Qiskit – Quantum Computing with Python

Quantum Mechanics is about understanding a world that is hard to see, <br> while Quantum Computing is about harnessing that world for computation.

Qiskit is an open-source quantum computing framework that allows you to create, simulate, and run quantum circuits using Python.

---

Installation

1️⃣ Install Python (3.8+)

Check version:

python --version

---

2️⃣ (Optional) Create Virtual Environment

python -m venv qiskit-env

Activate:

Windows

qiskit-env\Scripts\activate

Mac/Linux

source qiskit-env/bin/activate

---

3️⃣ Install Qiskit

pip install qiskit

Verify installation:

python -c "import qiskit; print(qiskit.__version__)"

---

Using Qiskit with Jupyter Notebook

Install Jupyter:

pip install notebook

Start Jupyter:

jupyter notebook

Create a new Python notebook and begin coding.

---

Basic Example: Bell State Circuit

from qiskit import QuantumCircuit
from qiskit_aer import Aer
from qiskit import transpile

# Create a 2-qubit circuit with 2 classical bits
qc = QuantumCircuit(2, 2)

# Apply gates
qc.h(0)
qc.cx(0, 1)

# Measure
qc.measure([0, 1], [0, 1])

print(qc)

# Simulate
simulator = Aer.get_backend('aer_simulator')
compiled = transpile(qc, simulator)
result = simulator.run(compiled).result()

counts = result.get_counts()
print(counts)

Expected Output (approximate):

{'00': ~50%, '11': ~50%}

---

Basic Concepts

Qubit

A quantum bit that can exist in superposition.

Common Gates

Gate	Description
H	Hadamard (superposition)
X	Bit flip
Z	Phase flip
CX	Controlled-NOT
RY	Rotation around Y-axis

Example:

qc.x(0)
qc.z(1)
qc.ry(1.57, 0)

---

Visualizing Circuits

qc.draw('mpl')

Install matplotlib if needed:

pip install matplotlib

---

Statevector Simulation

from qiskit.quantum_info import Statevector

state = Statevector.from_instruction(qc)
print(state)

---

Running on Real Hardware

Install IBM Runtime:

pip install qiskit-ibm-runtime

Authenticate and run jobs using IBM Quantum services.

---

@RajMajhi

📚 Resources

• Official Documentation: https://qiskit.org/documentation/
• Tutorials: https://qiskit.org/learn/