changed reference order

XanaduAI · May 11, 2018 · c9392a4 · c9392a4
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diff --git a/doc/references.bib b/doc/references.bib
@@ -738,19 +738,6 @@ @article{gianfranco2016b
 
 % further reading
 
-@article{FR-adesso2014,
-  doi = {10.1142/s1230161214400010},
-  year  = {2014},
-  month = {Jun},
-  publisher = {World Scientific Pub Co Pte Lt},
-  volume = {21},
-  number = {01n02},
-  pages = {1440001},
-  author = {Gerardo Adesso and Sammy Ragy and Antony R. Lee},
-  title = {Continuous Variable Quantum Information: Gaussian States and Beyond},
-  journal = {Open Systems {\&} Information Dynamics}
-}
-
 @article{FR-weedbrook2012,
   doi = {10.1103/revmodphys.84.621},
   archivePrefix = "arXiv",
@@ -766,6 +753,19 @@ @article{FR-weedbrook2012
   journal = {Reviews of Modern Physics}
 }
 
+@article{FR-adesso2014,
+  doi = {10.1142/s1230161214400010},
+  year  = {2014},
+  month = {Jun},
+  publisher = {World Scientific Pub Co Pte Lt},
+  volume = {21},
+  number = {01n02},
+  pages = {1440001},
+  author = {Gerardo Adesso and Sammy Ragy and Antony R. Lee},
+  title = {Continuous Variable Quantum Information: Gaussian States and Beyond},
+  journal = {Open Systems {\&} Information Dynamics}
+}
+
 @book{FR-serafini2017,
   title={Quantum Continuous Variables: A Primer of Theoretical Methods},
   author={Serafini, Alessio},

diff --git a/strawberryfields/ops.py b/strawberryfields/ops.py
@@ -1467,32 +1467,52 @@ def __init__(self, S, hbar=None, vacuum=False):
             else:
                 self.hbar = hbar
 
-        O1, smat, O2 = bloch_messiah(S, tol=10)
         N = S.shape[0]//2
 
-        X1 = O1[:N, :N]
-        P1 = O1[N:, :N]
-        X2 = O2[:N, :N]
-        P2 = O2[N:, :N]
+        # check if input symplectic is passive (orthogonal)
+        diffn = np.linalg.norm(S @ S.T - np.identity(2*N))
+
+        if np.round(diffn, 11) == 0.0:
+            # The transformation is passive, do Clements
+            self.active = False
+            X1 = S[:N, :N]
+            P1 = S[N:, :N]
+            self.U1 = X1+1j*P1
+        else:
+            # transformation is active, do Bloch-Messiah
+            self.active = True
+            O1, smat, O2 = bloch_messiah(S, tol=10)
+            N = S.shape[0]//2
+
+            X1 = O1[:N, :N]
+            P1 = O1[N:, :N]
+            X2 = O2[:N, :N]
+            P2 = O2[N:, :N]
+
+            self.U1 = X1+1j*P1
+            self.U2 = X2+1j*P2
+            self.Sq = np.diagonal(smat)[:N]
 
-        self.U1 = X1+1j*P1
-        self.U2 = X2+1j*P2
-        self.Sq = np.diagonal(smat)[:N]
         self.ns = N
         self.vacuum = vacuum
 
     def decompose(self, reg):
         cmds = []
-        if not self.vacuum:
-            cmds = [Command(Interferometer(self.U2), reg, decomp=True)]
 
-        for n, expr in enumerate(self.Sq):
-            if np.abs(np.round(expr, 13)) != 1.0:
-                r = abs(log(expr))
-                phi = np.angle(log(expr))
-                cmds.append(Command(Sgate(-r, phi), reg[n], decomp=True))
+        if self.active:
+            if not self.vacuum:
+                cmds = [Command(Interferometer(self.U2), reg, decomp=True)]
 
-        cmds.append(Command(Interferometer(self.U1), reg, decomp=True))
+            for n, expr in enumerate(self.Sq):
+                if np.abs(np.round(expr, 13)) != 1.0:
+                    r = abs(log(expr))
+                    phi = np.angle(log(expr))
+                    cmds.append(Command(Sgate(-r, phi), reg[n], decomp=True))
+
+            cmds.append(Command(Interferometer(self.U1), reg, decomp=True))
+        else:
+            if not self.vacuum:
+                cmds = [Command(Interferometer(self.U1), reg, decomp=True)]
 
         return cmds