Showing papers on "Quantum cryptography published in 1992"

Quantum cryptography using any two nonorthogonal states

Abstract: Quantum techniques for key distribution---the classically impossible task of distributing secret information over an insecure channel whose transmissions are subject to inspection by an eavesdropper, between parties who share no secret initially---have been proposed using (a) four nonorthogonally polarized single-photon states or low-intensity light pulses, and (b) polarization-entangled or spacetime-entangled two-photon states. Here we show that in principle any two nonorthogonal quantum states suffice, and describe a practical interferometric realization using low-intensity coherent light pulses.

Quantum cryptography without Bell's theorem.

Abstract: Ekert has described a cryptographic scheme in which Einstein-Podolsky-Rosen (EPR) pairs of particles are used to generate identical random numbers in remote places, while Bell's theorem certifies that the particles have not been measured in transit by an eavesdropper. We describe a related but simpler EPR scheme and, without invoking Bell's theorem, prove it secure against more general attacks, including substitution of a fake EPR source. Finally we show our scheme is equivalent to the original 1984 key distribution scheme of Bennett and Brassard, which uses single particles instead of EPR pairs.

Practical quantum cryptography based on two-photon interferometry.

Abstract: We propose an experimental realization of cryptographic-key-sharing scheme exploiting quantum correlations between pair photons. Our experimental setup consists of an external source of correlated photon pairs which propagate to two widely separated unbalanced Mach-Zehnder interferometers. The probability of detection of photon pairs in any two outputs of the interferometers can be fully modulated by phase plates in either interferometer.

Quantum cryptography: uncertainty in the service of privacy.

Abstract: Cryptography–the ancient art of secret messages–has broadened its scope to cover all situations in which it is desired to control the flow of information among two or more parties, not all of whom trust one another. Non-orthogonal quantum states of the optical radiation field, by virtue of the inherent limitations on measuring them imposed by the uncertainty principle, have recently emerged as a valuable adjunct to the traditional mathematical tools of cryptography. In particular, quantum optical communications systems can achieve a goal unattainable by classical mathematical means alone: to enable two parties, who share no secret Information initially, to exchange secret information even though all their transmissions are subject to monitoring by an eavesdropper.

Quantum cryptography and bell's theorem

Abstract: In this article, I would like to show you a glimpse of beauty which one can easily find in the union of cryptography and quantum theory. So this is a story about quanta and ciphers. I will show how quantum mechanics protects the so-called key distribution process in cryptography. The proposed scheme is based on the well-known Bohm’s version of the Einstein-Podolsky-Rosen gedankenexperiment 1,2; the generalized Bell’s theorem (Clauser - Horne - Shimony - Holt inequalities)3,4 is used to test for eavesdropping. However, before I proceed any further, let me start with some historical remarks followed by some basic notions of cryptography.

Quantum Cryptography Defies Eavesdropping

Abstract: Students of physics can be Students of physics can be excused for finding their quantum mechanics courses a little cryptic from time to time. Now researchers are using the properties of quantum mechanics to encrypt information for secure transmission.

Cryptographic Primitives And Quantum Theory

Abstract: only using public key cryptography, but using quantum mechanics as a support. This paper summarizes the current knowledge in the field of two-party cryptographic protocols devised f rom quantum systems. W e introduce the reader to the notion of cryptographic protocols and describe a number of sample building blocks to achieve them. W e also give pointers for the reader who i s interested to the quantum implementation of these building blocks. 2 Cryptographic Primitives We now introduce the main two basic primitives that have been widely considered as useful building blocks in the design of more elaborate cryptographic protocols:

Storage And Retrieval Of Quantum Information

Abstract: Information encoded in non-orthogonal quantum states cannot be duplicated, nor amplified, and in general at is only partly recoverable. The most efficient way of retrieving it is not a direct uquantum measurement” (as defined by von Neumann), but an indirect method similar to heterodyne detection in communications engineering. The mathematical representation of this process requires the introduction of a positive operator valued measure. The optimization of these measures is not yet fully undersiood. An interesting and potentially important application of quantum information is its use an cryptography.

Information, Quantum Correlations and Communication

Abstract: It has been known for more than fifty years1 that there is something special about quantum correlations The strength of these correlations leads to consequences that are incompatible with local reality2 and would appear to suggest the possibility of superluminal communication However, it has been proven that the statistical properties of one of a pair of correlated systems are unaltered by observation of its partner3 No information is transmitted by the action of the measurement Nonetheless, this does not imply that quantum correlations have no relevance in the discussion of communications