#!/usr/bin/env python
# coding: utf-8

# # Meyer Penny Game

# In[1]:


import pyquil.quil as pq
from pyquil import api
from pyquil.gates import I, H, X

import numpy as np


# In[2]:


def meyer_penny_program():
    """
    Returns the program to simulate the Meyer-Penny Game
    The full description is available in ../docs/source/exercises.rst

    :return: pyQuil Program
    """
    prog = pq.Program()
    ro = prog.declare("ro", memory_size=2)
    picard_register = ro[1]
    answer_register = ro[0]

    then_branch = pq.Program(X(0))
    else_branch = pq.Program(I(0))

    # Prepare Qubits in Heads state or superposition, respectively
    prog.inst(X(0), H(1))
    # Q puts the coin into a superposition
    prog.inst(H(0))
    # Picard makes a decision and acts accordingly
    prog.measure(1, picard_register)
    prog.if_then(picard_register, then_branch, else_branch)
    # Q undoes his superposition operation
    prog.inst(H(0))
    # The outcome is recorded into the answer register
    prog.measure(0, answer_register)

    return prog


# In[3]:


n_trials = 10
qvm = api.QVMConnection()
outcomes = np.asarray(qvm.run(meyer_penny_program(), [0, 1], trials=n_trials))

print("Number of games: {}".format(n_trials))
print("Q's winning average: {}".format(outcomes[:, 0].mean()))
print("Picard's flip-decision average: {}".format(outcomes[:, 1].mean()))