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The effect of mean photon number to the output key rate in quantum key distribution

Lizal Iswady Ahmad Ghazali, Wan Azizun Wan Adnan, Makhfudzah Binti Mokhtar, Ahmad Fauzi Abas, Mohd Adzir Mahdi, M. Iqbal Saripan

Published Jan 1, 2008• 0 citations
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Abstract

Quantum Cryptography guarantees absolute confidentiality for secret key exchanged via an optical fiber. The ability lies in the possibility of distributing the secret key securely in the form of photon. We show that there are different values of optimal mean photon number (μ) based on which assumption is considered for Eve's technology. For lower optimal μ such as μ=0.1 and &mu=0.4, the system is more robust to conservative attacks of Eve. However, the system could not support for higher distilled rate at large optimal μ of 1.

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Quantum Cryptography guarantees absolute confidentiality for secret key exchanged via an optical fiber. The ability lies in the possibility of distributing the secret key securely in the form of photon. We show that there are different values of optimal mean photon number (μ) based on which assumption is considered for Eve's technology. For lower optimal μ such as μ=0.1 and &mu=0.4, the system is more robust to conservative attacks of Eve. However, the system could not support for higher distilled rate at large optimal μ of 1.
The optimal mean photon number (mu) for quantum cryptography is the average photon number per transmitted pulse that results in the highest delivery rate of distilled cryptographic key bits, given a specific system scenario and set of assumptions about Eve's capabilities. Although many experimental systems have employed a mean photon number (mu) of 0.1 in practice, several research teams have pointed out that this value is somewhat arbitrary. In fact, various optimal values for mu have been described in the literature. In this paper we offer a detailed analytic model for an experimental, fiber-based quantum cryptographic system, and an explicit set of reasonable assumptions about Eve's current technical capabilities. We explicitly model total system behavior ranging from physical effects to the results of quantum cryptographic protocols such as error correction and privacy amplification. We then derive the optimal photon number (mu) for this system in a range of scenarios. One interesting result is that mu of approximately 1.1 is optimal for a wide range of realistic, fiber-based QKD systems; in fact, it provides nearly 10 times the distilled throughput of systems that employ a more conventional mu = 0.1, without any adverse affect on system security, as judged against a set of reasonable assumptions about Eve's current capabilities.
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 an emerging technology for secure key distribution with single-photon transmissions: Heisenburg'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 single-photon states to generate shared key material over multi-kilometer optical fiber paths and over line-of-sight links. In both cases, 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. In our optical fiber experiment we have performed quantum key distribution over 24-km of underground optical fiber using single-photon interference states, demonstrating that secure, real-time key generation over `open' multi-km node-to-node optical fiber communications links is possible.
The secure distribution of the secret random bit sequences known as {open_quotes}key{close_quotes} material, is an essential precursor to their use for the encryption and decryption of confidential communications. Quantum cryptography is an emerging technology for secure key distribution with single-photon 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 single-photon states to generate shared key material over multi-kilometer optical fiber paths and over line-of-sight links. In both cases, 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. In our optical fiber experiment we have performed quantum key distribution over 24-km of underground optical fiber using single-photon interference states, demonstrating that secure, real-time key generation over {open_quotes}open{close_quotes} multi-km node-to-node optical fiber communications links is possible. We have also constructed a quantum key distribution system for free-space, line-of-sight transmission using single-photon polarization states, which is currently undergoing laboratory testing. 7 figs.
Quantum Key Distribution (QKD) represents a revolutionary approach in the field of cryptography, offering the potential for unconditional security by leveraging the principles of quantum mechanics. This paper addresses the crucial issue of calculating secure key rates in entanglement based QKD systems. We present a method of key rate calculations that is independent of an eavesdropper's quantum system, relying solely on the quantum states shared between two communicating parties under the assumption of a worst-case attack. We undertake a comparison of asymptotic key rates with those observed in the finite regime, in which only a limited number of quantum states are exchanged. Furthermore, we investigate the influence of entanglement distillation on the achievable key rates. By identifying the numerically optimal number of entanglement distillation iterations based on the initial fidelity and the number of exchanged quantum states, we demonstrate how to achieve a balance between the quantity and quality of entangled states, thereby maximizing the secure key rate. Our results show that there is a unique optimum within a defined search range. Moreover, we determine the minimum number of exchanged quantum states necessary to attain a positive key rate and to obtain a desired number of secure key bits, which are both contingent upon the quality of the communication channel. It is anticipated that the insights gained from this work will prove instrumental in the development of optimal routing strategies in quantum communication networks.
In this work, we represent the principle of quantum cryptography (QC) that is based on fundamental laws of quantum physics.QC or Quantum Key Distribution (QKD) uses various protocols to exchange a secret key between two communicating parties.This research paper focuses and examines the quantum key distribution by using the protocol BB84 in the case of encoding on the single-photon polarization and shows the influence of optical components parameters on the quantum key distribution.We also introduce Quantum Bit Error Rate (QBER) to better interpret our results and show its relationship with the intrusion of the eavesdropper called Eve on the optical channel to exploit these vulnerabilities.