From e912506375f7feee84ad13e8082b601c446c32d8 Mon Sep 17 00:00:00 2001
From: Daniel Tsvetkov <danieltcv@gmail.com>
Date: Wed, 4 Dec 2019 17:26:41 +0100
Subject: [PATCH] some docs

---
 lib_q_computer.py | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/lib_q_computer.py b/lib_q_computer.py
index 21e9ac3..0085040 100644
--- a/lib_q_computer.py
+++ b/lib_q_computer.py
@@ -1,5 +1,6 @@
 import numpy as np
 
+# Raw matrixes to be used for initialization of qubits and gates
 __0 = [[1],
        [0]]
 
@@ -40,10 +41,21 @@ _CNOT = [
 
 
 class State(object):
+    """Represents a quantum state"""
     def __init__(self, matrix_state):
+        """
+        Can be initialized with a matrix, e.g. for |0> this is [[0],[1]]
+        :param matrix_state: a matrix representing the quantum state
+        """
         self.matrix_state = np.array(matrix_state)
 
     def __getitem__(self, item):
+        """
+        Kind of hacky way to store a substate of an item for use in Gate operations
+        so that one can use state[0] and the encompassing operator can access this.
+        :param item:
+        :return:
+        """
         if item >= len(self):
             raise IndexError
         self.item = item
@@ -70,9 +82,11 @@ def kron(_list):
 class Gate(State):
     def on(self, state):
         """
-        Applies
-        :param state: another state (e.g. H(q1) or a list of states (e.g. for CNOT([q1, q2]))
-        :return:
+        Applies a gate operation on a state.
+        If applying to a substate, use the index of the substate, e.g. `H.on(bell[0])` will apply the Hadamard gate
+        on the 0th qubit of the `bell` state.
+        :param state: another state (e.g. `H.on(q1)` or a list of states (e.g. for `CNOT.on([q1, q2])`)
+        :return: the state after the application of the Gate
         """
         this_state = self.matrix_state
         if type(state) == list:
@@ -81,7 +95,8 @@ class Gate(State):
             other_state = state.matrix_state
         if this_state.shape[1] != other_state.shape[0]:
             # The two arrays are different sizes
-            # Use the Kronicker product of Identity with the state.item
+            # Use the Kronicker product of Identity with the state.item where
+            # state.item is the substate
             larger_side = max(this_state.shape[1], this_state.shape[0])
             _list = [this_state if i == state.item else _I for i in range(larger_side)]
             this_state = kron(_list)