From 56914be36be5d44dadee563a80a25418f7a50fc8 Mon Sep 17 00:00:00 2001
From: Nuwan Yapa <yapanuwan@gmail.com>
Date: Fri, 11 Apr 2025 16:08:02 -0400
Subject: [PATCH] PMM implemented

---
 calculations/PMM.jl | 59 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)
 create mode 100644 calculations/PMM.jl

diff --git a/calculations/PMM.jl b/calculations/PMM.jl
new file mode 100644
index 0000000..32cdcb0
--- /dev/null
+++ b/calculations/PMM.jl
@@ -0,0 +1,59 @@
+using LinearAlgebra, Random, Plots
+include("../p_space.jl")
+
+μ = 0.5
+V_system(c) = (p, q) -> c*(-5*g0(sqrt(3), p, q) + 2*g0(sqrt(10), p, q)) # ResonanceEC: Eq. (20)
+
+training_c = range(1.2, 0.9, 9) # original: range(1.35, 0.9, 5)
+extrapolating_c = range(0.78, 0.45, 7) # original: range(0.75, 0.40, 8)
+
+# calculate training data
+data_c = vcat(training_c, extrapolating_c)
+data_E = [quick_pole_E(V_system(c)) for c in data_c]
+
+# hyperparameters
+N = 9
+
+# initialize random Hamiltonians
+H0 = randn(ComplexF64, N, N)
+#H0 = H0 + H0' # symmetric
+H1 = randn(ComplexF64, N, N)
+#H1 = H1 + H1' # symmetric
+
+# training
+Es = ComplexF64[]
+ψs = Vector{ComplexF64}[]
+
+lr = 0.05
+epochs = 100000
+for epoch in 1:epochs
+    empty!(Es)
+    empty!(ψs)
+    for (c, E) in zip(data_c, data_E)
+        H = H0 + c * H1
+        evals, evecs = eigen(H)
+        i = nearestIndex(evals, E) # TODO: more robust way to identify the eigenvector
+        push!(Es, evals[i])
+        push!(ψs, evecs[:, i])
+    end
+
+    if epoch % 1000 == 0
+        loss = sum(abs2, Es .- data_E)
+        println("Epoch:$epoch/$epochs \t Loss: $loss")
+    end
+
+    # gradient of the loss function
+    function grad(c_order=0)
+        out = zeros(ComplexF64, N, N)
+        for (c, E_target, ψ, E) in zip(data_c, data_E, ψs, Es)
+            out .+= (c^c_order * (E - E_target)) .* (ψ * ψ')
+        end
+        return out
+    end
+    H0 .-= lr .* grad(0) # update H0
+    H1 .-= lr .* grad(1) # update H1    
+end
+
+# plot the results
+scatter(real.(data_E), imag.(data_E), label="Target", title="PMM", xlabel="Re E", ylabel="Im E")
+scatter!(real.(Es), imag.(Es), label="Predicted")