Electrical and optical control of entanglement entropy in a coupled triple quantum dot system

We investigated theoretically the entanglement creation through tunneling rate and fields in a four-level triple quantum dot molecule based on InAs/GaAs/AlGaAs heterostructure in both steady state and transient state. We demonstrate that the entanglement entropy among the QDM and its spontaneous emission fields can be controlled by coherent and incoherent pumping field and tunnel-coupled electronics levels. The results may provide some new possibilities for technological applications in solid-state quantum information science, quantum computing, teleportation, encryption, compression codec, and optoelectronics.     

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.     

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.     

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.     

A general method of controlled bidirectional quantum teleportation of qudit state

Based on tensor representation and d-dimensional Bell basis measurements, we obtained a necessary condition for realizing controlled bidirectional quantum teleportation of qudit states. To verify its theoretical feasibility, we further give a general and simple method of selecting quantum channels for teleporting the ququart state.     

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.     

The signal recovery of continuous variable quantum communication system

In this paper, a novel continuous variable quantum teleportation (CVQTS) scheme based on quantum neural network (QNN) is proposed to implement the high-efficient and communication security. To achieve the teleportation in two-dimensional Hilbert space, the continuous variable quantum states are split into N modes by an array of N ? 1 beam splitters (N-splitter) in the continuous variable quantum teleportation channel (CVQTC). The QNN is applied to trace and restore the distortion signals. It used QNN training indirectly to obtain the weight parameters. In order to ensure the communication security, only a small number of information is extracted as training expectation. The results demonstrate that our scheme is capable of enhancing the fidelity close to 1 for almost all teleported information. Due to the simple structure of QNN, CVQTS scheme based on QNN can be applied to any other inputs and improves the maneuverability and realizability in the experiment.     

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.     

Teleportation of the states of motion of atoms by interaction with two-slit screens and cavities

We present a scheme of teleportation of the state of motion of atoms, making use of screens with slits and cavities. The fascinating aspects of quantum mechanics are highlighted, utilizing entanglement and the interaction of atoms with slits.     

d-Dimensional quantum secret sharing without entanglement

A d-dimensional quantum state secret sharing scheme without entanglement is proposed. In the proposed scheme, the dealer generates a single quantum state in d-dimensional Hilbert space, and performs the Pauli unitary operation on the quantum state according to the private keys of the participants. In the recovery phase, each participant performs the Pauli operation on the quantum state according to his private key, and the last participant will recover the original quantum state. Compared to the existing quantum secret sharing schemes, the main contribution of the proposed scheme is that the quantum state can be shared without the entanglement, so the sharing of the quantum state is more practical.     

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.     

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.     

Quantum state measurement of any arbitrary entangled field-state via Ramsey interferometry

Multipartite entangled states are the key resource and play a crucial role in latest applications of quantum mechanics. We propose a scheme for the measurement of quantum state of multimode entangled field state trapped in multiple cavities. The scheme is based on the measurement of photon statistics of the displaced entangled field state in Ramsey type set-up. In this set-up, the atoms undergo a dispersive phase shift when they pass through the off-resonant entangled field in cavities. By measuring the internal states of the atoms, the photon statistics and the Wigner function can be reconstructed.     

21世纪电子学的若干前沿课题

文章讨论了进入21世纪时物理学和电子学的现状和若干前沿课题,涉及真空能、电子负质量、量子势、虚粒子、超弦理论、快子,以及EPR思维实验、量子交缠与量子远距传物、量子信息学、量子计算机等方面的最新研究进展与成果。     

Scheme for implementing 1 → 2 symmetric economical phase-covariant telecloning of bipartite entangled state based on quantum logic network

A scheme for implementing 1 → 2 symmetric economical phase-covariant telecloning of a bipartite entangled state is proposed based on a quantum logic network. The quantum circuits for preparing the telecloning channel and for teleporting the input state are presented, respectively. There is no ancilla needed for preparing the channel, and the fidelity of telecloning is enhanced. Due to only single- and two-qubit operations being used in the whole process, it can be easily implemented in experiment.     

Controlled Cyclic Remote State Preparation of Arbitrary Qubit States

Quantum secure communications could securely transmit quantum information by using quantum resource. Recently, novel applications such as bidirectional and asymmetric quantum protocols have been developed. In this paper, we propose a new method for generating entanglement which is highly useful for multiparty quantum communications such as teleportation and Remote State Preparation (RSP). As one of its applications, we propose a new type of quantum secure communications, i.e. cyclic RSP protocols. Starting from a four-party controlled cyclic RSP protocol of one-qubit states, we show that this cyclic protocol can be generalized to a multiparty controlled cyclic RSP protocol for preparation of arbitrary qubit states. We point out that previous bidirectional and asymmetric protocols can be regarded as a simpler form of our cyclic RSP protocols.     

量子精密测量参数估计优化研究进展

量子精密测量是利用量子叠加与纠缠、量子相互作用过程与量子测量等方式增强参数估计精度与灵敏度的技术,是在短中期内最具前景的量子技术之一。本文从量子精密测量的最优化研究方案出发,通过对大量的相关文献进行梳理归纳,分析出量子精密测量三大优化方案：量子态制备与测量最优方案、量子演化过程调控方案与经典后处理优化方案,并对三个基本优化方案进行总结分析。同时介绍了国内外量子精密测量技术的最新理论与实验进展。最后,总结了量子精密测量存在的问题与挑战,并对未来工作进行了展望。     

Message Authentication with a New Quantum Hash Function

To ensure the security during the communication, we often adopt different ways to encrypt the messages to resist various attacks. However, with the computing power improving, the existing encryption and authentication schemes are being faced with big challenges. We take the message authentication as an example into a careful consideration. Then, we proposed a new message authentication scheme with the Advanced Encryption Standard as the encryption function and the new quantum Hash function as the authentication function. Firstly, the Advanced Encryption Standard algorithm is used to encrypt the result of the initial message cascading the corresponding Hash values, which ensures that the initial message can resist eavesdropping attack. Secondly, utilizing the new quantum Hash function with quantum walks can be much more secure than traditional classical Hash functions with keeping the common properties, such as one-wayness, resisting different collisions and easy implementation. Based on these two points, the message authentication scheme can be much more secure than previous ones. Finally, it is a new way to design the message authentication scheme, which provides a new thought for other researchers in the future. Our works will contribute to the study on the new encryption and authentication functions and the combination of quantum computing with traditional cryptology in the future.     

Quantum interference between an arbitrary-photon Fock state and a coherent state

Using the phase space method, we study the quantum interference through a Mach–Zehnder interferometer with an arbitrary-photon Fock state and a coherent state as two inputs. The statistical properties, in terms of the Wigner function, average photon number, photon number distribution and parity, are derived analytically for the field of the individual output port. These results indicate that the output state is actually a statistical mixture between a bunch of Fock state and coherent states. In addition, the phase sensitivity is also examined by using the detection scheme of intensity difference measurement.     

Rome teleportation experiment analysed in the Wigner representation: the role of the zeropoint fluctuations in complete one-photon polarization-momentum Bell-state analysis

The Wigner representation of parametric down conversion in the Heisenberg picture is applied to the study of the Rome teleportation experiment. We investigate the physical meaning of the zeropoint inputs at the different areas of the experimental set-up. In particular, we establish a quantitative relationship between the zeropoint sets of modes that are needed for the preparation of the quantum state to be teleported, the idle channels inside the one-photon polarization-momentum Bell-state analyser, and the possibility of performing teleportation of a polarization state with certainty.