How To Create Quantum Circuits With Qiskit

Solution to Question 1 and 2 of the ongoing Quantum programming challenge

Hey everyone!

Last week, I published a challenge with 6 Qiskit questions to get started with Quantum Computing.

Here are the solutions to the first two questions from the challenge.

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Question 1

Create a 1-qubit quantum circuit that:

1. Starts in the state |0>

2. Applies a Hadamard gate

3. Measures the qubit

Write the Qiskit code and simulate the circuit using a Qiskit simulator.

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Solution 1

We start by installing Qiskit and the Qiskit Aer library.

Qiskit Aer is a high-performance library with realistic noise models to run quantum computing simulations on classical computers.

!uv pip install qiskit qiskit-aer 

If you’re interested in running the following code on a real quantum computer, refer to the following article.

A Practical Guide To Running Your First Program On An IBM Quantum Computer

Next, we import the necessary packages.

from qiskit import QuantumCircuit # To create and manipulate quantum circuits

from qiskit_aer import Aer # Qiskit simulator backend 

from qiskit.visualization import plot_histogram # To visualise measurement results 

We then create the quantum circuit using QuantumCircuit(1, 1) where the:

• First 1 represents one qubit. This qubit is in state |0>.

• Second 1 represents one classical bit used to store the measurement result.

# Create circuit 
circuit = QuantumCircuit(1, 1) 

Next, we apply the Hadamard gate to the qubit and then measure it.

# Apply Hadamard gate to qubit at index 0
circuit.h(0) 

# Measure qubit at index 0 and store in classical bit at index 0
circuit.measure(0, 0)