Reference.Variables.time

Variable "time" in MATLAB version of WavePacket

This global, structured(!) variable contains all information about temporal discretization (TDSE or LvNE), external fields, etc ... for time.-dependent calculations using qm_propa or qm_control.

Settable parameters

For a better understanding of the following parameters, note that there are two types of time steps. Main time steps are time intervals after which certain actions are done: expectation values are calculated, and optionally the wave function is plotted and/or saved. Differing from this are sub or propagation time steps. These give the time stepping that is used for actually propagating the wave function forward in time (i.e., it is always propagated from time t to time t + length_of_sub_step).

Note that all of the parameters are ignored when you run a time-independent calculation using qm_bound.

time.main	Sets parameters concerning the main time steps (see text above).
start	Starting time of the propagation in integer units of time.main.delta.
stop	Finishing time of the propagation in integer units of time.main.delta.
delta	Length of one main time step. Setting this to negative values enables backwards propagation (version 4.8.0 and later); however, note that time.main.start and time.main.stop are then given in negative time units.

time.sub	Sets parameters concerning the sub time steps (see text above)
n	Number of sub time steps per main time step

time.propa	Choice and settings for the propagator. Click here for a list of available handles and their parameters.
handle	Function handle of the propagator to use.
params	Additional parameters xxx for the propagator are specified as time.propa.params.xxx.

time.efield	Optional: Specifies the electric field(s) to use. Note that you also need to set a dipole moment (via ''hamilt.dip.handle''), and set all non-optional parameters. Each laser field is given by the expression F(t) = F_0 f(t-τ) cos(ω(t-τ) ⋅ (t - τ) + φ0) with ω(t) = ω0 + α t + (β/2) t2. Click here for a list of available pulse shapes and associated parameters
dressed	Optional: If set to true, sets up the calculation using light-dressed states. Default is false since version 4.8.0. Using dressed states is a bit tricky, and is explained in this manual.
complex	Optional: If set to true, enables complex electric fields (rotating wave approximation). Default is false. This is a bit tricky to use, a bit of a hack, and has some limitations. See this manual for more details.
photons	Optional: Cell array whose ''m''-th element is an array of photon numbers with which to dress the ''m''-th (coupled) channel. This has to be set if ''dressed'' is set to true, otherwise it is ignored.
shape	String that specifies the shape function f(t) of the pulse. If multiple pulses are used, you have to specify each shape as a new row! I.e., write for example ''time.efield.shape = 'inter'; 'inter';'' (note the semicolon!).
ampli	Specifies the maximum amplitude E0 of the pulse(s).
delay	Specifies the delay time(s) τ of the center(s) of the pulse(s).
frequ	Specifies the constant part of the (carrier) frequency ω0 of the pulse(s).
phase	Specifies the phase shift φ0 of the pulse(s).
polar	Gives the polarization angle θ of each pulse. The Hamiltonian for the interaction with the electric field is given as H = - F(t) Dx cos θ - F(t) Dy sin θ, where Dx, Dy are the dipole moments along the first and second degree of freedom as set up by the dipole function ''hamilt.dip.handle''.
linear	Optional: Specifies the linear part α of the chirp. If not set, defaults to zero for every pulse.
quadratic	Optional: Specifies the quadratic part β of the chirp. If not set, defaults to zero for every pulse.

Internal variables

time.main	Sets parameters concerning the main time steps
n	The total number of main time steps.
tot	The total simulation time.
grid	An array of all main time steps.
alpha	The calculated Kosloff alpha number (used in the Chebychev expansion).

time.sub	Sets parameters concerning the sub time steps
delta	The length of a single propagation time step.
alpha	Another variant of the Kosloff alpha number used in the Chebychev expansion.
grid	An array of all propagation time steps.
short	The same as time.sub.grid, but this goes only from the current main time step to the next.

time.acf	Data about the autocorrelation function (ACF)
grid	An array with the ACF at every propagation time step.
short	The same as time.acf.grid, but this only runs from the current main time step to the next.

time.efield	Parameters concerning the electric fields
length	An array whose i-th element gives the real length of the i-th pulse.
grid	This has two fields, grid.x and grid.y, that give the electric field along the first and second degree of freedom at each propagation time step.
short	The same as time.efield.grid, but gives the electric field only from the current to the next main time step.
times	This field only exists if at least one electric field is interpolated from a file. It is a cell array, whose i-th element caches the time points loaded from the data file. If the i-th pulse is not interpolated, the entry is empty.
fields	The same as time.efield.times, but holds the envelope function interpolated from the data file.