Optics Express

LD light antisqueezing through fiber propagation in reflection-type interferometer

Tatsuya Tomaru

Published Jan 1, 2007• 4 citations

Abstract

Antisqueezed light is a possible resource to apply quantum information technologies to the real world. When antisqueezed light is used in secure optical communications, an LD is a preferable light source from an engineering point of view. Although LD output power is low, LD light can be antisqueezed with the help of an EDFA in a reflection-type interferometer consisting of a standard single-mode fiber of typically 5 km. The ellipticity of the obtained antisqueezed light was 9 at maximum in a balanced interferometer case, and the angle that was subtended by antisqueezed fluctuations at the origin of phase space was 23 degrees at maximum. The feasibility of secure optical communications using antisqueezed light is demonstrated.

DOI: 10.1364/oe.15.011241

Related papers

Secure optical communication using antisqueezing

Tatsuya Tomaru, Masashi Ban

When considering an application of quantum-information technology, we should consider realistic conditions first. From this point of view, we propose using antisqueezed light as a resource for optical communication because antisqueezing maintains its nature even after loss and amplification. Applying antisqueezed light to cipher communication using randomized sender bases, we can increase, by high order of magnitude, the bit-error rate of eavesdroppers who do not have the basis information. Even at macroscopic optical intensity, an ordinary level of optical communication, we can cause the bit-error rate of eavesdroppers to be as high as it would be at low intensity, through increased antisqueezing depending on optical intensity, leading to more secure optical communication.

Physical Review ASep 13, 20066 citations

Secure optical communications using antisqueezed light with enhanced fluctuations

Tatsuya Tomaru, Shinya Sasaki

Secure optical communications using antisqueezing are a realistic application of quantum information technologies. Antisqueezed light with enhanced fluctuations was transmitted over 100 km. Greater difficulty of eavesdropping than in a coherent-state case was shown.

Conference on Lasers and Electro-OpticsMay 4, 20080 citations

Optical quantum communications: an experimental approach

Armando N. Pinto, Álvaro J. Almeida, Nuno A. Silva +2 more

Quantum laws can be used to implement secure communication channels; this has been named quantum cryptography. In quantum cryptography the security does not depend of limited computational power, but is inherent to the laws that govern the propagation and detection of single and entangled photons. We show how single and entangled photon-pairs can be efficiently generated using four-wave mixing in optical fibers. We analyze the source statistics, degree of entanglement and impact of spontaneous Raman scattering. By coding information in the photons polarization we are able to transmit quantum information over 20 km of standard single mode fiber.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIEMay 21, 20115 citations

Discrete Variable Quantum Key Distribution over a Free-Space Optical Channel

John Gariano

When light is propagated through a channel that is not a waveguide, such as a fiber, it is known as a free-space optical channel. When used in communication systems, free-space optical channels provide the advantages of high communication rates, lower power, and minimal infrastructure installation. When the free-space optical channel has a random medium in it, such as the atmosphere, the distortions will be applied to the phase. The phase distortions can lead to intensity fluctuations and additional beam spreading. To compensate for the distortions adaptive optics can be used, allowing for the stability of the system to be improved. Additionally, post processing techniques on transmitted data can also be used to improve the stability of the channel. By significantly decreasing the number of photons transmitted, a classical communication channel can be considered as a quantum channel. Encoding information into the quantum states of the transmitted photons, quantum communication can be performed. When transmitting on the order of 1 photon per pulse, classical post processing techniques cannot be used to improve the stability of the channel. To stabilize the free-space optical channel, adaptive optics can be used at the transmitter or receiver. As no measurement of the quantum state is performed by the adaptive optics system, no information in the photon is lost. In this work, quantum key distribution will be implemented over the quantum channel. The focus of this work is on the design and study of how the channel degradations can be overcome, as well as the establishment of a free-space optical channel with adaptive optics in a quantum networking testbed. Quantum key distribution systems were simulated over a 30 km maritime channel as well as over a underwater channel. For the 30 km channel, the use of multiple parallel spatial modes results in the highest increases of the secure key rate at the cost of transmitting a lower average number of photons. When adaptive optics is applied, the secure key rates have a small increase, however as the strength of the turbulence increases from weak to moderate, the relative improvement is higher. For the underwater channel, operation at lower depths is optimal as fewer background photons reach the receiver and the channel attenuation is lower. In the experimental setup, it was found that the single photon detectors that are being used are the limiting the channel loss to be at most 6 dB. The free space optical link established between the Electrical and Computer Engineering building and College of Optical Sciences uses a corner cube retro-reflector to yield a distance of 1.45 km. The channel has been characterized at various times of day to determine the strength of the atmospheric turbulence, which ranges from a scintillation index of 0.07 to 2.21. A classical communication experiment was performed, resulting in error-free transmission while the input power to the EDFA before the photodetector was consistently above -25 dBm.

Jan 1, 20190 citations

Fiber interferometric communications using mach-zehnder interferometer topology

Jurij Tratnik, Boštjan Batagelj

A simple concept of fiber optic communication topology using Mach-Zehnder interferometer is presented. This kind of communication can be used for secure encryption-key distribution or secure point-to-point full-duplex data-transfer communication. In both interferometric-communication applications standard optical components and single-mode fibers are used. Maximum fiber length is dependent on system noise, which must not exceed the interference pattern.

IEEE EUROCON - International Conference on Computer as a Tool (EUROCON)May 1, 20094 citations

Secure Long-Distance Quantum Communication over Optical Fiber Quantum Channels

László Gyöngyösi, Sándor Imre

In today's communication networks, the widespread use of optical fiber and passive optical elements allows to use quantum key distribution (QKD) in the current standard optical network infrastructure. In the past few years, quantum key distribution schemes have attracted much study. The security of modern cryptographic methods, like asymmetric cryptography, relies heavily on the problem of factoring large integers (Rivest et al., 1978), (Schneier, 1996). In the future, if quantum computers become reality, any information exchange using current classical cryptographic schemes will be immediately insecure (Shor, 1994), (Shor, 1997). Current classical cryptographic methods are not able to guarantee longterm security. Other cryptographic methods, with absolute security must be applied in the future.

InTech eBooksFeb 1, 20120 citations