- #1
jk22
- 729
- 24
Basically the question is : since the experiments are repeated and results averaged, should not initial and endstates be mixed states ?
So now we should give two density matrices, so how do we average like in the trace formula : ##\langle A\rangle=tr(\rho A)## ?
Is it ##\rho=\sum_i p_i|\phi_i\rangle\langle\phi_i|## with ##p_i=\langle\phi_i\underbrace{|\Psi\rangle\langle\Psi|}_{\rho_{init}?}\phi_i\rangle##
So that now ##\rho_{init}## were the initial density matrix and hence shall be written as one of a mixed state too with now unknow probabilities ?
So now we should give two density matrices, so how do we average like in the trace formula : ##\langle A\rangle=tr(\rho A)## ?
Is it ##\rho=\sum_i p_i|\phi_i\rangle\langle\phi_i|## with ##p_i=\langle\phi_i\underbrace{|\Psi\rangle\langle\Psi|}_{\rho_{init}?}\phi_i\rangle##
So that now ##\rho_{init}## were the initial density matrix and hence shall be written as one of a mixed state too with now unknow probabilities ?