Getting Started with Quantum Programming — Your First Qiskit Circuit

Reading about quantum computing is one thing. Running quantum code is another. Today you’re going to write your first quantum program, run it on a simulator, and understand what every line does. By the end, you’ll have a working Bell state — the “hello world” of quantum computing.

1. Your First Quantum Circuit

Forget theory for a moment. Here’s what quantum programming actually looks like: create qubits, apply gates, measure results. That’s the entire workflow.

pip install qiskit qiskit-aer

from qiskit import QuantumCircuit

qc = QuantumCircuit(2, 2)  # 2 qubits, 2 classical bits
qc.h(0)                     # Hadamard on qubit 0
qc.cx(0, 1)                 # CNOT: control=0, target=1
qc.measure([0, 1], [0, 1])  # Measure both qubits

from qiskit_aer import AerSimulator

sim = AerSimulator()
result = sim.run(qc, shots=1000).result()
print(result.get_counts())
# {'00': 498, '11': 502}

Three steps: create a quantum circuit with qubits, apply gates to manipulate their states, then measure to read the output. The gates do the quantum magic. The measurement gives you classical bits you can work with.

The most important thing to understand: quantum programs aren’t deterministic. You run the same circuit 1,000 times and get a distribution of results. That’s not a bug — it’s the fundamental nature of quantum computing.

2. The Qiskit Ecosystem

Qiskit is IBM’s open-source quantum computing framework. It’s the most widely used quantum SDK, and it’s entirely Python-based. If you know Python, you can write quantum programs today.

You don’t need all of these to start. Install qiskit and qiskit-aer and you have everything needed to build circuits and run them on a local simulator. Add qiskit-ibm-runtime when you’re ready to run on real quantum hardware.

3. Choosing Your Quantum SDK

Qiskit isn’t the only option. Google, Amazon, Microsoft, and others all have quantum development kits. Each has different strengths.

My recommendation for beginners: start with Qiskit. It has the best documentation, the largest community, and free access to real quantum hardware. Once you understand the fundamentals, switching to any other SDK is straightforward — the concepts are the same, only the syntax changes.

4. Understanding Your Results

When you run a quantum circuit, you don’t get a single answer. You get a probability distribution. Here’s what to expect:

from qiskit import QuantumCircuit
from qiskit_aer import AerSimulator

# Create Bell state
qc = QuantumCircuit(2, 2)
qc.h(0)
qc.cx(0, 1)
qc.measure([0, 1], [0, 1])

# Run 1000 times
sim = AerSimulator()
result = sim.run(qc, shots=1000).result()
counts = result.get_counts()
print(counts)
# Output: {'00': 498, '11': 502}

What this means:

• You ran the circuit 1,000 times (“shots”)
• ~500 times you got 00 (both qubits measured 0)
• ~500 times you got 11 (both qubits measured 1)
• You never got 01 or 10 — that’s entanglement in action
• The exact numbers vary each run — that’s quantum randomness

If you run on real hardware instead of a simulator, you’ll also see some 01 and 10 noise. That’s quantum error — the qubits aren’t perfect.

5. Five Circuits to Build Next

Once your Bell state is working, build these to deepen your understanding:

Circuit 1: Random Number Generator

qc = QuantumCircuit(4, 4)
for i in range(4):
    qc.h(i)
qc.measure([0,1,2,3], [0,1,2,3])
# Produces truly random 4-bit numbers

Circuit 2: Three-Qubit GHZ State

qc = QuantumCircuit(3, 3)
qc.h(0)
qc.cx(0, 1)
qc.cx(0, 2)
qc.measure([0,1,2], [0,1,2])
# 50% |000⟩, 50% |111⟩

Circuit 3: Quantum Teleportation

qc = QuantumCircuit(3, 3)
# Prepare state to teleport
qc.rx(1.2, 0)  # Some arbitrary state on qubit 0
# Create entangled pair (qubits 1, 2)
qc.h(1)
qc.cx(1, 2)
# Bell measurement on qubits 0, 1
qc.cx(0, 1)
qc.h(0)
qc.measure([0, 1], [0, 1])
# Corrections on qubit 2 based on measurement
qc.cx(1, 2)
qc.cz(0, 2)
qc.measure(2, 2)

Circuit 4: Deutsch-Jozsa Algorithm — your first quantum algorithm. Determines if a function is constant or balanced in one query.

Circuit 5: Quantum Phase Estimation — the foundation of Shor’s algorithm. This is where you start transitioning from circuits to algorithms.

Build them in order. Run each one. Look at the output distributions. The patterns in the results will teach you more about quantum computing than any textbook.