updating DIRECTORY.md

Author: github-actions

Diff for: DIRECTORY.md

@@ -648,6 +648,8 @@
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_48/sol1.py)
   * Problem 49
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_49/sol1.py)
+  * Problem 51
+    * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_51/sol1.py)
   * Problem 52
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_52/sol1.py)
   * Problem 53
@@ -683,6 +685,7 @@
 
 ## Quantum
   * [Single Qubit Measure](https://github.com/TheAlgorithms/Python/blob/master/quantum/single_qubit_measure.py)
+  * [Single Qubit Not Gate](https://github.com/TheAlgorithms/Python/blob/master/quantum/single_qubit_not_gate.py)
 
 ## Scheduling
   * [First Come First Served](https://github.com/TheAlgorithms/Python/blob/master/scheduling/first_come_first_served.py)