擅长:python、mysql、java
<p>这是有效的:</p>
<pre><code>import numpy as np
import qutip as qt
N = 2
M = 2
Jp = qt.tensor(qt.qeye(M), qt.jmat(J, '+')) # J+
Jm = qt.tensor(qt.qeye(M), qt.jmat(J, '-')) # J-
# angular momentum
Jx = (Jp + Jm) / 2.0
# initial state
rho0 = qt.tensor(qt.basis(M,0), qt.basis(N+1,N))
R = (1j*0.5*np.pi*Jx).expm() # rotation transform
rho = R * rho0
</code></pre>