Adding operator support to time evolution problem #606

Gavin-Rockwood · 2025-12-01T05:49:16Z

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Description

Updated TimeEvolutionProblem be parametrically typed using the type of the starting state as well as expanded sesolve, mesolve and mcsolve to allow them to take in operators, superoperators and operators respectively (along with other changes to facilitate this). ssesolve and smesolve are still in progress.

Related issues or PRs

Working on #521

…nsions for examples.

…ions for usage.

…onProblem

…ense.

.gitignore

ytdHuang · 2025-12-01T17:54:19Z

src/time_evolution/time_evolution.jl

    For a given `prob::TimeEvolutionProblem`, `prob.dims` or `getproperty(prob, :dims)` returns its `dimensions` in the type of integer-vector.
 """
-struct TimeEvolutionProblem{PT<:AbstractSciMLProblem,TT<:AbstractVector,DT<:AbstractDimensions,KWT}
+struct TimeEvolutionProblem{ST,PT<:AbstractSciMLProblem,TT<:AbstractVector,DT<:AbstractDimensions,KWT}


How about

Suggested change

struct TimeEvolutionProblem{ST,PT<:AbstractSciMLProblem,TT<:AbstractVector,DT<:AbstractDimensions,KWT}

struct TimeEvolutionProblem{ST<:QuantumObjectType,DT<:AbstractDimensions,PT<:AbstractSciMLProblem,TT<:AbstractVector,KWT}

cause I think the type of state_type and dimensions will be used more frequently.

By the way, can you also add state_type to the docstring ?

src/time_evolution/mcsolve.jl

ytdHuang · 2025-12-01T18:01:21Z

src/time_evolution/mesolve.jl

+        ρt = map(ϕ -> QuantumObject(vec2mat(ϕ), type = X(), dims = prob.dimensions), sol.u)
    else
-        ρt = map(ϕ -> QuantumObject(vec2mat(ϕ), type = Operator(), dims = dimensions), sol.u)
+        ρt = map(ϕ -> QuantumObject(ϕ, type = X(), dims = prob.dimensions), sol.u)


same here, just use prob.states_type

Suggested change

ρt = map(ϕ -> QuantumObject(ϕ, type = X(), dims = prob.dimensions), sol.u)

ρt = map(ϕ -> QuantumObject(ϕ, type = prob.states_type, dims = prob.dimensions), sol.u)

ytdHuang · 2025-12-01T18:05:51Z

src/time_evolution/mesolve.jl

+        state_type = SuperOperator()
    else
-        to_dense(_complex_float_type(T), mat2vec(ket2dm(ψ0).data))
+        throw(ArgumentError("Unsupported state type for ψ0 in mesolveProblem."))


This is redundant cause there is no method for other state type (as you defined above).

ytdHuang · 2025-12-01T18:06:19Z

src/time_evolution/mesolve.jl

    prob = ODEProblem{getVal(inplace),FullSpecialize}(L, ρ0, tspan, params; kwargs4...)

-    return TimeEvolutionProblem(prob, tlist, L_evo.dimensions, (isoperket = Val(isoperket(ψ0)),))
+    return TimeEvolutionProblem(prob, tlist, state_type, L_evo.dimensions)#, (isoperket = Val(isoperket(ψ0)),))


can remove the comment directly

ytdHuang · 2025-12-01T18:06:32Z

src/time_evolution/mesolve.jl

    sol = solve(prob.prob, alg; kwargs...)

-    return _gen_mesolve_solution(sol, prob.times, prob.dimensions, prob.kwargs.isoperket)
+    return _gen_mesolve_solution(sol, prob)#, prob.kwargs.isoperket)


can remove the comment directly

ytdHuang · 2025-12-01T18:06:59Z

src/time_evolution/mesolve.jl

+            to_dense(_complex_float_type(T), copy(state.data))
        else
-            to_dense(T, mat2vec(ket2dm(state).data))
+            throw(ArgumentError("Unsupported state type for ψ0 in mesolveProblem."))


same, this is redundant

ytdHuang · 2025-12-01T18:09:55Z

src/time_evolution/mcsolve.jl

 function mcsolveProblem(
    H::Union{AbstractQuantumObject{Operator},Tuple},
-    ψ0::QuantumObject{Ket},
+    ψ0::QuantumObject{X},


We seldom use X here in Julia. Usually will be T or ST to represent (State) Type.

Can you also change it for the other places ?

…onProblem

…ussed in the PR comments.

ytdHuang · 2025-12-04T14:45:42Z

src/time_evolution/mcsolve.jl

    jump_callback::TJC = ContinuousLindbladJumpCallback(),
    kwargs...,
-) where {TJC<:LindbladJumpCallbackType}
+) where {TJC<:LindbladJumpCallbackType,ST<:Union{Ket,Operator}}


Suggested change

) where {TJC<:LindbladJumpCallbackType,ST<:Union{Ket,Operator}}

) where {ST<:Union{Ket,Operator},TJC<:LindbladJumpCallbackType}

ytdHuang · 2025-12-04T14:46:00Z

src/time_evolution/mcsolve.jl

    output_func::Union{Tuple,Nothing} = nothing,
    kwargs...,
-) where {TJC<:LindbladJumpCallbackType}
+) where {TJC<:LindbladJumpCallbackType,ST<:Union{Ket,Operator}}


Suggested change

) where {TJC<:LindbladJumpCallbackType,ST<:Union{Ket,Operator}}

) where {ST<:Union{Ket,Operator},TJC<:LindbladJumpCallbackType}

ytdHuang · 2025-12-04T14:47:02Z

src/time_evolution/mcsolve.jl

    ensemble_prob = TimeEvolutionProblem(
        EnsembleProblem(prob_mc.prob, prob_func = _prob_func, output_func = _output_func[1], safetycopy = false),
        prob_mc.times,
+        ST(),


Suggested change

ST(),

ψ0.type,

This was replaced with prob_mc.states_type.

ytdHuang · 2025-12-04T14:47:19Z

src/time_evolution/mcsolve.jl

    normalize_states::Union{Val,Bool} = Val(true),
    kwargs...,
-) where {TJC<:LindbladJumpCallbackType}
+) where {TJC<:LindbladJumpCallbackType} where {ST<:Union{Ket,Operator}}


Suggested change

) where {TJC<:LindbladJumpCallbackType} where {ST<:Union{Ket,Operator}}

) where {ST<:Union{Ket,Operator},TJC<:LindbladJumpCallbackType}

ytdHuang · 2025-12-04T14:50:55Z

src/time_evolution/mesolve.jl

    ens_prob = TimeEvolutionProblem(
        EnsembleProblem(prob.prob, prob_func = _prob_func, output_func = _output_func[1], safetycopy = false),
        prob.times,
+        StateOpType(),


Suggested change

StateOpType(),

prob.state_type,

ytdHuang · 2025-12-04T14:51:31Z

src/time_evolution/sesolve.jl

    prob = ODEProblem{getVal(inplace),FullSpecialize}(U, ψ0, tspan, params; kwargs4...)

-    return TimeEvolutionProblem(prob, tlist, H_evo.dimensions)
+    return TimeEvolutionProblem(prob, tlist, ST(), H_evo.dimensions)


Suggested change

return TimeEvolutionProblem(prob, tlist, ST(), H_evo.dimensions)

return TimeEvolutionProblem(prob, tlist, ψ0.type, H_evo.dimensions)

This is needed because psi0 gets overwritten in line 82 and is no longer a quantum object in line 93. I can leave like this or I can put a line states_type = ѱ0.data somewhere before 82.

Edit: actually that is exactly what I did for mesolve so I will do the same for sesolve and elsewhere.

ytdHuang · 2025-12-04T14:53:02Z

src/time_evolution/smesolve.jl

    )

-    return TimeEvolutionProblem(prob, tlist, dims, (isoperket = Val(isoperket(ψ0)),))
+    return TimeEvolutionProblem(prob, tlist,StateOpType(), dims, ())


Suggested change

return TimeEvolutionProblem(prob, tlist,StateOpType(), dims, ())

return TimeEvolutionProblem(prob, tlist,ψ0.type, dims)

Similar to mesolve, I introduced a states_type variable that is defined during the definition of $\rho 0$.

ytdHuang · 2025-12-04T14:54:00Z

src/time_evolution/smesolve.jl

    ensemble_prob = TimeEvolutionProblem(
        EnsembleProblem(prob_sme, prob_func = _prob_func, output_func = _output_func[1], safetycopy = true),
        prob_sme.times,
+        StateOpType(),


Suggested change

StateOpType(),

ψ0.type,

this was replaced with prob_sme.states_type.

ytdHuang · 2025-12-04T14:54:43Z

src/time_evolution/ssesolve.jl

    )

-    return TimeEvolutionProblem(prob, tlist, dims)
+    return TimeEvolutionProblem(prob, tlist, ST(), dims)


Suggested change

return TimeEvolutionProblem(prob, tlist, ST(), dims)

return TimeEvolutionProblem(prob, tlist, ψ0.type, dims)

Similar to sesolve, this got updated to a states_type variable defined near the top of the function.

ytdHuang · 2025-12-04T14:56:00Z

src/time_evolution/ssesolve.jl

    ensemble_prob = TimeEvolutionProblem(
        EnsembleProblem(prob_sme, prob_func = _prob_func, output_func = _output_func[1], safetycopy = true),
        prob_sme.times,
+        ST(),


Suggested change

ST(),

ψ0.type,

This became prob_sme.times. (actually prob_sse, I changed it to be consistent). Though, as of right now, the only type ssesolve will take is just Ket. The there is some issue with how the problem is defined that makes it so it cannot take in matrices. Same also didn't update smesolve for the same reason.

Gavin-Rockwood added 5 commits November 30, 2025 22:25

made most of the changes. Look at testing.ipynb ##Testing Solver Exte…

571abc9

…nsions for examples.

Added operator support. Look at testing.ipynb ##Testing Solver Extens…

9665194

…ions for usage.

Merge branch 'qutip:main' into Adding-Operator-Support-to-TimeEvoluti…

0e6036a

…onProblem

updated testing.ipynb

01baa16

added to_dense call to sesolve_map to ensure all initial states are d…

e575f7d

…ense.

ytdHuang reviewed Dec 1, 2025

View reviewed changes

Gavin-Rockwood added 4 commits December 2, 2025 18:40

fixed .gitignore and removed testing.ipynb

71842a7

Merge branch 'qutip:main' into Adding-Operator-Support-to-TimeEvoluti…

41e8216

…onProblem

Updated the state type variable to ST and made the other changes disc…

5a354fe

…ussed in the PR comments.

fixed a bug with smesolve!

d8d26a3

ytdHuang reviewed Dec 4, 2025

View reviewed changes

	struct TimeEvolutionProblem{ST,PT<:AbstractSciMLProblem,TT<:AbstractVector,DT<:AbstractDimensions,KWT}
	struct TimeEvolutionProblem{ST<:QuantumObjectType,DT<:AbstractDimensions,PT<:AbstractSciMLProblem,TT<:AbstractVector,KWT}

	ρt = map(ϕ -> QuantumObject(ϕ, type = X(), dims = prob.dimensions), sol.u)
	ρt = map(ϕ -> QuantumObject(ϕ, type = prob.states_type, dims = prob.dimensions), sol.u)

	) where {TJC<:LindbladJumpCallbackType,ST<:Union{Ket,Operator}}
	) where {ST<:Union{Ket,Operator},TJC<:LindbladJumpCallbackType}

	) where {TJC<:LindbladJumpCallbackType} where {ST<:Union{Ket,Operator}}
	) where {ST<:Union{Ket,Operator},TJC<:LindbladJumpCallbackType}

	return TimeEvolutionProblem(prob, tlist, ST(), H_evo.dimensions)
	return TimeEvolutionProblem(prob, tlist, ψ0.type, H_evo.dimensions)

Adding operator support to time evolution problem #606

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Gavin-Rockwood commented Dec 1, 2025 •

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