Search

A successful implementation of any secure communication protocols requires the identity authentication as a prerequisite. Quantum identity authentication (QIA) can ensure the unconditional security of identity code. In this paper, we propose a multi-party simultaneous quantum identity authentication (MSQIA) protocol based on the Greenberger-Horne-Zeilinger (GHZ) state. In the protocol, N certified users can directly send their identity codes to the authenticator Alice simultaneously through quantum channels without classical communication, which enables Alice to authenticate their identity at the same time. Our protocol only requires Alice to perform the single-photon measurement. In theory, this protocol is unconditionally secure and one pair of (N+1)-photon GHZ state can transmit N bits of identity codes. Our MSQIA protocol has application potential in the quantum communication field in the near future.

Metal oxide solar absorbers are well suited for photoelectrochemical applications where requisite properties include stability in highly oxidizing environments, in addition to solar energy conversion. Metal vanadates are of particular interest due to their relatively low band gap energies compared to traditional, wide-gap photocatalysts. Concerted efforts on BiVO4-based photoanodes have revealed multiple avenues for improving the solar conversion efficiencies for photon energies above 2.5 eV but have not addressed the ultimate performance limitations from the undesirably high band gap energy. Fe and Cr vanadates have a lower band gap and thus a higher potential solar conversion efficiency, although to-date the absorbed 2–2.5 eV photons are not effectively converted to the desired anodic photocurrent. By using combinatorial synthesis and high throughput screening, we demonstrate that cation substitutions with the monoclinic MVO4 phase (M = Cr, Fe) improves the utilization of photons in this energy range. Given the portfolio of photoanode improvement techniques available, we suggest optimization of (Cr0.5Fe0.5)VO4-based photoanodes as a promising path for enable solar fuel technologies.

Quantum secret sharing (QSS) is a multi-party quantum communication mode, which allows the dealer to split a key into several parts and send each part of a key to a participant. The participants can obtain the key only by cooperation. Entanglement swapping is a promising method to construct the entanglement channel. In the paper, we propose a multiple-participant measurement-device-independent QSS protocol based on entanglement swapping. All the measurement tasks are handed over to an untrusted measurement party, so that our protocol can resist all possible attacks from imperfect measurement devices. Our protocol requires the linear-optical Bell state analysis, which is easy to operate. Our protocol has application potential in the future quantum communication field.

The one-step quantum secure direct communication (QSDC) (Sci. Bull. 67, 367 (2022)) can effectively simplify QSDC’s operation and reduce message loss. For enhancing its security under practical experimental condition, we propose two measurement-device-independent (MDI) one-step QSDC protocols, which can resist all possible attacks from imperfect measurement devices. In both protocols, the communication parties prepare identical polarization-spatial-mode two-photon hyperentangled states and construct the hyperentanglement channel by hyperentanglement swapping. The first MDI one-step QSDC protocol adopts the nonlinear-optical complete hyperentanglement Bell state measurement (HBSM) to construct the hyperentanglement channel, while the second protocol adopts the linear-optical partial HBSM. Then, the parties encode the photons in the polarization degree of freedom and send them to the third party for the hyperentanglement-assisted complete polarization Bell state measurement. Both protocols are unconditionally secure in theory. The simulation results show the MDI one-step QSDC protocol with complete HBSM attains the maximal communication distance of about 354 km. Our MDI one-step QSDC protocols may have potential applications in the future quantum secure communication field.

We investigate few-photon scattering properties in two one-dimensional waveguides chirally coupled to a nonlinear cavity. The quantum states of scattered few photons are solved analytically via a real-space approach, and the solution indicates the few-photon reflection and transmission properties. When inputting two photons of equal energy to resonate with the cavity, the propagation characteristics of the two photons will be interesting, which is different from the previous anti-bunching effects with a quantum emitter. More importantly, when the total energy of the two incident photons equals the energy of a nonlinear cavity accommodating two photons, influence of the bound state will become larger to result in disappearance of antibunching effect. However, the bound state has no effect on probability of routing to another waveguide.

Quantum scissor (QS) is a powerful tool to realize the optical truncation and noiseless linear amplification (NLA) of the Fock state. The hyper-encoding technology which encodes messages in two or more degrees of freedom of a photon is a promising tool for increasing the channel capacity of photons and has been widely used in quantum computing and quantum communication fields. Here, we propose the one-photon and three-photon QSs for the frequency-encoded and polarization frequency hyper-encoded coherent states, which can realize the one-order and three-order truncation and NLA of the coherent state, and preserve the encoded features of the photons. The quantum scissors for the hyper-encoded coherent state would introduce some unwanted disturb items with small probability. Our QSs can be extended to distill the hyper-encoded multi-spatial-mode entanglement. Our QSs have application potential in the future quantum information processing field.

Quantum secret sharing (QSS) is a typical multi-party quantum communication mode, in which the key sender splits a key into several parts and the participants can obtain the key by cooperation. Measurement-device-independent quantum secret sharing (MDI-QSS) is immune to all possible attacks from measurement devices and can greatly enhance QSS’s security in practical applications. However, previous MDI-QSS’s key generation rate is relatively low. Here, we adopt the polarization-spatial-mode hyper-encoding technology in the MDI-QSS, which can increase single photon’s channel capacity. Meanwhile, we use the cross-Kerr nonlinearity to realize the complete hyper-entangled Greenberger–Horne–Zeilinger state analysis. Both above factors can increase MDI-QSS’s key generation rate by about 103. The proposed hyper-encoded MDI-QSS protocol may be useful for future multiparity quantum communication applications.

A quantum router is one of the essential elements in the quantum network. Conventional routers only direct a single photon from one quantum channel into another. Here, we propose a few-photon router. The active element of the router is a single qubit chirally coupled to two independent waveguides simultaneously, where each waveguide mode provides a quantum channel. By introducing the operators of the scatter-free space and the controllable space, the output state of the one-photon and two-photon scattering are derived analytically. It is found that the qubit can direct one and two photons from one port of the incident waveguide to an arbitrarily selected port of the other waveguide with unity, respectively. However, two photons cannot be simultaneously routed to the same port due to the anti-bunch effect.

The distribution of quantum entanglement is essential for quantum communication. Contrary to classical communication, the signal in quantum communication is impossible to copy due to the basic principles of quantum mechanics, i.e., quantum state collapse and no-cloning theorem. However, the communication range is limited by inevitable photon loss. To counteract this issue, one can insert several repeater stations between two remote end nodes to divide the full distance into several shorter segments and successively operate entanglement swapping between adjacent repeater stations to enable long-distance quantum communication. Up to now, one can classify quantum repeaters (QRs) into three generations based on the methods of reducing errors resulted from photon loss and imperfect operations. In this paper, we will briefly review advances for each generation of QRs and discuss the advantages and challenges of each generation. Moreover, we also discuss some efficient proposals of building blocks to overcome the bottlenecks for QRs.

Quantum multiplexing provides us with a powerful approach that can distribute entanglement using only a single photonic pulse to interact with remote quantum memories. In common entanglement distribution protocols, the entanglement purification is often exploited if the distributed entanglement is degraded by the channel noise. In this protocol, we propose a faithful entanglement distribution protocol using quantum multiplexing of photon in a collective noise channel. By designing the encoding and decoding setup, our protocol can resist the collective noise. When the protocol is successful, the parties can obtain two pairs of maximally entangled states. When the protocol fails, the parties can still obtain one pair of maximally entangled state. Our protocol does not require the entanglement purification, so that it is more efficient. The above advantages enable our protocol to have important application potential in the future quantum communication field.

Multipartite entanglement has been widely employed in quantum information processing. However, the unavoidable noise in quantum channels causes the maximally multipartite entangled state to degrade to the mixed state. In this paper, we propose a highly efficient multipartite entanglement purification protocol (MEPP) for the polarization Greenberger–Horne–Zeilinger state. Unlike conventional MEPPs, where two pairs of polluted entanglement are usually required, our protocol only requires one noisy copy of polarization-time-bin hyperentanglement and exploits the time-bin entanglement to purify the polarization entanglement. This feature increases the efficiency of our MEPP. Our MEPP may have potential applications in long-distance quantum communication.

A single-photon qudit encoded in more than one degree of freedom (DOF) can effectively enlarge a single photon’s capacity and has great potential for applications in future high-capacity quantum communication fields. During the photon transmission in practical noisy channels, photon qudits may suffer from photon transmission loss, which largely limits their application. In this paper, we propose a practical noiseless linear amplification (NLA) protocol for protecting the single-photon qudit encoded in polarization and double-longitudinal momentum DOFs. This NLA adopts the imperfect entangled state generated from a practical spontaneous parametric down-conversion (SPDC) source as the auxiliary state and can be realized under current experimental conditions. After performing the NLA protocol, the fidelity of the target single-photon qudit can be increased and the encoded information in all DOFs can be well preserved. We show the adoption of the imperfect entangled state generated from SPDC source is superior to that of the imperfect single-photon state from a practical heralded single-photon source. Our NLA protocol has application potential in current and future quantum communications.

Quantum secure direct communication (QSDC) can realize the direct and secure transmission of information instead of sharing secure keys between two parties. Similar to quantum key distribution (QKD), in practical applications, QSDC may suffer from attacks from imperfect detector. Measurement-device–independent QSDC (MDI-QSDC) can remove all attacks at detector's side and close all loopholes in the detection system. However, existing MDI-QSDC protocols have relatively low capacity. In this paper, we propose a high-capacity MDI-QSDC protocol of multiple degrees of freedom of a single photon. Compared with original MDI-QSDC protocols, our protocol has larger channel capacity which can use a single photon to transmit multi-bit of secure information. This protocol may have potential application in future quantum secure communication.

Personalized recommendation services have been widely applied to improve users’ search efficiency, but when filtering information for users, they also hide the risk of the declining in content diversity, which is information narrowing. In this study, comprehensive news and information platforms in China were taken as the empirical research object. The experimental tracking method was used to collecting the content data of client end recommended news. Simpson and Shannon-Wiener indexes were used to measure the information narrowing phenomenon. Questionnaires were used to collect users’ data of news and information applications usage, the perception of information overload, and the perception of information narrowing. The data of questionnaire was analyzed and processed by MATLAB and SPSS 20.0, and the hypothesizes were tested by statistical methods. The results reveal that there is indeed information narrowing phenomenon in news information personalized recommendation service, but most users are unaware of this.

We theoretically study the phase sensitivities of two different phase-shift configurations in an SU(1,1) interferometer with coherent ⊗ squeezed vacuum states. According to quantum Cramér-Rao theorem, we analytically obtain the ultimate phase sensitivities for two types of phase shift accumulating in one- and two-arm. Compared with the case of one-arm phase shift, the model with phase shift encoding in both arms may provide a better sensitivity when the strength of squeezed vacuum state is large enough. Furthermore, we discuss the achievable sensitivities with the homodyne measurement by invoking of error-propagation formula. In addition, we study the effect of internal and outernal photon losses on the phase sensitivity of the SU(1,1) interferometer and find that the unbalanced interferometer is helpful to improve precision even with high external losses.

The research focuses on China’s environmental quality and economic system. Using the endogenous growth model and Davoodi & Zou model, a four-sector endogenous growth model with variables of ecological environment and fiscal decentralization is constructed and the static and dynamic panel models are further constructed. The conclusions are as follows: ①Fiscal decentralization and tax burden have non-linear effects on environmental quality;②Fiscal decentralization and tax burden have a deteriorating effect on environmental quality while the synergy of the two produces a dilution effect that weakens each other; ③Environmental quality itself has lagged effect. Therefore, it is proposed to coordinate and consist the fiscal decentralization and tax system and cultivate innovation capabilities, reduce unit energy consumption.

The construction of environmental governance system is attracting more attention. Using game-based learning theory for reference, this paper builds an evolutionary model among central government, local government and enterprises in the context of fiscal decentralization system. The findings suggest that three parties reach an effective and stable solution under the scenario of low fiscal decentralization, active governance, and up-to-standard pollution control. Furthermore, suggestions such as a combination between governments, the increase of environmental protection expenditure and strengthening political constraints are recommended.

We study the fringe visibility and the distinguishability of a general Mach-Zehnder interferometer with an asymmetric beam splitter. Both the fringe visibility V and the distinguishability D are affected by the input state of the particle characterized by the Bloch vector S=(Sx,Sy,Sz) and the second asymmetric beam splitter characterized by paramter /beta. For the total system is initially in a pure state, it is found that the fringe visibility reaches the upper bound and the distinguishability reaches the lower bound when cos(/beta) = -Sx. The fringe visibility obtain the maximum only if Sx = 0 and /beta = /pi/2 when the input particle is initially in a mixed state. The complementary relationship V2 + D2, 5 pages, 3 figures

Ti-Al-N hard films have been prepared by cathodic arc deposition by using an unipolar pulsed bias. In the present study, Ti-Al-N films were deposited on stainless steel and silicon wafers. The deposition rate, micrograph, preferred orientation and composition were systematically investigated by usingx-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and a scanning electron microscope (SEM). It is shown that substate bias duty cycle and frequency have a great effect on film structure. A simple explanation for the results is also presented.

We study a quantum electrodynamics (QED) system made of an two-level atom and a semi-infinite rectangular waveguide, which behaves as a perfect mirror in one end. The spatial dependence of the atomic spontaneous emission has been included in the coupling strength relevant to the eigenmodes of the waveguide. The role of retardation is studied for the atomic transition frequency far away from the cutoff frequencies. The atom-mirror distance introduces different phases and retardation times into the dynamics of the atom interacting resonantly with the corresponding transverse modes. It is found that the upper state population decreases from its initial as long as the atom-mirror distance does not vanish, and is lowered and lowered when more and more transverse modes are resonant with the atom. The atomic spontaneous emission can be either suppressed or enhanced by adjusting the atomic location for short retardation time. There are partial revivals and collapses due to the photon reabsorbed and re-emitted by the atom for long retardation time., Comment: 8 pages, 5 figures

The in-plane exchange anisotropy in a ferromagnetic (FM)/antiferromagnetic (AFM) bilayer under strain field has been investigated. Both cubic and uniaxial magnetocrystalline anisotropies are taken into account for the FM layer while the AFM layer is only considered as uniaxial magnetocrystalline anisotropy. In the semi-infinite limit for the AFM layer, the equilibrium energy for the system is established, and the analytical expressions are derived for exchange anisotropy constant, effective exchange bias, and pinning angle. The results show that not only the strain field angle but also its size will affect the effective exchange bias. The reason is that the pinning angle can be affected by the strain field including its size and direction but only affected by the size of the applied magnetic field. In addition, the effective measured exchange anisotropy from the hysteresis loop, ac susceptibility and ferromagnetic resonance are derived, and the comparison with previously reported theoretical results is made.

In this study, we choose that the 'db3' wavelet as the basis function to decompose the electric wave signal in 5 levels and a low and high frequency coefficient of 6 species plants are obtained, and coefficients after denoise are reconstructed for the first time. A result of the analysis of the wavelet in plant electric wave signals indicates that plant electric wave signals are of changing of characters in the each frequencies scale. In the low frequency level, the main character of the plant electric wave signal is reflected; in the high frequency level, the noise of the determined signal and also the mutation of the signal are reflected respectively. That the denoised signal of plants by wavelet analysis is similar with the original one indicates that the wavelet analysis is fit for studies on the plant electric wave signal. There are −200–500μV of the electric wave signals in growing plants.

The entanglement of two atoms is studied when the two atoms are coupled to a single-mode thermal field with different couplings. The different couplings of two atoms are in favor of entanglement preparation: it not only makes the case of absence entanglement with same coupling appear entanglement, but also enhances the entanglement with the increasing of the relative difference of two couplings. We also show that the diversity of coupling can improved the critical temperature. If the optical cavity is leaky during the time evolution, the dissipative thermal environment is benefit to produce the entanglement.

We propose a scheme for entangling two field modes in two high-Q optical cavities. Making use of a virtual two-photon process, our scheme achieves maximally entangled states without any real transitions of atomic internal states, hence it is immune to the atomic decay.

ZrO2 thin films were fabricated in O2 ambient and in N2 ambient by pulsed laser deposition (PLD), respectively. X-ray diffraction revealed that films prepared at 400°C remained amorphous. The dielectric properties of amorphous ZrO2 films were investigated by measuring the capacitance–frequency characteristics of Pt/ZrO2/Pt capacitor structures. The dielectric constant of the films deposited in N2 ambient was larger than that of the films deposited in O2 ambient. The dielectric loss was lower for films prepared in N2 ambient. Atom force microscopy investigation indicated that films deposited in N2 ambient had smoother surface than films deposited in O2 ambient. Capacitance–voltage and current–voltage characteristics were studied. The equivalent oxide thickness (EOT) of films with 6.6 nm physical thickness deposited in N2 ambient is lower than that of films deposited in O2 ambient. An EOT of 1.38 nm for the film deposited in N2 ambient was obtained, while the leakage current density was 94.6 mA cm−2. Therefore, ZrO2 thins deposited in N2 ambient have enhanced dielectric properties due to the incorporation of nitrogen which leads to the formation of Zr-doped nitride interfacial layer, and is suggested to be a potential material for alternative high-k (high dielectric constant) gate dielectric applications.

The concatenated Greenberger–Horne–Zeilinger (C-GHZ) state is a new kind of logic-qubit entangled state, which may have extensive applications in future quantum communication. In this letter, we propose a protocol for constructing an arbitrary C-GHZ state with single photons. We exploit the cross-Kerr nonlinearity for this purpose. This protocol has some advantages over previous protocols. First, it only requires two kinds of cross-Kerr nonlinearities to generate single phase shifts ±θ. Second, it is not necessary to use sophisticated m-photon Toffoli gates. Third, this protocol is deterministic and can be used to generate an arbitrary C-GHZ state. This protocol may be useful in future quantum information processing based on the C-GHZ state.

It is studied in this paper that the electrical characteristics of the interface between SiOyNx/SiNx stack and silicon wafer affect silicon surface passivation. The effects of precursor flow ratio and deposition temperature of the SiOyNx layer on interface parameters, such as interface state density Dit and fixed charge Qf, and the surface passivation quality of silicon are observed. Capacitance–voltage measurements reveal that inserting a thin SiOyNx layer between the SiNx and the silicon wafer can suppress Qf in the film and Dit at the interface. The positive Qf and Dit and a high surface recombination velocity in stacks are observed to increase with the introduced oxygen and minimal hydrogen in the SiOyNx film increasing. Prepared by deposition at a low temperature and a low ratio of N2O/SiH4 flow rate, the SiOyNx/SiNx stacks result in a low effective surface recombination velocity (Seff) of 6 cm/s on a p-type 1 Ωcm–5 Ωcm FZ silicon wafer. The positive relationship between Seff and Dit suggests that the saturation of the interface defect is the main passivation mechanism although the field-effect passivation provided by the fixed charges also make a contribution to it.

We describe an entanglement purification protocol for a polarization Bell state. Different from the previous protocols, it does not require the controlled-not gate, and only uses linear optical elements to complete the task. This protocol requires multi-copy degraded mixed states, which can make this protocol obtain a high fidelity in one purification step. It can also be extended to purify the multi-photon Greenberger–Horne–Zeilinger (GHZ) state. This protocol may be useful in future long-distance communication.

Photon loss is one of the main obstacles in long-distance quantum communication. In this letter, we put forward a highly efficient recyclable amplification protocol for protecting the single-photon entangled state. Different from all of the existing amplification protocols, by repeating the protocol, the discarded items can be reused to increase the success probability and the distilled new mixed state can be further amplified in a next round to increase its fidelity. In particular, this protocol is quite useful under high photon loss conditions. These features make our amplification protocol useful in future long-distance quantum communications.

Macroscopic entanglement, or say the Schrodinger's Cat state has attracted much attention for a long time. Recently, the first theoretical work of Frowis and Dur (Phys. Rev. Lett., 106 (2011) 110402) and the first experiment of Lu et al. (Nat. Photon., 8 (2014) 364) both showed that, a new type of Schrodinger's Cat state, the logic-qubit entanglement (concatenated Greenberger-Horne-Zeilinger (C-GHZ) state) is immune and robust to the noise, and is possible to be applied in future large-scale quantum networks. In this paper, we describe a protocol of entanglement analysis for this kind of Schrodinger's Cat state. Both the Bell-state type of logic-qubit entanglement and multipartite C-GHZ state can be completely distinguished. Based on the entanglement analysis, an arbitrary unknown macroscopic Schrodinger's Cat superposed state can be teleportated and we can also perform the macroscopic entanglement swapping. Our protocol shows that it is possible to realize long-distance quantum communication and large-scale quantum network based on logic-qubit entanglement.

We describe an efficient entanglement concentration protocol (ECP) for an arbitrary partially entangled three-electron W state. We show that with the help of two ancillary single electrons, the concentration task can be well completed. This ECP has several advantages: Firstly, we only require one pair of partially entangled states. Secondly, only two single electrons are used during the whole protocol. Thirdly, we do not require all the parties to participate in the whole process, and only two parties are needed to perform the operation. Fourthly, the protocol can be repeated to obtain a high success probability. This ECP may be useful in current quantum computation and quantum communication.

Nano-Ag incorporated hydroxyapatite/titania (HA/TiO2) coatings were deposited on Ti6Al4V substrates by the plasma electrolytic oxidation process. Compared with the substrate, the deposited coatings display attractive mechanical and biomedical properties. First, the coatings have stronger wear resistance and corrosion resistance. Second, they show a strong antibacterial ability. The mean vitality of the P. gingivalis on the coating surfaces is reduced to about 21%. Third, the coatings have good biocompatibility. The mean viability of the fibroblast cells on the coating surface is increased to about 130%. With these attractive properties, Ag incorporated HA/TiO2 coatings may be useful in the biomedical field.

We propose a scheme capable of performing complete Bell-state analysis for a single-photon hybrid entangled state. Our single-photon state is encoded in both polarization and frequency degrees of freedom. The setup of the scheme is composed of polarizing beam splitters, half wave plates, frequency shifters, and independent wavelength division multiplexers, which are feasible using current technology. We also show that with this setup we can perform complete two-photon Bell-state analysis schemes for polarization degrees of freedom. Moreover, it can also be used to perform the teleportation scheme between different degrees of freedom. This setup may allow extensive applications in current quantum communications.

We present an efficient entanglement concentration protocol (ECP) for the less-entangled W state with some identical conventional polarized single photons. In the protocol, two of the parties say Alice and Charlie should perform the parity check measurements and they can ultimately obtain the maximally entangled W state with a certain success probability Otherwise, they can obtain another less-entangled W state, which can be reconcentrated into the maximally entangled W state. By iterating this ECP, a high success probability can be achieved. This ECP may be an optimal one and it is useful in current quantum information processing.

We present an efficient entanglement purification protocol (EPP) with controlled-not (CNOT) gates and linear optics. With the CNOT gates, our EPP can reach a higher fidelity than the conventional one. Moreover, it does not require the fidelity of the initial mixed state to satisfy F > 1/2. If the initial state is not entangled, it still can be purified. With the linear optics, this protocol can get pure maximally entangled pairs with some probabilities. Meanwhile, it can be used to purify the entanglement between the atomic ensembles in distant locations. This protocol may be useful in long-distance quantum communication.

Polytetrafluoroethylene films are treated by room temperature helium atmospheric pressure plasma plumes, which are generated with a home-made single liquid electrode plasma device. After plasma treatment, the water contact angle of polytetrafluoroethylene film drops from 114° to 46° and the surface free energy increases from 22.0 mJ/m2 to 59.1 mJ/m2. The optical emission spectrum indicates that there are reactive species such as O+2, O and He in the plasma plume. After plasma treatment, a highly crosslinking structure is formed on the film surface and the oxygen element is incorporated into the film surface in the forms of —C—O—C—, —C=O, and —O—C=O groups. Over a period of 10 days, the contact angle of the treated film is recovered by only about 10°, which indicates that the plasma surface modification is stable with time.