feat: add numeric and symbolic scripts

scripts/party_blocks.py

@@ -0,0 +1,18 @@
+"""party_blocks.py -- extract the raw (unnormalized) single-party-to-single-party 3x3
+correlation blocks M_{a->b} from the Pauli correlation tensor."""
+import numpy as np
+
+
+def party_block(C, a, b):
+    M = np.zeros((3, 3))
+    for i, ia in enumerate([1, 2, 3]):
+        for j, ib in enumerate([1, 2, 3]):
+            idx = [0, 0, 0, 0]
+            idx[a] = ia
+            idx[b] = ib
+            M[i, j] = C[tuple(idx)]
+    return M
+
+
+def nuc(M):
+    return np.linalg.svd(M, compute_uv=False).sum()