Physical Review Letters

Quantum cryptography using any two nonorthogonal states

Charles H. Bennett

Published May 25, 1992• 3,034 citations

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.

DOI: 10.1103/physrevlett.68.3121

Related papers

Experimental System for Quantum Cryptography Based on Two Nonorthogonal Photon Polarization States

Yong Zhang, Le Deng, Min Mao +1 more

Quantum cryptography allows the establishing of a highly confidential sequence of random bits between two parties who share no secret information in advance. Its security is guaranteed by the basic laws of quantum mechanics rather than mathematical difficulty. An experimental system based on a novel protocol for quantum cryptography using only two nonorthogonal photon polarization states is implemented. The photon sources are two semiconductor laser diodes operated at 680 nm, their light pulses which are heavily attenuated to far below one photon per pulse are employed to encode the key. Gated single photon detection technique is used to minimize the dark count effect of the photon multiplier tube. Key establishing rate of 40 b/s and error rate of 2.1% are obtained. Compared with other systems, our system has the simplest experimental setup.

Chinese Physics LettersApr 1, 199813 citations

An Invention of Quantum Cryptography over the Classical Cryptography for Enhancing Security

Payal P. Wasankar, Pranjal Soni

Quantum Cryptography is based on the use of subatomic particles (photons) and their intrinsic quantum properties (photon polarization) to develop an unbreakable system. It is not possible to measure the quantum state of any system without affecting the system. This property provides secure transmission of key between sender and receiver. Quantum Cryptography is a way to combine the relative ease and convenience of key exchange in public key cryptography with the ultimate security of a one-time pad. 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 key initially. Quantum Cryptography uses the principles of Quantum Mechanics to implement a cryptographic system. The key problem which is solved by using quantum techniques is that of eavesdropping detection. The bits are represented as qubits, physically modeled by photons, and communicated over a quantum channel. The polarization states of photons represent 0's and 1's. Keyword: Asymmetric key, Cryptography, Protocols, Quantum, symmetric key

Jan 1, 20139 citations

Quantum cryptography: Public key distribution and coin tossing

Charles H. Bennett, Gilles Brassard A

When elementary quantum systems, such as polarized photons, are used to transmit digital information, the uncertainty principle gives rise to novel cryptographic phenomena unachievable with traditional transmission media, e.g. a communications channel on which it is impossible in principle to eavesdrop without a high probability of disturbing the transmission in such a way as to be detected. Such a quantum channel can be used in conjunction with ordinary insecure classical channels to distribute random key information between two users with the assurance that it remains unknown to anyone else, even when the users share no secret information initially. We also present a protocol for coin-tossing by exchange of quantum messages, which is secure against traditional kinds of cheating, even by an opponent with unlimited computing power, but ironically can be subverted by use of a still subtler quantum phenomenon, the Einstein-Podolsky-Rosen paradox.

arXiv:2003.06557Theoretical Computer ScienceOct 8, 20148,288 citations

Counterfactual Quantum Cryptography

Tae-Gon Noh

Quantum cryptography allows one to distribute a secret key between two remote parties using the fundamental principles of quantum mechanics. The well-known established paradigm for the quantum key distribution relies on the actual transmission of signal particle through a quantum channel. In this Letter, we show that the task of a secret key distribution can be accomplished even though a particle carrying secret information is not in fact transmitted through the quantum channel. The proposed protocols can be implemented with current technologies and provide practical security advantages by eliminating the possibility that an eavesdropper can directly access the entire quantum system of each signal particle.

arXiv:0809.3979Physical Review LettersDec 1, 2009249 citations

Quantum cryptography for secure free-space communications

Richard J. Hughes, William T. Buttler, Paul G. Kwiat +5 more

The secure distribution of the secret random bit sequences known as 'key' material, is an essential precursor to their use for the encryption and decryption of confidential communications. Quantum cryptography is a new technique for secure key distribution with single-photon transmissions: Heisenberg's uncertainty principle ensures that an adversary can neither successfully tap the key transmissions, nor evade detection (eavesdropping raises the key error rate above a threshold value). We have developed experimental quantum cryptography systems based on the transmission of non- orthogonal photon polarization states to generate shared key material over line-of-sight optical links. Key material is built up using the transmission of a single-photon per bit of an initial secret random sequence. A quantum-mechanically random subset of this sequence is identified, becoming the key material after a data reconciliation stage with the sender. We have developed and tested a free-space quantum key distribution (QKD) system over an outdoor optical path of approximately 1 km at Los Alamos National Laboratory under nighttime conditions. Results show that free-space QKD can provide secure real-time key distribution between parties who have a need to communicate secretly. Finally, we examine the feasibility of surface to satellite QKD.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIEApr 26, 199910 citations

A Secure Key Distribution System of Quantum Cryptography Based on the Coherent State

Guang‐Can Guo, Xiaoyu Zhang

The cryptographic communication has a lot of important applications, particularly in the magnificent prospects of private communication. As one knows, the security of cryptographic channel depends crucially on the secrecy of the key. The Vernam cipher is the only cipher system which has guaranteed security. In that system the key must be as long as the message and most be used only once. Quantum cryptography is a method whereby key secrecy can be guaranteed by a physical law. So it is impossible, even in principle, to eavesdrop on such channels. Quantum cryptography has been developed in recent years. Up to now, many schemes of quantum cryptography have been proposed. Now one of the main problems in this field is how to increase transmission distance. In order to use quantum nature of light, up to now proposed schemes all use very dim light pulses. The average photon number is about 0.1. Because of the loss of the optical fiber, it is difficult for the quantum cryptography based on one photon level or on dim light to realize quantum key-distribution over long distance. A quantum key distribution based on coherent state is introduced in this paper. Here we discuss the feasibility and security of this scheme.

Jan 1, 19960 citations