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Support autodiff for SteadyStateODESolver #538

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e7c12f6
support autodiff for `SteadyStateODESolver`
ytdHuang Sep 2, 2025
d1b186a
fix typo
ytdHuang Sep 2, 2025
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5 changes: 3 additions & 2 deletions src/steadystate.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -214,15 +214,16 @@ end
function _steadystate(L::AbstractQuantumObject{SuperOperator}, solver::SteadyStateODESolver; kwargs...)
ψ0 = isnothing(solver.ψ0) ? rand_ket(L.dimensions) : solver.ψ0
ftype = _float_type(ψ0)
tlist = [ftype(0), ftype(solver.tmax)]
tmax = ftype(solver.tmax)
tlist = [ftype(0), tmax]

# overwrite some kwargs and throw warning message to tell the users that we are ignoring these settings
haskey(kwargs, :progress_bar) && @warn "Ignore keyword argument 'progress_bar' for SteadyStateODESolver"
haskey(kwargs, :save_everystep) && @warn "Ignore keyword argument 'save_everystep' for SteadyStateODESolver"
haskey(kwargs, :saveat) && @warn "Ignore keyword argument 'saveat' for SteadyStateODESolver"
kwargs2 = merge(
NamedTuple(kwargs), # we convert to NamedTuple just in case if kwargs is empty
(progress_bar = Val(false), save_everystep = false, saveat = ftype[]),
(progress_bar = Val(false), save_everystep = false, saveat = ftype[tmax]),
)

# add terminate condition (callback)
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15 changes: 15 additions & 0 deletions test/ext-test/cpu/autodiff/autodiff.jl
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Expand Up @@ -67,6 +67,17 @@ function my_f_mesolve(p)
return real(expect(a' * a, sol.states[end]))
end

function my_f_steadystate(p)
ρss = steadystate(
L;
solver = SteadyStateODESolver(ψ0 = ψ0_mesolve, tmax = tlist_mesolve[end]),
params = p,
sensealg = BacksolveAdjoint(autojacvec = EnzymeVJP()),
)

return real(expect(a' * a, ρss))
end

# Analytical solution
n_ss(Δ, F, γ) = abs2(F / (Δ + 1im * γ / 2))

Expand Down Expand Up @@ -113,8 +124,12 @@ n_ss(Δ, F, γ) = abs2(F / (Δ + 1im * γ / 2))

my_f_mesolve_direct(params)
my_f_mesolve(params)
my_f_steadystate(params)

# calculate exact solution and check if steadystate works
grad_exact = Zygote.gradient((p) -> n_ss(p[1], p[2], p[3]), params)[1]
grad_ss = Zygote.gradient(my_f_steadystate, params)[1]
@test grad_ss ≈ grad_exact atol=1e-5

@testset "ForwardDiff.jl" begin
grad_qt = ForwardDiff.gradient(my_f_mesolve_direct, params)
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