Quantum theory has found a new field of applications in the realm of information and computation during the recent years. This paper reviews how quantum physics allows information coding in classically unexpected and subtle nonlocal ways, as well as information processing with an efficiency largely surpassing that of the present and foreseeable classical computers. Some outstanding aspects of classical and quantum information theory will be addressed here. Quantum teleportation, dense coding, and quantum cryptography are discussed as a few samples of the impact of quanta in the transmission of information. Quantum logic gates and quantum algorithms are also discussed as instances of the improvement in information processing by a quantum computer. We provide finally some examples of current experimental

ABSTRACT. Quantum cryptography could be integrated in various existing concepts and protocols to secure Metropolitan Area Networks communications. One of the possible use of quantum cryptography is within IPSEC. The applications of quantum cryptography are linked to telecommunication services that require very high level of security in Metropolitan Area Networks. The aim of this paper is to analyse the use of quantum cryptography within IPSEC to secure MAN communications and to present the estimated performances of this solution. We analyse classical IPSEC advantage and limits to point out how quantum cryptography could enhance the security level of IPSEC. After having introduced basic concepts in quantum cryptography, we propose a solution that integrate quantum key distribution into IPSEC. A performance analysis is done to demonstrate the operational feasibility of this solution.

Abstract not found

We have implemented a quantum key distribution (QKD) system with polarization encoding at 850 nm over 1 km of optical fiber. The high-speed management of the bit-stream, generation of random numbers and processing of the sifting algorithm are all handled by a pair of custom data handling circuit boards. As a complete system using a clock rate of 1.25 Gbit/s, it produces sifted keys at a rate of 1.1 Mb/s with an error rate lower than 1.3 % while operating at a transmission rate of 312.5 Mbit/s and a mean photon number µ = 0.1. With a number of proposed improvements this system has a potential for a higher key rate without an elevated error rate.

A theoretical model of truly autonomic computing systems (ACS), with infinitely many constraints, is proposed. An argument similar to Turing’s for the unsolvability of the halting problem, which is permitted in classical logic, shows that such systems cannot exist. Turing’s argument fails in the recently proposed non-Aristotelian finitary logic (NAFL), which permits the existence of ACS. NAFL also justifies quantum superposition and entanglement, which are essential ingredients of quantum algorithms, and resolves the Einstein-Podolsky-Rosen (EPR) paradox in favour of quantum mechanics and non-locality. NAFL requires that the autonomic manager (AM) must be conceptually and architecturally distinct from the managed element, in order for the ACS to exist as a nonself-referential entity. Such a scenario is possible if the AM uses quantum algorithms and is protected from all problems by (unbreakable) quantum encryption, while the managed element remains classical. NAFL supports such a link between autonomic and quantum computing, with the AM existing as a metamathematical entity. NAFL also allows quantum algorithms to access truly random elements and thereby supports non-standard models of quantum (hyper-) computation that permit infinite parallelism. 1.

We previously demonstrated a high speed, point to point, quantum key distribution (QKD) system with polarization coding over a fiber link, in which the resulting cryptographic keys were used for one-time pad encryption of real time video signals. In this work, we extend the technology to a three-node active QKD network- one Alice and two Bobs. A QKD network allows multiple users to generate and share secure quantum keys. In comparison with a passive QKD network, nodes in an active network can actively select a destination as a communication partner and therefore, its sifted-key rate can remain at a speed almost as high as that in the point-to-point QKD. We demonstrate our three-node QKD network in the context of a QKD secured real-time video surveillance system. In principle, the technologies for the three-node network are extendable to multi-node networks easily. In this paper, we report our experiments, including the techniques for timing alignment and polarization recovery during switching, and discuss the network architecture and its expandability to multi-node networks.

A complete fiber-based polarization encoding quantum key distribution (QKD) system based on the BB84 protocol has been developed at National Institute of Standard and Technology (NIST). The system can be operated at a sifted key rate of more than 4 Mbit/s over optical fiber of length 1 km and mean photon number 0.1. The quantum channel uses 850 nm photons from attenuated high speed VCSELs and the classical channel uses 1550 nm light from normal commercial coarse wavelength division multiplexing devices. Sifted-key rates and quantum error rates at different transmission rates are measured as a function of distance (fiber length). A polarization auto-compensation module has been developed and utilized to recover the polarization state and to compensate for temporal drift. An automatic timing alignment device has also been developed to quickly handle the initial configuration of quantum channels so that detection events fall into the correct timing window. These automated functions make the system more practical for integration into existing optical local area networks.

We study private quantum channels on a single qubit, which encrypt given set of plaintext states P. Specifically, we determine all achievable states ρ (0) (average output of encryption) and for each particular set P we determine the entropy of the key necessary and sufficient to encrypt this set. It turns out that single bit of key is sufficient when the set P is two dimensional. However, the necessary and sufficient entropy of the key in case of three dimensional P varies continuously between 1 and 2 bits depending on the state ρ (0). Finally, we derive private quantum channels achieving these bounds. We show that the impossibility of universal NOT operation on qubit can be derived from the fact that one bit of key is not sufficient to encrypt qubit.

We report our recent results in development of the secure fiber-optics communication system based upon quantum key distribution. Emphasize is made on the limitation imposed by the state-of-the-art components crucial for the system performance. We discuss the problem of the interferometer design and highlight the possible security loopholes known. Together with single photon counting performance it places the main restriction on the distance range and the secure key rate of the QKD system based upon the week coherent pulses. Finally we describe the result of the first test of the system using single photons produced by non-degenerate parametric down-conversion as a source.

Communication schemes employing quantum entanglement open a wide field of possible applications with properties outperforming their classical counterparts. Promising examples are quantum key distribution, quantum dense coding, and quantum state teleportation. We investigate the potential of quantum cryptography, i.e. quantum key distribution (QKD), with special emphasis on the demands and opportunities provided by intersatellite links. I.