Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

European Quantum Electronics Conference (EQEC)

Free space quantum cryptography with compact modules

H. Weier, T. Schmitt-Manderbach, Patrick Zarda, M. Halder, Christian Kurtsiefer, Harald Weinfurter, P.M. Gorman, P. R. Tapster, John Rarity

Published Nov 15, 2004• 0 citations
Publisher

Abstract

The paper reports on a free space quantum cryptography experiment over a distance of 24.3 km using a BB84 protocol between the summits of two mountains. The obtained bit error rates in this experiment using faint coherent pulses with an average photon number ranging from 0.1 to 0.7 was measured to range from 3 to 5 percent for experiments carried out during night, leading to raw key rates (before error correction and privacy amplification) of 1500 bits per second.

DOI
10.1109/eqec.2003.1314260

Related papers

Practical free space quantum cryptography

T. Schmitt-Manderbach, H. Weier, Nadja Regner +2 more

A successful free space quantum cryptography experiment over a distance of 500 m using the BB84 protocol is reported. The obtained bit error rates of this experiment using faint coherent pulses with an average photon number ranging from 0.1 to 1.0 was measured to be below 3 percent for experiments carried out during night, leading to average raw key rates (before error correction and privacy amplification) of 50 kBits per second.

European Quantum Electronics Conference (EQEC)•Jan 18, 2006•4 citations

Free space Quantum Cryptography at 1.9km range

Paul R. Tapster

We have recently demonstrated a free space quantum cryptography system which performed secure communication over a range of 1.9 kilometers. We exchanged a few thousand bits of key (after error correction) at rates of around a hundred bits per second. I will give details of the experimental system and discuss the results obtained. Plans for further experiments will also be discussed.

Optical Fiber Communication Conference•Jan 1, 2001•0 citations

Developments towards practical free-space quantum cryptography

P. R. Tapster, P.M. Gorman, David M. Benton +2 more

We describe a free space Quantum cryptography system which is designed to allow continuous unattended key exchanges for periods of several days, and over ranges of a few kilometres. The system uses a four laser faint pulse transmission system running at a pulse rate of 10MHz to generate the required four alternative polarization states. The receiver module similarly automatically selects a measurement basis and performs polarization measurements with four avalanche photodiodes. The controlling software can implement the full key exchange including sifting, error correction, and privacy amplification required to generate a secure key.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•May 25, 2005•4 citations

Long distance free-space quantum key distribution

T. Schmitt-Manderbach

In the age of information and globalisation, secure communication as well as the protection of sensitive data against unauthorised access are of utmost importance. Quantum cryptography currently provides the only way to exchange a cryptographic key between two parties in an unconditionally secure fashion. Owing to losses and noise of today's optical fibre and detector technology, at present quantum cryptography is limited to distances below a few 100 km. In principle, larger distances could be subdivided into shorter segments, but the required quantum repeaters are still beyond current technology. An alternative approach for bridging larger distances is a satellite-based system, that would enable secret key exchange between two arbitrary points on the globe using free-space optical communication. The aim of the presented experiment was to investigate the feasibility of satellite-based global quantum key distribution. In this context, a free-space quantum key distribution experiment over a real distance of 144 km was performed. The transmitter and the receiver were situated in 2500 m altitude on the Canary Islands of La Palma and Tenerife, respectively. The small and compact transmitter unit generated attenuated laser pulses, that were sent to the receiver via a 15-cm optical telescope. The receiver unit for polarisation analysis and detection of the sent pulses was integrated into an existing mirror telescope designed for classical optical satellite communications. To ensure the required stability and efficiency of the optical link in the presence of atmospheric turbulence, the two telescopes were equipped with a bi-directional automatic tracking system. Still, due to stray light and high optical attenuation, secure key exchange would not be possible using attenuated pulses in connection with the standard BB84 protocol. The photon number statistics of attenuated pulses follows a Poissonian distribution. Hence, by removing a photon from all pulses containing two or more photons, an eavesdropper could measure its polarisation without disturbing the polarisation state of the remaining pulse. In this way, he can gain information about the key without introducing detectable errors. To protect against such attacks, the presented experiment employed the recently developed method of using additional "decoy" states, i.e., the the intensity of the pulses created by the transmitter were varied in a random manner. By analysing the detection probabilities of the different pulses individually, a photon-number-splitting attack can be detected. Thanks to the decoy-state analysis, the secrecy of the resulting quantum key could be ensured despite the Poissonian nature of the emitted pulses. For a channel attenuation as high as 35 dB, a secret key rate of up to 250 bit/s was achieved. Our outdoor experiment was carried out under real atmospheric conditions and with a channel attenuation comparable to an optical link from ground to a satellite in low earth orbit. Hence, it definitely shows the feasibility of satellite-based quantum key distribution using a technologically comparatively simple system.

•Jan 1, 2007•16 citations

Quantum cryptography

V. L. Kurochkin, Igor G. Neizvestny

Work presents the brief review of the contemporary state of quantum cryptography science. Main principles of the quantum cryptography protocol development are illustrated by giving the example of BB84 protocol. Examples of experimental setups for the quantum key distribution through the atmosphere and fiber quantum channel are described in this work. The work presents results of experiments conducted on the developed setup based on single photon polarization coding. Problem of single photon detection in the visible and near IR area is considered. Work describes developed fiber based quantum cryptography working with the telecom wavelength 1555 nm. With the use of this experimental setup using the 25 km single mode telecom fiber (1555 nm wavelength) between sender and receiver we achieved the 450 bit/s quantum key generation with the use of 5 MHz pulse repetition rate, ~0.2 photon/pulse. Given the achieved photodetector parameters an average quantum bit error rate is less than 3.7%.

International Conference of Young Specialists on Micro/Nanotechnologies and Electron Devices•Jul 1, 2009•6 citations

Quantum key distribution over distances as long as 30 km

C. Marand, Paul D. Townsend

We report the secure transmission of cryptographic keys over as long as 30 km of optical fiber, using an interferometric quantum cryptography scheme. Low error rates in the range 1.2–4% were obtained for the quantum transmissions, and error-free secret keys were distilled from the raw data by use of secure error-correction and privacy-amplification protocols.

Optics Letters•Aug 15, 1995•254 citations
The paper reports on a free space quantum cryptography experiment over a distance of 24.3 km using a BB84 protocol between the summits of two mountains. The obtained bit error rates in this experiment using faint coherent pulses with an average photon number ranging from 0.1 to 0.7 was measured to range from 3 to 5 percent for experiments carried out during night, leading to raw key rates (before error correction and privacy amplification) of 1500 bits per second.
We describe a free space Quantum cryptography system which is designed to allow continuous unattended key exchanges for periods of several days, and over ranges of a few kilometres. The system uses a four laser faint pulse transmission system running at a pulse rate of 10MHz to generate the required four alternative polarization states. The receiver module similarly automatically selects a measurement basis and performs polarization measurements with four avalanche photodiodes. The controlling software can implement the full key exchange including sifting, error correction, and privacy amplification required to generate a secure key.
In the age of information and globalisation, secure communication as well as the protection of sensitive data against unauthorised access are of utmost importance. Quantum cryptography currently provides the only way to exchange a cryptographic key between two parties in an unconditionally secure fashion. Owing to losses and noise of today's optical fibre and detector technology, at present quantum cryptography is limited to distances below a few 100 km. In principle, larger distances could be subdivided into shorter segments, but the required quantum repeaters are still beyond current technology. An alternative approach for bridging larger distances is a satellite-based system, that would enable secret key exchange between two arbitrary points on the globe using free-space optical communication. The aim of the presented experiment was to investigate the feasibility of satellite-based global quantum key distribution. In this context, a free-space quantum key distribution experiment over a real distance of 144 km was performed. The transmitter and the receiver were situated in 2500 m altitude on the Canary Islands of La Palma and Tenerife, respectively. The small and compact transmitter unit generated attenuated laser pulses, that were sent to the receiver via a 15-cm optical telescope. The receiver unit for polarisation analysis and detection of the sent pulses was integrated into an existing mirror telescope designed for classical optical satellite communications. To ensure the required stability and efficiency of the optical link in the presence of atmospheric turbulence, the two telescopes were equipped with a bi-directional automatic tracking system. Still, due to stray light and high optical attenuation, secure key exchange would not be possible using attenuated pulses in connection with the standard BB84 protocol. The photon number statistics of attenuated pulses follows a Poissonian distribution. Hence, by removing a photon from all pulses containing two or more photons, an eavesdropper could measure its polarisation without disturbing the polarisation state of the remaining pulse. In this way, he can gain information about the key without introducing detectable errors. To protect against such attacks, the presented experiment employed the recently developed method of using additional "decoy" states, i.e., the the intensity of the pulses created by the transmitter were varied in a random manner. By analysing the detection probabilities of the different pulses individually, a photon-number-splitting attack can be detected. Thanks to the decoy-state analysis, the secrecy of the resulting quantum key could be ensured despite the Poissonian nature of the emitted pulses. For a channel attenuation as high as 35 dB, a secret key rate of up to 250 bit/s was achieved. Our outdoor experiment was carried out under real atmospheric conditions and with a channel attenuation comparable to an optical link from ground to a satellite in low earth orbit. Hence, it definitely shows the feasibility of satellite-based quantum key distribution using a technologically comparatively simple system.
Work presents the brief review of the contemporary state of quantum cryptography science. Main principles of the quantum cryptography protocol development are illustrated by giving the example of BB84 protocol. Examples of experimental setups for the quantum key distribution through the atmosphere and fiber quantum channel are described in this work. The work presents results of experiments conducted on the developed setup based on single photon polarization coding. Problem of single photon detection in the visible and near IR area is considered. Work describes developed fiber based quantum cryptography working with the telecom wavelength 1555 nm. With the use of this experimental setup using the 25 km single mode telecom fiber (1555 nm wavelength) between sender and receiver we achieved the 450 bit/s quantum key generation with the use of 5 MHz pulse repetition rate, ~0.2 photon/pulse. Given the achieved photodetector parameters an average quantum bit error rate is less than 3.7%.