Quadrature operators with arbitrary phase and applications to phase-space distribution and quantum communication

Quadrature operators with arbitrary phase are studied from a point of view of the phase-space representation of quantum states, and the results are applied to simultaneous measurement and quantum communication. The Wigner function of arbitrary phase quadrature variables is introduced, which is a generalization of the usual Wigner function of position and momentum. The Kirkwood distribution is also extended for arbitrary phase quadrature variables. The simultaneous measurement of two quadrature operators is investigated using a beam splitter model and a generalized version of the Arthurs-Kelley model. The quantum teleportation of continuous variables is considered in terms of arbitrary phase quadrature variables. A general formula is derived that provides the quantum teleportation channel. The fidelity of the quantum teleportation with an uncontrollable phase is calculated for a coherent state. Furthermore, the mutual information of the quantum dense coding of continuous variables is obtained when classical information is encoded on arbitrary phase quadrature variables. The result is compared with that of the communication system, where information is transmitted using coherent and squeezed states.     

Long-distance teleportation based on a selected receiver in a quantum network

Quantum networks are useful for global communication. A new multi-hop scheme of single unitary transformation method (SUTM) is proposed for long-distance teleportation of an unknown W state in a quantum network. All the measurement outcomes are sent to the selected receiver independently. The initial quantum state can be recovered by a corresponding local operation. The probability of successful teleportation can reach 1 without auxiliary particles. Our scheme is superior to the hop-by-hop method owing to lower delays.     

Quantum teleportation with a complete Bell state measurement

By using the quantum teleportation protocol, Alice can send an unknown quantum state (e.g. the polarization of a single photon) to Bob without ever knowing about it. This paper discusses a quantum teleportation experiment in which nonlinear interactions are used for the Bell state measurement. Since the Bell state measurement is based on nonlinear interactions, all four Bell states can be distinguished. Therefore, teleportation of a polarization state can occur with certainty, in principle. Details of the theory and the experimental set-up are discussed.     

Perfect transmission of the sub-poissonian character of a field via continuous-variable teleportation

Abstract

We optimize the transmission of quantum features in light fields, such as squeezing and antibunching, using continuous variable teleportation and tuning the variable gain in Bob's output.     

Quantum Remote State Preparation Based on Quantum Network Coding

As an innovative theory and technology, quantum network coding has become the research hotspot in quantum network communications. In this paper, a quantum remote state preparation scheme based on quantum network coding is proposed. Comparing with the general quantum remote state preparation schemes, our proposed scheme brings an arbitrary unknown quantum state finally prepared remotely through the quantum network, by designing the appropriate encoding and decoding steps for quantum network coding. What is worth mentioning, from the network model, this scheme is built on the quantum k-pair network which is the expansion of the typical bottleneck network—butterfly network. Accordingly, it can be treated as an efficient quantum network preparation scheme due to the characteristics of network coding, and it also makes the proposed scheme more applicable to the large-scale quantum networks. In addition, the fact of an arbitrary unknown quantum state remotely prepared means that the senders do not need to know the desired quantum state. Thus, the security of the proposed scheme is higher. Moreover, this scheme can always achieve the success probability of 1 and 1-max flow of value k. Thus, the communication efficiency of the proposed scheme is higher. Therefore, the proposed scheme turns out to be practicable, secure and efficient, which helps to effectively enrich the theory of quantum remote state preparation.     

Creating quantum entanglement between multi-atom Dicke states and two cavity modes

We present a scheme to create quantum entanglement between multi-atom Dicke states and two cavity modes by passing N three-level atoms in Λ configuration through a resonant two-mode cavity one by one. We further show that such a scheme can be used to generate arbitrary two-mode N-photon entangled states, arbitrary superposition of Dicke states, and a maximal entangled state of Dicke states. These states may find applications in the demonstration of quantum non-locality, high-precision spectroscopy and quantum information processing.     

A quantum secret sharing scheme on access structure

Based on the Einstein-Podolsky-Rosen (EPR) entangled state and the unitary operation, a quantum secret-sharing (QSS) scheme on access structure is proposed. The participants randomly choose their private keys themselves. Each participant keeps one private key even though he belongs to several qualified subsets. In the recovery, the participants in the qualified subset perform the unitary operations on the EPR pairs, and recover the secret through the Bell-state measurement. Compared to the existing QSS schemes on (n, n) or (t, n) structure, the proposed scheme on access structure is more flexible in practice.     

Entanglement and quantum teleportation with multi-atom ensembles

Atomic ensembles containing a large number of atoms have been proved to be an effective medium for quantum-state (quantum information) engineering and processing via their coupling with multi-photon light pulses. The general mechanism of this coupling, which involves continuous quantum variables for light and atoms, is described. The efficient quantum interface between light and atoms has led to the recent demonstration of an entangled state of two macroscopic atomic objects, more precisely two caesium gas samples. Based on this result, a proposal for teleportation of an entangled state of two atomic samples (entanglement swapping) is presented.     

Proposal for optical parity state re-encoder

We propose a re-encoder to generate a refreshed parity encoded state from an existing parity encoded state. This is the simplest case of the scheme by Gilchrist et al. [Phys. Rev. A 2007 75, 052328]. We give a detailed experimental arrangement for the re-encoder and show that it is possible to experimentally demonstrate with existing technology parity encoded quantum gates and teleportation.     

Quantum communications with compressed decoherence using bright squeezed light

We propose a scheme for long-distance distribution of quantum entanglement in which the entanglement between qubits at intermediate stations of the channel is established by using bright light pulses in squeezed states coupled to the qubits in cavities with a weak dispersive interaction. The fidelity of the entanglement between qubits at the neighbor stations (10 km apart from each other) obtained by postselection through the balanced homodyne detection of 7 dB squeezed pulses can reach F = 0.99 without using entanglement purification, at the same time, the probability of successful generation of entanglement is 0.34.     

Hyper Elliptic Curve Based Certificateless Signcryption Scheme for Secure IIoT Communications

Industrial internet of things (IIoT) is the usage of internet of things (IoT) devices and applications for the purpose of sensing, processing and communicating real-time events in the industrial system to reduce the unnecessary operational cost and enhance manufacturing and other industrial-related processes to attain more profits. However, such IoT based smart industries need internet connectivity and interoperability which makes them susceptible to numerous cyber-attacks due to the scarcity of computational resources of IoT devices and communication over insecure wireless channels. Therefore, this necessitates the design of an efficient security mechanism for IIoT environment. In this paper, we propose a hyperelliptic curve cryptography (HECC) based IIoT Certificateless Signcryption (IIoT-CS) scheme, with the aim of improving security while lowering computational and communication overhead in IIoT environment. HECC with 80-bit smaller key and parameters sizes offers similar security as elliptic curve cryptography (ECC) with 160-bit long key and parameters sizes. We assessed the IIoT-CS scheme security by applying formal and informal security evaluation techniques. We used Real or Random (RoR) model and the widely used automated validation of internet security protocols and applications (AVISPA) simulation tool for formal security analysis and proved that the IIoT-CS scheme provides resistance to various attacks. Our proposed IIoT-CS scheme is relatively less expensive compared to the current state-of-the-art in terms of computational cost and communication overhead. Furthermore, the IIoT-CS scheme is 31.25% and 51.31% more efficient in computational cost and communication overhead, respectively, compared to the most recent protocol.     

Partial teleportation of entanglement in a noisy environment

Abstract

Partial teleportation of entanglement is to teleport one particle of an entangled pair through a quantum channel. This is conceptually equivalent to quantum swapping. We consider the partial teleportation of entanglement in the noisy environment, employing the Werner-state representation of the noisy channel for the simplicity of calculation. To have the insight of the many-body teleportation, we introduce the measure of correlation information and study the transfer of the correlation information and entanglement. We find that the fidelity becomes smaller as the initial state is entangled more for a given entanglement of the quantum channel. The entangled channel transfers at least some of the entanglement to the final state.     

Continuous-Variable Quantum Network Coding Based on Quantum Discord

Establishing entanglement is an essential task of quantum communication technology. Beyond entanglement, quantum discord, as a measure of quantum correlation, is a necessary prerequisite to the success of entanglement distribution. To realize efficient quantum communication based on quantum discord, in this paper, we consider the practical advantages of continuous variables and propose a feasible continuous-variable quantum network coding scheme based on quantum discord. By means of entanglement distribution by separable states, it can achieve quantum entanglement distribution from sources to targets in a butterfly network. Compared with the representative discrete-variable quantum network coding schemes, the proposed continuous-variable quantum network coding scheme has a higher probability of entanglement distribution and defends against eavesdropping and forgery attacks. Particularly, the deduced relationship indicates that the increase in entanglement is less than or equal to quantum discord.     

Optical setups for probabilistic bipartite and tripartite entanglement generation and quantum teleportation in optical networks

In this work we present optical setups for a polarization encoded qubit, based only on common linear optical devices, which implement probabilistic bipartite and tripartite entanglement generation, as well probabilistic quantum teleportation. The setups can be implemented with current technology and they permit the realization of several quantum communication protocols.     

A Novel Quantum Stegonagraphy Based on Brown States

In this paper, a novel quantum steganography protocol based on Brown entangled states is proposed. The new protocol adopts the CNOT operation to achieve the transmission of secret information by the best use of the characteristics of entangled states. Comparing with the previous quantum steganography algorithms, the new protocol focuses on its anti-noise capability for the phase-flip noise, which proved its good security resisting on quantum noise. Furthermore, the covert communication of secret information in the quantum secure direct communication channel would not affect the normal information transmission process due to the new protocol’s good imperceptibility. If the number of Brown states transmitted in carrier protocol is many enough, the imperceptibility of the secret channel can be further enhanced. In aspect of capacity, the new protocol can further expand its capacity by combining with other quantum steganography protocols. Due to that the proposed protocol does not require the participation of the classic channel when it implements the transmission of secret information, any additional information leakage will not be caused for the new algorithm with good security. The detailed theoretical analysis proves that the new protocol can own good performance on imperceptibility, capacity and security.     

Secure video distribution scheme based on partial encryption

In TV program distribution, the receiver's identification information is embedded into video data in order to trace illegal distributors, and video data are encrypted in order to protect the confidentiality against unauthorized users. In traditional method, the TV program is firstly fingerprinted, then encrypted, and finally transmitted. For N receivers, N times of encryption, and N times of fingerprinting operations are required, which makes the sender of high loading. In another method, the media content is decrypted and fingerprinted simultaneously by the joint fingerprint embedding and decryption, which is difficult to obtain reasonable performances. In this article, a commutative encryption and fingerprinting scheme is proposed to reduce the sender's loading. In this scheme, the TV program is firstly encrypted, then fingerprinted, and finally transferred. When compared with the traditional method, in the proposed method, only once encryption and N times of fingerprinting are required, which reduces the sender's loading greatly. Based on MPEG2 videos, a commutative encryption and fingerprinting scheme is presented, whose performances including security, efficiency, robustness, and imperceptibility are evaluated. Experimental results show that the scheme obtains good performances and is suitable for TV program distribution. © 2009 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 19, 227–235, 2009     

Preparation and gas-sensing properties of SnO<Subscript>2</Subscript>/graphene quantum dots composites via solvothermal method

SnO₂/graphene quantum dots (GQDs) nano-composites were prepared via solvothermal method (160 °C, 10 h), in which graphene quantum dots were synthesized from graphene oxide by one-step solvothermal method. The nano-composites were characterized by means of HRTEM, XRD, SEM, FTIR, XPS and N₂ adsorption–desorption, respectively. The sensor devices were fabricated using SnO₂/GQDs nano-composites as sensing materials. The effect of the GQDs content on the gas-sensing responses and the gas-sensing selectivity was investigated. The experimental results showed that the sensor based on SnO₂/GQDs nano-composite (S-2) exhibited good response and good selectivity to acetone vapor. When operating at 275 °C, the responses of the sensor based on SnO₂/GQDs nano-composite (S-2) to 1000 and 0.1 ppm acetone reached 120.6 and 1.3, respectively; the response time and the recovery time for 1000 ppm acetone were 17 and 13 s, respectively.     

Proposal for a new scheme for producing a two-photon,high dimensional hyperentangled state

We propose an experimentally feasible scheme for generating a two 2?×?4?×?4 dimensional photon hyperentangled state, entangled in polarization, frequency and spatial mode. This scheme is mainly based on a parametric down-conversion source and cross-Kerr nonlinearities, which avoids the complicated uncertain post-selection. Our method can be easily expanded to the production of hyperentangled states with more photons in multidimensions. Hence the expectation for vast quantities of information in quantum information processing will possibly come true. Finally, we put forward a realizable quantum key distribution (QKD) protocol based on the high dimensional hyperentangled state.     

Privacy Data Management Mechanism Based on Blockchain and Federated Learning

Due to the extensive use of various intelligent terminals and the popularity of network social tools, a large amount of data in the field of medical emerged. How to manage these massive data safely and reliably has become an important challenge for the medical network community. This paper proposes a data management framework of medical network community based on Consortium Blockchain (CB) and Federated learning (FL), which realizes the data security sharing between medical institutions and research institutions. Under this framework, the data security sharing mechanism of medical network community based on smart contract and the data privacy protection mechanism based on FL and alliance chain are designed to ensure the security of data and the privacy of important data in medical network community, respectively. An intelligent contract system based on Keyed-Homomorphic Public Key (KH-PKE) Encryption scheme is designed, so that medical data can be saved in the CB in the form of ciphertext, and the automatic sharing of data is realized. Zero knowledge mechanism is used to ensure the correctness of shared data. Moreover, the zero-knowledge mechanism introduces the dynamic group signature mechanism of chosen ciphertext attack (CCA) anonymity, which makes the scheme more efficient in computing and communication cost. In the end of this paper, the performance of the scheme is analyzed from both asymptotic and practical aspects. Through experimental comparative analysis, the scheme proposed in this paper is more effective and feasible.     

Cylinder and metal grating polarization beam splitter

We propose a novel and compact metal grating polarization beam splitter (PBS) based on its different reflected and transmitted orders. The metal grating exhibits a broadband high reflectivity and polarization dependence. The rigorous coupled wave analysis is used to calculate the reflectivity and the transmitting spectra and optimize the structure parameters to realize the broadband PBS. The finite-element method is used to calculate the field distribution. The characteristics of the broadband high reflectivity, transmitting and the polarization dependence are investigated including wavelength, period, refractive index and the radius of circle grating. When grating period d = 400 nm, incident wavelength λ = 441 nm, incident angle θ = 60° and radius of circle d/5, then the zeroth reflection order R₀ = 0.35 and the transmission zeroth order T₀ = 0.08 for TE polarization, however, T₀ = 0.34 and R₀ = 0.01 for TM mode. The simple fabrication method involves only single etch step and good compatibility with complementary metal oxide semiconductor technology. PBS designed here is particularly suited for optical communication and optical information processing.