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Use Styles interface for expectation values #391

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Use Styles interface for expectation values #391

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4308fa2
update expval with styles
AFeuerpfeil Feb 27, 2026
bc3e449
for now there are no styles for environments, so I will not dispatch …
AFeuerpfeil Feb 27, 2026
4e0eebb
format
AFeuerpfeil Feb 27, 2026
edf69a3
fix dispatch ambiguity
AFeuerpfeil Feb 27, 2026
a8d3010
fix
AFeuerpfeil Feb 27, 2026
611a7e4
format
AFeuerpfeil Feb 27, 2026
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24 changes: 17 additions & 7 deletions src/algorithms/expval.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -121,16 +121,20 @@ function contract_mpo_expval2(
τ[3 4; 9 10] * A1[8 1 2; 5] * A2[5 7 13; 14] * O[10 12; 6 7]
end

function expectation_value(ψ::AbstractMPS, H::AbstractMPO, envs...)
return expectation_value(GeometryStyle(ψ, H), OperatorStyle(H), ψ, H, envs...)
end

function expectation_value(
ψ::FiniteMPS, H::FiniteMPOHamiltonian,
envs::AbstractMPSEnvironments = environments(ψ, H)
::FiniteChainStyle, ::HamiltonianStyle,
ψ, H, envs = environments(ψ, H)
)
return dot(ψ, H, ψ, envs) / dot(ψ, ψ)
end

function expectation_value(
ψ::InfiniteMPS, H::InfiniteMPOHamiltonian,
envs::AbstractMPSEnvironments = environments(ψ, H)
::InfiniteChainStyle, ::HamiltonianStyle,
ψ, H, envs = environments(ψ, H)
)
return sum(1:length(ψ)) do site
return contract_mpo_expval(
Expand All @@ -152,13 +156,16 @@ end

# DenseMPO
# --------
function expectation_value(ψ::FiniteMPS, mpo::FiniteMPO)
function expectation_value(::FiniteChainStyle, ::MPOStyle, ψ, mpo)
return dot(ψ, mpo, ψ) / dot(ψ, ψ)
end
function expectation_value(ψ::FiniteQP, mpo::FiniteMPO)
return expectation_value(convert(FiniteMPS, ψ), mpo)
end
function expectation_value(ψ::InfiniteMPS, mpo::InfiniteMPO, envs...)
function expectation_value(
::InfiniteChainStyle, ::MPOStyle,
ψ::InfiniteMPS, mpo::InfiniteMPO, envs...
) # TODO: Discuss style convention for multiline!
return expectation_value(convert(MultilineMPS, ψ), convert(MultilineMPO, mpo), envs...)
end
function expectation_value(
Expand All @@ -176,7 +183,10 @@ function expectation_value(ψ::MultilineMPS, mpo::MultilineMPO, envs...)
return prod(x -> expectation_value(x...), zip(parent(ψ), parent(mpo)))
end
# fallback
function expectation_value(ψ::AbstractMPS, mpo::AbstractMPO, envs...)
function expectation_value(
::GeometryStyle, ::OperatorStyle,
ψ, mpo, envs...
)
return dot(ψ, mpo, ψ) / dot(ψ, ψ)
end

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