Qiskit

Introduction

https://quantum-computing.ibm.com/

https://quantum-computing.ibm.com/challenges/fall-2020

https://quantum-computing.ibm.com/jupyter/user/IBMQuantumChallenge2020/week-1/ex_1a_en.ipynb

Installation

Installation https://qiskit.org/documentation/install.html

conda create -n qiskit python=3
conda activate qiskit
pip install qiskit /////_OR_////// pip install qiskit[visualization]

Did not work using Python 3.9. Instead, downgrade to Python 3.8.3 in your virtual environment.

conda create -n qiskit python=3
conda activate qiskit
conda install python=3.8.3
pip install qiskit ///////_OR_////// pip install qiskit[visualization]

Set up the Spyder IDE https://stackoverflow.com/questions/30170468/how-to-run-spyder-in-virtual-environment#47615445

Setting Up Qiskit

https://qiskit.org/textbook/ch-states/representing-qubit-states.html

from qiskit import QuantumCircuit, execute, Aer

qc = QuantumCircuit(1)  # Create a quantum circuit with one qubit
initial_state = [0,1]   # Define initial_state as |1>
qc.initialize(initial_state, 0) # Apply initialisation operation to the 0th qubit
qc.draw('text')  # Let's view our circuit (text drawing is required for the 'Initialize' gate due to a known bug in qiskit)

backend = Aer.get_backend('statevector_simulator') # Tell Qiskit how to simulate our circuit
result = execute(qc,backend).result() # Do the simulation, returning the result
out_state = result.get_statevector()
print(out_state) # Display the output state vector

from qiskit.visualization import plot_histogram, plot_bloch_vector

qc.measure_all()
qc.draw()
result = execute(qc,backend).result()
counts = result.get_counts()
plot_histogram(counts)

Take superposition as initial state

initial_state = [1/sqrt(2), 1j/sqrt(2)]  # Define state |q>

The Bloch Sphere

from qiskit_textbook.widgets import plot_bloch_vector_spherical
coords = [pi/2,0,1] # [Theta, Phi, Radius]
plot_bloch_vector_spherical(coords) # Bloch Vector with spherical coordinates

Qiskit allows measuring in the Z-basis, only.

Theory

Quantum operations are reversible, thus the reversible computing. That makes some complications to the gate design.

Exercises

Week 1

Week 2

Week 3