quantum computing python

If you’re keen on delving into quantum computing using Python, you’re at the right place! While many of us don’t have access to an actual quantum computer, simulators are here to save the day. They might not match the performance of a real quantum computer, but they’re perfect for running and testing quantum applications. For this, you have three choices for simulators: PyQu, QuTip, and Qitensor. After a thorough review, we’re zeroing in on QuTip due to its expansive codebase and up-to-date modifications. Notably, PyQu hasn’t seen updates since 2010, and Qitensor has been dormant for a year.

Related course:
Quantum Computing: An Applied Approach

Installation Guide
This tutorial assumes you’re on a Unix machine, but other OS users can also follow along. To install, execute the following commands:

sudo add-apt-repository ppa:jrjohansson/qutip-releases
sudo apt-get update
sudo apt-get install python-qutip

Once installed, initiate Python via command line and input the subsequent commands:

$ python
Python 2.7.6 (default, Mar 22 2014, 22:59:38) 
[GCC 4.8.2] on linux2
>>> from qutip import *
>>> about()

Successful installation will display QuTip details.

Understanding Quantum Data Structures
To accurately simulate quantum systems, it’s essential to use data structures that can encapsulate the properties of quantum operators, ket vectors, and bra vectors. The Qobj data structure serves this purpose well. Here’s an example to illustrate this:

#!/usr/bin/env python
from qutip import *
from scipy import *

r = rand(4, 4)
print Qobj(r)

Executing the above code will provide an output of the quantum object.

If you wish to input custom data, the following approach works:

#!/usr/bin/env python
from qutip import *
from scipy import *

x = array([[1],[2],[3],[4],[5]])
q = Qobj(x)
print q

This will display the quantum object containing the user-provided data.

Engaging with Quantum States and Operators
Quantum systems are multi-state systems. QuTip boasts a variety of predefined states and quantum operators, all of which are detailed here.

Demystifying Qubits and Operators
A Qubit, the quantum version of a classical bit, can exist in a superposition of two states simultaneously, a phenomenon pivotal for quantum computing. Here’s how you can create one:

#!/usr/bin/env python
from qutip import *
from scipy import *

spin = basis(2, 0)
print spin

Following this, you can execute quantum system operators on this qubit:

#!/usr/bin/env python
from qutip import *
from scipy import *

spin = basis(2, 0)
print sigmam() * spin
print sigmap() * spin

Integrating Multiple Qubits
To effectively describe the states of two intertwined qubits, the tensor product of their state vectors is imperative. Here’s a demonstration:

#!/usr/bin/env python
from qutip import *
from scipy import *

q1 = basis(2, 0)
q2 = basis(2,0)

print q1
print q2
print tensor(q1,q2)

Exploring Further
With this foundation in place, you’re all set to develop basic quantum applications. Should you wish to dive deeper and design a truly functional application, it’s advisable to deepen your understanding of quantum computing and explore tutorials like this one on QuTip.

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