From 5a084aea55e929687931fa180c547bacfe5fa34a Mon Sep 17 00:00:00 2001 From: Daniel Tsvetkov Date: Thu, 20 Feb 2020 11:24:42 +0100 Subject: [PATCH] partial measurement collapse --- lib_q_computer_math.py | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/lib_q_computer_math.py b/lib_q_computer_math.py index 2853673..2f3826e 100644 --- a/lib_q_computer_math.py +++ b/lib_q_computer_math.py @@ -284,14 +284,23 @@ class State(Vector): if not (0 < qubit_n <= max_qubits): raise Exception("Partial measurement of qubit_n must be between 1 and {}".format(max_qubits)) 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))] + # 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] + # [0, 1, 4, 5] 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] choices_0 = [format_str.format(i) for i in indexes_for_p_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 + 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 def pretty_print(self):