arXiv subjects

Jane E. Nordholt

Publications and source records attributed to Jane E. Nordholt.

8 recordsLinked to original sources

arXiv2014

Long-range Quantum Cryptography: Amplified Quantum Key Distribution (AQKD)

Recently, Takeoka, Guha and Wilde have established a new (loose) upper bound on the secret key capacity of a pure-loss bosonic channel that is several times larger than an error-free BB84 QKD channel with same transmittance. This suggests that new QKD protocols may exist with higher secret key rates and effective ranges larger than the metro-area limits of BB84 QKD over optical fiber. In this paper we illustrate such a possibility with a new protocol called Amplified Quantum Key Distribution (AQKD), which will be compatible with the optical amplification typically encountered on inter-city fiber spans. We analyze one instantiation of AQKD, in which the transmitter enclave contains an optical amplifier (OA), with security against passive optical tapping. For this scenario AQKD is shown to: give three times the secret key rate of BB84 at spans up to 100km, increasing to more than a ten-fold gain at 140km; and double the maximum single-span optical fiber transmission range to inter-city distances (300km). Essential to these performance gains is a new information-theoretic protocol post-processing stage called generalized advantage distillation (GAD). AQKD could be implemented with commercial off-the-shelf (COTS) hardware as an augmentation of present-day BB84 QKD. AQKD avoids the expense, complexity and resource duplication of "trusted relay" approaches to QKD range extension. We expect AQKD to be compatible with fiber spans containing intermediate OAs, which will facilitate its deployment as an overlay on existing fiber networks.

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arXiv2013

Network-Centric Quantum Communications with Application to Critical Infrastructure Protection

Network-centric quantum communications (NQC) - a new, scalable instantiation of quantum cryptography providing key management with forward security for lightweight encryption, authentication and digital signatures in optical networks - is briefly described. Results from a multi-node experimental test-bed utilizing integrated photonics quantum communications components, known as QKarDs, include: quantum identification; verifiable quantum secret sharing; multi-party authenticated key establishment, including group keying; and single-fiber quantum-secured communications that can be applied as a security retrofit/upgrade to existing optical fiber installations. A demonstration that NQC meets the challenging simultaneous latency and security requirements of electric grid control communications, which cannot be met without compromises using conventional cryptography, is described.

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arXiv2007

Long distance decoy state quantum key distribution in optical fiber

The theoretical existence of photon-number-splitting attacks creates a security loophole for most quantum key distribution (QKD) demonstrations that use a highly attenuated laser source. Using ultra-low-noise, high-efficiency transition-edge sensor photodetectors, we have implemented the first version of a decoy-state protocol that incorporates finite statistics without the use of Gaussian approximations in a one-way QKD system, enabling the creation of secure keys immune to photon-number-splitting attacks and highly resistant to Trojan horse attacks over 107 km of optical fiber.

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arXiv2005

Quantum key distribution at telecom wavelengths with noise-free detectors

The length of a secure link over which a quantum key can be distributed depends on the efficiency and dark-count rate of the detectors used at the receiver. We report on the first demonstration of quantum key distribution using transition-edge sensors with high efficiency and negligible dark-count rates. Using two methods of synchronization, a bright optical pulse scheme and an electrical signal scheme, we have successfully distributed key material at 1,550 nm over 50 km of optical fiber. We discuss how use of these detectors in a quantum key distribution system can result in dramatic increases in range and performance.

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arXiv2005

Enhancing practical security of quantum key distribution with a few decoy states

Quantum key distribution establishes a secret string of bits between two distant parties. Of concern in weak laser pulse schemes is the especially strong photon number splitting attack by an eavesdropper, but the decoy state method can detect this attack with current technology, yielding a high rate of secret bits. In this Letter, we develop rigorous security statements in the case of finite statistics with only a few decoy states, and we present the results of simulations of an experimental setup of a decoy state protocol that can be simply realized with current technology.

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arXiv2004

Comment on "Quantum key distribution with 1.25 Gbps clock synchronization" by J.C. Bienfang et al., quant-ph/0405097

We analyze the significance for quantum key distribution (QKD) of free-space quantum communications results reported in a recent paper (J. C. Bienfang et al., quant-ph/0405097, hereafter referred to as "Bienfang et al."), who contrast the quantum communications rate of their partial QKD implementation (which does not produce cryptographically useful shared, secret keys) over a short transmission distance, with the secret bit rates of previous full QKD implementations over much longer distances. We show that when a cryptographically relevant comparison with previous results is made, the system described by Bienfang et al. would offer no advantages for QKD, contrary to assertions in their paper and in spite of its high clock rate. Further, we show that the claim made by Bienfang et al. that "high transmission rates serve ... to extend the distance over which a QKD system can operate" is incorrect. Our analysis illustrates an important aspect of QKD that is too often overlooked in experiments: the sifted bit rate can be a highly misleading indicator of the performance of a QKD system.

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arXiv2002

Practical free-space quantum key distribution over 10 km in daylight and at night

We have demonstrated quantum key distribution (QKD) over a 10-km, 1-airmass atmospheric range during daylight and at night. Secret random bit sequences of the quality required for the cryptographic keys used to initialize secure communications devices were transferred at practical rates with realistic security. By identifying the physical parameters that determine the system's secrecy efficiency, we infer that free-space QKD will be practical over much longer ranges under these and other atmospheric and instrumental conditions.

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arXiv1999

Practical quantum cryptography for secure free-space communications

Quantum cryptography is an emerging technology in which two parties may simultaneously generate shared, secret cryptographic key material using the transmission of quantum states of light. The security of these transmissions is based on the inviolability of the laws of quantum mechanics and information-theoretically secure post-processing methods. An adversary can neither successfully tap the quantum transmissions, nor evade detection, owing to Heisenberg's uncertainty principle. In this paper we describe the theory of quantum cryptography, and the most recent results from our experimental free-space system with which we have demonstrated for the first time the feasibility of quantum key generation over a point-to-point outdoor atmospheric path in daylight. We achieved a transmission distance of 0.5 km, which was limited only by the length of the test range. Our results provide strong evidence that cryptographic key material could be generated on demand between a ground station and a satellite (or between two satellites), allowing a satellite to be securely re-keyed on orbit. We present a feasibility analysis of surface-to-satellite quantum key generation.

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