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我正在尝试最大化一个函数的值，qutip以找到使该函数最大化的迹线等于 1 的厄尔米特半正定矩阵，但 CVXPY 总是返回值 0.0 和一个对角矩阵，我是否必须为求解器做点什么允许矩阵上的复杂值？

我的代码如下：

import numpy as np
from qutip import *
import matplotlib.pyplot as plt
import cvxpy as cp


def Coherence(density_matrix):
    rho = Qobj(density_matrix)
    diag = rho.diag()
    matrix_diag = np.diag(diag)
    rho_diag = Qobj(matrix_diag)
    coherence = entropy_vn(rho_diag, 2) - entropy_vn(rho, 2)
    return coherence

n = 2**7

density_matrix = cp.Variable((n,n), hermitian=True)
constraints = [cp.trace(density_matrix) == 1]

prob = cp.Problem(cp.Maximize(Coherence(density_matrix.value)),constraints)
prob.solve()

# Print result.
print("The optimal value is", prob.value)
print("A solution density matrix is")
print(density_matrix.value)

总是返回这个结果：

The optimal value is -0.0
A solution density matrix is
[[0.0078125+0.j 0.       +0.j 0.       +0.j ... 0.       +0.j
  0.       +0.j 0.       +0.j]
 [0.       +0.j 0.0078125+0.j 0.       +0.j ... 0.       +0.j
  0.       +0.j 0.       +0.j]
 [0.       +0.j 0.       +0.j 0.0078125+0.j ... 0.       +0.j
  0.       +0.j 0.       +0.j]
 ...
 [0.       +0.j 0.       +0.j 0.       +0.j ... 0.0078125+0.j
  0.       +0.j 0.       +0.j]
 [0.       +0.j 0.       +0.j 0.       +0.j ... 0.       +0.j
  0.0078125+0.j 0.       +0.j]
 [0.       +0.j 0.       +0.j 0.       +0.j ... 0.       +0.j
  0.       +0.j 0.0078125+0.j]]
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