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Atoma??photon entanglement near a plasmonic nanostructure
摘要： We investigate the atom–photon entanglement between a four-level double V-type quantum system and a linearly polarized ?eld near a plasmonic nanostructure in the presence of a static magnetic ?eld. It is demonstrated that the magneto-optical effect can affect the atom–photon entanglement only when the atom is near the plasmonic nanostructure. We show that atom–photon entanglement increases when the quantum system is placed near the plasmonic nanostructure in order to modi?cation of the spontaneous decays of the quantum system. It is demonstrated that the degree of entanglement (DEM) increases by increasing the intensity of the linearly polarized ?eld when the quantum system is close to the surface of the plasmons. Moreover, we ?nd that near the plasmonic nanostructure, the static magnetic ?eld has a major role in increasing the steady-state DEM so that the DEM is completely demolished in the absence of the static magnetic ?eld. Finally, it is shown that the atom–photon entanglement near a plasmonic nanostructure is destroyed by free space decay rate.
关键词： degree of entanglement,static magnetic ?eld,atom–photon entanglement,plasmonic nanostructure,spontaneous emission
更新于2025-09-19 17:13:59
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Quantum collapse as reduction from a continuum of conditional amplitudes in an entangled state to a single actualized amplitude in the collapsed state
摘要： According to the Copenhagen interpretation of quantum mechanics a measurement leads to the collapse of a quantum system. A uni?ed description of a quantum system before and after measurement of the position ra1 and the spin sa1 of one of its electrons is proposed based on the conditional amplitude and its density. Quantum collapse is described as reduction from continuum of the conditional amplitudes {(cid:2)(x2, . . . , xN |rh1 )} in an initial quantum state to the single actualized amplitude (cid:2)(x2, . . . , xN |ra1 ) in a collapsed state. The latter state contains the information about quantum entanglement, the extraction of which with fragment entanglement measure is demonstrated for the realistic valence bond models of the dissociating dihydrogen and ethylene molecules.
关键词： ethylene molecules,quantum collapse,dihydrogen,conditional amplitude,quantum entanglement,valence bond models
更新于2025-09-19 17:13:59
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Non-Kolmogorov atmospheric turbulence and orbital angular momentum of entangled states for optical communication
摘要： We extend the theory of detection probabilities of single-photon communication in turbulent atmosphere to the entangled case and derive analytical expressions for detection probabilities. We show that the rotational ?eld correlation in the entangled case cannot be expressed as a straightforward extension from the disentangled case. By considering the orbital angular momentum (OAM) entangled Laguerre-Gaussian (LG) beams for illustration, we explore the e?ect of non-Kolmogorov atmospheric turbulence on the probabilities of both the biphoton detection and the single-photon detection. The entanglement of OAM LG beams contributes positively to the faithful detection probability. The change of maximal crosstalk probability in the detection process is also explored, which displays the non-linear dependence on the crosstalk quantum number.
关键词： Atmospheric turbulence,Orbital angular momentum,Entanglement,Optical communication
更新于2025-09-19 17:13:59
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Error correction of polarization entanglement in hyper-entangled state
摘要： We present two schemes for error-correction of polarization entanglement with time-bin entanglement and frequency entanglement in hyper-entangled state. In these two protocols, by performing the polarization parity-check operation, the bit-flip and phase-flip errors on the polarization part can be corrected and eliminated in one step. The parties in quantum communication can obtain a maximally hyper-entangled states in two degrees of freedom in a deterministic way. Our protocols for purification are useful in practical applications for long-distance quantum communication.
关键词： quantum communication,hyper-entangled state,error correction,polarization parity-check operation,quantum entanglement
更新于2025-09-19 17:13:59
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Non-Markovian entanglement transfer to distant atoms in a coupled superconducting resonator
摘要： In this paper, we investigate the non-Markovian effects on the entanglement transfer to the distant non-interacting atom qubits, which are embedded in a coupled superconducting resonator. The master equation governing the dynamics of the system is derived by the non-Markovian quantum state diffusion (NMQSD) method. Based on the solution, we show that the memory effect of the environment can lead to higher entanglement revival and make the entanglement last for a longer time. That is to say, the non-Markovian environment can enhance the entanglement transfer. It is also found that the maximum entanglement transferred to distant atoms can be modified by appropriately selecting the frequency of the modulated inter-cavity coupling. Moreover, with the initially anti-correlated state, the entanglement between the cavity fields can be almost completely transferred to the separated atoms. At last, we also show that the memory effect have a significant impact on the generation of entanglement from the initially non-entangled states.
关键词： quantum state diffusion,Non-Markovian,Entanglement transfer
更新于2025-09-19 17:13:59
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Hybrid Entangled States With Multi-Degree of Freedom and High Purity for Internet of Vehicles
摘要： The development of intelligent Internet of vehicles (IoV) is based on communication technology, especially the quantum communication of hybrid entangled states based on orbital angular momentum (OAM). The quantum key distribution (QKD) method is demonstrated using hybrid entangled states with multi-degree of freedom and high purity based on OAM. First, the polarization entangled photon pairs are produced by two type I BBO crystals by means of spontaneous parametric down-conversion (SPDC). The polarization-OAM hybrid entangled states are created by q-plate (QP) to realize QKD. It is found that the polarization entangled photon pairs have the characteristics of OAM. A single mode fiber (SMF) is proposed to filter the topological charge non-zero photons and purify the polarization entangled photon pairs. Then the purification setup with M-Z interferometer and beam rotator (BR) is presented which can purify the polarization-OAM hybrid entangled states. The high purity polarization-OAM hybrid entangled states are implemented, and the QP conversion rate of 3 secondary feedbacks is 99.84% theoretically. Analysis indicates that precise purity polarization-OAM hybrid entangled state can increase the fidelity of information and improve the anti-interference ability in this program without mutually unbiased bases (MUBs). The photon utilization rate, energy-efficient and low-latency communication can be greatly improved by using the OAM carrying information.
关键词： hybrid entanglement,orbital angular momentum (OAM),coincidence measurement,high purity,Internet of vehicles (IoV),low-latency
更新于2025-09-19 17:13:59
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Entanglement Swapping with Photons Generated on Demand by a Quantum Dot
摘要： Photonic entanglement swapping, the procedure of entangling photons without any direct interaction, is a fundamental test of quantum mechanics and an essential resource to the realization of quantum networks. Probabilistic sources of nonclassical light were used for seminal demonstration of entanglement swapping, but applications in quantum technologies demand push-button operation requiring single quantum emitters. This, however, turned out to be an extraordinary challenge due to the stringent prerequisites on the efficiency and purity of the generation of entangled states. Here we show a proof-of-concept demonstration of all-photonic entanglement swapping with pairs of polarization-entangled photons generated on demand by a GaAs quantum dot without spectral and temporal filtering. Moreover, we develop a theoretical model that quantitatively reproduces the experimental data and provides insights on the critical figures of merit for the performance of the swapping operation. Our theoretical analysis also indicates how to improve state-of-the-art entangled-photon sources to meet the requirements needed for implementation of quantum dots in long-distance quantum communication protocols.
关键词： quantum communication,quantum dot,entanglement swapping,quantum networks
更新于2025-09-19 17:13:59
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Entanglement of two distant quantum dots with the flip-flop interaction coupled to plasmonic waveguide
摘要： The entanglement of two distant quantum dots coupled to metallic waveguide has been investigated theoretically in the presence of the flip-flop interaction with the analytic solutions of eigenvalue equations of the system. High entanglement of two quantum dots could be achieved by adjusting the direct-coupling strength of two quantum dots, the coupling strength of quantum dots with surface plasmon along metallic waveguide, the group velocity of surface plasmon and detuning. The discussed system with the flip-flop interaction provides us with a rich way to realize the quantum device for quantum information processing, such as quantum communication and quantum computation.
关键词： surface plasmon,Quantum dot,entanglement,waveguide
更新于2025-09-19 17:13:59
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[IEEE 2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring) - Rome, Italy (2019.6.17-2019.6.20)] 2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring) - Interaction between Microwave and Mesoscopic Circuits in Cavity-circuit Quantum Electrodynamics
摘要： Mesoscopic electric circuits can exhibit a large number of effects relevant to quantum mechanics, quantum electrodynamics and quantum statistics. The topic presented here can be identified as an analog of conventional cavity quantum electrodynamics, where the quantum objects are multilevel atoms and quantized optical fields (photons), namely, a theoretical subject called “cavity-circuit quantum electrodynamics”, where the atoms are replaced with quantum mesoscopic circuits, will be developed. We will study the quantum characteristics of the interaction between the quantum mesoscopic circuits and the quantized electromagnetic field at microwave frequencies. These issues include quantum entangled eigenstates of two coupled mesoscopic circuits, time evolution of the circuit energy quanta (governed by the time-dependent Schr?dinger equation) and entanglement transfer between external photons and mesoscopic circuit energy quanta. Since there is inevitable electromagnetic interaction such as mutual capacitance and inductance coupling between two neighboring circuits, the quantum effects resulting from the aforementioned quantized circuit coupling would unavoidably affect the relevant processes in quantum computing devices and hence they deserve consideration in some issues of quantum information.
关键词： Quantum computing,Microwave photons,Quantum entanglement,Mesoscopic circuits,Quantum electrodynamics
更新于2025-09-19 17:13:59
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Tunable nonlocal valley-entangled Cooper pair splitter realized in bilayer-graphene van der Waals spin valves
摘要： We investigate the Cooper pair splitting based on crossed Andreev reflection in a two-dimensional narrow superconductor coupled to two leads, where the two leads are van der Waals (vdW) spin valves formed by inserting bilayer graphene (BLG) between two antiparallel insulating ferromagnetic layers. In this BLG-based n-type vdW spin valve/superconductor/p-type vdW spin valve junction with edge-contact geometry, when controlling the Fermi energy and the interlayer electric field in BLG independently by top- and bottom-gate voltages in the vdW spin valve region, we first demonstrate that the two electrons of perfect Cooper pair splitting can remain nonlocal valley entanglement. This effect can be explained as follows: When both the two antiparallel insulating ferromagnetic layers and the interlayer electric field are taken into account, BLG exhibits a spin-splitting but valley-degenerate band gap near the Dirac point. Thus, our setups allow the Cooper pair in the BCS scenario to serve as a natural source of valley entanglement. We further predict large oscillations of cross conductance as a function of the doping of the superconductor, the junction length, and the bias voltage. Our results may provide a tool for realizing fast nonlocal switching of the valley-entanglement state.
关键词： valley entanglement,crossed Andreev reflection,Cooper pair splitting,van der Waals spin valves,bilayer graphene
更新于2025-09-19 17:13:59