#!/usr/bin/env python
# coding: utf-8

# # Writing a basic quantum program
# 
# In this notebook, you will learn how to write a quantum program in Python on the Quantum Learning Machine.
# 
# 
# In the QLM python framework, a quantum program is contained in a ``Program`` class. It comes with methods to allocate quantum and classical registers, apply gates, measures and resets. A given instance of a ``Program`` can then be converted to a quantum ``Circuit``, which is the object that can be fed to a quantum processor.
# 
# ### Initializaton of a Quantum Program
# 
# In the following snippet, we instantiate a quantum program object called ``prog``:

# In[ ]:


from qat.lang.AQASM import Program

prog = Program()


# ### Quantum bit allocation
# 
# The allocation of quantum bits is done via the ``qalloc`` method. It returns a register, which will then be used to refer to the qubits.
# 
# In the following snippet, we allocated an 8-qubit register:

# In[ ]:


qbits = prog.qalloc(8)


# ### Applying quantum gates
# 
# The application of quantum gates is carried out through the ``apply`` method.
# 
# Here, we apply standard Hadamard gate on qbit 0, a Pauli X gate on qubit 1, a CNOT gate on qubits 1 and 5, and a phase gate with angle $\pi/6$ to qubit 5.

# In[ ]:


from qat.lang.AQASM import H, X, CNOT, PH
from math import pi

prog.apply(H, qbits[0])
prog.apply(X, qbits[1])
prog.apply(CNOT, qbits[1], qbits[5])
prog.apply(PH(pi/6), qbits[5])


# ### Generation of a quantum circuit
# 
# Before we describe other common operations such as measurements, let us introduce the final step that allows to generate a quantum-simulation-ready quantum circuit out of the quantum program. 
# 
# This generation is done via the ``to_circ`` method: 

# In[ ]:


circ = prog.to_circ()


# ### Circuit display
# The ``.display`` method outputs a graphical representation of the quantum circuit:

# In[ ]:


circ.display()


# For a more comprehensive reference on the Python AQASM library, including **measures, classical control, custom gates, etc.**, check out [this tutorial](py_aqasm.ipynb).
# You will find a list of all available gates [here](available_gates.ipynb).

# In[ ]: