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Longer distance continuous variable quantum key distribution protocol with photon subtraction at the receiver
摘要： One of the limitations of continuous variable quantum key distribution is the relatively short transmission distance of secure keys. Some solutions have been proposed to overcome the limitation including reverse reconciliation, trusted noise concept, and non-Gaussian operation. In this paper, we propose a protocol using photon subtraction at the receiver, which combines the synergetic benefits of the aforementioned approaches. Using simulations, we show that the performance of the proposed protocol outperforms other conventional protocols. The results showed that an improvement in secure key distance can be obtained using a non-Gaussian operation, depending on the position where the operation is performed, similar to the trusted noise concept. Furthermore, the result implies existence of some Gaussian operations which increases security without using a beam splitter.
关键词： Continuous variable quantum key distribution,Quantum cryptography,Quantum information and processing,Non-Gaussian state
更新于2025-09-19 17:15:36
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Gaussian random number generator: Implemented in FPGA for quantum key distribution
摘要： Quantum key distribution is the process of using quantum communication to establish a shared key between two parties. It has been demonstrated the unconditional security and effective communication of quantum communication system can be guaranteed by an excellent Gaussian random number (GRN) generator with high speed and an extended random period. In this paper, we propose to construct the Gaussian random number generator by using field‐programmable gate array (FPGA), which is able to process large data in high speed. We also compare three algorithms of GRN generation: Box‐Muller algorithm, polarization decision algorithm, and central limit algorithm. We demonstrate that the polarization decision algorithm implemented in FPGA requires less computing resources and also produces a high‐quality GRN through the null hypothesis test.
关键词： field‐programmable gate array,numerical modeling,quantum key distribution,Gaussian random numbers
更新于2025-09-19 17:15:36
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Improvement of Passivation Quality by Post-Crystallization Treatments with Different Methods for High Quality Tunnel Oxide Passivated Contact c-Si Solar Cells
摘要： We present practical GHz-clocked QKD systems, next generation entanglement QKD technologies, and QKD platform to manage the secure keys and to support a variety of applications. We then show the intrinsic limit of QKD, i.e., a key rate bound, and discuss how to realize the provable (information theoretic) security with a larger secrecy capacity over longer distances. In particular, we present a basic theory of physical layer cryptography, which characterizes the secrecy capacity, and engineers the tradeoff between the efficiency of reliable transmission and secrecy of communication. We introduce a concept to unify these schemes in photonic network, referred to as quantum photonic network. Future issues for realizing this new network paradigm are discussed.
关键词： Quantum communication,photonic network,quantum key distribution,quantum cryptography
更新于2025-09-19 17:13:59
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[IEEE 2019 Photonics North (PN) - Quebec City, QC, Canada (2019.5.21-2019.5.23)] 2019 Photonics North (PN) - Performance of diode-pumped Yb:CALGO and Yb:KYW lasers
摘要： Quantum key distribution (QKD) is an innovative technology that exploits the laws of quantum mechanics to generate and distribute unconditionally secure shared key for use in cryptographic applications. However, QKD is a relatively nascent technology where real-world system implementations differ significantly from their ideal theoretical representations. In this paper, we introduce a modeling framework built upon the OMNeT++ discrete event simulation framework to study the impact of implementation nonidealities on QKD system performance and security. Specifically, we demonstrate the capability to study the device imperfections and practical engineering limitations through the modeling and simulation of a polarization-based, prepare and measure BB84 QKD reference architecture. The reference architecture allows users to model and study complex interactions between physical phenomenon and system-level behaviors representative of real-world design and implementation tradeoffs. Our results demonstrate the flexibility of the framework to simulate and evaluate current, future, and notional QKD protocols and components.
关键词： system performance,system security,Quantum key distribution,modeling & simulation
更新于2025-09-19 17:13:59
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Laser-Damage Attack Against Optical Attenuators in Quantum Key Distribution
摘要： Many quantum key distribution systems employ a laser followed by an optical attenuator to prepare weak coherent states in the source. Their mean photon number must be precalibrated to guarantee the security of key distribution. Here we experimentally show that this calibration can be broken with a high-power laser attack. We test four fiber-optic attenuator types used in quantum key distribution systems, and find that two of them exhibit a permanent decrease in attenuation after laser damage. This results in higher mean photon numbers in the prepared states and may allow an eavesdropper to compromise the key.
关键词： laser damage,optical attenuator,quantum key distribution,security
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Field Trial of a Finite-Key Quantum Key Distribution System in the Metropolitan Florence Area
摘要： In a society based on the continuous exchange of sensitive data and information, the importance of secure and trustful communications is essential. Quantum key distribution (QKD) makes it possible to share data in an unconditionally secure way exploiting the basic principles of Quantum Mechanics [1]. During the last 30 years, many QKD protocols have been developed and tested, achieving long distance transmission [2] and secret key rates up to hundreds of Mbits per second [3]. However, this technology is still far from a large-scale deployment in existing fiber networks and telecom infrastructures, due to multiple factors: low secret-key rate, limited distance between users, lack of applications, high costs and high requirements in terms of low noise fiber links. In order to reveal practical issues in real-world deployments, quantum field trials have been implemented by exploiting installed fiber links on a metropolitan scale. While many of these experiments were performed on a dark fiber (thus requiring a dedicated link for quantum key transmission only), other field trials explored the coexistence between weak coherent pulses and classical signals propagating through the same fiber [4-7], see Figure 1 a). In this work we report a low-cost field trial demonstration of a complete QKD system working in the C-band telecom wavelength, performed over an installed fiber situated in Florence. A time-bin three-stateprotocol with one-decoy state method is implemented in the experiment [2]. As illustrated in Figure 1 b), theexperimental setup consists of a transmitter (Alice), working at ch 21 of 100GHz DWDM grid, and a receiver(Bob) connected by a metropolitan dark-fiber link in a loop-back configuration. The total distance covered in thefiber link is about 40 km, with an overall transmission loss of 21 dB. Secure key generation of 3.4 kbps (in thefinite key scenario) is achieved, with simultaneous transmission of a classical synchronization signal, at adifferent wavelength (ch 51 of 100GHz DWDM grid with -29 dBm input power), through the same fiber. InFigure 1 c) we report the secret key rate and the bit error rate, measured for several hours to prove the stability ofthe apparatus.
关键词： metropolitan network,QKD,finite-key analysis,Quantum key distribution,field trial
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Highly Efficient Ultra-Broadband Entangled Photon-Pair Generation using a Chirped PPSLT Ridge Waveguide
摘要： As some of the most promising quantum applications such as high resolution quantum optical coherence tomography (QOCT) with dispersion cancellation as well as quantum key distribution require frequency entanglement. Therefore, frequency entanglement light sources are an essential importance for implement of many quantum optical applications. So Far, the most prominent method used for the entangled photon pair generation is spontaneous parametric down-conversion (SPDC) in nonlinear crystals. Recently, with adopting chirp quasi-phase matching (QPM) PPSLT (periodically poled stoichiometric lithium tantalate) has been used as source of entangled photons with large bandwidth. However, improving the overall system ef?ciency is still remain challenging. One realistic approach is improving the generation ef?ciency of the entanglement source, we developed a source for highly ef?cient frequency entangled photon pairs generation utilizing type-0 PPSLT by adopting chirp QPM technology together with ridge waveguide structure. In experiments, we use 10 mm long waveguides with chirp rate of 0%, 3% and 6.7%. After coupling 405 nm CW pump light into a waveguide we fed the collinearly emitted photons into a single mode ?ber then observed its spectrum with a spectroscope. During experiments, temperature of all waveguides were set to 70.8?C with an accuracy of 0.1?C to ensure the degenerated phase matching condition of fundamental modes for signal, idler and pump lights is met in our multi-mode waveguides. As results are shown in Fig.1 (a), we observed a ～ 20 nm bandwidth sinc function-like spectrum emitted from the 0% chirp waveguide (blue dots), moreover, with increasing device chirp rate we also managed to obtain the broadening of spectra. The measured result of a 3% chirp rate device shows a spectrum with ～ 240 nm bandwidth, as well as ～ 340 nm bandwidth (orange dots) spectrum generated via the 6.7% one. In order to properly evaluate the generation ef?ciency of collinearly emitted photons we separate them with a 50:50 ?ber beam splitter, since signal and idler photons share the same spatial mode (fundamental mode of ridge waveguide) and identical in both frequency and polarization degree of freedom. Fig.1 (b) is the power dependency measurement results measured with a 3% chirp rate waveguide, signal and idler counts are the recorded counting rate of events from two SSPDs. We estimate the generation ef?ciency as 3.2×106 pairs/s·μW. This result appears 1000 times higher compared to our previous result (2×103 pairs/s·μW) observed using a chirped bulk QPM device.
关键词： ridge waveguide structure,frequency entanglement,quantum optical coherence tomography,quantum key distribution,PPSLT,chirp quasi-phase matching,spontaneous parametric down-conversion
更新于2025-09-16 10:30:52
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Self-error-rejecting quantum state transmission of entangled photons for faithful quantum communication without calibrated reference frames
摘要： We propose an alignment-free two-party polarization-entanglement transmission scheme for entangled photons by using only linear-optical elements, requiring neither ancillary photons nor calibrated reference frames. The scheme is robust against both the random channel noise and the instability of reference frames. Furthermore, the success probabilities for entanglement transmission are, in principle, improved to unity when active polarization controllers are used. The distinct characters of a simple structure, being easy to implement, and the high fidelity and efficiency make our protocol very useful for long-distance quantum communications and distributed quantum networks in practical applications. As an example, we give its application in a reference-frame-alignment-free quantum key distribution protocol with entanglement.
关键词： quantum communication,quantum key distribution,entanglement transmission,polarization-entangled photons,linear-optical elements
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Quantum Key Distribution Exploiting a Faraday Rotator and a Single Spad
摘要： Nowadays encryption is exploited for protecting information exchange in several applications. Nevertheless the security of commonly used algorithms of encryption is based on the extremely high computational cost required for message decryption. On the other hand, quantum key distribution (QKD) allows for exchanging a key between two users (Alice and Bob) in a way that has been proved as unconditional secure, thanks to the fundamental principles of quantum physics [1-3]. However to make the QKD a reliable and effective widespread solution, it is essential to reduce the cost and expand the scalability. In the present work we show the experimental validation of a novel implementation of the BB84 protocol, where Bob uses a Faraday rotator (FR) variable over four states and only one single-photon avalanche detector (SPAD), as schematized in Fig. 1(a). Alice transmit to Bob a stream of polarized single photons, obtained by a strongly attenuated laser followed by a polarization controller. The polarization of each photon is set by Alice in one state of polarization among four possible states (horizontal, vertical, diagonal, antidiagonal). A key bit is exchanged in a secure way through the quantum channel when Alice and Bob choose the same basis (either "rectilinear" or "diagonal") and a photon is detected by the SPAD after a polarizer set in a fixed state (e.g., vertical). Bob chooses the rotation angle of FR among four possible values (0°, 45°, 90°, 135°), hence making two binary choices. The first one (i.e., a rotation of either 0° or 45°) represents the choice of the measurement basis and is communicated to Alice through the public channel, while the second one (i.e., an additional rotation of either 0° or 90°) is maintained secret and allows Bob for determining the key bit.
关键词： Single SPAD,BB84 protocol,Quantum Key Distribution,Faraday Rotator
更新于2025-09-16 10:30:52
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[IEEE 2019 21st International Middle East Power Systems Conference (MEPCON) - Cairo, Egypt (2019.12.17-2019.12.19)] 2019 21st International Middle East Power Systems Conference (MEPCON) - Negative-Positive Neutral Point Based Two-Stage Inverter for Photovoltaic Application
摘要： The quantum key distribution protocol uses one degree of freedom of a single quantum system to encode information. If this information has correlations with the system’s other degrees of freedom, or if the measurement efficiencies on the receiver side depend on them, a security loophole called side channel is created. An eavesdropper can exploit it to gain information without disturbing the system, and thus, without revealing the attack. Here, we analyze side channels in a free-space QKD sender and receiver implementation and focus especially on the dependencies and side channels for the spatial degree of freedom.
关键词： Cryptographic protocols,optical transmitters,optical receivers,quantum key distribution (QKD)
更新于2025-09-16 10:30:52