Quantum cryptography is the science of exploiting quantum mechanical properties such as quantum entanglement, measurement disturbance, no-cloning theorem, and the principle of superposition to perform various cryptographic tasks. Historically defined as the practice of encoding messages, a concept now referred to as encryption, quantum cryptography plays a crucial role in the secure processing, storage, and transmission of information across various domains.
One aspect of quantum cryptography is quantum key distribution (QKD), which offers an information-theoretically secure solution to the key exchange problem. The advantage of quantum cryptography lies in the fact that it allows the completion of various cryptographic tasks that are proven or conjectured to be impossible using only classical (i.e. non-quantum) communication. Furthermore, quantum cryptography affords the authentication of messages, which allows the legitimates parties to prove that the messages were not wiretapped during transmission. For example, in a cryptographic set-up, it is impossible to copy with perfect fidelity, the data encoded in a quantum state. If one attempts to read the encoded data, the quantum state will be changed due to wave function collapse (no-cloning theorem). This could be used to detect eavesdropping in QKD schemes, or in quantum communication links and networks. These advantages have significantly influenced the evolution of quantum cryptography, making it practical in today's digital age, where devices are increasingly interconnected and cyberattacks have become more sophisticated. As such quantum cryptography is a critical component in the advancement of a quantum internet, as it establishes robust mechanisms to ensure the long-term privacy and integrity of digital communications and systems.
