Correction in quantum register declaration for composite Gates exampl… (#996)

* Correction in quantum register declaration for composite Gates example. q --> qr.

* Correction in quantum register declaration for composite Gates examples.

Author: Emixem

tutorials/circuits_advanced/1_advanced_circuits.ipynb

@@ -146,12 +146,12 @@
     "# Convert to a gate and stick it into an arbitrary place in the bigger circuit\n",
     "sub_inst = sub_circ.to_instruction()\n",
     "\n",
-    "q = QuantumRegister(3, 'q')\n",
-    "circ = QuantumCircuit(q)\n",
+    "qr = QuantumRegister(3, 'q')\n",
+    "circ = QuantumCircuit(qr)\n",
     "circ.h(qr[0])\n",
     "circ.cx(qr[0], qr[1])\n",
     "circ.cx(qr[1], qr[2])\n",
-    "circ.append(sub_inst, [q[1], q[2]])\n",
+    "circ.append(sub_inst, [qr[1], qr[2]])\n",
     "\n",
     "circ.draw()"
    ]