In today’s digital age, the need for secure communication is more critical than ever. With the rise of cyber-threats and the potential vulnerabilities in classical encryption methods, the demand for more robust security systems is growing. One of the most promising solutions to this problem lies in the field of quantum cryptography, specifically through Quantum Key Distribution (QKD). QKD offers an unprecedented level of security by utilizing the fundamental principles of quantum mechanics, such as superposition and entanglement. These principles enable the detection of eavesdropping attempts, as any observation of the quantum states involved would inherently alter them, thus alerting the communicating parties to potential threats
Project description
A core element of QKD is the generation and detection of quantum bits, or qubits, which are often represented as photons. These photons, when manipulated appropriately, allow for the secure transmission of cryptographic keys over vast distances. Among the various techniques used to generate and detect photons, the generation of single photons, those that exist in a definite quantum state and can be individually detected, has become a key area of research. The ability to control and detect these singular photons is crucial for ensuring the integrity and security of quantum communication channels.
This project focuses on the generation and detection of singular photons, specifically within the context of QKD. It aims to explore the various methods for creating single photon sources and the challenges involved in accurately detecting these photons in real-time. The research conducted in this project is intended to further the understanding of photon-based QKD, laying the groundwork for future developments in quantum encryption techniques for follow-up Fontys projects. The main part of our project is to provide functional hardware with a single photon source and detector.
Project result
The team developed a solid understanding of the theoretical and practical aspects of single-photon systems, which will serve as a strong foundation for future work. This included learning about laser safety protocols and the importance of handling high-intensity light sources responsibly to avoid hazards. We also became proficient in using LTSpice for simulating and analyzing electronic circuits, which was critical for the design of the system. In addition, we gained insight into designing a housing for sensitive optical and electronic components to protect them from
environmental factors and ensure stable operation.
To built a single photon generator and detector for the use in quantum key distribution the work can be divided in three main parts: the detector, the source and the optical setup. The whole process starts with a continuous wave laser diode, which gets powered on a low level to reduce the laser power output. Next, the laser beam has to collimated and attenuated to a density so low that, in this case, the probability for 0,1 photons arriving each microsecond is a few percent. At the same time, the probability for zero photons has to be very high, so that the probability for more than one photon is lower than for one. This means that, at least in theory, we have created a single photon.
After sending the single photon over a distance (as used for QKD), the setup with the two mirrors allow a travel simulation and the full control over the beam to direct it into the detector. The APD (Avelance Photo Diode) is the main part which is used to create a current out of the incoming photons. With the help of two electrical circuits, the APD works well in its intended operating region. Finally, by adding the signal processing circuit, the team was able to display the incoming photons.
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Acknowledgement
The student team (Ferran, Lara, Mihail and Nico) would like to thank Fontys Applied Science and Fontys Engineering departments for their valuable support during the proejct. And special thanks go to our project mentor Ing. T. Ditewig and Dr. C. Lee of Fontys Electrical Engineering and to the Minor BeCreative teaching team.