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  • Committer: Paul Nation
  • Date: 2011-04-21 04:46:56 UTC
  • Revision ID: git-v1:dd4c966b490aa468dfbd28cef66694df4bf235c8

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qutip/probss.py
 
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#This file is part of QuTIP.
 
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#
 
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#    QuTIP is free software: you can redistribute it and/or modify
 
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#    it under the terms of the GNU General Public License as published by
 
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#    the Free Software Foundation, either version 3 of the License, or
 
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#   (at your option) any later version.
 
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#
 
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#    QuTIP is distributed in the hope that it will be useful,
 
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#    but WITHOUT ANY WARRANTY; without even the implied warranty of
 
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#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 
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#    GNU General Public License for more details.
 
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#
 
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#    You should have received a copy of the GNU General Public License
 
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#    along with QuTIP.  If not, see <http://www.gnu.org/licenses/>.
 
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#
 
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# Copyright (C) 2011, Paul D. Nation & Robert J. Johansson
 
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#
 
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###########################################################################
 
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from qobj import *
 
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from tensor import *
 
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from spre import *
 
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from spost import *
 
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from steady import *
 
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from operators import *
 
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from expect import *
 
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def probss(E,kappa,gamma,g,wc,w0,wl,N):
 
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        ida=qeye(N)
 
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        idatom=qeye(2)
 
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        a=tensor(destroy(N),idatom)
 
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        sm=tensor(ida,sigmam())
 
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        #Hamiltonian
 
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        H=(w0-wl)*sm.dag()*sm+(wc-wl)*a.dag()*a+1j*g*(a.dag()*sm-sm.dag()*a)+E*(a.dag()+a)
 
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        #Collapse operators
 
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        C1=sqrt(2*kappa)*a
 
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        C2=sqrt(gamma)*sm
 
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        C1dC1=C1.dag()*C1
 
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        C2dC2=C2.dag()*C2
 
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        #Liouvillian
 
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        LH=-1j*(spre(H)-spost(H))
 
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        L1=spre(C1)*spost(C1.dag())-0.5*spre(C1dC1)-0.5*spost(C1dC1)
 
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        L2=spre(C2)*spost(C2.dag())-0.5*spre(C2dC2)-0.5*spost(C2dC2)
 
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        L=LH+L1+L2
 
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        #find steady state
 
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        rhoss=steady(L)
 
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        #calculate expectation values
 
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        count1=expect(C1dC1,rhoss)
 
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        count2=expect(C2dC2,rhoss)
 
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        infield=expect(a,rhoss)
 
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        return count1,count2,infield
 
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