Stuck in code book exercise H.5.3

Codebook
1

I have tried to solve this way. I do not know where it went wrong

def ham_close_spins(B, J):
    """Creates the Hamiltonian for two close spins.

    Args:
        B (float): The strength of the field, assumed to point in the z direction.
        J (list[float]): A vector of couplings [J_X, J_Y, J_Z].

    Returns:
        qml.Hamiltonian: The Hamiltonian of the system.
    """
    e = 1.6e-19
    m_e = 9.1e-31
    alpha = B*e/(2*m_e)
    hbar = 1e-34
    ##################
    # YOUR CODE HERE #
    ##################
    coeffs = [-alpha*hbar,-alpha*hbar, hbar*hbar*J[0]/4, hbar*hbar*J[1]/4,hbar*hbar*J[2]/4] # MODIFY THIS
    obs = [qml.PauliZ(0), qml.PauliZ(1), qml.PauliX(0)@qml.PauliX(1), qml.PauliY(0)@qml.PauliY(1), qml.PauliZ(0)@qml.PauliZ(1)] # MODIFY THIS
    return qml.Hamiltonian(coeffs, obs)
2

Hello @SUDHIR_KUMAR_SAHOO

I think you need to multiply alpha in your coeffs by hbar.

Hope this helps!

Alvaro

3

I got it. Thanks @Alvaro_Ballon

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