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Highly efficient acousto-optic modulation plays a vital role in the microwave-to-optical conversion. Herein, we demonstrate a hybrid thin-film lithium niobate (TFLN) racetrack micro-ring acousto-optic modulator (AOM) implemented with low-loss chalcogenide (ChG) waveguide. By engineering the electrode configuration of the interdigital transducer, the double-arm micro-ring acousto-optic modulation is experimentally confirmed in nonsuspended ChG loaded TFLN waveguide platform. Varying the position of blue-detuned bias point, the half-wave-voltage-length product VpaiL of the hybrid TFLN micro-ring AOM is as small as 9 mVcm. Accordingly, the acousto-optic coupling strength is estimated to be 0.48 Hz s1/2 at acoustic frequency of 0.84 GHz. By analyzing the generation of phonon number from the piezoelectric transducer, the microwave-to-optical conversion efficiency is calculated to be 0.05%, approximately one order of magnitude larger than that of the state-of-the-art suspended counterpart. Efficient microwave-to-optical conversion thus provides new opportunities for low-power-consumption quantum information transduction using the TFLN-ChG hybrid piezo-optomechanical devices.

Since it is difficult to apply the existing method of friction and heat flux decomposition on the complex surface, a combined decomposition method of friction and heat flux with clear physical interpretation is proposed, which is based on FIK and RD decomposition method and can be applied to arbitrary surface. Based on this method, the aerothermodynamic characteristics of bistable states of curved compression ramps are analyzed from the perspective of energy transformation. The results show that the decrease of friction in the interaction region of the attachment state and the minimum values of friction in the separation bubble are all caused by the energy injection of the work by the adverse pressure gradient. The peak friction is mainly induced by the viscous dissipation, and its position is affected by the mechanical energy transport. The peak heat flux is mainly induced by viscous dissipation, and the enthalpy transport of the separation state plays a greater role in the peak heat flux generation than that of the attachment state. These results indicate that reducing viscous dissipation is a potential way for realizing friction and heat flux control simultaneously.

A highly efficient on-chip acousto-optic modulator, as a key component, occupies an exceptional position in microwave-to-optical conversion. Homogeneous thin-film lithium niobate is preferentially employed to build the suspended configuration forming the acoustic resonant cavity to improve the modulation efficiency of the device. However, the limited cavity length and complex fabrication recipe of the suspended prototype restrain further breakthrough in the modulation efficiency and impose challenges for waveguide fabrication. In this work, based on a nonsuspended thin-film lithium niobate-chalcogenide glass hybrid Mach-Zehnder interferometer waveguide platform, we propose and demonstrate a built-in push-pull acousto-optic modulator with a half-wave-voltage-length product as low as 0.03 V cm, presenting a modulation efficiency comparable to that of the state-of-the-art suspended counterpart. Based on the advantage of low power consumption, a microwave modulation link is demonstrated using our developed built-in push-pull acousto-optic modulator. The nontrivial acousto-optic modulation performance benefits from the superior photoelastic property of the chalcogenide membrane and the completely bidirectional participation of the antisymmetric Rayleigh surface acoustic wave mode excited by the impedance-matched interdigital transducer, overcoming the issue of amplitude differences of surface acoustic waves applied to the Mach-Zehnder interferometer two arms in traditional push-pull acousto-optic modulators.

Data security and privacy is an important but challenging problem in cloud computing. One of the security concerns from cloud users is how to efficiently verify the integrity of their data stored on the cloud server. Third Party Auditing (TPA) is a new technique proposed in recent years to achieve this goal. In a recent paper (IEEE Transactions on Computers 62(2): 362-375 (2013)), Wang et al. proposed a highly efficient and scalable TPA protocol and also a Zero Knowledge Public Auditing protocol which can prevent offline guessing attacks. However, in this paper, we point out several security weaknesses in Wang et al's protocols: first, we show that an attacker can arbitrarily modify the cloud data without being detected by the auditor in the integrity checking process, and the attacker can achieve this goal even without knowing the content of the cloud data or any verification metadata maintained by the cloud server; secondly, we show that the Zero Knowledge Public Auditing protocol cannot achieve its design goal, that is to prevent offline guessing attacks., Comment: arXiv admin note: text overlap with arXiv:1912.00446

With the wide application of cloud storage, cloud security has become a crucial concern. Related works have addressed security issues such as data confidentiality and integrity, which ensure that the remotely stored data are well maintained by the cloud. However, how to define zero-knowledge proof algorithms for stored data integrity check has not been formally defined and investigated. We believe that it is important that the cloud server is unable to reveal any useful information about the stored data. In this paper, we introduce a novel definition of data privacy for integrity checks, which describes very high security of a zero-knowledge proof. We found that all other existing remote integrity proofs do not capture this feature. We provide a comprehensive study of data privacy and an integrity check algorithm that captures data integrity, confidentiality, privacy, and soundness.

It is a crucial mechanism of access control to determine that data can only be accessed for allowed purposes. To achieve this mechanism, we propose purpose-based access policies in this paper. Different from provenance-based policies that determine if a piece of data can be accessed or not, purpose-based access policies determines for what purposes can data be accessed. Particularly, the purposes can be classified as different sensitivity levels. For the first time, We tailor policy algebras to include internal and external policy operators for hierarchical purposes, in order to merge purpose sets generated by individual policies. We also created external policy algebras to merge policies from multi-parties. With different types' testing experiments, our model is proved to be feasible and practical.