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%pylab inline
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from qutip import *
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delta = 0.0 * 2 * pi
epsilon = 0.5 * 2 * pi
gamma = 0.25
times = linspace(0, 10, 100)
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H = delta/2 * sigmax() + epsilon/2 * sigmaz()
H
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psi0 = (2 * basis(2, 0) + basis(2, 1)).unit()
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c_ops = [sqrt(gamma) * sigmam()]
a_ops = [sigmax()]
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e_ops = [sigmax(), sigmay(), sigmaz()]
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result_me = mesolve(H, psi0, times, c_ops, e_ops)
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result_brme = brmesolve(H, psi0, times, a_ops, e_ops, spectra_cb=[lambda w : gamma * (w > 0)])
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plot_expectation_values([result_me, result_brme]);
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b = Bloch()
b.add_points(result_me.expect, meth='l')
b.add_points(result_brme.expect, meth='l')
b.make_sphere()
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N = 10
w0 = 1.0 * 2 * pi
g = 0.05 * w0
kappa = 0.15
times = linspace(0, 25, 1000)
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a = destroy(N)
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H = w0 * a.dag() * a + g * (a + a.dag())
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# start in a superposition state
psi0 = ket2dm((basis(N, 4) + basis(N, 2) + basis(N,0)).unit())
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c_ops = [sqrt(kappa) * a]
a_ops = [a + a.dag()]
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e_ops = [a.dag() * a, a + a.dag()]
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result_me = mesolve(H, psi0, times, c_ops, e_ops)
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result_brme = brmesolve(H, psi0, times, a_ops, e_ops, spectra_cb=[lambda w : kappa * (w > 0)])
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plot_expectation_values([result_me, result_brme]);
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times = linspace(0, 25, 250)
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n_th = 1.5
c_ops = [sqrt(kappa * (n_th + 1)) * a, sqrt(kappa * n_th) * a.dag()]
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result_me = mesolve(H, psi0, times, c_ops, e_ops)
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w_th = w0/log(1 + 1/n_th)
def S_w(w):
if w >= 0:
return (n_th + 1) * kappa
else:
return (n_th + 1) * kappa * exp(w / w_th)
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result_brme = brmesolve(H, psi0, times, a_ops, e_ops, [S_w])
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plot_expectation_values([result_me, result_brme]);
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result_me = mesolve(H, psi0, times, c_ops, [])
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result_brme = brmesolve(H, psi0, times, a_ops, [], [S_w])
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n_me = expect(a.dag() * a, result_me.states)
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n_brme = expect(a.dag() * a, result_brme.states)
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fig, ax = plt.subplots()
ax.plot(times, n_me, label='me')
ax.plot(times, n_brme, label='brme')
ax.legend()
ax.set_xlabel("t");
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N = 10
a = tensor(destroy(N), identity(2))
sm = tensor(identity(N), destroy(2))
psi0 = ket2dm(tensor(basis(N, 1), basis(2, 0)))
a_ops = [(a + a.dag())]
e_ops = [a.dag() * a, sm.dag() * sm]
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w0 = 1.0 * 2 * pi
g = 0.05 * 2 * pi
kappa = 0.05
times = linspace(0, 5 * 2 * pi / g, 1000)
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c_ops = [sqrt(kappa) * a]
H = w0 * a.dag() * a + w0 * sm.dag() * sm + g * (a + a.dag()) * (sm + sm.dag())
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result_me = mesolve(H, psi0, times, c_ops, e_ops)
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result_brme = brmesolve(H, psi0, times, a_ops, e_ops, spectra_cb=[lambda w : kappa*(w > 0)])
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plot_expectation_values([result_me, result_brme]);
In the weak coupling regime there is no significant difference between the Lindblad master equation and the Bloch-Redfield master equation.
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w0 = 1.0 * 2 * pi
g = 0.75 * 2 * pi
kappa = 0.05
times = linspace(0, 5 * 2 * pi / g, 1000)
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c_ops = [sqrt(kappa) * a]
H = w0 * a.dag() * a + w0 * sm.dag() * sm + g * (a + a.dag()) * (sm + sm.dag())
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result_me = mesolve(H, psi0, times, c_ops, e_ops)
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result_brme = brmesolve(H, psi0, times, a_ops, e_ops, spectra_cb=[lambda w : kappa*(w > 0)])
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plot_expectation_values([result_me, result_brme]);
In the strong coupling regime there are some corrections to the Lindblad master equation that is due to the fact system eigenstates are hybridized states with both atomic and cavity contributions.
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from qutip.ipynbtools import version_table
version_table()
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