Trap states in oxidation layer of nanocrystal Si

The photoluminescence （PL） of nanocrystal present in porous silicon shifts from the near infrared to the ultraviolet depending on the size when the surface is passivated with Si-H bonds. After oxidation, the centre wavelength of PL band is pinned in a region of 700-750 nm and its intensity increases obviously. Calculation shows that trap electronic states appear in the band gap of a smaller nanocrystal when Si = O bonds or Si-O-Si bonds are formed. The changes in PL intensity and wavelength can be explained by both quantum confinement and trap states in an oxidation layer of nanocrystal. In the theoretical model, the most important factor in the enhancement and the pinning effects of PL emission is the relative position between the level of the trap states and the level of the photoexcitation in the silicon nanocrystal.

Suppressing trap states and energy loss by optimizing vertical phase distribution through ternary strategy in organic solar cells

Suppressing the trap-state density and the energy loss via ternary strategy was demonstrated.Favorable vertical phase distribution with donors(acceptors)accumulated(depleted)at the interface of active layer and charge extraction layer can be obtained by introducing appropriate amount of polymer acceptor N2200 into the systems of PBDB-T:IT-M and PBDB-TF:Y6.In addition,N2200 is gradiently distributed in the vertical direction in the ternary blend film.Various measurements were carried out to study the effects of N2200 on the binary systems.It was found that the optimized morphology especially in vertical direction can significantly decrease the trap state density of the binary blend films,which is beneficial for the charge transport and collection.All these features enable an obvious decrease in charge recombination in both PBDB-T:IT-M and PBDB-TF:Y6 based organic solar cells(OSCs),and power conversion efficiencies(PCEs)of 12.5%and 16.42%were obtained for the ternary OSCs,respectively.This work indicates that it is an effective method to suppress the trap state density and thus improve the device performance through ternary strategy.

Nanoscale control of grain boundary potential barrier, dopant density and filled trap state density for higher efficiency perovskite solar cells

In this work,grain boundary(GB)potential barrier(ΔφGB),dopant density(Pnet),and filled trap state density(PGB,trap)were manipulated at the nanoscale by exposing the fabricated perovskite films to various relative humidity(RH)environments.Spatial mapping of surface potential in the perovskite film revealed higher positive potential at GBs than inside the grains.The averageΔφGB,Pnet,and PGB,trap in the perovskite films decreased from 0%RH to 25%RH exposure,but increased when the RH increased to 35%RH and 45%RH.This clearly indicated that perovskite solar cells fabricated at 25%RH led to the lowest average GB potential,smallest dopant density,and least filled trap states density.This is consistent with the highest photovoltaic efficiency of 18.16%at 25%RH among the different relative humidities from 0%to 45%RH.

Scheme for implementing quantum dense coding with four-particle decoherence-free states in an ion trap

This paper proposes an experimentally feasible scheme for implementing quantum dense coding of trapped-ion system in decoherence-free states. As the phase changes due to time evolution of components with different eigenenergies of quantum superposition are completely frozen, quantum dense coding based on this model would be perfect. The scheme is insensitive to heating of vibrational mode and Bell states can be exactly distinguished via detecting the ionic state.

Photoluminescence of carbon quantum dots:coarsely adjusted by quantum confinement effects and finely by surface trap states

Photoluminescence(PL) mechanism of carbon quantum dots(CQDs) remains controversial up to now even though a lot of approaches have been made. In order to do that, herein a PL color ladder from blue to near infrared of CQDs with the absolute quantum yields higher than 70% were prepared via a one-pot hydrothermal synthesis route and separated by silica gel column.Time-correlated single photon counting measurements suggest that the electron transition takes in effect in the PL progress of the crystalline core-shell structured CQDs, and the PL properties could be coarsely adjusted by tuning the size of the crystalline carbon core owing to quantum confinement effects, and finely adjusted by changing the surface functional groups consisted shell owing to surface trap states,respectively. Both coarse and fine adjustments of PL, as optical and photoelectrical characterizations and density-functional theory(DFT) calculations have demonstrated, make it possible for top-level design and precise synthesis of new CQDs with specific optical properties.

Two Feasible Schemes for Preparing Cluster States with Ion-Trap Setup

我们在场为准备的二个计划在一个离子陷井系统与原子 qubits 聚类状态。在第一个计划，辅助原子水平被需要。当在第二个计划一块另外的古典驾驶的地被使用时，并且多离子簇状态能被一个步骤产生。两计划对离子的热运动感觉迟钝，在他们使用的所有设备在现状以内好。

Preparation of the four-qubit cluster states in cavity QED and the trapped-ion system

This paper proposes a simple scheme to generate a four-atom entangled cluster state in cavity quantum electrodynamics. With the assistantce of a strong classical field the cavity is only virtually excited and no quantum information will be transferred from the atoms to the cavity during the preparation for a four-atom entangled cluster state, and thus the scheme is insensitive to the cavity field states and cavity decay. Assuming that deviation of laser intensity is 0.01 and that of simultaneity for the interaction is 0.01, it shows that the fidelity of the resulting four-atom entangled cluster state is about 0.9886. The scheme can also be used to generate a four-ion entangled cluster state in a hot trapped-ion system. Assuming that deviation of laser intensity is 0.01, it shows that the fidelity of the resulting four-ion entangled cluster state is about 0.9990. Experimental feasibility for achieving this scheme is also discussed.

Generation of Multi-mode Entangled Coherent States for N Trapped Ions in Strong-Excitation Regime

We propose a scheme to generate entangled coherent states for the vibrational modes of N trapped ions.In the scheme the first ion is sequentially excited by two travelling wave laser fields tuned to the ion transition. The scheme works in the strong-excitation regime, which is of experimental importance in view of decoherence.

Preparation of Squeezed State and Entanglement State Between Vibrational Motion of Trapped Ion and Light

Several schemes have been proposed to prepare two-mode squeezed state and entanglement state betweenmotional states of a single trapped ion and light.Preparation of two-mode squeezed state is based on interaction ofa trapped ion located in light cavity with cavity field.Preparation of entanglement state is based on interaction of atrapped ion located in light cavity with cavity field and a traveling wave light field.

Generation of a Four-Particle Cluster State and Perfect Teleportation of an Arbitrary Two-Particle State in an Ion-Trap System

We propose a scheme for generating a four-particle cluster state in an ion-trap system.The scheme isinsensitive to the thermal motion of the ions,and needs less operations than previous ones.With such a setup,we alsodemonstrate a procedure for perfectly teleporting an arbitrary two-particle state via a single multipartite entanglementchannel,a four-particle cluster state.

Cluster states prepared by using hot trapped ions

We propose a scheme for the preparation of one-dimensional and two-dimensional cluster states by using hot trapped ions. The scheme is based on the interaction between two ions and bichromatic radiation. The vibrational mode in our protocol is only virtually excited so that the system is insensitive to the thermal field. In addition, we only use two levels of ions as qubits and the successful probability may achieve 100%.

Deterministic and Multi-Controlled Teleportation of an Arbitrary Unknown Two-Ion State in Ion-Trap System

我们在离子陷井系统为一个任意的未知二水平的二离子的状态的确定、多控制的远距传物建议一个简单计划。在计划，当量隧道和需要的单一的转变可以分别地经由一个单个反响的相互作用被完成，特殊纠缠的 W 状态使用了。完成整个过程的要求的时间不与代理人的数字增加。

Fast scheme for generating quantum-interference states and GHZ state of N trapped ions

We propose a fast scheme to generate the quantum-interference states of N trapped ions. In the scheme the ions are driven by a standing-wave laser beam whose carrier frequency is tuned such that the ion transition can take place. We also propose a simple and fast scheme to produce the GHZ state of N hot trapped ions and this scheme is insensitive to the heating of vibrational motion, which is important from the viewpoint of decoherence.

Electronic relaxation of deep bulk trap and interface state in ZnO ceramics

This paper investigates the electronic relaxation of deep bulk trap and interface state in ZnO ceramics based on dielectric spectra measured in a wide range of temperature, frequency and bias, in addition to the steady state response. It discusses the nature of net current flowing over the barrier affected by interface state, and then obtains temperature-dependent barrier height by approximate calculation from steady I-V （current-voltage） characteristics. Additional conductance and capacitance arising from deep bulk trap relaxation are calculated based on the displacement of the cross point between deep bulk trap and Fermi level under small AC signal. From the resonances due to deep bulk trap relaxation on dielectric spectra, the activation energies are obtained as 0.22 eV and 0.35 eV, which are consistent with the electronic levels of the main defect interstitial Zn and vacancy oxygen in the depletion layer. Under moderate bias, another resonance due to interface relaxation is shown on the dielectric spectra. The DC-like conductance is also observed in high temperature region on dielectric spectra, and the activation energy is much smaller than the barrier height in steady state condition, which is attributed to the displacement current coming from the shallow bulk trap relaxation or other factors.

Two Schemes for Generation of Entanglement for Vibronic Collective States of Multiple Trapped Ions

我们建议二个计划为多重套住的离子的电子振动的集体状态准备纠纷。第一个计划瞄准到为套住的离子的震动的模式产生多国参加的纠纷，它仅仅要求调节到离子的搬运人频率的一根单个激光横梁。我们的计划在调停的刺激政体， correspondingRabi 频率在等于陷井频率工作。在他们的基本重要性以外，自从礼品，这些状态也许为 decoherence 上的试验性的研究的兴趣策划以一个快方法操作。第二个计划瞄准模式 maximallyGreenberger 到多准备连续变量—Horne-Zeilinger 状态。明显的优点是操作时间被可得到的激光紧张，不是由象 off-resonantexcitations 那样的固有的机制仅仅限制。这使在一合理时间与需要的振幅获得多重协调、压榨的状态的纠纷有希望。

Teleportation of an Unknown Entangled State in Trapped Ions

A scheme is presented for teleportation of an unknown entangled ionic state between ions kept in two wellseparated traps,which is induced by means of two dispersive laser excitations.The scheme is insensitive to the thermalmotion and its successful probability can reach 1.

Preparation of Macroscopic Quantum-Interference States for a Collection of Trapped Ions Via a Single Geometric Operation

我们由单个几何阶段操作为许多套住的离子为宏观的量干扰状态的产生描述一个计划。在计划，震动的模式处于某个扎根的电子状态与与离子的数字成正比的半径沿着一个圆被代替。在一给定的相互作用时间，震动的模式回到原来的状态，并且离子的系统获得与圆的区域成正比的一个几何阶段，从一个协调状态演变到二个协调状态的重叠。离子不在操作期间经历电子转变。利用几何操作的固有的差错容忍的特征，我们的计划对 decoherence 是柔韧的。

Storage of Entangled States with Multiple Trapped Ions in Thermal Motion

<正> This paper presents an alternative scheme to realize the storage of entangled states for multiple trappedions including W state,Bell states,and GHZ stares even with ions which exchange vibrational energy with a heatingsurrounding.Our scheme requires that the ions be simultaneously excited by two laser beams with different frequencies.In this scheme the vibrational degrees of freedom are only regarded as intermediate states and the ions exchange energyvia the mediation of the vibration of the vibrational mode in coupling processes.The scheme is insensitive to both theinitial vibrational state and heating if the system remains in the Lamb-Dicke regime.Since the effective Rabi frequencyhas a small dependence on the vibrational quantum number the heating will have no direct effect on the internal stateevolution.

Generation of Superpositions of Two-Mode Coherent States for the Motion of Two Trapped Ions

We propose a method for the generation of superpositions of two-mode coherent states for the center-of-mass and relative vibrational modes of two trapped ions. In the scheme the ions are driven by a single travelling-wave laser field tuned to the carrier. Then a measurement of the internal states collapses the vibrational modes to the entangled coherent state.