Heterodyne_detection

[rubbersou1]

Hello, I am learning quantum stochastic processes. When I try to run codes given in this example https://qojulia.github.io/QuantumCumulants.jl/stable/examples/heterodyne_detection/#, the program reported an error:

when running this part:

I tried to fix this program but couldn't. Here is my julia and packages' versions:

Thanks in advance!

[david-pl]

Huh, that example isn't included in the build of the docs since it's a bit experimental. Not sure what version stuck on the docs page is now showing. Fyi, @ChristophHotter

Regarding your issue: you should be able to fix it by doing

@named sys = SDESystem(eqs_scaled)
sys = complete(sys)

The rest should work the same.

[rubbersou1]

I have tried this code, it reported a new error:

[david-pl]

I had another look and I think the problem comes from this time variable that's defined in the beginning of the example.

@syms t::Real

It's used in the definition of the Hamiltonian, but it's then not passed in explicitly when the equations are derived. That used to work since, by coincidence, it was the exact same definition as the time variable used internally as default when no independent variable was passed into the meanfield function.

The time variable should actually be defined with

@independent_variables t::Real

and then passed into the meanfield function as

eqs = meanfield(ops,H,J; rates = rates, efficiencies = efficiencies, order = 2, iv = t)

Using this, you can get the code to run.

However, please note that the solution here is unstable, i.e. the photon number diverged when I ran the example locally. Not sure how to fix that, there's a reason why this example is not really part of the documentation. @ChristophHotter @Nico0oblr any ideas here?