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International Journal of Computer Applications

A Practical Quantum Cryptography Transmitter

Fouad Ali Yaseen

Published Feb 14, 2014• 0 citations
OpenAlex

Abstract

Computer center The extend success of any communication system essentially depends on the strength of the secrecy of transporting the information between the partners. The classical cryptography for the wired and wireless communication systems can not withstand against the challenges of new technologies. So, it is necessary to invent a new method to encrypt the information. The solution is quantum cryptography in communication system. The absolute security can be achieve with quantum cryptography protocol via building an effective hardware for satisfying the single-photon source must requirement by controlling the value of mean photon number. This was approximately achieved in this work by building a driving circuit that provide very short pulses, less than 10 ns for Laser Diode with output maximum power of 0.99 mW and wavelength 650 nm. These short pulses enable getting faint laser pulses that were further attenuated to reach mean photon number equal to 0.08 or less.

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A Practical Quantum Cryptography Transmitter

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The extend success of any communication system essentially depends on the strength of the secrecy of transporting the information between the partners.The classical cryptography for the wired and wireless communication systems can not withstand against the challenges of new technologies.So, it is necessary to invent a new method to encrypt the information.The solution is quantum cryptography in communication system.The absolute security can be achieve with quantum cryptography protocol via building an effective hardware for satisfying the single-photon source must requirement by controlling the value of mean photon number.This was approximately achieved in this work by building a driving circuit that provide very short pulses, less than 10 ns for Laser Diode with output maximum power of 0.99 mW and wavelength 650 nm.These short pulses enable getting faint laser pulses that were further attenuated to reach mean photon number equal to 0.08 or less.

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Computer center The extend success of any communication system essentially depends on the strength of the secrecy of transporting the information between the partners. The classical cryptography for the wired and wireless communication systems can not withstand against the challenges of new technologies. So, it is necessary to invent a new method to encrypt the information. The solution is quantum cryptography in communication system. The absolute security can be achieve with quantum cryptography protocol via building an effective hardware for satisfying the single-photon source must requirement by controlling the value of mean photon number. This was approximately achieved in this work by building a driving circuit that provide very short pulses, less than 10 ns for Laser Diode with output maximum power of 0.99 mW and wavelength 650 nm. These short pulses enable getting faint laser pulses that were further attenuated to reach mean photon number equal to 0.08 or less.
The extend success of any communication system essentially depends on the strength of the secrecy of transporting the information between the partners.The classical cryptography for the wired and wireless communication systems can not withstand against the challenges of new technologies.So, it is necessary to invent a new method to encrypt the information.The solution is quantum cryptography in communication system.The absolute security can be achieve with quantum cryptography protocol via building an effective hardware for satisfying the single-photon source must requirement by controlling the value of mean photon number.This was approximately achieved in this work by building a driving circuit that provide very short pulses, less than 10 ns for Laser Diode with output maximum power of 0.99 mW and wavelength 650 nm.These short pulses enable getting faint laser pulses that were further attenuated to reach mean photon number equal to 0.08 or less.
Quantum mechanics allows a number of communications protocols that would not be possible classically, including provably-secure messages (quantum cryptography), increased channel capacity, and the ability to transmit an unknown quantum state (quantum teleportation). This tutorial will provide an introductory description of what appear to be the most promising applications of quantum communications, including quantum cryptography and quantum repeaters. The most commonly-used methods for quantum cryptography will be described, including the advantages and disadvantages of each in practical applications. The maximum range of current quantum cryptography systems is limited by the fact that optical amplifiers would destroy the quantum coherence of single photons and cannot be used in these kinds of systems. One potential solution to this problem is the transmission of single photons in free space, which would allow a global system for quantum cryptography based on a network of satellites and ground stations. Free-space quantum cryptography systems of that kind have now been demonstrated over relatively short distances. The range of quantum cryptography systems in optical fibers can also be extended using quantum repeaters that make use of entanglement purification and quantum teleportation. These same techniques could also be used to implement a “quantum Internet” for the transmission of qubits from one quantum computer to another. The practical challenges that will have to be met in order to implement quantum repeaters and quantum teleportation over large distances will be discussed.
Communications in secrecy are often required in many commercial and military applications. Unfortunately, many cryptographic schemes in use today such as public-key cryptography based on the RSA algorithm would be broken with either unanticipated advances in hardware and algorithm or the advent of quantum computers. Quantum cryptography, on the other hand, has been proven secure even against the most general attack allowed by the laws of physics and is a promising technology poised for widespread adoption in realistic cryptographic applications. Quantum cryptography allows two parties to expand on a secret key that they have previously shared. Various quantum cryptographic protocols have been proposed to perform this task. In this paper, we survey some popular quantum cryptographic protocols (including the famous Bennett-Brassard 1984 protocol) and discuss their security. Specifically, we consider their security in two cases: the ideal case where a perfect single-photon source is used and the practical case where a realistic laser source is used. We compare the protocols and find that the efficient six-state protocol outperforms the others both in the tolerable quantum bit error rate and in the key generation rate when a realistic laser source is used.
Quantum cryptography or quantum key distribution (QKD) applies fundamental laws of quantum physics to guarantee secure communication. The security of quantum cryptography was proven in the last decade. Many security analyses are based on the assumption that QKD system components are idealized. In practice, inevitable device imperfections may compromise security unless these imperfections are well investigated.\n\nA highly attenuated laser pulse which gives a weak coherent state is widely used in QKD experiments. A weak coherent state has multi-photon components, which opens up a security loophole to the sophisticated eavesdropper. With a small adjustment of the hardware, we will prove that the decoy state method can close this loophole and substantially improve the QKD performance. We also propose a few practical decoy state protocols, study statistical fluctuations and perform experimental demonstrations. Moreover, we will apply the methods from entanglement distillation protocols based on two-way classical communication to improve the decoy state QKD performance. Furthermore, we study the decoy state methods for other single photon sources, such as triggering parametric down-conversion (PDC) source. Note that our work, decoy state protocol, has attracted a lot of scientific and media interest. The decoy state QKD becomes a standard technique for prepare-and-measure QKD schemes.\n\nAside from single-photon-based QKD schemes, there is another type of scheme based on entangled photon sources. A PDC source is commonly used as an entangled photon source. We propose a model and post-processing scheme for the entanglement-based QKD with a PDC source. Although the model is proposed to study the entanglement-based QKD, we emphasize that our generic model may also be useful for other non-QKD experiments involving a PDC source. By simulating a real PDC experiment, we show that the entanglement-based QKD can achieve longer maximal secure distance than the single-photon-based QKD schemes.\n\nWe propose a time-shift attack that exploits the efficiency mismatch of two single photon detectors in a QKD system. This eavesdropping strategy can be realized by current technology. We will also discuss counter measures against the attack and study the security of a QKD system with efficiency mismatch detectors.
Among various implementations of single-photon sources, faint-pulse single-photon sources provide a simple and practical approach based on attenuated coherent laser pulses. This work presents an experimental realization of a faint-pulse single-photon source using a 785-nm Grating Stabilized Laser Diode system, driven by a laser diode controller and modulated by a Field Programmable Gate Array (FPGA). The system's performance was evaluated by analyzing the photon detection rate as a function of pulse width and driving current. Results indicated a linear relationship between the single-photon detection rate and pulse width and an exponential dependence on driving current. The system achieved a photon emission probability of 10% per pulse, aligning with the requirements of practical quantum key distribution systems. This implementation demonstrates a cost-effective, scalable, and accessible platform for single-photon experiments, providing a foundation for future implementations of quantum communication protocols.