arXiv subjects

Xiaoyu Ai

Publications and source records attributed to Xiaoyu Ai.

11 recordsLinked to original sources

arXiv2026

Quantum Secure Time Transfer for Satellites

We experimentally demonstrate an entanglement-based Quantum-Secure Time Transfer (QSTT) system in an emulated low Earth orbit satellite-to-ground channel using a type-0 Sagnac-based entangled-photon source. Our new QSTT system delivers a finite Quantum Key Distribution (QKD) key rate of approximately $3~$bits$~\text{s}^{-1}$ with a $10^{-10}$ security parameter, providing a $30$-fold increase in the QKD key rate compared to the state-of-the-art entanglement-based QKD system delivered by the Micius satellite. Beyond this high key rate outcome, novel to our QSTT system is a GPS-free clock synchronization, optimized use of QKD, embedded post-quantum security, and obfuscation of the system configuration via use of a pre-shared key. Collectively, these enhancements deliver the most efficient and secure deployment of QSTT to date, and point the way forward to high-accuracy ultra-secure time transfer in space.

quant-ph↗

arXiv2025

Combined Quantum and Post-Quantum Security Performance Under Finite Keys

Recent advances in quantum-secure communication have highlighted the value of hybrid schemes that combine Quantum Key Distribution (QKD) with Post-Quantum Cryptography (PQC). Yet most existing hybrid designs omit realistic finite-key effects on QKD key rates and do not specify how to maintain security when both QKD and PQC primitives leak information through side-channels. These gaps limit the applicability of hybrid systems in practical, deployed networks. In this work, we advance a recently proposed hybrid QKD-PQC system by integrating tight finite-key security to the QKD primitive and improving the design for better scalability. This hybrid system employs an information-theoretically secure instruction sequence that determines the configurations of different primitives and thus ensures message confidentiality even when both the QKD and the PQC primitives are compromised. The novelty in our work lies in the implementation of the tightest finite-key security to date for the BBM92 protocol and the design improvements in the primitives of the hybrid system that ensure the processing time scales linearly with the size of secret instructions.

quant-ph↗

arXiv2025

A New Quantum Secure Time Transfer System

High-precision clock synchronization is essential for a wide range of network-distributed applications. In the quantum space, these applications include communication, sensing, and positioning. However, current synchronization techniques are vulnerable to attacks, such as intercept-resend attacks, spoofing, and delay attacks. Here, we propose and experimentally demonstrate a new quantum secure time transfer (QSTT) system, subsequently used for clock synchronization, that largely negates such attacks. Novel to our system is the optimal use of self-generated quantum keys within the QSTT to information-theoretically secure the maximum amount of timing data; as well as the introduction, within a hybrid quantum/post-quantum architecture, of an information-theoretic secure obfuscated encryption sequence of the remaining timing data. With these enhancements, we argue that our new system represents the most robust implementation of QSTT to date.

quant-ph↗

arXiv2025

Obfuscated Quantum and Post-Quantum Cryptography

In this work, we present an experimental deployment of a new design for combined quantum key distribution (QKD) and post-quantum cryptography (PQC). Novel to our system is the dynamic obfuscation of the QKD-PQC sequence of operations, the number of operations, and parameters related to the operations; coupled to the integration of a GPS-free quantum synchronization protocol within the QKD process. We compare the performance and overhead of our QKD-PQC system relative to a standard QKD system with one-time pad encryption, demonstrating that our design can operate in real time with little additional overhead caused by the new security features. Since our system can offer additional defensive strategies against a wide spectrum of practical attacks that undermine deployed QKD, PQC, and certain combinations of these two primitives, we suggest that our design represents one of the most secure communication systems currently available. Given the dynamic nature of its obfuscation attributes, our new system can also be adapted in the field to defeat yet-to-be-discovered practical attacks.

quant-ph↗

arXiv2025

A Position- and Energy-Aware Routing Strategy for Subterranean LoRa Mesh Networks

Although LoRa is predominantly employed with the single-hop LoRaWAN protocol, recent advancements have extended its application to multi-hop mesh topologies. Designing efficient routing for LoRa mesh networks remains challenging due to LoRa's low data rate and ALOHA-based MAC. Prior work often adapts conventional protocols for low-traffic, aboveground networks with strict duty cycle constraints or uses flooding-based methods in subterranean environments. However, these approaches inefficiently utilize the limited available network bandwidth in these low-data-rate networks due to excessive control overhead, acknowledgments, and redundant retransmissions. In this paper, we introduce a novel position- and energy-aware routing strategy tailored for subterranean LoRa mesh networks aimed at enhancing maximum throughput and power efficiency while also maintaining high packet delivery ratios. Our mechanism begins with a lightweight position learning phase, during which LoRa repeaters ascertain their relative positions and gather routing information. Afterwards, the network becomes fully operational with adaptive routing, leveraging standby LoRa repeaters for recovery from packet collisions and losses, and energy-aware route switching to balance battery depletion across repeaters. The simulation results on a representative subterranean network demonstrate a 185% increase in maximum throughput and a 75% reduction in energy consumption compared to a previously optimized flooding-based approach for high traffic.

cs.NI↗

arXiv2025

Combined Quantum and Post-Quantum Security for Earth-Satellite Channels

Experimental deployment of quantum communication over Earth-satellite channels opens the way to a secure global quantum Internet. In this work, we present results from a real-time prototype quantum key distribution (QKD) system, which entails the development of optical systems including the encoding of entangled photon pairs, the development of transmitters for quantum signaling through an emulated Earth-satellite channel, and the development of quantum-decoding receivers. A unique aspect of our system is the integration of QKD with existing cryptographic methods to ensure quantum-resistant security, even at low-key rates. In addition, we report the use of specially designed error-reconciliation codes that optimize the security versus key-rate trade-off. Our work demonstrates, for the first time, a deployment of the BBM92 protocol that offers both post-quantum security via the advanced encryption standard (AES) and quantum security via an entanglement-based QKD protocol. If either the AES or the QKD is compromised through some adversary attack, our system still delivers state-of-the-art communications secure against future quantum computers.

quant-ph↗

arXiv2024

Robot-As-A-Sensor: Forming a Sensing Network with Robots for Underground Mining Missions

Nowadays, robots are deployed as mobile platforms equipped with sensing, communication and computing capabilities, especially in the mining industry, where they perform tasks in hazardous and repetitive environments. Despite their potential, individual robots face significant limitations when completing complex tasks that require the collaboration of multiple robots. This collaboration requires a robust wireless network to ensure operational efficiency and reliability. This paper introduces the concept of "Robot-As-A-Sensor" (RAAS), which treats the robots as mobile sensors within structures similar to Wireless Sensor Networks (WSNs). We later identify specific challenges in integrating RAAS technology and propose technological advancements to address these challenges. Finally, we provide an outlook about the technologies that can contribute to realising RAAS, suggesting that this approach could catalyse a shift towards safer, more intelligent, and sustainable industry practices. We believe that this innovative RAAS framework could significantly transform industries requiring advanced technological integration.

cs.NI↗

arXiv2024

Seeing Text in the Dark: Algorithm and Benchmark

Localizing text in low-light environments is challenging due to visual degradations. Although a straightforward solution involves a two-stage pipeline with low-light image enhancement (LLE) as the initial step followed by detector, LLE is primarily designed for human vision instead of machine and can accumulate errors. In this work, we propose an efficient and effective single-stage approach for localizing text in dark that circumvents the need for LLE. We introduce a constrained learning module as an auxiliary mechanism during the training stage of the text detector. This module is designed to guide the text detector in preserving textual spatial features amidst feature map resizing, thus minimizing the loss of spatial information in texts under low-light visual degradations. Specifically, we incorporate spatial reconstruction and spatial semantic constraints within this module to ensure the text detector acquires essential positional and contextual range knowledge. Our approach enhances the original text detector's ability to identify text's local topological features using a dynamic snake feature pyramid network and adopts a bottom-up contour shaping strategy with a novel rectangular accumulation technique for accurate delineation of streamlined text features. In addition, we present a comprehensive low-light dataset for arbitrary-shaped text, encompassing diverse scenes and languages. Notably, our method achieves state-of-the-art results on this low-light dataset and exhibits comparable performance on standard normal light datasets. The code and dataset will be released.

cs.CV↗

arXiv2023

Quantum Key Distribution Using a Quantum Emitter in Hexagonal Boron Nitride

Quantum Key Distribution (QKD) is considered the most immediate application to be widely implemented amongst a variety of potential quantum technologies. QKD enables sharing secret keys between distant users, using photons as information carriers. An ongoing endeavour is to implement these protocols in practice in a robust, and compact manner so as to be efficiently deployable in a range of real-world scenarios. Single Photon Sources (SPS) in solid-state materials are prime candidates in this respect. Here, we demonstrate a room temperature, discrete-variable quantum key distribution system using a bright single photon source in hexagonal-boron nitride, operating in free-space. Employing an easily interchangeable photon source system, we have generated keys with one million bits length, and demonstrated a secret key of approximately 70,000 bits, at a quantum bit error rate of 6%, with $\varepsilon$-security of $10^{-10}$. Our work demonstrates the first proof of concept finite-key BB84 QKD system realised with hBN defects.

quant-ph↗

arXiv2022

Integrated Room Temperature Single Photon Source for Quantum Key Distribution

High-purity single photon sources (SPS) that can operate at room temperature are highly desirable for a myriad of applications, including quantum photonics and quantum key distribution. In this work, we realise an ultra-bright solid-state SPS based on an atomic defect in hexagonal boron nitride (hBN) integrated with a solid immersion lens (SIL). The SIL increases the source efficiency by a factor of six, and the integrated system is capable of producing over ten million single photons per second at room temperature. Our results are promising for practical applications of SPS in quantum communication protocols.

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arXiv2021

Optimised Multithreaded CV-QKD Reconciliation for Global Quantum Networks

Designing a practical Continuous Variable (CV) Quantum Key Distribution (QKD) system requires an estimation of the quantum channel characteristics and the extraction of secure key bits based on a large number of distributed quantum signals. Meeting this requirement in short timescales is difficult. On standard processors, it can take several hours to reconcile the required number of quantum signals. This problem is exacerbated in the context of Low Earth Orbit (LEO) satellite CV-QKD, in which the satellite flyover time is constrained to be less than a few minutes. A potential solution to this problem is massive parallelisation of the classical reconciliation process in which a large-code block is subdivided into many shorter blocks for individual decoding. However, the penalty of this procedure on the important final secured key rate is non-trivial to determine and hitherto has not been formally analysed. Ideally, a determination of the optimal reduced block size, maximising the final key rate, would be forthcoming in such an analysis. In this work, we fill this important knowledge gap via detailed analyses and experimental verification of a CV-QKD sliced reconciliation protocol that uses large block-length low-density parity-check decoders. Our new solution results in a significant increase in the final key rate relative to non-optimised reconciliation. In addition, it allows for the acquisition of quantum secured messages between terrestrial stations and LEO satellites within a flyover timescale even using off-the-shelf processors. Our work points the way to optimised global quantum networks secured via fundamental physics.

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