LindbladSolver

LindbladSolver(
    system=None,
    t_min=0.0,
    t_max=1.0,
    t_steps=100,
    method='mesolve',
    opts=None,
    savefile=None,
    *,
    atom=None,
)

Time-domain master equation solver for a single spatial point.

Wraps :func:qutip.mesolve to evolve the density matrix of a :class:~clerq.system.System over a user-defined time grid, and can save/load results to avoid recomputation.

Parameters

Name	Type	Description	Default
system	dict | None	Dict (or empty dict for defaults) describing the quantum system; passed to :class:~clerq.system.System.	None
t_min	float	Start time of the simulation.	0.0
t_max	float	End time of the simulation.	1.0
t_steps	int	Number of time steps.	100
method	str	Solver method — 'mesolve' (Lindblad master equation) is the only supported value.	'mesolve'
opts	dict | None	Dict of QuTiP solver options passed to qutip.Options.	None
savefile	str | None	Path prefix for caching solved results ('.qu' extension appended automatically). Pass None to disable caching.	None
atom	dict | None	Deprecated name for system.	None

Attributes

Name	Description
atom	Deprecated name for system.

Methods

Name	Description
build_opts	Build the options dict to be passed into the QuTiP solver.
from_json	Initialise LindbladSolver from JSON file.
from_json_str	Initialise LindbladSolver from JSON string.
obsolve	Deprecated name for :meth:LindbladSolver.solve.
savefile_exists	Returns true if savefile (with appended extension .qu) exists.
set_field_rabi_freq_t_args	Set the Rabi frequency time function arguments. To be used with
set_field_rabi_freq_t_func	Set the Rabi frequency time function of a field to a new time
solve	Solves the Lindblad master equation for the system.

build_opts

LindbladSolver.build_opts(opts=None)

Build the options dict to be passed into the QuTiP solver.

Any option available to the QuTiP solver is available here, we provide defaults for solving the optical Bloch equations. See 0 for details of all the available options.

Notes

• For a stiff problem, it may help to set ‘method’ to ‘bdf’ instead of ‘adams’.
• If the solver times out, try more ‘nsteps’, though this will take longer.
• To speed up the solver, reduce atol and rtol, though this will reduce accuracy.

Warning

There is no validation checking here. If you pass in an option which is not known to QuTiP it will throw an exception.

from_json

LindbladSolver.from_json(file_path)

Initialise LindbladSolver from JSON file.

from_json_str

LindbladSolver.from_json_str(json_str)

Initialise LindbladSolver from JSON string.

obsolve

LindbladSolver.obsolve(*args, **kwargs)

Deprecated name for :meth:LindbladSolver.solve.

savefile_exists

LindbladSolver.savefile_exists()

Returns true if savefile (with appended extension .qu) exists.

set_field_rabi_freq_t_args

LindbladSolver.set_field_rabi_freq_t_args(field_idx, t_args)

Set the Rabi frequency time function arguments. To be used with set_field_rabi_freq_t_func

Parameters

Name	Type	Description	Default
field_idx	int	The field for which to set the Rabi frequency t_args	required
t_args	dict	A dict representing the args to go with the t_func.	required

set_field_rabi_freq_t_func

LindbladSolver.set_field_rabi_freq_t_func(field_idx, t_func)

Set the Rabi frequency time function of a field to a new time function. This is useful when you want to set a custom function, not one available in t_funcs.py

Parameters

Name	Type	Description	Default
field_idx	int	The field for which to set the Rabi frequency t_func	required
t_func	Any	Rabi frequency as a function of time, f(t, args)	required

solve

LindbladSolver.solve(
    e_ops=None,
    opts=None,
    recalc=True,
    show_pbar=False,
    save=True,
)

Solves the Lindblad master equation for the system.

Parameters

Name	Type	Description	Default
e_ops	list | None	Expectation value operators passed to the QuTiP solver.	None
opts	dict | None	QuTiP solver options, overriding those set at initialisation.	None
recalc	bool	Recalculate the solution even if a savefile exists?	True
show_pbar	bool	Show the QuTiP text progress bar.	False
save	bool	Save the result to savefile, if one is set.	True

Returns

Name	Type	Description
	np.ndarray	The solved density matrix at each time, shape
	np.ndarray	(t_steps+1, num_states, num_states).