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partial measurement collapse

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This commit is contained in:
Daniel Tsvetkov 2020-02-20 11:24:42 +01:00
parent aa06605f6c
commit 5a084aea55
1 changed files with 10 additions and 1 deletions
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11
lib_q_computer_math.py
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@ -284,14 +284,23 @@ class State(Vector):
if not (0 < qubit_n <= max_qubits): if not (0 < qubit_n <= max_qubits):
raise Exception("Partial measurement of qubit_n must be between 1 and {}".format(max_qubits)) raise Exception("Partial measurement of qubit_n must be between 1 and {}".format(max_qubits))
format_str = self.get_fmt_of_element() format_str = self.get_fmt_of_element()
# e.g. for state |000>:
# ['000', '001', '010', '011', '100', '101', '110', '111']
bin_repr = [format_str.format(i) for i in range(len(self))] bin_repr = [format_str.format(i) for i in range(len(self))]
# e.g. for qbit_n = 2
# [0, 0, 1, 1, 0, 0, 1, 1]
partial_measurement_of_qbit = [int(b[qubit_n - 1]) for b in bin_repr] partial_measurement_of_qbit = [int(b[qubit_n - 1]) for b in bin_repr]
# [0, 1, 4, 5]
indexes_for_p_0 = [i for i, index in enumerate(partial_measurement_of_qbit) if index==0] indexes_for_p_0 = [i for i, index in enumerate(partial_measurement_of_qbit) if index==0]
weights_0 = [self.get_prob(j) for j in indexes_for_p_0] weights_0 = [self.get_prob(j) for j in indexes_for_p_0]
choices_0 = [format_str.format(i) for i in indexes_for_p_0] choices_0 = [format_str.format(i) for i in indexes_for_p_0]
measurement_result = random.choices(choices_0, weights_0)[0] measurement_result = random.choices(choices_0, weights_0)[0]
# TODO: collapse the state and change the probabilities of the rest # TODO: Verify if this is the correct collapse to lower dimension after partial measurement
# https://www.youtube.com/watch?v=MG_9JWsrKtM&list=PL1826E60FD05B44E4&index=16 # https://www.youtube.com/watch?v=MG_9JWsrKtM&list=PL1826E60FD05B44E4&index=16
normalization_factor = np.sqrt(np.sum([self.m[i][0] for i in indexes_for_p_0]))
self.m = [
[(self.m[i][0]**2)/normalization_factor] for i in indexes_for_p_0
]
return measurement_result return measurement_result
def pretty_print(self): def pretty_print(self):