QisKit: Statevector上的差异/ Vizualization上的无差异

Question

为什么状态向量有差异，而可视化却没有区别？

还有其他的视觉效果来显示这些差异吗？

qiskit: 0.23.3

python: 3.8

circuit-1 + statevector:
q_0: 
[1.+0.j 0.+0.j] ==> +1

circuit-2 + statevector
     ┌───┐┌───┐┌───┐┌───┐┌───┐
q_0: ┤ X ├┤ H ├┤ X ├┤ H ├┤ X ├
     └───┘└───┘└───┘└───┘└───┘
[-1.+0.j -0.-0.j] ==> -1

代码示例

import numpy as np
from qiskit import *
import qiskit.tools.visualization as vis
import matplotlib. pyplot as plt
from qiskit import Aer

circ = QuantumCircuit(1)

circ.x(0)
circ.h(0)
circ.x(0)
circ.h(0)
circ.x(0)

backend = Aer.get_backend('statevector_simulator')
result = execute(circ, backend).result()
statevector = result.get_statevector()

vis.plot_bloch_multivector(statevector)
vis.plot_state_city(statevector)
vis.plot_state_qsphere(statevector)
vis.plot_state_paulivec(statevector)
circ.draw(output='mpl')
print(np.around(statevector,5))
plt.show()

两个状态器的可视化是相等的！！

​

Answer 1

在我看来，这似乎是个bug (我报告了这里)

无论如何，我建议您使用万花筒来可视化状态。它有交互式的图表。下面是您的示例(重构短小)：

from qiskit import QuantumCircuit
from qiskit.quantum_info import Statevector
from kaleidoscope import qsphere

circ = QuantumCircuit(1)

circ.x(0)
circ.h(0)
circ.x(0)
circ.h(0)
circ.x(0)

state = Statevector.from_instruction(circ)
qsphere(state)

​

​

将颜色与另一个示例进行比较：

circ = QuantumCircuit(1)

state = Statevector.from_instruction(circ)
qsphere(state)

​

​

不同的颜色是相位。第一种情况是π。