arXiv subjects

Guang-Can Guo

Publications and source records attributed to Guang-Can Guo.

At least 919 records · Page 51Linked to original sources

arXiv2007

Experimental entanglement verification and quantification via uncertainty relations

We report on experimental studies on entanglement quantification and verification based on uncertainty relations for systems consisting of two qubits. The new proposed measure is shown to be invariant under local unitary transformations, by which entanglement quantification is implemented for two-qubit pure states. The nonlocal uncertainty relations for two-qubit pure states are also used for entanglement verification which serves as a basic proposition and promise to be a good choice for verification of multipartite entanglement.

quant-ph↗

arXiv2007

Decoy State Quantum Key Distribution With Modified Coherent State

To beat PNS attack, decoy state quantum key distribution (QKD) based on coherent state has been studied widely. We present a decoy state QKD protocol with modified coherent state (MCS). By destruction quantum interference, MCS with fewer multi-photon events can be get, which may improve key bit rate and security distance of QKD. Through numerical simulation, we show about 2-dB increment on security distance for BB84 protocol.

quant-ph↗

arXiv2007

Influence of unsymmetrical periodicity on extraordinary transmission through periodic arrays of subwavelength holes

Quadrate hole array is explored to study the influence of unsymmetrical periodicity on extraordinary optical transmission through periodic arrays of subwavelength holes. It is found that the transmission efficiency of light and the ratio between transmission efficiencies of horizontal and vertical polarized light can be continuously tuned by rotating the quadrate hole array. We can calculate out the transmission spectra (including the heights and locations of peaks) for any rotation angle $θ$ with a simple theoretical model.

physics.optics↗

arXiv2007

One-step preparation of cluster states in quantum dot molecules

Cluster states, a special type of highly entangled states, are a universal resource for measurement-based quantum computation. Here, we propose an efficient one-step generation scheme for cluster states in semiconductor quantum dot molecules, where qubits are encoded on singlet and triplet state of two coupled quantum dots. By applying a collective electrical field or simultaneously adjusting interdot bias voltages of all double-dot molecule, we get a switchable Ising-like interaction between any two adjacent quantum molecule qubits. The initialization, the single qubit measurement, and the experimental parameters are discussed, which shows the large cluster state preparation and one-way quantum computation implementable in semiconductor quantum dots with the present techniques.

quant-ph↗

arXiv2007

Scaling Behavior and Variable Hopping Conductivity in the Quantum Hall Plateau Transition

We have measured the temperature dependence of the longitudinal resistivity $% ρ_{xx}$ of a two-dimensional electron system in the regime of the quantum Hall plateau transition. We extracted the quantitative form of scaling function for $ρ_{xx}$ and compared it with the results of ordinary scaling theory and variable range hopping based theory. We find that the two alternative theoretically proposed scaling functions are valid in different regions.

cond-mat.mes-hall↗

arXiv2007

Nonclassicality of quantum excitation of classical coherent field in photon loss channel

We investigate the nonclassicality of photon-added coherent states in the photon loss channel by exploring the entanglement potential and negative Wigner distribution. The total negative probability defined by the absolute value of the integral of the Wigner function over the negative distribution region reduces with the increase of decay time. The total negative probability and the entanglement potential of pure photon-added coherent states exhibit the similar dependence on the beam intensity. The reduce of the total negative probability is consistent with the behavior of entanglement potential for the dissipative single-photon-added coherent state at short decay times.

quant-ph↗

arXiv2006

Fidelity, entanglement, and information complementarity relation

We investigate the dynamics of information in isolated multi-qubit systems. It is shown that information is in not only local form but also nonlocal form. We apply a measure of local information based on fidelity, and demonstrate that nonlocal information can be directly related to some appropriate well defined entanglement measures. Under general unitary transformations, local and nonlocal information will exhibit unambiguous complementary behavior with the total information conserved.

quant-ph↗

arXiv2006

Plasmon assisted transmission of high dimensional orbital angular momentum entangled state

We present an experimental evidence that high dimensional orbital angular momentum entanglement of a pair of photons can be survived after a photon-plasmon-photon conversion. The information of spatial modes can be coherently transmitted by surface plasmons. This experiment primarily studies the high dimensional entangled systems based on surface plasmon with subwavelength structures. It maybe useful in the investigation of spatial mode properties of surface plasmon assisted transmission through subwavelength hole arrays.

quant-ph↗

arXiv2006

Physical accessible transformations on a finite number of quantum states

We consider to treat the usual probabilistic cloning, state separation, unambiguous state discrimination, \emph{etc} in a uniform framework. All these transformations can be regarded as special examples of generalized completely positive trace non-increasing maps on a finite number of input states. From the system-ancilla model we construct the corresponding unitary implementation of pure $\to$ pure, pure $\to$ mixed, mixed $\to$ pure, and mixed $\to$ mixed states transformations in the whole system and obtain the necessary and sufficient conditions on the existence of the desired maps. We expect our work will be helpful to explore what we can do on a finite set of input states.

quant-ph↗

arXiv2006

Local Operations in qubit arrays via global but periodic Manipulation

We provide a scheme for quantum computation in lattice systems via global but periodic manipulation, in which only effective periodic magnetic fields and global nearest neighbor interaction are required. All operations in our scheme are attainable in optical lattice or solid state systems. We also investigate universal quantum operations and quantum simulation in 2 dimensional lattice. We find global manipulations are superior in simulating some nontrivial many body Hamiltonians.

quant-ph↗

arXiv2006

Practical decoy state method in quantum key distribution with heralded single photon source

We propose a practical decoy state method with heralded single photon source for quantum key distribution (QKD). In the protocol, 3 intensities are used and one can estimate the fraction of single-photon counts. The final key rate over transmission distance is simulated under various parameter sets. Due to the lower dark count than that of a coherent state, it is shown that a 3-intensity decoy-state QKD with a heralded source can work for a longer distance than that of a coherent state.

quant-ph↗

arXiv2006

Quantum key distribution network with wavelength addressing

Most traditional applications of quantum cryptography are point-to-point communications, in which only two users can exchange keys. In this letter, we present a network scheme that enable quantum key distribution between multi-user with wavelength addressing. Considering the current state of wavelength division multiplexing technique, dozens or hundreds of users can be connected to such a network and directly exchange keys with each other. With the scheme, a 4-user demonstration network was built up and key exchanges were performed.

quant-ph↗

arXiv2006

Linear Optical Implemention of a Quantum Network for Quantum Estimation

We present a scheme for simulating the quantum network of quantum estimation proposed by A. K. Ekert et al. [Phys. Rev. Lett. 88, 217901 (2002)]. We experimentally implement the scheme with linear optical elements. We perform overlap measurements of two single-qubit states and entanglement-witness measurements of some two-qubit states. In addition, it can also be used for entanglement quantification for some kinds of states. From the other perspective, we physically realize the positive but not completely positive map, transposition.

quant-ph↗

arXiv2006

Quantum Non-Demolition Bell State Measurement and N-party GHZ State Preparation in Quantum Dot

By exploiting the fermionic qubit parity measurement, we present a scheme to realize quantum non-demolition (QND) measurement of Bell-states and generate n-party GHZ state in quantum dot. Compared with the original protocol, the required electron transfer before and after parity measurement can be nonadiabatic, which may speed up the operation speed and make the omitting of spin-orbit interaction more reasonable. This may help us to construct CNOT gate without highly precise control of coupling as the way of D. Gottesman and I. L. Chuang.

quant-ph↗

arXiv2006

Entanglement measurement based on two-particle interference

We propose a simple and realizable method using a two-particle interferometer for the experimental measurement of pairwise entanglement, assuming some prior knowledge about the quantum state. The basic idea is that the properties of the density matrix can be revealed by the single- and two-particle interference patterns. The scheme can easily be implemented with polarized entangled photons.

quant-ph↗

arXiv2006

State estimation from pair of conjugate qudits

We show that, for $N$ parallel input states, an anti-linear map with respect to a specific basis is essentially a classical operator. We also consider the information contained in phase-conjugate pairs $|ϕ> |ϕ^*>$, and prove that there is more information about a quantum state encoded in phase-conjugate pairs than in parallel pairs.

quant-ph↗

arXiv2006

Spatial mode properties of plasmon assisted transmission

Orbital angular momentum of photons is explored to study the spatial mode properties of plasmon assisted transmission process. We found that photons carrying different orbital angular momentums have different transmission efficiencies, while the coherence between these spatial modes can be preserved.

quant-ph↗

arXiv2006

Information-Theoretic Measure of Genuine Multi-Qubit Entanglement

We consider pure quantum states of N qubits and study the genuine N-qubit entanglement that is shared among all the N qubits. We introduce an information-theoretic measure of genuine N-qubit entanglement based on bipartite partitions. When N is an even number, this measure is presented in a simple formula, which depends only on the purities of the partially reduced density matrices. It can be easily computed theoretically and measured experimentally. When N is an odd number, the measure can also be obtained in principle.

quant-ph↗