The University of Canberra and its research collaborators have established a dedicated free-space laser communications test-bed between a national telecommunications facility and four selected monitoring sites at distances ranging from 4 to 47 km. This test-bed is currently being used to simulate and characterize the free-space quantum channel along which secure quantum key exchanges could take place between earth stations and low earth orbit satellites, the latter acting as global key couriers. We present the results of these trials conducted under a variety of atmospheric conditions. We use the results to estimate error rates and secure key exchange rates for ground/satellite key exchange systems employing weak Poissonian pulses with more stringent security requirements than are sometimes quoted.
Free-space quantum key exchanges between ground stations and low earth orbiting satellites will be characterized by high link losses, typically of the order of 30 dB or higher. These losses, together with the need to transmit weak Poissonian laser pulses containing on average substantially less than 0.1 photons per transmitted bit to preserve security, will result in exceedingly low channel efficiencies, typically of the order of 10-5. In order to achieve even a relatively modest secure key bit rate of 100 kbps, it will therefore often be necessary to key the transmitter at rates in excess of 10 Gbps. In this paper we outline several different methods of achieving such fast polarization keying including the use of dual drive Mach-Zehnder intensity modulators on lithium niobate in a hybrid fibre-guided modulator structures. We then propose a total integrated polarization keying structure in LiNbO3. We describe the fabrication and testing of such ultra-broadband polarization keyers suitable for use in high loss, short-wave free-space quantum key distribution systems employing silicon photon counters. We also indicate how these devices may be incorporated into quantum key satellite courier payloads and ground station terminals.
Single photon per bit optical communication between ground stations and low earth orbit satellites will enable the secure global distribution of cryptographic keys.
The communications satellite AO-40 contains an experimental infra-red payload consisting of a low power 835 nm laser diode transmitter coupled to a small fixed orientation telescope transmitting 400 baud Manchester encoded data [1]. The received signal levels are of the order of 10 photons/bit for an effective telescope aperture of diameter 100 mm [2]. They therefore offer a means of validating models of low photon number OOK signal propagation and detection in the presence of atmospheric turbulence, an issue relevant to free-space quantum communications. This paper describes the design, testing and implementation of a photon counting receiver for AO-40 signals using a Labview software platform to display received data, error statistics, detection and correction (using cyclic redundancy check code CRCC 32), and clock synchronization [3]. Signals are acquired with a 300 mm f/6.3 Schmidt-Cassegrain tracking telescope coupled by 100 micron multimode fibre to a silicon APD photon counting module.
References
1. R. Purvinskis, Use of the fixed orientation optical transmitter on AO-40, Internal Report, Centre for Advanced Telecommunications and Quantum Electronics, University of Canberra, 2001.
2. A. Arora, Oscar 40: A Complete Link Analysis, University of Canberra BE (Hons) Report, November 2001.
3. A. Arora, Optical Modulator and Demodulator for the Oscar-40 Satellite, University of Canberra BE Project Report , November 2001.
This paper reviews the development of the theory and measurement of recombination noise in semiconductor junction devices. It traces this development from van der Ziel's corpuscular models of noise in junction diodes and transistors through to recent models of shot-noise suppression and non-classical light emission from laser and light-emitting diodes due to Yamamoto and co-workers.
Conference Committee Involvement (5)
Noise and Information in Nanoelectronics, Sensors, and Standards II
26 May 2004 | Maspalomas, Gran Canaria Island, Spain
Noise in Devices and Circuits II
26 May 2004 | Maspalomas, Gran Canaria Island, Spain
Noise and Information in Nanoelectronics, Sensors, and Standards
2 June 2003 | Santa Fe, New Mexico, United States
Fluctuations and Noise in Photonics and Quantum Optics
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.