(#217) fix qu discord for diag rho

jcmgray · Jan 24, 2024 · 95b4473 · 95b4473
1 parent 71b82c8
commit 95b4473
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Showing 2 changed files with 216 additions and 147 deletions.
diff --git a/quimb/calc.py b/quimb/calc.py
@@ -949,7 +949,14 @@ def gen_paj():
 
 
 @zeroify
-def quantum_discord(p, dims=(2, 2), sysa=0, sysb=1):
+def quantum_discord(
+    p,
+    dims=(2, 2),
+    sysa=0,
+    sysb=1,
+    method="COBYLA",
+    tol=1e-12,
+):
     """Quantum Discord for two qubit density operator.
 
     If ``len(dims) > 2``, then the non-target dimensions will be traced out
@@ -984,7 +991,11 @@ def trial_qd(a):
         return iab - owci((prja, prjb))
 
     opt = minimize(
-        trial_qd, (pi / 2, pi), method="SLSQP", bounds=((0, pi), (0, 2 * pi))
+        trial_qd,
+        (pi / 2, pi),
+        method=method,
+        bounds=((0, pi), (0, 2 * pi)),
+        tol=tol,
     )
     if opt.success:
         return opt.fun