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International Symposium on Information Theory and its Applications

Error performance of semi-classical quantum receivers for CPPM signals in KCQ key generation

Hiro Yamashita, Tsuyoshi Sasaki Usuda, Shogo Usami

Published Oct 1, 2012• 0 citations
OpenAlex

Abstract

Properties of the keyed communication in quantum noise (KCQ) key generation by coherent pulse position modulation (CPPM) are considered. We derive the error performance of an eavesdropper using the square-root measurement for 2-CPPM, the so-called 2-slot amplitude-shift-keying, with a very short initial key. We consider individual and collective semi-classical quantum receivers as the attacker's receivers.

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Properties of the keyed communication in quantum noise (KCQ) key generation by coherent pulse position modulation (CPPM) are considered. We derive the error performance of an eavesdropper using the square-root measurement for 2-CPPM, the so-called 2-slot amplitude-shift-keying, with a very short initial key. We consider individual and collective semi-classical quantum receivers as the attacker's receivers.
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A new approach to quantum cryptography to be called KCQ, keyed communication in quantum noise, is developed on the basis of quantum detection and communication theory for classical information transmission. By the use of a shared secret key that determines the quantum states generated for different data bit sequences, the users may employ the corresponding optimum quantum measurement to decode the data. This gives them a better error performance than an attacker who does not know the key when she makes her quantum measurement, and an overall generation of a fresh key may be obtained from the resulting advantage. This principle is illustrated in the operation of a concrete qubit system A general information-theoretic description of the overall approach will be presented, and contrasted with the detection/coding description necessary for specific protocols.
We analyze the performance of the error probability and the mutual information for quadrature amplitude modulation (QAM) and phase-shift keying systems based on quantum detection theory. It is shown that the quantum receiver called square root measurement gives about 5.7 dB improvement in power in comparison with the classical one. Furthermore, we show that the quantum QAM system can achieve the same reliability as the conventional intensity modulation-direct detection (IM-DD) system with almost equal power, compressing the required bandwidth, while the reliability is degraded in general.
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