mutual_information.py 2.64 KB
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import numpy as np
import yaml
import time
import matplotlib.pyplot as plt

from create_model import spin_model
from entropy_new import compute_MI, compute_entropy, reduced_dm

def test_mutual_information():
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    # change return in compute_MI to run this function [S_A, S_B, S_AB] instead of S_A + S_B - S_AB
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    model_name = 'xxz'
    number_spins = 10
    periodic = False
    spin_inversion = None
    param = 1.0
    if param < -1.0:
        hamming_weight = None
    else: 
        hamming_weight = number_spins // 2
    model = spin_model(model_name=model_name, number_spins=number_spins, periodic=periodic, 
                            param=param, hamming_weight=hamming_weight ,spin_inversion=spin_inversion)
    model.compute_ew_and_ev()
    print('EIGENSTATE at h/J = ', param, 'is: ', model.eigenstates[:,0])
    sub_dim = 4
    first_trace_spin = 4
    basis_states = model.basis.states
    gs = model.eigenstates[:,0]
    print('Number Spins: ', model.basis.number_spins)
    print('States', model.basis.states)
    print('Sub Dimension is ', sub_dim)
    entropies = compute_MI(sub_dim, number_spins, hamming_weight, gs, basis_states, spin_inversion=None, first_trace_spin=first_trace_spin)
    MI = entropies[0] + entropies[1] - entropies[2]
    print(MI)
    print(entropies)
    print('--------------------Test-----------------------')
    rhos4 = reduced_dm(4, number_spins, hamming_weight, gs, basis_states)
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    rhos6 = reduced_dm(6, number_spins, hamming_weight, gs, basis_states)
    print(compute_entropy(rhos4), compute_entropy(rhos6))

def MI_vs_Entropy():

    model_name = 'xxz'
    dim = 14#[8, 10, 12, 14]#, 16, 18]
    periodic = False
    spin_inversion = None
    params = np.linspace(-1.5, 1.5, 51)

    sub_dim = 4
    first_trace_spin = 4
    MIs = []
    Entropies = []

    print('Number Spins: ', dim)
    print('Sub Dimension is ', sub_dim)
    for param in params:
        if param < -1.0:
            hamming_weight = None
        else: 
            hamming_weight = dim // 2
        model = spin_model(model_name=model_name, number_spins=dim, periodic=periodic, 
                            param=param, hamming_weight=hamming_weight ,spin_inversion=spin_inversion)
        model.compute_ew_and_ev()
        basis_states = model.basis.states
        gs = model.eigenstates[:,0]
        MI = compute_MI(sub_dim, dim, hamming_weight, gs, basis_states, spin_inversion=None, first_trace_spin=first_trace_spin)
        MIs.append(MI)
        rho_half = reduced_dm(dim // 2, dim, hamming_weight, gs, basis_states)
        Entropies.append(compute_entropy(rho_half))
    
    plt.figure()
    plt.plot(params, entropies)
    plt.plot(params, MIs)
    plt.savefig('test.jpg')