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Conference on Lasers and Electro-Optics

Practical quantum cryptography in free space

W. T. Buttler, Richard Hughes, Paul G. Kwiat, S. K. Lamoreaux, G. G. Luther, George L. Morgan, J. E. Nordholt, Charles G. Peterson, Charles M. Simmons, Andrew G. White

Published Nov 27, 2002• 1 citation
Publisher

Abstract

Summary form only given.We demonstrated quantum cryptography, or quantum key distribution (QKD), in free space over an outdoor optical path of /spl sim/950 m under nighttime conditions. The success of free space QKD against a high background depends on the transmission and detection of single photons through an optically thick and turbulent medium. It has been shown that a combination of sub-nanosecond timing, narrow filters, spatial filtering, and adaptive optics can render the difficult detection problem tractable. Further, the nonbirefringent nature of the atmosphere at optical wavelengths allows the transmission of the single photon polarization states used in the free-space QKD protocol.

DOI
10.1109/iqec.1998.680185

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Summary form only given.We demonstrated quantum cryptography, or quantum key distribution (QKD), in free space over an outdoor optical path of /spl sim/950 m under nighttime conditions. The success of free space QKD against a high background depends on the transmission and detection of single photons through an optically thick and turbulent medium. It has been shown that a combination of sub-nanosecond timing, narrow filters, spatial filtering, and adaptive optics can render the difficult detection problem tractable. Further, the nonbirefringent nature of the atmosphere at optical wavelengths allows the transmission of the single photon polarization states used in the free-space QKD protocol.
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.
An experimental free-space quantum key distribution (QKD) system has been tested over an outdoor optical path of {approx} 1 km under nighttime conditions at Los Alamos National Laboratory. This system employs the Bennett 92 protocol; here the authors give a brief overview of this protocol, and describe the experimental implementation of it. An analysis of the system efficiency is presented, as well as a description of the error detection protocol, which employs a two-dimensional parity check scheme. Finally, the susceptibility of this system to eavesdropping by various techniques is determined, and the effectiveness of privacy amplification procedures is discussed. The conclusions are that free-space QKD is both effective and secure; possible applications include the rekeying of satellites in low earth orbit.
In quantum key distribution (QKD) single-photon transmissions generate the shared, secret random number sequences, known as cryptographic keys that are used to encrypt and decrypt secret communications. Because the security of QKD is based on principles of quantum physics 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 an experimental QKD system that uses the four-state BB84 protocol with non-orthogonal photon polarization states and lowest-order adaptive optics to generate shared key material over multi-kilometer atmospheric, line-of-sight paths. I will present results of a daylight demonstration of this system. Key material is built up using the transmission of a photon-pulse per bit of an initial secret random sequence. I will describe the design and operation of the system, present an analysis of the system's security, efficiency, error rate, and secret key rate, as well as cryptographic testing of the key bits produced. I will describe the prospects for longer-distance applications of free-space QKD, particularly for satellite communications.
An experimental free-space quantum key distribution (QKD) system has been tested over an outdoor optical path of approximately 1 km under nighttime conditions at Los Alamos National Laboratory. This system employs the Bennett 92 protocol; here we give a brief overview of this protocol, and describe our experimental implementation of it. An analysis of the system efficiency is presented as well as a description of our error detection protocol, which employs a 2D parity check scheme. Finally, the susceptibility of this system to eavesdropping by various techniques is determined, and the effectiveness of privacy amplification procedures is discussed. Our conclusions are that free-space QKD is both effective and secure; possible applications include the rekeying of satellites in low earth orbit.
An experimental free-space quantum key distribution (QKD) system has been tested over an outdoor optical path of ~ 1 km under nighttime conditions at Los Alamos National Laboratory. This system employs the Bennett 92 protocol; here we give a brief overview of this protocol, and describe our experimental implementation of it. An analysis of the system efficiency is presented, as well as a description of our error detection protocol, which employs a two-dimensional parity check scheme. Finally, the susceptibility of this system to eavesdropping by various techniques is determined. Possible applications include the rekeying of satellites in low earth orbit. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.