QUANTUM COMMUNICATIONS AND NETWORKS: After successful completion of the course, the student should have a good understanding of the physics and engineering behind the high-fidelity transmission of individual and entangled photonic quantum systems over a communication channel. The student should be able to give an overview of quantum communication systems, both from theoretical and experimental aspects, with a focus on quantum key distribution (QKD) and quantum networks. This means that the student is expected to be able to: • Define basic concepts in optical communication systems and networks. • Explain how information encoding is done at the single-photon level and the different degrees-of-freedom employed. • Define basic concepts in quantum key distribution. • Define entanglement-based quantum cryptography, the concept of device-independence • and similar protocols. • Analyze the security models of quantum key distribution systems and related attacks. • Design and analyze the performance of a QKD link using two or more different protocols (with and without coexistence with classical signals over the same fiber) • Describe other entanglement-based techniques such as quantum repeaters, entanglement swapping and quantum teleportation. • Approach the design of a quantum network for QKD or quantum computing applications. QUANTUM CRYPTOGRAPHY: Expected knowledge: basic knowledge of steganography, cryptography, cryptoanalysis. How to use quantum phenomena for coding, and how a classical system can resist to a quantum attack. Expected competence and skills: Basic coding and cryptoanalysis. Use of simple classical and quantum protocols. Ability to follow the continuous progresses in the field, both at a theoretical and at a practical level.

QUANTUM COMMUNICATIONS AND NETWORKS: Linear algebra, fundamentals of quantum mechanics. QUANTUM CRYPTOGRAPHY: Elementary algebra, finite-dimensional linear algebra, basics of quantum mechanics (superposition principle), binary system, basic logical gates (And, or, not, nand, xor).

QUANTUM COMMUNICATIONS AND NETWORKS: Classroom lessons will cover the following topics (CFUs are indicative, and variations are possible): • Introduction to optical communication systems and networks (1.5 CFU) • Introduction to classical and quantum information theory and error correction (1 CFU) • Quantum key distribution (QKD) communication systems and protocols (DV-QKD, CV-QKD, MDI-QKD) (2 CFU) • Coexistence of quantum and classical communication links over the same fiber (0.5 CFU) • Introduction to quantum networks and their applications (QKD networks, entanglement distribution, teleportation, etc.) (1 CFU) QUANTUM CRYPTOGRAPHY: Historical ciphers: Cesare, Vigenere, One Time Pad, Hill. Cryptanalysis of classical ciphers. Modular algebra. Kerchoffs principle. Security and attacks of classic ciphers. Block Ciphers and Stream ciphers. Basics of Galois theory. Public Key Cryptography: RSA, Rabin, ElGamal, elliptic curves cryptography. Diffie-Hellman key exchange. Main cryptographic protocols: authentication, digital signature, blind signature, zero-knowledge proof. Some notions of quantum mechanics: pure and non-pure states, density operator, partial trace, non saparability, entanglement, EPR, Bell inequalities. Quantum cryptography and exchange of keys. Post-quantum cryptography.

QUANTUM COMMUNICATIONS AND NETWORKS: Theoretical lectures will be complemented by practice classes, which will be devoted mostly to small design projects on classical and QKD systems by leveraging existing simulation tools (e.g. VPI Photonics). The course might also take advantage of flipped classes and team-based learning projects. QUANTUM CRYPTOGRAPHY: Blackboard and slide lecture, with written material, links, exercises made available on the Portale della Didattica.

QUANTUM COMMUNICATIONS AND NETWORKS: • The slides and the handouts used by the Professors during the classes will be available on the POLITO Didattica web portal. • Quantum Communication, Quantum Networks, and Quantum Sensing, 1st Edition - July 14, 2022; Author: Ivan Djordjevic; Academic Press 2022. • Quantum Key Distribution Networks, A Quality of Service Perspective, 1st Edition – Springer, 2022 • Quantum Key Distribution, An Introduction with Exercises, Springer, 2021 • J.F. Kurose, K.W. Ross: Computer Networking: A Top-Down Approach Featuring the Internet QUANTUM CRYPTOGRAPHY: • Paar, Pelzl, "Understanding cryptography", Springer 2009 (lecture by Paar are available on YouTube) • Smart, "Cryptography made simple", Springer 2016

Exam: Written test; Optional oral exam; Individual project; Group project;

QUANTUM COMMUNICATIONS AND NETWORKS: The written exam is based on 2-3 problems (like those that will be solved during the course) and a few theoretical open and multiple-choice questions. The written exam will last two hours, and it will be scored on a full scale up to 25 points. The evaluation of the written exam is based on the correct development of the proposed exercises and correctness of the results. The theoretical questions will be judged according to the completeness of the answers, but also on the ability of the students to reply in a concise way. This written exam is a “closed-book exam”. Formulas needed will be provided together with the written test. The students who will get a score above 15/30 at the written exam can ask for an optional oral exam, where the questions will mostly regard the theoretical aspects of the course. The oral exam will allow to modify the score of +- 5 points. During the semester, the Teacher will propose some optional individual or team-based projects that the students may use to gain an additional 3 points for the final score. The final exam score will be the sum of the written test, optional oral test and optional projects, If this final sum is above 32, the student will get “30 cum laude”. QUANTUM CRYPTOGRAPHY: Written exercise on the topics of the course.

In addition to the message sent by the online system, students with disabilities or Specific Learning Disorders (SLD) are invited to directly inform the professor in charge of the course about the special arrangements for the exam that have been agreed with the Special Needs Unit. The professor has to be informed at least one week before the beginning of the examination session in order to provide students with the most suitable arrangements for each specific type of exam.