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Fix time dependent integral of TDVP and TDVP2 #279

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Merged
lkdvos merged 3 commits into from
Apr 21, 2025
Merged

Fix time dependent integral of TDVP and TDVP2 #279

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0a9f4b4
try fix
GiggleLiu Apr 20, 2025
c9f7813
try fix
GiggleLiu Apr 20, 2025
239f79d
format documents
GiggleLiu Apr 20, 2025
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9 changes: 5 additions & 4 deletions src/algorithms/timestep/tdvp.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -78,7 +78,7 @@
ψ.AC[i] = integrate(h_ac, ψ.AC[i], t, dt / 2, alg.integrator)

h_c = ∂∂C(i, ψ, H, envs)
ψ.C[i] = integrate(h_c, ψ.C[i], t, -dt / 2, alg.integrator)
ψ.C[i] = integrate(h_c, ψ.C[i], t + dt / 2, -dt / 2, alg.integrator)

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end

# edge case
Expand All @@ -91,7 +91,7 @@
ψ.AC[i] = integrate(h_ac, ψ.AC[i], t + dt / 2, dt / 2, alg.integrator)

h_c = ∂∂C(i - 1, ψ, H, envs)
ψ.C[i - 1] = integrate(h_c, ψ.C[i - 1], t + dt / 2, -dt / 2, alg.integrator)
ψ.C[i - 1] = integrate(h_c, ψ.C[i - 1], t + dt, -dt / 2, alg.integrator)

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end

# edge case
Expand Down Expand Up @@ -148,7 +148,8 @@
ψ.AC[i + 1] = (complex(nc), _transpose_front(nar))

if i != (length(ψ) - 1)
ψ.AC[i + 1] = integrate(∂∂AC(i + 1, ψ, H, envs), ψ.AC[i + 1], t, -dt / 2,
ψ.AC[i + 1] = integrate(∂∂AC(i + 1, ψ, H, envs), ψ.AC[i + 1], t + dt / 2,

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-dt / 2,
alg.integrator)
end
end
Expand All @@ -164,7 +165,7 @@
ψ.AC[i] = (complex(nc), _transpose_front(nar))

if i != 2
ψ.AC[i - 1] = integrate(∂∂AC(i - 1, ψ, H, envs), ψ.AC[i - 1], t + dt / 2,
ψ.AC[i - 1] = integrate(∂∂AC(i - 1, ψ, H, envs), ψ.AC[i - 1], t + dt,

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-dt / 2, alg.integrator)
end
end
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12 changes: 12 additions & 0 deletions test/algorithms.jl
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Expand Up @@ -356,6 +356,18 @@ end
@test E ≈ Et atol = 1e-8
end

Ht2 = MultipliedOperator(H, t -> t < 0 ? error("t < 0!") : 4) +
MultipliedOperator(H, 1.45)
@testset "Finite TimeDependent LazySum (fix negative t issue) $(alg isa TDVP ? "TDVP" : "TDVP2")" for alg in
algs
ψ, envs = timestep(ψ₀, Ht2, 0.0, dt, alg)
E = expectation_value(ψ, Ht2(0.0), envs)

ψt, envst = timestep(ψ₀, Ht2, 0.0, dt, alg)
Et = expectation_value(ψt, Ht2(0.0), envst)
@test E ≈ Et atol = 1e-8
end

H = repeat(force_planar(heisenberg_XXX(; spin=1)), 2)
ψ₀ = InfiniteMPS([ℙ^3, ℙ^3], [ℙ^50, ℙ^50])
E₀ = expectation_value(ψ₀, H)
Expand Down
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