Question

IBM Q Experience用户指南中的Bloch sphere example应该在最后显示一个图。当我运行示例时，它不会显示绘图。

我可以内联（以jupyter）绘制电路图和其他图，但是对我来说这是行不通的。

代码（完全从示例页面复制）如下所示。

我的环境是：

Fedora Core 30
  Qiskit 0.8.2
  Matplotlib 3.1.0
  Python 3.7.3
  Conda 4.6.11（conda构建版本：3.17.8）
  jupyter核心：4.5.0
  jupyter-notebook：5.7.8
  qtconsole：未安装
  ipython：7.5.0
  ipykernel：5.1.1
  jupyter客户：5.2.4
  jupyter实验室：未安装
  nbconvert：5.5.0
  ipywidgets：7.4.2
  nbformat：4.4.0
  特质：4.3.2

# quantum_phase_bloch.py
import numpy as np

from qiskit import QuantumCircuit, QuantumRegister, ClassicalRegister, execute, Aer
from qiskit.tools.visualization import plot_bloch_vector

# Define the Quantum and Classical Registers
q = QuantumRegister(1)
c = ClassicalRegister(1)

# Build the circuits
pre = QuantumCircuit(q, c)
pre.h(q)
pre.barrier()

meas_x = QuantumCircuit(q, c)
meas_x.barrier()
meas_x.h(q)
meas_x.measure(q, c)

meas_y = QuantumCircuit(q, c)
meas_y.barrier()
meas_y.s(q).inverse()
meas_y.h(q)
meas_y.measure(q, c)

meas_z = QuantumCircuit(q, c)
meas_z.barrier()
meas_z.measure(q, c)

bloch_vector = ['x', 'y', 'z']
exp_vector = range(0, 21)
circuits = []
for exp_index in exp_vector:
    middle = QuantumCircuit(q, c)
    phase = 2*np.pi*exp_index/(len(exp_vector)-1)
    middle.u1(phase, q)
    circuits.append(pre + middle + meas_x)
    circuits.append(pre + middle + meas_y)
    circuits.append(pre + middle + meas_z)

# Execute the circuit
job = execute(circuits, backend = Aer.get_backend('qasm_simulator'), shots=1024)
result = job.result()

# Plot the result
for exp_index in exp_vector:
    bloch = [0, 0, 0]
    for bloch_index in range(len(bloch_vector)):
        data = result.get_counts(circuits[3*exp_index+bloch_index])
        try:
            p0 = data['0']/1024.0
        except KeyError:
            p0 = 0
        try:
            p1 = data['1']/1024.0
        except KeyError:
            p1 = 0
        bloch[bloch_index] = p0-p1
    plot_bloch_vector(bloch)

Answer 1

ImportanceOfBeingErnest提供的最后一个链接显示了一个解决该问题的函数（它可能不是最好的方法，但是它对我有帮助，所以我在这里为其他人发布了经过修改的代码）。

修改后的代码是：

# quantum_phase_bloch.py
%matplotlib inline
import matplotlib.pyplot as plt

def show_figure(fig):
    # See https://github.com/Qiskit/qiskit-terra/issues/1682
    new_fig = plt.figure()
    new_mngr = new_fig.canvas.manager
    new_mngr.canvas.figure = fig
    fig.set_canvas(new_mngr.canvas)
    plt.show(fig)

import numpy as np

from qiskit import QuantumCircuit, QuantumRegister, ClassicalRegister, execute, Aer
from qiskit.tools.visualization import plot_bloch_vector

# Define the Quantum and Classical Registers
q = QuantumRegister(1)
c = ClassicalRegister(1)

# Build the circuits
pre = QuantumCircuit(q, c)
pre.h(q)
pre.barrier()

meas_x = QuantumCircuit(q, c)
meas_x.barrier()
meas_x.h(q)
meas_x.measure(q, c)

meas_y = QuantumCircuit(q, c)
meas_y.barrier()
meas_y.s(q).inverse()
meas_y.h(q)
meas_y.measure(q, c)

meas_z = QuantumCircuit(q, c)
meas_z.barrier()
meas_z.measure(q, c)

bloch_vector = ['x', 'y', 'z']
exp_vector = range(0, 21)
circuits = []
for exp_index in exp_vector:
    middle = QuantumCircuit(q, c)
    phase = 2*np.pi*exp_index/(len(exp_vector)-1)
    middle.u1(phase, q)
    circuits.append(pre + middle + meas_x)
    circuits.append(pre + middle + meas_y)
    circuits.append(pre + middle + meas_z)

# Execute the circuit
job = execute(circuits, backend = Aer.get_backend('qasm_simulator'), shots=1024)
result = job.result()

# Plot the result
for exp_index in exp_vector:
    bloch = [0, 0, 0]
    phase = 2*np.pi*exp_index/(len(exp_vector)-1)
    phase_deg = phase / (2.0*np.pi) * 360.0
    for bloch_index in range(len(bloch_vector)):
        data = result.get_counts(circuits[3*exp_index+bloch_index])
        try:
            p0 = data['0']/1024.0
        except KeyError:
            p0 = 0
        try:
            p1 = data['1']/1024.0
        except KeyError:
            p1 = 0
        bloch[bloch_index] = p0-p1
    show_figure(plot_bloch_vector(bloch, title='Bloch sphere with phase {:.1f} degrees'.format(phase_deg)))

《 Q Experience用户指南》中的qiskit示例未显示图

1 个答案: