Re: State evolution NOT starting at time t=0

[Paul Menczel]

Hi Khamul,

The tlist that you pass to the solvers defines the time interval for the evolution. That is, if tlist is [t0, ..., tn], then the "initial state" passed to the solvers is the state at time t0 (not at time 0).

If you would like to specify an initial state at time t=0 and are only interested at the expectation values at times given in a tlist, there are (at least) two options. You could either add "0" as the first entry of the tlist, and discard the first expectation values returned by the solver. Or, you could call the solver twice, first to determine the state at time t0 and then again to find those expectation values.

Best,

Paul

On Thursday 4 April 2024 at 00:21:01 UTC+9 Khamul wrote:

Hello,

Forgive me if there is a simple solution to this post or an oversight on my part, but I haven't been able to find anything regarding this problem yet.

If I want to perform evolution of an initial state using the SE or ME solvers, and I supply a tlist starting at time t=0, then all is good (meaning the expectation values of e_ops match the times in tlist). However, if I supply a tlist that does NOT start at time t=0 (e.g. tlist = [1, ..., 10]), then the expectation values seem to be computed starting at t=0 regardless of the initial time value in tlist. In this example, it seems the expectations returned would have been computed at times [0,...,9].

If I am doing something wrong, any help would be very much appreciated. If this is an oversight in the solver code, it seems quite a major problem as many people want to perform numerical simulations for some time range not starting at t=0. In the case it is a solver code oversight, what is the best way to bring this up?

Thank you,

Khamul