Complete Bell-state analysis for single-photon hybrid entangled state

We propose a scheme capable of performing complete Bell-state analysis for single-photon hybrid entangled state. Our single-photon state is encoded in both polarization and frequency degrees of freedom. The setup of scheme is composed of polarizing beam splitters, half wave plates, frequency shifters, and independent wavelength division multiplexers, which are feasible with current technology. We also show that, with this setup, we can perform the schemes for complete two-photon Bell-state analysis for polarization degree 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.     

Quantum superdense coding based on hyperentanglement

We present a scheme for quantum superdense coding with hyperentanglement,in which the sender can transfer four bits of classical information by sending only one photon.The important device in the scheme is the hyperentangled Bell-state analyzer in both polarization and frequency degrees of freedom,which is also constructed in the paper by using a quantum nondemolition detector assisted by cross-Kerr nonlinearity.Our scheme can transfer more information with less resources than the existing schemes and is nearly deterministic and nondestructive.     

Efficient faithful qubit transmission with frequency degree of freedom

We propose an efficient faithful polarization-state transmission scheme by utilizing frequency degree of freedom besides polarization and an additional qubit prepared in a fixed polarization. An arbitrary single-photon polarization state is protected against the collective noise probabilistically. With the help of frequency beam splitter and frequency shifter, the success probability of our faithful qubit transmission scheme with frequency degree of freedom can be 1/2 in principle.     

Complete <Emphasis Type="Italic">N</Emphasis>-Photon Greenberger-Horne-Zeilinger State Analysis Using Hyperentanglement

We present a scheme for N-photon Greenberger-Horne-Zeilinger (GHZ) state analysis using hyperentanglement in polarization and time-bin degrees of freedom. The scheme only needs linear optics elements and single-photon detectors, which is feasible with current technology. The set of 2 ^N mutual orthogonal states can be unambiguously distinguished and the protocol is expected to find useful applications in quantum information processing.     

High-Capacity Quantum Secure Direct Communication with Single Photons in Both Polarization and Spatial-Mode Degrees of Freedom

We present a high-capacity quantum secure direct communication (QSDC) protocol with single photons in both the polarization and the spatial-mode degrees of freedom. With a single photon traveling forth and back from the receiver to the sender, it can carry 2 bits of information as the sender can encode his message on both the polarization states and the spatial-mode states of single photons independently. Moreover, our QSDC protocol is feasible as the preparation and the measurement of a single-photon quantum state in both the polarization and the spatial-mode degrees of freedom is not difficult with current technology.     

Remote preparation for single-photon state in two degrees of freedom with hyper-entangled states

Remote state preparation (RSP) provides a useful way of transferring quantum information between two distant nodes based on the previously shared entanglement. In this paper, we study RSP of an arbitrary single-photon state in two degrees of freedom (DoFs). Using hyper-entanglement as a shared resource, our first goal is to remotely prepare the single-photon state in polarization and frequency DoFs and the second one is to reconstruct the single-photon state in polarization and time-bin DoFs. In the RSP process, the sender will rotate the quantum state in each DoF of the photon according to the knowledge of the state to be communicated. By performing a projective measurement on the polarization of the sender’s photon, the original single-photon state in two DoFs can be remotely reconstructed at the receiver’s quantum systems. This work demonstrates a novel capability for longdistance quantum communication.     

Simple experimental scheme of teleporting a two-qubit state via linear optical elements

We propose a simple experimental scheme in which an unknown two-qubit state is faithfully and deterministically teleported from Alice to Bob. The scheme is constructed with four photons from parametric down conversion, linear optical elements, and conventional photon detectors, all of which are available in current technology. It is shown that the probability of successful teleportation ideally reaches 100% based on single-photon two-qubit-assisted Bell-state measurement, which can distinguish all four Bell-states simultaneously via conventional photon detectors. By generalizing the scheme, the teleportation of an unknown multi-qubit system can also be realized.     

High-Capacity Three-Party Quantum Secret Sharing with Single Photons in Both the Polarization and the Spatial-Mode Degrees of Freedom

We present a high-capacity three-party quantum secret sharing (QSS) protocol with a sequence of single photons in both the polarization and the spatial-mode degrees of freedom. By inserting the boss Alice into the middle position between the two agents Bob and Charlie, our QSS protocol is secure in theory. The boss Alice chooses some unitary operations to encode her information on the single photons. It is interesting to point out the fact that Alice does not change the bases of the single photons which are used to carry the useful information about the private key, which improves its success probability for obtaining a private key. Compared with the QSS protocol by Zhou et al. (Chin. Phys. Lett. 24, 2181 (2007)), our QSS protocol has a higher capacity without increasing the difficulty of its implementation in experiment as each correlated photon can carry two bits of useful information. Compared with those QSS protocols based on entangled photon pairs and Bell-state measurements, our QSS protocol is more feasible as it does not require the complete Bell-state analysis which is not easy with linear optics. We give out the setup for the implementation of our QSS protocol with linear optical elements.     

Experimental realization of deterministic entanglement transformations of bipartite pure states

We experimentally realize a kind of entanglement transformations of bipartite pure states with 100% efficiency. The protocol employs two-outcome positive operator-valued measures (POVMs) and can transform two-photon maximally entangled state to any two-photon entangled pure state with 100% efficiency. The average fidelity of all output states is 96%. Moreover, the scheme to implement arbitrary POVM on single-photon polarization state is also discussed. In principle, our setup can be applied to any kind of entanglement transformations of two-qubit entangled states to achieve optimal successful probability.     

Deterministic Tripartite Entanglement Distributions of the W State over Collective-Noise Channels

A deterministic entanglement distribution protocol (EDP) is proposed in principle for transmitting a maximally entangled W state over collective-noise channels. Using this EDP, a W state can be reconstructed directly from a three-photon entangled state in the frequency degree of freedom prepared among three remote participants due to the fact that it suffers little from the channel noise. In essence, it is a entanglement transformation between different degrees of freedom in three-photon entangled system. This EDP adopts the cross-Kerr nonlinearity media to complete the task of the single-photon detections, which can increase the efficiency of entanglement distribution since it does not require the sophisticated single-photon detectors for the usual measurements and the retained photons can be still held solely by three respective participants after entanglement distillation.     

Self-error-rejecting photonic qubit transmission in polarization-spatial modes with linear optical elements

We present an original self-error-rejecting photonic qubit transmission scheme for both the polarization and spatial states of photon systems transmitted over collective noise channels. In our scheme, we use simple linear-optical elements, including half-wave plates, 50:50 beam splitters, and polarization beam splitters, to convert spatial-polarization modes into different time bins. By using postselection in different time bins, the success probability of obtaining the uncorrupted states approaches 1/4 for single-photon transmission, which is not influenced by the coefficients of noisy channels. Our self-error-rejecting transmission scheme can be generalized to hyperentangled n-photon systems and is useful in practical high-capacity quantum communications with photon systems in two degrees of freedom.     

Quantum State Sharing of an Arbitrary Three-Atom State by Using Five-Atom Cluster State in Cavity QED

We present a scheme for implementing the deterministic quantum state sharing of an arbitrary three-atom state by using a five-atom cluster state and a Bell-state in cavity QED. In the scheme, it does not involve Bell-state measurement and only needs to perform the single-atom measurements. Our scheme is not sensitive to both the cavity decay and the atom radiation, which is of importance in view of decoherence.     

Scheme for linear optical preparation of a type of four-photon entangled state with conventional photon detectors

We propose a simple experimental scheme to prepare a type of four-photon entangled state |χ〉 that has many interesting entanglement properties and possible applications in quantum information processing with a certain success probability. The proposed setup involves only simple linear optical devices, a single-photon polarization state, three pairs of two-photon polarization entangled states, and the conventional photon detectors that cannot distinguish a single photon from two or more photons, which greatly simplify the experimental realization of the scheme.     

High-Capacity Quantum Summation with Single Photons in Both Polarization and Spatial-Mode Degrees of Freedom

In this paper, we employ single photons in both polarization and spatial-mode degrees of freedom to design a quantum summation protocol. We assume that the third party, i.e. TP, is semi-honest in our protocol. That TP is semi-honest means TP executes the protocol loyally, keeps a record of all its intermediate computations and might try to steal the participants’ private inputs from the record, but he cannot be corrupted by the adversary. Participants can independently encode their private inputs on the polarization states and the spatial-mode states of single photons. Thus our protocol doubles the capacity of quantum communication compared with those based on single photons with only one degree of freedom. In addition, our protocol is feasible as the preparation and the measurement of single-photon quantum states in both the polarization and the spatial-mode degrees of freedom are available with current quantum techniques. We also analyze its security in this paper.     

Efficient Multipartite Polarization Entanglement Distribution Over Arbitrary Noise Channel

We present an efficient faithful multipartite polarization entanglement distribution protocol over an arbitrary noisy channel. The spatial degree of freedom is used to carry the entanglement during the transmission. We describe the principle by distributing n-qubit Greenberge-Horne-Zeilinger state and n-qubit W state. Our scheme can be used to distribute arbitrary n-qubit entangled states to n distant locations. The remote parties can obtain maximally entangled states deterministically on the polarization of photons. Only passive linear optics are employed in our setup, which makes our scheme more feasible and efficient for practical application in long distance quantum communication.     

基于光量子态避错及容错传输的量子通信

量子通信以量子态为信息载体在远距离的通信各方之间传递信息,因此量子态的传输和远距离共享是量子通信的首要步骤.信道噪声不仅会影响通信效率还可能被窃听者利用从而威胁通信安全,对抗信道噪声是实现安全高效量子通信亟需解决的问题.本文介绍基于光量子态的两类对抗信道噪声的实用方法——量子态的避错传输和容错的量子通信,包括对抗噪声的基本原理和两种方法的代表性方案,并从资源消耗和可操作性的角度分析了方案的实用价值.     

Heralded amplification of single-photon entanglement with polarization feature

Heralded noiseless amplification is beneficial in overcoming transmission photon loss in a noisy quantum channel. We propose a single-photon-assisted heralded noiseless amplification protocol of the singlephoton entanglement (SPE), where the single-photon qubit has an arbitrary unknown polarization feature. We focus on both the complete and partial photon loss during the transmission process. After the amplification, the parties can recover the pure less-entangled SPE into a maximally entangled SPE and increase its fidelity. Moreover, the polarization feature of the single-photon qubit will be well preserved and not be leaked. Our protocol can be realized under our current experimental condition. Based on the features above, our protocol may be useful in the quantum secure communication schemes that encode information in the polarization degree of freedom of photons.     

Quantum Information Splitting of an Arbitrary Three-Atom State in Cavity Quantum Electrodynamics

A cavity quantum electrodynamics scheme for implementing the deterministic quantum information splitting of an arbitrary three-atom state is proposed. In the scheme, a genuine five-atom entangled state and a Bell-state can be used as the quantum channel, which does not involve Bell-state measurement and only needs to perform the single-atom measurements. Our scheme is insensitive to both the cavity decay and the atom radiation, and considered here is secure against certain eavesdropping attacks.     

Efficient Polarization Entanglement Distribution for W State Assisted by Frequency Degree of Freedom

We present an efficient faithful polarization entanglement distribution protocol for W state over an arbitrary noise channel,which use the frequency degree of freedom to carry the entanglement during the transmission.We describe the transmission of three-photon W state as an example,and then generalize this scheme to n-qubit W state situation.The remote parties can obtain maximally entangled W states on the polarization of photons,and the success probability is 100% in principle.As there was few entanglement purification for W state,our scheme is an efficient and practical method to share W state entanglement between distant parties,which will be useful in quantum communication.We also show that our scheme can be used to distribute arbitrary multi-particle entangled state.     

Optical realization of optimal symmetric real state quantum cloning machine

We present an experimentally uniform linear optical scheme to implement the optimal 1→2 symmetric and optimal 1→3 symmetric economical real state quantum cloning machine of the polarization state of the single photon. This scheme requires single-photon sources and two-photon polarization entangled state as input states. It also involves linear optical elements and three-photon coincidence. Then we consider the realistic realization of the scheme by using the parametric down-conversion as photon resources. It is shown that under certain condition, the scheme is feasible by current experimental technology.