An integrated space-to-ground quantum communication network over 4,600 kilometres.

Quantum key distribution (QKD)1,2 has the potential to enable secure communication and information transfer3. In the laboratory, the feasibility of point-to-point QKD is evident from the early proof-of-concept demonstration in the laboratory over 32 centimetres4; this distance was later extended to the 100-kilometre scale5,6 with decoy-state QKD and more recently to the 500-kilometre scale7-10 with measurement-device-independent QKD. Several small-scale QKD networks have also been tested outside the laboratory11-14. However, a global QKD network requires a practically (not just theoretically) secure and reliable QKD network that can be used by a large number of users distributed over a wide area15. Quantum repeaters16,17 could in principle provide a viable option for such a global network, but they cannot be deployed using current technology18. Here we demonstrate an integrated space-to-ground quantum communication network that combines a large-scale fibre network of more than 700 fibre QKD links and two high-speed satellite-to-ground free-space QKD links. Using a trusted relay structure, the fibre network on the ground covers more than 2,000 kilometres, provides practical security against the imperfections of realistic devices, and maintains long-term reliability and stability. The satellite-to-ground QKD achieves an average secret-key rate of 47.8 kilobits per second for a typical satellite pass-more than 40 times higher than achieved previously. Moreover, its channel loss is comparable to that between a geostationary satellite and the ground, making the construction of more versatile and ultralong quantum links via geosynchronous satellites feasible. Finally, by integrating the fibre and free-space QKD links, the QKD network is extended to a remote node more than 2,600 kilometres away, enabling any user in the network to communicate with any other, up to a total distance of 4,600 kilometres.

Entanglement-based secure quantum cryptography over 1,120 kilometres.

Quantum key distribution (QKD)1-3 is a theoretically secure way of sharing secret keys between remote users. It has been demonstrated in a laboratory over a coiled optical fibre up to 404 kilometres long4-7. In the field, point-to-point QKD has been achieved from a satellite to a ground station up to 1,200 kilometres away8-10. However, real-world QKD-based cryptography targets physically separated users on the Earth, for which the maximum distance has been about 100 kilometres11,12. The use of trusted relays can extend these distances from across a typical metropolitan area13-16 to intercity17 and even intercontinental distances18. However, relays pose security risks, which can be avoided by using entanglement-based QKD, which has inherent source-independent security19,20. Long-distance entanglement distribution can be realized using quantum repeaters21, but the related technology is still immature for practical implementations22. The obvious alternative for extending the range of quantum communication without compromising its security is satellite-based QKD, but so far satellite-based entanglement distribution has not been efficient23 enough to support QKD. Here we demonstrate entanglement-based QKD between two ground stations separated by 1,120 kilometres at a finite secret-key rate of 0.12 bits per second, without the need for trusted relays. Entangled photon pairs were distributed via two bidirectional downlinks from the Micius satellite to two ground observatories in Delingha and Nanshan in China. The development of a high-efficiency telescope and follow-up optics crucially improved the link efficiency. The generated keys are secure for realistic devices, because our ground receivers were carefully designed to guarantee fair sampling and immunity to all known side channels24,25. Our method not only increases the secure distance on the ground tenfold but also increases the practical security of QKD to an unprecedented level.

A novel therapeutic approach to modulate the inflammatory cascade: A timely exogenous local inflammatory response attenuates the sepsis-induced cytokine storm.

BACKGROUND: The emergence of severe sepsis is contingent upon the occurrence of a cytokine storm (CS), a multifaceted process intricately entwined with the temporal dimension, thereby rendering the infection response remarkably intricate. Consequently, it becomes imperative to discern and accurately identify the optimal timing for interventions, predicated upon the dynamic timeline of inflammatory changes. Moreover, the administration of exogenous low-dose pro-inflammatory agents has exhibited the potential to impede the relentless progression of the inflammatory cascade. Hence, the present study aims to scrutinize the impact of exogenous Local Inflammatory Response (eLIR) on the body surface in the context of the inflammatory cascade during sepsis, within a temporal framework, with a particular emphasis on the point of exacerbation of inflammation. METHODS: Rats were induced sterile sepsis by intraperitoneal injection of zymosan (ZY) at an appropriate dosage. The temporal progression of inflammatory changes and eLIR effects were described based on the trend of serum crucial inflammatory cytokines, tring to quest time-point of inflammatory aggravation in sepsis. Then, the varying degrees of surface inflammation caused by eLIR on this time point leading to the final effects on the inflammatory cascade response were explored. In addition, given the authentic pathological progression of sepsis, further observation was conducted on the impact of another intervention timing of eLIR on the inflammatory cascade. The survival rate was measured. Serum and organ related inflammatory cytokines were detected, and organ histopathology was investigated. RESULTS: In present study, a dosage of 600 mg/kg ZY was found to be optimal for the sterile sepsis model. Initiating eLIR 6 h prior to ZY injection, the maximum effect point of eLIR could be precisely align with the inflammatory aggravation point of sterile sepsis. Initiating eLIR at this time, 3 sessions of eLIR were found to be more effective than 1 or 2 sessions in mitigating inflammatory responses during the initial stage of inflammation and the peak of inflammation. Notably, the findings also suggested that this intervention improve survival rate. In addition, the anti-inflammatory efficacy has been substantially diminished by the prompt initiation of 3 sessions of eLIR immediately after ZY injection at the onset of sepsis. Similarly, the current findings did not demonstrate a statistically significant enhancement in survival rates with eLIR at this time point. CONCLUSIONS: Compared with the initial stage of inflammation, low-scale inflammation caused by a certain intensity of eLIR (3 sessions) on the body surface can more effectively pry the inflammation aggravation time-point, thereby shifting the pro-inflammatory to anti-inflammatory milieu, impeding the disproportionate cytokines release in inflammatory diseases, slowing down the inflammatory cascade, and improving the survival rate of sepsis.

Twin-Field Quantum Key Distribution with Local Frequency Reference.

Twin-field quantum key distribution (TFQKD) overcomes the linear rate-loss limit, which promises a boost of secure key rate over long distance. However, the complexity of eliminating the frequency differences between the independent laser sources hinders its practical application. We analyzed and determined the frequency stability requirements for implementing TFQKD using frequency-stabilized lasers. Based on this analysis, we proposed and demonstrated a simple and practical approach that utilizes the saturated absorption spectroscopy of acetylene as an absolute reference, eliminating the need for fast frequency locking to achieve TFQKD. Adopting the 4-intensity sending-or-not-sending TFQKD protocol, we experimentally demonstrated the TFQKD over 502, 301, and 201 km ultralow-loss optical fiber, respectively. We expect this high-performance scheme will find widespread usage in future intercity and free-space quantum communication networks.

Case report: A complete lower cervical fracture dislocation without permanent neurological impairment.

BACKGROUND: Complete fractures and dislocations of the lower cervical spine are usually associated with severe spinal cord injury. However, a very small number of patients do not have severe spinal cord injury symptoms, patients with normal muscle strength or only partial nerve root symptoms, known as "lucky fracture dislocation". The diagnosis and treatment of such patients is very difficult. Recently, we successfully treated one such patient. CASE PRESENTATION: A 73-year-old male patient had multiple neck and body aches after trauma, but there was sensory movement in his limbs. However, preoperative cervical radiographs showed no significant abnormalities, and computed tomography (CT) and magnetic resonance imaging (MRI) confirmed complete fracture and dislocation of C7. Before operation, the halo frame was fixed traction, but the reduction was not successful. Finally, the fracture reduction and internal fixation were successfully performed by surgery. The postoperative pain of the patient was significantly relieved, and the sensory movement of the limbs was the same as before. Two years after surgery, the patient's left little finger and ulnar forearm shallow sensation recovered, and the right flexion muscle strength basically returned to normal. CONCLUSION: This case suggests that when patients with trauma are encountered in the clinic, they should be carefully examined, and the presence of cervical fracture and dislocation should not be ignored because of the absence of neurological symptoms or mild symptoms. In addition, positioning during handling and surgery should be particularly avoided to increase the risk of paralysis.

Virus-like Plasmonic Nanoprobes for Quick Analysis of Antiviral Efficacy and Mutation-Induced Drug Resistance.

As the pathogenic viruses and the variants of concern greatly threaten human health and global public safety, the development of convenient and robust strategies enabling rapid analysis of antiviral drug efficacy and mutation-induced resistance is quite important to prevent the spread of human epidemics. Herein, we introduce a simple single-particle detection strategy for quick analysis of anti-infective drugs against SARS-CoV-2 and mutation-induced drug resistance, by using the wild-type and mutant spike protein-functionalized AuNPs as virus-like plasmonic nanoprobes. Both the wild-type and mutant virus-like plasmonic nanoprobes can form core-satellite nanoassemblies with the ACE2@AuNPs, providing the opportunity to detect the drug efficacy and mutation-induced resistance by detecting the changes of nanoassemblies upon drug treatment with dark-field microscopy. As a demonstration, we applied the single-particle detection strategy for quantitative determination of antiviral efficacy and mutation-induced resistance of ceftazidime and rhein. The mutations in the receptor-binding domain of Omicron variant could lead to an increase of EC50 values of ceftazidime and rhein, formerly from 49 and 57 µM against wild-type SARS-CoV-2, to 121 and 340 µM, respectively. The mutation-induced remarkable decline in the inhibitory efficacy of drugs was validated with molecule docking analysis and virus-like plasmonic nanoprobe-based cell-incubation assay. Due to the generality and feasibility of the strategy for the preparation of virus-like plasmonic nanoprobes and single-particle detection, we anticipated that this simple and robust method is promising for the discovery and efficacy evaluation of anti-infective drugs against different pathogenic viruses.

Twin-Field Quantum Key Distribution without Phase Locking.

Twin-field quantum key distribution (TF-QKD) has emerged as a promising solution for practical quantum communication over long-haul fiber. However, previous demonstrations on TF-QKD require the phase locking technique to coherently control the twin light fields, inevitably complicating the system with extra fiber channels and peripheral hardware. Here, we propose and demonstrate an approach to recover the single-photon interference pattern and realize TF-QKD without phase locking. Our approach separates the communication time into reference frames and quantum frames, where the reference frames serve as a flexible scheme for establishing the global phase reference. To do so, we develop a tailored algorithm based on fast Fourier transform to efficiently reconcile the phase reference via data postprocessing. We demonstrate no-phase-locking TF-QKD from short to long distances over standard optical fibers. At 50-km standard fiber, we produce a high secret key rate (SKR) of 1.27 Mbit/s, while at 504-km standard fiber, we obtain the repeaterlike key rate scaling with a SKR of 34 times higher than the repeaterless secret key capacity. Our work provides a scalable and practical solution to TF-QKD, thus representing an important step towards its wide applications.

Free-Space and Fiber-Integrated Measurement-Device-Independent Quantum Key Distribution under High Background Noise.

Measurement-device-independent quantum key distribution (MDI QKD) provides immunity against all attacks targeting measurement devices. It is essential to implement MDI QKD in the future global-scale quantum communication network. Toward this goal, we demonstrate a robust MDI QKD fully covering daytime, overcoming the high background noise that prevents BB84 protocol even when using a perfect single-photon source. Based on this, we establish a hybrid quantum communication network that integrates free-space and fiber channels through Hong-Ou-Mandle (HOM) interference. Additionally, we investigate the feasibility of implementing HOM interference with moving satellites. Our results serve as a significant cornerstone for future integrated space-ground quantum communication networks that incorporate measurement-device-independent security.

Experimental Twin-Field Quantum Key Distribution over 1000 km Fiber Distance.

Quantum key distribution (QKD) aims to generate secure private keys shared by two remote parties. With its security being protected by principles of quantum mechanics, some technology challenges remain towards practical application of QKD. The major one is the distance limit, which is caused by the fact that a quantum signal cannot be amplified while the channel loss is exponential with the distance for photon transmission in optical fiber. Here using the 3-intensity sending-or-not-sending protocol with the actively-odd-parity-pairing method, we demonstrate a fiber-based twin-field QKD over 1002 km. In our experiment, we developed a dual-band phase estimation and ultra-low noise superconducting nanowire single-photon detectors to suppress the system noise to around 0.02 Hz. The secure key rate is 9.53×10^{-12} per pulse through 1002 km fiber in the asymptotic regime, and 8.75×10^{-12} per pulse at 952 km considering the finite size effect. Our work constitutes a critical step towards the future large-scale quantum network.

Satellite-to-ground quantum key distribution.

Quantum key distribution (QKD) uses individual light quanta in quantum superposition states to guarantee unconditional communication security between distant parties. However, the distance over which QKD is achievable has been limited to a few hundred kilometres, owing to the channel loss that occurs when using optical fibres or terrestrial free space that exponentially reduces the photon transmission rate. Satellite-based QKD has the potential to help to establish a global-scale quantum network, owing to the negligible photon loss and decoherence experienced in empty space. Here we report the development and launch of a low-Earth-orbit satellite for implementing decoy-state QKD-a form of QKD that uses weak coherent pulses at high channel loss and is secure because photon-number-splitting eavesdropping can be detected. We achieve a kilohertz key rate from the satellite to the ground over a distance of up to 1,200 kilometres. This key rate is around 20 orders of magnitudes greater than that expected using an optical fibre of the same length. The establishment of a reliable and efficient space-to-ground link for quantum-state transmission paves the way to global-scale quantum networks.

Four-intensity measurement-device-independent quantum key distribution protocol with modified coherent state sources.

We propose a scheme of double-scanning 4-intensity MDI-QKD protocol with the modified coherent state (MCS) sources. The MCS sources can be characterized by two positive parameters, ξ and c. In all prior works, c was set to be the same for all sources. We show that the source parameter c can be different for the sources in the X basis and those in the Z basis. Numerical results show that removing such a constraint can greatly improve the key rates of the protocol with MCS sources. In the typical experiment conditions, comparing with the key rates of WCS sources, the key rates of MCS sources can be improved by several orders of magnitude, and the secure distance is improved by about 40 km. Our results show that MCS sources have the potential to improve the practicality of the MDI-QKD protocol.

Experimental Side-Channel-Secure Quantum Key Distribution.

Quantum key distribution can provide unconditionally secure key exchange for remote users in theory. In practice, however, in most quantum key distribution systems, quantum hackers might steal the secure keys by observing the side channels in the emitted photons, such as the photon frequency spectrum, emission time, propagation direction, spatial angular momentum, and so on. It is hard to prevent such kinds of attacks because side channels may exist in many dimensions of the emitted photons. Here we report an experimental realization of a side-channel-secure quantum key distribution protocol which is not only measurement-device independent, but also immune to all side-channel attacks to the photons emitted from Alice's and Bob's labs. We achieve a secure key rate of 1.73×10^{-6} per pulse through 50 km fiber spools.

Quantum Key Distribution over 658 km Fiber with Distributed Vibration Sensing.

Twin-field quantum key distribution (TFQKD) promises ultralong secure key distribution which surpasses the rate distance limit and can reduce the number of the trusted nodes in long-haul quantum network. Tremendous efforts have been made toward implementation of TFQKD, among which, the secure key with finite size analysis can distribute more than 500 km in the lab and in the field. Here, we demonstrate the sending-or-not-sending TFQKD experimentally, achieving a secure key distribution with finite size analysis over a 658 km ultra-low-loss optical fiber. Meanwhile, in a TFQKD system, any phase fluctuation due to temperature variation and ambient variation during the channel must be recorded and compensated, and all this phase information can then be utilized to sense the channel vibration perturbations. With our quantum key distribution system, we recovered the external vibrational perturbations generated by artificial vibroseis on both the quantum and frequency calibration link, and successfully located the perturbation position in the frequency calibration fiber with a resolution better than 1 km. Our results not only set a new distance record of quantum key distribution, but also demonstrate that the redundant information of TFQKD can be used for remote sensing of the channel vibration, which can find applications in earthquake detection and landslide monitoring besides secure communication.

Field Test of Twin-Field Quantum Key Distribution through Sending-or-Not-Sending over 428 km.

Quantum key distribution endows people with information-theoretical security in communications. Twin-field quantum key distribution (TF-QKD) has attracted considerable attention because of its outstanding key rates over long distances. Recently, several demonstrations of TF-QKD have been realized. Nevertheless, those experiments are implemented in the laboratory, and therefore a critical question remains about whether the TF-QKD is feasible in real-world circumstances. Here, by adopting the sending-or-not-sending twin-field QKD (SNS-TF-QKD) with the method of actively odd parity pairing (AOPP), we demonstrate a field-test QKD over 428 km of deployed commercial fiber and two users are physically separated by about 300 km in a straight line. To this end, we explicitly measure the relevant properties of the deployed fiber and develop a carefully designed system with high stability. The secure key rate we achieved breaks the absolute key rate limit of repeaterless QKD. The result provides a new distance record for the field test of both TF-QKD and all types of fiber-based QKD systems. Our work bridges the gap of QKD between laboratory demonstrations and practical applications and paves the way for an intercity QKD network with measurement-device-independent security.

Brain connectivity abnormalities and treatment-induced restorations in patients with cervical dystonia.

BACKGROUND: The relationship between brain abnormalities and phenotypic characteristics in cervical dystonia (CD) patients has not been fully established, and little is known about the neuroplastic changes induced by botulinum toxin type A (BoNT-A) treatment. METHODS: Ninety-two CD patients presenting with rotational torticollis and 45 healthy controls from our database were retrospectively screened. After clinical assessment, the 92 patients underwent baseline magnetic resonance imaging (MRI) followed by a single-dose injection of BoNT-A. Four weeks later, 76 out of the 92 patients were re-evaluated with the Tsui scale for dystonia severity, and 33 out of 76 patients completed post-treatment MRI scanning. Data-driven global brain connectivity and regional homogeneity in tandem with seed-based connectivity analyses were used to examine the functional abnormalities in CD and longitudinal circuit alterations that scaled with clinical response to BoNT-A. Multiple regression models were employed for the prediction analysis of treatment efficacy. RESULTS: Cervical dystonia patients exhibited elevated baseline connectivity of the right postcentral gyrus with the left dorsomedial prefrontal cortex and right caudate nucleus, which was associated with their symptom severity. BoNT-A reduced excessive functional connectivity between the sensorimotor cortex and right superior frontal gyrus, which was significantly correlated with changes in Tsui score. Moreover, pre-treatment regional homogeneity of the left middle frontal gyrus was linearly related to varied response to treatment. CONCLUSIONS: Our findings unravel dissociable connectivity of the sensorimotor cortex underlying the pathology of CD and central effects of BoNT-A therapy. Furthermore, baseline regional homogeneity with the left middle frontal gyrus may represent a potential evidence-based marker of patient stratification for BoNT-A therapy in CD.

End-to-End AUV Motion Planning Method Based on Soft Actor-Critic.

This study aims to solve the problems of poor exploration ability, single strategy, and high training cost in autonomous underwater vehicle (AUV) motion planning tasks and to overcome certain difficulties, such as multiple constraints and a sparse reward environment. In this research, an end-to-end motion planning system based on deep reinforcement learning is proposed to solve the motion planning problem of an underactuated AUV. The system directly maps the state information of the AUV and the environment into the control instructions of the AUV. The system is based on the soft actor-critic (SAC) algorithm, which enhances the exploration ability and robustness to the AUV environment. We also use the method of generative adversarial imitation learning (GAIL) to assist its training to overcome the problem that learning a policy for the first time is difficult and time-consuming in reinforcement learning. A comprehensive external reward function is then designed to help the AUV smoothly reach the target point, and the distance and time are optimized as much as possible. Finally, the end-to-end motion planning algorithm proposed in this research is tested and compared on the basis of the Unity simulation platform. Results show that the algorithm has an optimal decision-making ability during navigation, a shorter route, less time consumption, and a smoother trajectory. Moreover, GAIL can speed up the AUV training speed and minimize the training time without affecting the planning effect of the SAC algorithm.

Kinect V2-Based Gait Analysis for Children with Cerebral Palsy: Validity and Reliability of Spatial Margin of Stability and Spatiotemporal Variables.

Children with cerebral palsy (CP) have high risks of falling. It is necessary to evaluate gait stability for children with CP. In comparison to traditional motion capture techniques, the Kinect has the potential to be utilised as a cost-effective gait stability assessment tool, ensuring frequent and uninterrupted gait monitoring. To evaluate the validity and reliability of this measurement, in this study, ten children with CP performed two testing sessions, of which gait data were recorded by a Kinect V2 sensor and a referential Motion Analysis system. The margin of stability (MOS) and gait spatiotemporal metrics were examined. For the spatiotemporal parameters, intraclass correlation coefficient (ICC2,k) values were from 0.83 to 0.99 between two devices and from 0.78 to 0.88 between two testing sessions. For the MOS outcomes, ICC2,k values ranged from 0.42 to 0.99 between two devices and 0.28 to 0.69 between two test sessions. The Kinect V2 was able to provide valid and reliable spatiotemporal gait parameters, and it could also offer accurate outcome measures for the minimum MOS. The reliability of the Kinect V2 when assessing time-specific MOS variables was limited. The Kinect V2 shows the potential to be used as a cost-effective tool for CP gait stability assessment.

Hybrid protocol for sending-or-not-sending twin-field quantum key distribution.

We propose a hybrid protocol for sending-or-not-sending (SNS) twin-field quantum key distribution: replacing the signal source by heralded single-photon source (HSPS) in the original SNS protocol, while decoy sources are still unchanged. Numerical simulation shows that after adopting this HSPS, the performance in key rate and secure distance is much improved.

Sending-or-Not-Sending with Independent Lasers: Secure Twin-Field Quantum Key Distribution over 509 km.

Twin-field (TF) quantum key distribution (QKD) promises high key rates over long distances to beat the rate-distance limit. Here, applying the sending-or-not-sending TF QKD protocol, we experimentally demonstrate a secure key distribution that breaks the absolute key-rate limit of repeaterless QKD over a 509-km-long ultralow loss optical fiber. Two independent lasers are used as sources with remote-frequency-locking technique over the 500-km fiber distance. Practical optical fibers are used as the optical path with appropriate noise filtering; and finite-key effects are considered in the key-rate analysis. The secure key rate obtained at 509 km is more than seven times higher than the relative bound of repeaterless QKD for the same detection loss. The achieved secure key rate is also higher than that of a traditional QKD protocol running with a perfect repeaterless QKD device, even for an infinite number of sent pulses. Our result shows that the protocol and technologies applied in this experiment enable TF QKD to achieve a high secure key rate over a long distribution distance, and is therefore practically useful for field implementation of intercity QKD.

Long-Distance Free-Space Measurement-Device-Independent Quantum Key Distribution.

Measurement-device-independent quantum key distribution (MDI-QKD), based on two-photon interference, is immune to all attacks against the detection system and allows a QKD network with untrusted relays. Since the MDI-QKD protocol was proposed, fiber-based implementations aimed at longer distance, higher key rates, and network verification have been rapidly developed. However, owing to the effect of atmospheric turbulence, MDI-QKD over a free-space channel remains experimentally challenging. Herein, by developing a robust adaptive optics system, high-precision time synchronization and frequency locking between independent photon sources located far apart, we realized the first free-space MDI-QKD over a 19.2-km urban atmospheric channel, which well exceeds the effective atmospheric thickness. Our experiment takes the first step toward satellite-based MDI-QKD. Moreover, the technology developed herein opens the way to quantum experiments in free space involving long-distance interference of independent single photons.