Practical Guide to Using a Quantum Computer (Based on Materials from the International Quantum Center at CERN, Switzerland) # 6

Abstract This laboratory work presents a practical implementation of the Deutsch–Jozsa algorithm using the Qiskit framework, complemented by the application of artificial intelligence tools such as GPT-based systems to assist in circuit design, debugging, and conceptual analysis. The material is based on educational resources developed by the International Quantum Center at CERN (Switzerland) and aims to bridge theoretical quantum algorithms with executable quantum programs. In Laboratory Work No. 6, participants construct the Deutsch–Jozsa algorithm for n=4n = 4n=4 input qubits within an oracle-based computational model. The circuit includes a quantum register qqq representing the oracle input qubits, an output qubit outoutout, and a classical register ccc for measurement results. The algorithm begins by applying Hadamard (H) gates to all oracle qubits to create a uniform superposition over the input space. The output qubit is prepared using Pauli-X (X) and Hadamard (H) gates to establish the appropriate phase kickback configuration. A visual barrier is introduced in the circuit to clearly separate initialization, oracle evaluation, and interference stages. After the oracle operation, a second layer of Hadamard gates is applied to the input qubits, followed by measurement into classical bits. The resulting measurement pattern allows deterministic distinction between constant and balanced Boolean functions with a single oracle query—demonstrating exponential speedup compared to classical deterministic algorithms. The laboratory exercise emphasizes structured circuit design, oracle modeling, phase interference analysis, and measurement interpretation. Additionally, GPT-based AI tools are used to support code generation, algorithm explanation, and optimization, illustrating how modern artificial intelligence systems can enhance quantum programming workflows. Through simulation and execution on cloud-based quantum hardware, participants gain both theoretical insight and practical experience with one of the foundational quantum algorithms and its implementation in contemporary quantum computing ecosystems.