N.2.2.b Compilation error even code is correct with correct probability

Codebook
1

Here I am getting the error messages as

Blockquote Your code isn't giving the correct probabilities!Your code isn'tgiving the correct probabilities!

My code is as follows:

``
def outcome_probs(rho, B):

"""
Args:
    rho (np.array([array[complex]])): The density matrix of the state before measurement
    B (np.array([array[complex]])): Matrix representation of the measured observable
Returns:
    (np.array(float)): List of measurement probabilities, in no particular order.
"""

eigen_projectors =  eigenprojectors(B)# Use a previously defined function to obtain the eigenprojectors

prob_list = np.real(np.trace(np.dot(rho,eigen_projectors)))# Use list comprehension and the relevant formula to find the probabilities

return prob_list

rho = np.array([[3/4,0],[0,1/4]])
B = qml.matrix(qml.PauliY(0))

print(“State: [[3/4,0],[0,1/4]], Observable: {}”.format(B))
print(“Measurement probabilities {}”.format(outcome_probs(rho,B).round(2)))``

2

Hey @SUDHIR_KUMAR_SAHOO,

The problem is with how you’re calculating prob_list. You have to return the trace of rho times each value of the eigenprojectors:

    prob_list = [np.trace(np.dot(rho,elem)) for elem in eigen_projectors]

Let me know if that helps!

3

Yes It helps. Thank you so much.

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