The decoherence of two initially entangled qubits in anisotropic band gap photonic crystal has been studied analytically without Born or Markovian approximation. It is shown that the decoherence dynamics of two qubits in photonic crystal is greatly different from that of two qubits in vacuum or subjected to usual non-Markovian reservoir. The results also show that the finite time decoherence invoked by spontaneous emission could be suppressed efficiently and the entanglement of the Bell state possesses odd parity is more easily preserved in photonic crystal than that of the Bell state possesses even parity under the same condition. A store scheme for entangled particle pair is proposed.Entanglement is recognized as a global quantummechanical effect and has played a key role in quantum information [1,2], quantum computation [3,4], quantum cryptography [5], and so on. However, the phenomenon , termed as "entanglement sudden death"(ESD), has been found theoretically [6,7] and shown experimentally [8,9]. It is shown that spontaneous disentanglement may take only a finite-time to be completed, while local decoherence (the normal single-atom transverse and longitudinal decay) takes an infinite time [7]. And some issues have been devoted to extending the results in Markovian regime to non-Markovian case [10,11].On the other hand, photonic crystals form a new class of dielectric materials, in which the electromagnetic interaction is controllably altered over certain frequency [12]. The periodic dielectric structures leads to the formation of a photonic band gap( PBG), a range of frequencies for which no propagating electromagnetic modes are allowed [12]. The presence of the photonic band gap in the dispersion relation of the electromagnetic field results in a series of new phenomena, including the inhibition of the spontaneous emission [13], strong localization of light [14], formation of atom-photon bound states [15]. In this Letter, we will investigate how the entanglement of two qubits evolute in photonic crystal. Now we restrict our attention to two noninteracting two-level atoms A and B coupled individually to two photonic crystal environment reservoirs which are initially in vacuum states. To this aim, we first consider the Hamiltonian of the subsystem of single qubit coupled to its reservoir as(1) where ω 0 is the atomic transition frequency between the ground state |g and excited state |e . The index k labels * Electronic address: zmzhang@scnu.edu.cn the field modes of the reservoir with frequency ω k , a † k and a k are the modes' creation and annihilation operators, and g k is the frequency-dependent coupling constant between the transition e − g and the field mode k. For a single excitation of the subsystem, these states arewhere the ket |0 k indicates the field mode k is in vacuum state. |1 k indicates the field mode k is in the first excited state. The unexcited stateis not coulped to any other state. Now we could expand a general state vector of the subsystem as[16]in terms of the states (2)and (3 )and inse...
We propose a new quantum network scheme using orbital angular momentum states of photons to route the network and spin angular momentum states to encode the information. A four-user experimental scheme based on this efficient quantum network is analyzed in detail, which is particularly appealing for the free space quantum key distribution.Users can freely exchange quantum keys with each other.
In this paper, we propose a bilayer metasurface with dual-operating modes to realize the generation and conversion of dual-band Laguerre-Gaussian beam with different OAM. The bilayer metasurface consists of amorphous silicon (a-Si) and amorphous antimony selenide (a-Sb2Se3). In transmission mode, the metasurface can transform incident left-handed circularly polarized (LCP) Gaussian beam into one LCP Laguerre-Gaussian beam carrying topological charge l=−2 and one right-handed circularly polarized (RCP) Laguerre-Gaussian beam carrying topological charge l=−1, which enabled OAM modes multiplexing. In reflection mode, the metasurface can convert an incident LCP Gaussian beam into a LCP Laguerre-Gaussian beam carrying a topological charge l=−3 owing to the a-Sb2Se3 nanopillar that acts as a half-wave plate with high reflectivity. In addition, the OAM conversion between two arbitrary modes can be realized by the proposed metasurface. This work provides a valid method for OAM multiplexing and conversion, which holds a great applications value in high-speed optical communication systems.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.