check if Alice and Bob won the round.
    return output_parity == (not (alice_input and bob_input))

def estimate_quantum_win_probability(n_trials : int) -> Tuple[float, float]:
    est = np.mean([
        referee_single_round()
        for _ in range(n_trials)
    ])

    return est, np.sqrt(est * (1 - est) / n_trials)

if __name__ == "__main__":
    est_win_pr, error = estimate_quantum_win_probability(400)
    print(f"Estimated quantum win probability: {est_win_pr:%} ± {error:%}")