Merge pull request #170 from BoxiLi/plotting_swap

- Add a minus sign for plotting the swap gate

- Add a border so that SWAP gates are not cropped.

- Remove the unnecessary redefinition of qswap

src/qutip_qip/circuit/circuit.py

@@ -967,7 +967,7 @@ def latex_code(self):
                                 distance = abs(
                                     gate.targets[1] - gate.targets[0]
                                 )
-                                col.append(r" \qswap \qwx[%d] \qw" % distance)
+                                col.append(r" \qswap \qwx[-%d] \qw" % distance)
                                 _swap_processing = True
 
                             elif (
@@ -1171,9 +1171,8 @@ def _to_qasm(self, qasm_out):
 
 
 _latex_template = r"""
-\documentclass{standalone}
+\documentclass[border=3pt]{standalone}
 \usepackage[braket]{qcircuit}
-\renewcommand{\qswap}{*=<0em>{\times}}
 \begin{document}
 \Qcircuit @C=1cm @R=1cm {
 %s}

tests/test_circuit.py

@@ -667,9 +667,8 @@ def test_wstate(self):
                 assert sum(result_cbits[i]) == 1
 
     _latex_template = r"""
-\documentclass{standalone}
+\documentclass[border=3pt]{standalone}
 \usepackage[braket]{qcircuit}
-\renewcommand{\qswap}{*=<0em>{\times}}
 \begin{document}
 \Qcircuit @C=1cm @R=1cm {
 %s}