arXiv subjects

Guang-Can Guo

Publications and source records attributed to Guang-Can Guo.

At least 937 records · Page 52Linked to original sources

arXiv2006

Extensible router for multi-user quantum key distribution network

A feasible quantum key distribution (QKD) network scheme has been proposed with the wavelength routing. An apparatus called "quantum router", which is made up of many wavelength division multiplexers, can route the quantum signals without destroying their quantum states. Combining with existing point-to-point QKD technology, we can setup a perfectly QKD star-network. A simple characteristic and feasibility of this scheme has also been obtained.

quant-ph↗

arXiv2006

Interference of quantum channels in single photon interferometer

We experimently demonstrate the interference of dephasing quantum channel using single photon Mach-Zender interferometer. We extract the information inaccessible to the technology of quantum tomography. Further, We introduce the application of our results in quantum key distribution.

quant-ph↗

arXiv2006

Generation of a High-Visibility Four-Photon Entangled State and Realization of a Four-Party Quantum Communication Complexity Scenario

We obtain a four-photon polarization-entangled state with a visibility as high as (95.35\pm 0.45)% directly from a single down-conversion source. A success probability of (81.54\pm 1.38)% is observed by applying this entangled state to realize a four-party quantum communication complexity scenario (QCCS), which comfortably surpass the classical limit of 50%. As a comparison, two Einstein-Podolsky-Rosen (EPR) pairs are shown to implement the scenario with a success probability of (73.89\pm 1.33)%. This four-photon state can be used to fulfill decoherence-free quantum information processing and other advanced quantum communication schemes.

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arXiv2006

A Hybrid Quantum Encoding Algorithm of Vector Quantization for Image Compression

Many classical encoding algorithms of Vector Quantization (VQ) of image compression that can obtain global optimal solution have computational complexity O(N). A pure quantum VQ encoding algorithm with probability of success near 100% has been proposed, that performs operations 45sqrt(N) times approximately. In this paper, a hybrid quantum VQ encoding algorithm between classical method and quantum algorithm is presented. The number of its operations is less than sqrt(N) for most images, and it is more efficient than the pure quantum algorithm. Key Words: Vector Quantization, Grover's Algorithm, Image Compression, Quantum Algorithm

cs.MM↗

arXiv2006

Decoherence effects on the quantum spin channels

An open ended spin chain can serves as a quantum data bus for the coherent transfer of quantum state information. In this paper, we investigate the efficiency of such quantum spin channels which work in a decoherence environment. Our results show that, the decoherence will significantly reduce the fidelity of quantum communication through the spin channels. Generally speaking, as the distance increases, the decoherence effects become more serious, which will put some constraints on the spin chains for long distance quantum state transfer.

quant-ph↗

arXiv2006

Experimental Entanglement Distillation of Two-qubit Mixed States Under Local filtering Operations

We experimentally demonstrate optimal entanglement distillation from two forms of two-qubit mixed states under local filtering operations according to the constructive method intruduced by F. Verstraete et al. [Phys. Rev. A 64, 010101(R) (2001)]. In principle, our set-up can be easily applied to distilling entanglement from arbitrary two-qubit partially mixed states. We also test the violation of the Clauser-Horne-Shinmony-Holt (CHSH) inequality for the distilled state from the first form of mixed state to show its "hidden non-locality".

quant-ph↗

arXiv2006

Always On Non-Nearest-Neighbor Coupling in Scalable Quantum Computing

We investigate the non-nearest-neighbor interaction effect in 1-D spin-1/2 chain model. In many previous schemes this long-range coupling is omitted because of its relative weak strength compared with the nearest-neighbor coupling. We show that the quantum gate deviation induced by the omitted long-range interaction depends on not only its strength but also the scale of the system. This implies that omitting the long-range interaction may challenge the scalability of previous schemes. We further consider how to suppress this unwanted effect. We propose a quantum computation scheme. In this scheme, by using appropriate encoding method, we effectively negate the influence of the next-nearest-neighbor interaction in order to improve the precision of quantum gates. We also discuss the feasibility of this scheme in 1-D Josephson charge qubit array system. This work may offer improvement in scalable quantum computing.

quant-ph↗

arXiv2006

Nonlocal Gate Of Quantum Network Via Cavity Quantum Electrodynamics

We propose an experimentally feasible scheme to realize the nonlocal gate between two different quantum network nodes. With an entanglement-qubit (ebit) acts as a quantum channel, our scheme is resistive to actual environment noise and can get high fidelity in current cavity quantum electrodynamics (C-QED) system.

quant-ph↗

arXiv2006

Observation of the Preservation of the Two-Photon Coherence in Plasmon-assisted Transmission

We experimentally study two-photon coherence in plasmon-assisted transmission with a two-photon Mach-Zehnder (MZ) interferometer. Two collinear photons of identical or orthogonal polarization are simultaneously incident on one optically thick metal film, perforated with a periodic array of subwavelength holes. The de Broglie wavelength of plasmon-assisted transmitted photons is measured, which shows that two photons are re-eradiated by the plasmons and the quantum coherence of biphoton is preserved in the conversion process of transforming biphoton to plasmons and then back to biphoton.

quant-ph↗

arXiv2005

Local Distinguishability and Schmidt Number of Orthogonal States

Now, the known ensembles of orthogonal states which are distinguishable by local operators and classical communication (LOCC) satisfy the condition that the sum of Schmidit numbers of the orthogonal states is not bigger than the dimensions of the whole space. A natural question is whether an arbitary ensembles of LOCC-distinguishable orthogonal states satisfies the condition. We first show that, in this paper, the answer is positive. Then we generalize it into multipartite systems, and show that a necessary condition for LOCC-distinguishability of multipartite orthogonal quantum states is that the sum of the least numbers of the product states (For bipartite system, the least number of product states is Schmidit number) of the orthogonal states is not bigger than the dimensions of the Hilbert space of the multipartite system. This necessary condition is very simple and general, and one can get many cases of indistinguishability by it. It means that the least number of the product states acts an important role in distinguishablity of states, and implies that the least number of the product states may be an good manifestion of quantum nonlocality in some sense. In fact, entanglement emphases the "amount" of nonlocality, but the least number of the product states emphases the types of nonlocality. For example, the known W states and GHZ states have different least number of the product states, and are different in type.

quant-ph↗

arXiv2005

Efficient Implementation of Controlled-Rotations by Using Entanglement

Implementation of controlled-rotations using entanglement is considered. We show that the successful probability is closely related to the entanglement and the rotation angle. The successful probability will increase if we increase the entanglement we use or decrease the controlled-rotation angle and the probability will trend to unit when the entangled state trends to a Bell state or the controlled-rotation angle trends to zero.

quant-ph↗

arXiv2005

Condition for the adiabatic approximation

We give a sufficient condition for the quantum adiabatic approximation, which is quantitative and can be used to estimate error caused by this approximation. We also discuss when the traditional condition is sufficient.

quant-ph↗

arXiv2005

Remote Implementation of Quantum Operations

Shared entanglement allows, under certain conditions, the remote implementation of quantum operations. We revise and extend recent theoretical results on the remote control of quantum systems as well as experimental results on the remote manipulation of photonic qubits via linear optical elements.

quant-ph↗

arXiv2005

Manipulating quantum states with aspheric lenses

We present an experimental demonstration to manipulate the width and position of the down-converted beam waist. Our results can be used to engineer the two-photon orbital angular momentum (OAM) entangled states (such as concentrating OAM entangled states) and generate Hermite-Gaussian (HG) modes entangled states.

quant-ph↗

arXiv2005

Stability of Pairwise Entanglement in a Decoherent Environment

Consider the dynamics of a two-qubit entangled system in the decoherence environment, we investigate the stability of pairwise entanglement under decoherence. We find that for different decoherence models, there exist some special class of entangled states of which the pairwise entanglement is the most stable. The lifetime of the entanglement in these states is larger than other states with the same initial entanglement. In addition, we also investigate the dynamics of pairwise entanglement in the ground state of spin models such as Heisenberg and XXY models.

quant-ph↗

arXiv2005

Entanglement of the Hermite-Gaussian modes states of photons

We found that the Hermit-Gaussian(HG) modes of the down converted beams from the spontaneous parametric down conversion are quasi-conserved and the generated photon pairs are HG modes entangled for some special cases. This is valuable for either the investigation of fundament properties of multi-dimensional entanglement or quantum information applications.

quant-ph↗

arXiv2005

Teleporting a rotation on remote photons

Quamtum remote rotation allows implement local quantum operation on remote systems with shared entanglement. Here we report an experimental demonstration of remote rotation on single photons using linear optical element. And the local dephase is also teleported during the process. The scheme can be generalized to any controlled rotation commutes with $σ_{z}$.

quant-ph↗

arXiv2005

Limitations of practical multi-photon decoherence-free states

It is shown in this paper that decoherence-free subspace (DFS) of practical multi-photon polarization can not avoid the exponential decoherence even in the same extra-environment if the photons are frequency-anticorrelated. The reason lies in that the condition of collective decoherence is not satisfied in this case. As an example, the evolution of biphoton's decoherence-free state is given. Possible solution for feasible multi-photon's DFS state is also given.

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