Quantum cryptography could well be the first application of quantum mechanics at the single-quantum level. The rapid progress in both theory and experiment in recent years is reviewed, with emphasis on open questions and technological issues.
In a series of recent experiments a radical new technique has been demonstrated that could have far-reaching consequences for the way in which the confidentiality and integrity of our networks is protected. This technique, known as quantum cryptography, is the result of a synthesis of ideas from fundamental quantum physics and classical encryption and has lead to a radical new approach to the business of secure communications. We review the origins of and developments in this rapidly growing field and assess the current status of both the theory and the experiments.
Abstract Recent progress in the development of quantum technologies, most notably in the context of quantum computing and cryptography, poses the question of whether and how to teach the modern and sophisticated underlying theory of quantum physics, and its applications, at school. To this end, we present a game-based approach to teach Bell inequalities and quantum cryptography at undergraduate level. The approach is based on kinesthetic activities and allows students to experience and discover quantum features and their applications first-hand. The students obtain the same results as if they were in a real laboratory performing sophisticated experiments such as Bell tests, without requiring expensive tools and facilities. Specifically, quantum states are represented by the orientation of students, who also play the role of quantum particles, and mimic quantitative random behaviour and measurements using dice and apps.
We have experimentally realised free-space distribution of entangled photon pairs through a noisy ground atmosphere of 13km. It is shown that the desired entanglement can still survive after both photons have traversed a distance beyond the effective thickness of the aerosphere. We observe a spacelike separated violation of the Bell-Clauser-Horne-Shimony inequality of 2.45±0.09. With this source we have demonstrated the BB84-Ekert91 quantum cryptography protocol. Our experiment has shown for the first time the feasibility of using entangled photons for ground-to-satellite quantum communication, and presents a significant step towards satellite-based global quantum communication in the future. We first review the rapid progress in quantum cryptography over recent years and then describe our experiment in detail.