We propose an efficient phase-encoding quantum secret key generation scheme with heralded narrow-band single photons.The key information is carried by the phase modulation directly on the single-photon temporal wavefo...We propose an efficient phase-encoding quantum secret key generation scheme with heralded narrow-band single photons.The key information is carried by the phase modulation directly on the single-photon temporal waveform.We show that when the technique is applied to the conventional single photon phase-encoding BB84 and differential phase shift(DPS)quantum key distribution schemes,the key generation efficiencies can be improved by factors of 2 and 3,respectively.For N(≥3)−period DPS systems,the key generation efficiency can be improved by a factor of N.The technique is suitable for quantum-memory-based long-distance fiber communication systems.展开更多
It is well known that multiple superconducting charge qubits coupled to a transmission line resonator can be controlled to achieve quantum logic gates between two arbitrary qubits. We propose a scheme to realize a qua...It is well known that multiple superconducting charge qubits coupled to a transmission line resonator can be controlled to achieve quantum logic gates between two arbitrary qubits. We propose a scheme to realize a quantum conditional phase gate with a geometric property by circuit electrodynamics, and it is applied naturally to reaJize the quantum Fourier transform with high fidelity. It is also demonstrated that the application is feasible and considerable under the present experimental technology.展开更多
We present a universal Holevo-like upper bound on the locally accessible information for arbitrary multipartite ensembles. This bound allows us to analyze the indistinguishability of a set of orthogonal states under l...We present a universal Holevo-like upper bound on the locally accessible information for arbitrary multipartite ensembles. This bound allows us to analyze the indistinguishability of a set of orthogonal states under local operations and classical communication. We also derive the upper bound for the capacity of distributed dense coding with multipartite senders and multipartite receivers.展开更多
Transport properties are theoretically studied through an anisotropy single-molecule magnet symmetrically connected to two identical ferromagnetic leads. It is found that even though in parallel configuration of leads...Transport properties are theoretically studied through an anisotropy single-molecule magnet symmetrically connected to two identical ferromagnetic leads. It is found that even though in parallel configuration of leads’ magnetizations, the total current still greatly depends on the spin polarization of leads at certain particular bias region, and thus for large polarization a prominent negative differential conductance （NDC） emerges. This originates from the joint effect of single-direction transitions and spin polarization, which removes the symmetry between spin-up and spin-down transitions. The present mechanism of NDC is remarkably different from the previously reported mechanisms. To clarify the physics of the NDC, we further monitored the shot noise spectroscopy and found that the appearance of the NDC is accompanied by the rapid decrease of Fano factor.展开更多
A single-molecule magnet （SMM） coupled to two normal metallic electrodes can both switch spin-up and spin- down electronic currents within two different windows of SMM gate voltage. Such spin current switching in th...A single-molecule magnet （SMM） coupled to two normal metallic electrodes can both switch spin-up and spin- down electronic currents within two different windows of SMM gate voltage. Such spin current switching in the SMM tunnel junction arises from spin-selected single electron resonant tunneling via the lowest unoccupied molecular orbit of the SMM. Since it is not magnetically controlled but all-electrically controlled, the proposed spin current switching effect may have potential applications in future spintronics.展开更多
We propose a scheme for a chip-based dynamic micro atom trap where the trap potentials are created by square wave radiation and an inhomogeneoas static magnetic field. The parameters of this kind of trap array can be ...We propose a scheme for a chip-based dynamic micro atom trap where the trap potentials are created by square wave radiation and an inhomogeneoas static magnetic field. The parameters of this kind of trap array can be modulated dynamically. Both one-dimensional （I-D） and two-dimensional （2-D） trap array potentials for 6Li atoms are discussed. The 1-D trap is combined by a square wave radiation （6 kHz） and a gradient magnetic field （300G/cm）, the array constant of 1-D trap is 0.85 μm. Since the trap array does not require any laser field, it can be easily integrated on a chip and it is useful in applications of scalable quantum information processing.展开更多
We have investigated the transport properties of the Dirac fermions through a ferromagnetic barrier junction on the surface of a strong topological insulator.The current-voltage characteristic curve and the tunneling ...We have investigated the transport properties of the Dirac fermions through a ferromagnetic barrier junction on the surface of a strong topological insulator.The current-voltage characteristic curve and the tunneling conductance are calculated theoretically.Two interesting transport features are predicted:observable negative differential conductances and linear conductances tunable from unit to nearly zero.These features can be magnetically manipulated simply by changing the spacial orientation of the magnetization.Our results may contribute to the development of high-speed switching and functional applications or electrically controlled magnetization switching.展开更多
We study the thermal transport of few-layer graphene nanoribbons in the presence of the transversal pressure by using molecular dynamics simulations.It is reported that the pressure can improve the thermal conductivit...We study the thermal transport of few-layer graphene nanoribbons in the presence of the transversal pressure by using molecular dynamics simulations.It is reported that the pressure can improve the thermal conductivity of few-layer graphene nanoribbons.This improvement can reach 37.5%in the low temperature region.The pressure dependence of thermal conductivity is also investigated for diferent length,width and thickness of few-layer graphene.Our results provide an alternative option to tuning thermal conductivity of few-layer graphene nanoribbons.Furthermore,it maybe indicate a so-called pressure-thermal efect in nanomaterials.展开更多
基金by the Hong Kong Research Council Project(No HKUST600809)the National Natural Science Foundation of China under Grant No 1097405the National Basic Research Program of China under Grant Nos 2011CB922104 and 2007CB925204.
文摘We propose an efficient phase-encoding quantum secret key generation scheme with heralded narrow-band single photons.The key information is carried by the phase modulation directly on the single-photon temporal waveform.We show that when the technique is applied to the conventional single photon phase-encoding BB84 and differential phase shift(DPS)quantum key distribution schemes,the key generation efficiencies can be improved by factors of 2 and 3,respectively.For N(≥3)−period DPS systems,the key generation efficiency can be improved by a factor of N.The technique is suitable for quantum-memory-based long-distance fiber communication systems.
基金Supported by the National Natural Science Foundation of China under Grant No 10905024, and the Doctoral Startup Natural Science Foundation of Guangdong Province. The authors thank Professor Zhu S. L. for useful suggestions.
文摘It is well known that multiple superconducting charge qubits coupled to a transmission line resonator can be controlled to achieve quantum logic gates between two arbitrary qubits. We propose a scheme to realize a quantum conditional phase gate with a geometric property by circuit electrodynamics, and it is applied naturally to reaJize the quantum Fourier transform with high fidelity. It is also demonstrated that the application is feasible and considerable under the present experimental technology.
基金Supported by the National Natural Science Foundation of China under Grant No.30600122GuangDong Provincial Natural Science Foundation under Grant No.06025073
基金Supported by the National Natural Science Foundation of China under Grants No 10674049, and the National Basic Research Program of China under Grant Nos 2006CB921800 and 2007CB925204.
文摘We present a universal Holevo-like upper bound on the locally accessible information for arbitrary multipartite ensembles. This bound allows us to analyze the indistinguishability of a set of orthogonal states under local operations and classical communication. We also derive the upper bound for the capacity of distributed dense coding with multipartite senders and multipartite receivers.
基金Project supported by the Program for New Century Excellent Talents in University of China (Grant No. NCET-10-0090)the National Natural Science Foundation of China (Grant Nos. 10974058, 11174088, and 11274124)the Natural Science Foundation of Guangdong Province of China (Grant No. S2012010010681)
文摘Transport properties are theoretically studied through an anisotropy single-molecule magnet symmetrically connected to two identical ferromagnetic leads. It is found that even though in parallel configuration of leads’ magnetizations, the total current still greatly depends on the spin polarization of leads at certain particular bias region, and thus for large polarization a prominent negative differential conductance （NDC） emerges. This originates from the joint effect of single-direction transitions and spin polarization, which removes the symmetry between spin-up and spin-down transitions. The present mechanism of NDC is remarkably different from the previously reported mechanisms. To clarify the physics of the NDC, we further monitored the shot noise spectroscopy and found that the appearance of the NDC is accompanied by the rapid decrease of Fano factor.
基金supported by the National Natural Science Foundation of China (Grant Nos. 60825402,60421003,11074111 and 10974058)the State Key Program for Basic Research of China (Grant Nos. 2011CB922103,2009CB929504 and 2011CBA00205)
文摘A single-molecule magnet （SMM） coupled to two normal metallic electrodes can both switch spin-up and spin- down electronic currents within two different windows of SMM gate voltage. Such spin current switching in the SMM tunnel junction arises from spin-selected single electron resonant tunneling via the lowest unoccupied molecular orbit of the SMM. Since it is not magnetically controlled but all-electrically controlled, the proposed spin current switching effect may have potential applications in future spintronics.
基金Supported by the National Basic Research Program of China under Grant Nos 2005CB724505/1 and 2006CB921203, the National Natural Science Foundation of China under Grant No 10774160, and Wuhan National Laboratory for Optoelectronics under Grant No P080001.
文摘We propose a scheme for a chip-based dynamic micro atom trap where the trap potentials are created by square wave radiation and an inhomogeneoas static magnetic field. The parameters of this kind of trap array can be modulated dynamically. Both one-dimensional （I-D） and two-dimensional （2-D） trap array potentials for 6Li atoms are discussed. The 1-D trap is combined by a square wave radiation （6 kHz） and a gradient magnetic field （300G/cm）, the array constant of 1-D trap is 0.85 μm. Since the trap array does not require any laser field, it can be easily integrated on a chip and it is useful in applications of scalable quantum information processing.
基金Supported by National Natural Science Foundation of China under Grant Nos.11174088,11175067,11274124
文摘We have investigated the transport properties of the Dirac fermions through a ferromagnetic barrier junction on the surface of a strong topological insulator.The current-voltage characteristic curve and the tunneling conductance are calculated theoretically.Two interesting transport features are predicted:observable negative differential conductances and linear conductances tunable from unit to nearly zero.These features can be magnetically manipulated simply by changing the spacial orientation of the magnetization.Our results may contribute to the development of high-speed switching and functional applications or electrically controlled magnetization switching.
基金Supported in part by the National Natural Science Foundation of China under Grant Nos.11004082 and 11175067the Natural Science Foundation of Guangdong Province under Grant Nos.10451063201005249 and S201101000332the Fundamental Research Funds for the Central Universities,JNU under Grant Nos.21611437 and 50421288
文摘We study the thermal transport of few-layer graphene nanoribbons in the presence of the transversal pressure by using molecular dynamics simulations.It is reported that the pressure can improve the thermal conductivity of few-layer graphene nanoribbons.This improvement can reach 37.5%in the low temperature region.The pressure dependence of thermal conductivity is also investigated for diferent length,width and thickness of few-layer graphene.Our results provide an alternative option to tuning thermal conductivity of few-layer graphene nanoribbons.Furthermore,it maybe indicate a so-called pressure-thermal efect in nanomaterials.
