AlGaN-based solar-blind ultraviolet photodetectors have attractive potential applications in the fields of missile plume detection, biochemical sensing, solar astronomy, etc. In this work, significant deep ultraviolet detection enhancement is demonstrated on AlGaN-based metal–semiconductor–metal (MSM) solar-blind ultraviolet photodetectors by introducing the coupling of localized surface plasmon from Al nanoparticles with the high-Al-content AlGaN epilayer. The size-controlled Al nanoparticle arrays fabricated by nanosphere lithography can not only reduce the detectors' dark current but also bring about greatly enhanced responsivity. The peak responsivity of AlGaN-based MSM solar-blind ultraviolet photodetectors with Al nanoparticles can reach 2.34 A/W at 269 nm under 20 V bias, enhanced more than 25 times than that without Al nanoparticles. Our approach shows an efficient fabrication technique of high-performance and low-cost plasmonic enhanced AlGaN solar-blind MSM ultraviolet photodetectors.
Quantum key distribution (QKD) has been proved to be information-theoretically secure in theory. Unfortunately, the imperfect devices in practice compromise its security. Thus, to improve the security property of practical QKD systems, a commonly used method is to patch the loopholes in the existing QKD systems. However, in this work, we show an adversary’s capability of exploiting the imperfection of the patch itself to bypass the patch. Specifically, we experimentally demonstrate that, in the detector under test, the patch of photocurrent monitor against the detector blinding attack can be defeated by the pulse illumination attack proposed in this paper. We also analyze the secret key rate under the pulse illumination attack, which theoretically confirmed that Eve can conduct the attack to learn the secret key. This work indicates the importance of inspecting the security loopholes in a detection unit to further understand their impacts on a QKD system. The method of pulse illumination attack can be a general testing item in the security evaluation standard of QKD.
Quantum key distribution (QKD) generates symmetric keys between two authenticated parties with the guarantee of information-theoretically security. A vital step in QKD to obtain fully-matched key between two parties is information reconciliation. the blind reconciliation protocol provides a useful tool that corrects the mismatch in a wide range of qubit error rate (QBeR) but without a prior error estimation. However, there is a contradiction between the reconciliation efficiency and the processing time in this protocol. in this work, we propose a blind reconciliation protocol with variable step sizes to relieve this contradiction. the analysis and simulation results show that the improved protocol inherits all the advantages of the original blind reconciliation protocol and can obtain better reconciliation efficiency with less operation time. The improved blind reconciliation protocol enhances the final secret key rate and accelerates the processing speed of a QKD system.Quantum key distribution (QKD) 1,2 allows two parties, usually called Alice and Bob, to share a pair of secret key via an insecure channel. QKD is proved to be information-theoretically secure owing to the solid foundation of quantum physics without computational assumptions 3-5 . The technology of QKD has been developed quickly in the past three decades and has achieved remarkable milestones. For example, QKD products has been commercialized with growing market 6 ; QKD networks has been constructed in several countries around the world 7-9 ; a QKD satellite realizes secure communication in global scale 10,11 . Thus, QKD is one of the most mature fields in quantum information.In the implementation of QKD, a system operates two main phases to establish the shared key -the phase of quantum raw key exchange and the phase of classical post-processing 12 . At the first phase, Alice and Bob share the raw key by transmitting quantum states prepared by Alice through a quantum channel and measuring them by Bob. Then, sifting as the first step of classical post-processing helps Alice and Bob to maintain the cases that they are using the matched bases. The raw key is obtained after this step. However, the raw key shared between Alice and Bob may contain errors due to the channel noise and adversary's attacks. To eliminate the mismatch of the raw key between Alice and Bob, the system runs information reconciliation to guarantee that the same string of key shared at both sides. The reconciled key maybe partially correlated with an adversary, since the adversary can interact with the quantum states during the raw key exchange via quantum channel and listen to the public information during the information reconciliation via the classical channel. Thus, privacy amplification is applied to remove the leaked information, thereby obtaining the final secret key share between Alice and Bob. The sifting, information reconciliation, and privacy amplification are called as the post-processing phase.In the post-processing, it is obvious that information reconciliation is...
Simulators for photonic quantum information processing (PQIP) experiments are essentially different with currently available quantum-circuit simulators. In PQIP experiments, photons are usually encoded by multiple degrees of freedom, some of which are multi-level or even infinite-level. Moreover, the evolution of indistinguishable photons cannot be described elegantly by the model used in quantum-circuit simulators. A simulator focusing on PQIP experiments is urgently needed, as it plays an important role in PQIP experiments designing and verification. We developed PhotoniQLAB, an object-oriented framework designed for simulating PQIP experiments, which provides a virtual-lab user experience. The core simulation unit is a computer algebraic system based on the second quantization method. PhotoniQLAB only requires users to enter the structure information of a target PQIP experiment to conduct a simulation, as it can understand the topological structure by itself. The mathematical foundation and technical details of PhotoniQLAB are discussed in the paper. The performance of PhotoniQLAB, which is analyzed and used to simulate several experimental schemes in this paper, has been shown to be efficient enough for near-term PQIP experiments. PhotoniQLAB shows its flexibility and universality, through simulating more than 60 existing PQIP experiments in published papers. We believe that PhotoniQLAB will become a fundamental PQIP software infrastructure facilitating the analyses and designs of PQIP experiments.
The physical imperfections of quantum key distribution systems compromise their information-theoretic security. By exploiting the imperfections on the detection unit, an eavesdropper can launch various detector-control attacks to steal the secret key. Recently, in Optica 6, 1178 (2019)OPTIC82334-253610.1364/OPTICA.6.001178 entitled “Robust countermeasure against detector control attack in a practical quantum key distribution system,” Qian et al. proposed a countermeasure using variable attenuators in the detection unit that was claimed to be effective against detector-control attacks with or without blinding light. We comment on this paper, disputing this countermeasure by showing that their assumptions for proving this effectiveness are unrealistic.
Cytochrome P450 (CYP) 1B1 has been found to be overexpressed specifically in tumor tissues at an early stage, which makes it a potential cancer biomarker for molecular imaging. Multimodal imaging combines different imaging modalities and offers more comprehensive information. Thus, imaging probes bearing more than one kind of signal fragment have been extensively explored and display great promise. Herein, we developed a near infrared (NIR) probe with a chelator moiety targeting CYP1B1 by conjugating α‐naphthoflavone (ANF) derivatives with both an NIR dye and a chelator for potential application in bimodal imaging. Enzymatic inhibitory studies demonstrated inhibitory activity against CYP1B1 and selectivity among CYP1 were successfully retained after chemical modification. Cell‐based saturation studies indicated nanomolar range binding affinity between the probe and CYP1B1 overexpressed cancer cells. In vitro competitive binding assays monitored by confocal microscopy revealed that the probe could specifically accumulate in tumor cells. In vivo and ex vivo imaging studies demonstrated that the probe could effectively light‐up the tumor tissues as early as 2 hours post‐injection. In addition, the fluorescence was significantly blocked by co‐injection of CYP1B1 inhibitor, which indicated the probe accumulation in tumor sites was due to specific binding to CYP1B1.
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