Circuit quantum electrodynamics with a quadruple quantum dot

In this theoretical work,we describe a mechanism for the coupling between a plane structure consisting of four quantum dots and a resonator.We systematically study the dependence of the quadruple coupling strength and the qubit decoherence rate and point out the optimized operating position of the hybrid system.According to the transmission given by the input-output theory,the signatures in the resonator spectrum are predicted.Furthermore,based on the parameters already achieved in previous works,we prove that the device described in this paper can achieve the strong coupling limit,i.e.,this approach can be used for system extension under the existing technical conditions.Our results show an effective and promotable approach to couple quantum dot structures in plane with the resonator and propose a meaningful extension method.

Dynamical chiral symmetry breaking in QED_3

In order to examine how a propagator behaves in non-perturbative theories and how its behavior is influenced by the choice of a covariant gauge a truncated Dyson-Schwinger equation is used to numerically investigate the properties of fermions and bosons in 3D quantum electrodynamics QED and a series of self-consistent solutions for the fermion propagator in the Nambu and Wigner phases are obtained. These numerical solutions show that the propagator behaves very differently in the Landau gauge domain and in the infrared energy region outside it.By using the propagators in the Nambu and Wigner phases under various gauges it is further investigated how the fermion equivalent pressure difference and fermion condensation change with the gauge parameters.These results indicate that the phase transition described by the CJT equivalent potential and the chiral phase transition described by the chiral condensation are not completely identical.

A New Approach for Calculating Spin Susceptibility in QED_3

Based on the study of the linear response of the fermion propagator to the presence of an external scalar field, a new method for calculating the staggered spin susceptibility in QED3 is presented, in which the influence of the full vertex function is included. The numerical values of the staggered spin susceptibility are calculated within the framework of the rainbow-ladder approximation of the Dyson-Schwinger approach. A comparison between the result calculated using the full vertex and that using the bare vertex is given.

Analytic Method to Study Influence of Finite Chemical Potential in QED_3~*

Adopting the approximation to the first order of chemical potential μ, we resolve rigidly the influence on fermion condensate from μ in QED3. We show that this condensate does not respond linear expression to μ. Moreover, the influence on fermion chiral condensate from chemieal potential is investigated.

Calculation of Particle-Number Susceptibility of QED3 at Finite Temperature

Based on the external field approach and the differential form of Ward identity, we derive a more compact formula for the particle-number susceptibility in QED3 at finite temperature. Using the zero frequency approximation the numerical value of the particle-number susceptibility is calculated in the Dyson-Schwinger approach for the case that the number of fermion flavours equals one and two, respectively. An enhanced fluctuation of the particlenumber density is observed across the transition temperature, which should be an essential characteristic of chiral phase transition in QED3.

Critical Behavior of Dynamical Chiral Symmetry Breaking with Gauge Boson Mass in QED3

Since the massless quantum electrodynamics in 2＋1 dimensions （QEDa） with nonzero gauge boson mass ζ can be used to explain some important traits of high-Tc superconductivity in planar cuprates, it is worthwhile to apply this model to analyze the nature of chiral phase transition at the critical value ζ. Based on the feature of chiral susceptibility, we show that the system at ζ exhibits a second-order phase transition which accords with the nature of appearance of the high-To superconductivity, and the estimated critical exponents around ζ are illustrated.

Discussion for the Solutions of Dyson-Schwinger Equations at <i>m</i>≠ 0 in QED₃

In the case of nonzero fermion mass, within a range of Ansatze for the full fermion-boson vertex, we show that Dyson-Schwinger equation for the fermion propagator in QED3 has two qualitatively distinct dynamical chiral symmetry breaking solutions. As the fermion mass increases and reaches to a critical value mc, one solution disappears, and the dependence of mc on the number of fermion flavors is also given.

The Magnetic Longitudinal (P-) Wave’s Propagation and Energy Models Underlying the Mechanisms of Its Capacity to Absorb Free Energy

The longitudinal wave term within Faraday’s law of electromagnetic induction (Faraday’s law) underwent recovery to ensure its suitability for theoretical derivation of the equation governing longitudinal electromagnetic (LEM) waves. The revised Maxwell’s equations include the crucial parameters being the attenuation time constants of magnetic vortex potential and electric vortex potential generated by external electromagnetic field within the propagation medium. Specific expressions for them are obtained through theoretical analysis. Subsequently, a model for propagating magnetic P-wave generated by the superposition of a left-handed photo and a right-handed photon in a vacuum is formulated based on reevaluated total current law and revised Faraday’s law, covering wave equations, energy equation, as well as propagation mode involving mutual induction and conversion between scalar magnetic field and vortex electric field. Furthermore, through theoretical derivations centered around magnetic P-wave, evidence was presented regarding its ability to absorb huge free energy through the entangled interaction between zero-point vacuum energy field and the torsion field produced by the vortex electric field.

腔QED中利用超导量子干涉仪实现Toffoli门

基于腔量子电动力学技术,提出了利用三能级超导量子干涉仪实现Toffoli门的理论方案.利用超导量子干涉仪与腔场发生耦合,以及与外加经典脉冲发生共振跃迁来实现量子态的演化控制.该方案可以拓展到N比特Toffoli门的实现.最后,讨论了逻辑门的实验可行性,四比特Toffoli门的作用时间约为30 nm,它远小于腔衰减时间和较高能级的能量驰豫时间,从而足以实现量子态的操控.并且随着比特数的增多,Toffoli门作用时间的增幅较慢.

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.

Scheme for implementing quantum dense coding with W-class state in cavity QED

An experimentally feasible protocol for realizing dense coding by using a class of W-state in cavity quantum electrodynamics （QED） is proposed in this paper. The prominent advantage of our scheme is that the successful probability of the dense coding with a W-class state can reach 1. In addition, the scheme can be implemented by the present cavity QED techniques.

A simple scheme for implementing four-atom quantum dense coding in cavity QED

An experimentally feasible scheme for implementing four-atom quantum dense coding of an atom-cavity system is proposed. The cavity is only virtually excited and no quantum information will be transferred from the atoms to the cavity. Thus the scheme is insensitive to cavity decay and the thermal field. In the scheme, Alice can send faithfully 4 bits of classical information to Bob by sending two qubits. Generalized Bell states can be exactly distinguished by detecting the atomic state, and quantum dense coding can be realized in a simple way.

Change-over switch for quantum states transfer with topological channels in a circuit-QED lattice

We propose schemes to realize robust quantum states transfer between distant resonators using the topological edge states of a one-dimensional circuit quantum electrodynamics(QED)lattice.Analyses show that the distribution of edge states can be regulated accordingly with the on-site defects added on the resonators.And we can achieve different types of quantum state transfer without adjusting the number of lattices.Numerical simulations demonstrate that the on-site defects can be used as a change-over switch for high-fidelity single-qubit and two-qubit quantum states transfer.This work provides a viable prospect for flexible quantum state transfer in solid-state topological quantum system.

Realization of the iSWAP-like gate among the superconducting qutrits

High-dimensional quantum systems, such as qutrits(quantum three-level systems), have multiple accessible energy levels beyond the two-level qubits. Therefore, qutrits can offer a larger state space to improve the efficiency of quantum computation. Here, we demonstrate a high-fidelity iSWAP-like gate operation on a frequency-tunable superconducting qutrits system. The superconducting quantum system consists of two qutrits that are coupled via a resonator with fixed qutrit-resonator coupling strengths. Through designing the frequency pulse profile and optimizing the parameter values,the gate error can be suppressed below 1.5 × 10^(-3). To bear out the feasibility of the proposal, we have conducted our study with experimentally accessible parameters. As the resonator can mediate the interaction between the irrelevant qutrits, the presented approach can also be used to couple multiple qutrits together, providing a good platform for quantum information processing.

Is Zero Point Energy(ZPE)True Science or Fiction?(A Short Memorandum)

ZPE(zero-point energy)is a concept in physics that refers to the lowest possible energy state that a quantum mechanical physical system can have.It is the energy that remains even at absolute zero temperature,where all classical forms of energy are assumed to be absent.Within quantum physics,the idea of ZPE is well-established.According to quantum field theory,quantum fields fluctuate even in empty space,resulting in a constant emergence and disappearance of particles and antiparticles.The ZPE comes from these fluctuations.ZPE can be used as a useful energy source;however,this idea is still up for discussion.ZPE has occasionally been linked in popular culture to pseudoscientific claims about“free energy”and perpetual motion machines.These assertions are usually unfounded and go beyond what is currently known about ZPE.There are currently no practical applications or tools that can extract useful energy from ZPE,even though it has fascinating theoretical implications and has been researched in the context of quantum field theory.Within the confines of currently understood physics,researchers are still exploring the concept’s potential ramifications and uses.

Longitudinal Scalar Wave(LSW)Fact:It Is a True Science,Neither Pseudoscience Nor Fiction(A Short Memorandum)

The discovery of scalar energy many years ago has mostly been ignored since then.Scalar energy is still misunderstood,underappreciated,and underutilized today.To comprehend the future,one must look back at the past.Scalar energy was first discovered by Scottish physicist James Clark Maxwell,who was born in 1831.Maxwell made significant advances in mathematical physics.He developed the theories relating to electromagnetic fields and radiation.Maxwell’s discoveries were advanced by Nikola Tesla,who also created instruments that demonstrated the presence of scalar energy.Nicola Tesla discovered an electromagnetic longitudinal wave in the early 1900s.It is capable of lossless energy transmission over great distances,lossless power transmission through solid metal objects,and wireless energy transmission.In this patent,Tesla neither named it nor provided a description of how it operated.Now,in the twenty-first century,it is referred to as LSWs(longitudinal scalar waves).Instantaneous longitudinal waves called scalars cover the entire field.In contrast to electromagnetic waves,which are transverse and move along an axis in a certain direction,they do not propagate along an axis or have a direction.As“vector”waves,electromagnetic waves lose power as they travel farther and pass through solid metal objects.Scalar waves also offer a unique property that Tesla does not include in his patent,which concentrates on the transportation of energy.These waves can transmit information as well.

Gauge dependence of chiral condensate and fermion mass by an unquenched model

Based on three-dimensional quantum electrodynamics theory,a set of truncated Dyson-Schwinger（D-S） equations are solved to study photon and fermion propagators with the effect of vacuum polarization.Numerical studies show that condensation and the value of fermion mass depends heavily on how the D-S equations are truncated.By solving a set of coupled D-S equations,it is also found that the fermion propagator shows a clear dependence on the order parameter.The truncated D-S equations under unquenched approximation are used to study the mass-function and chiral condensation of the fermions.The results under the unquenched approximation are clearly different from the ones under quenched approximation.With the increase in the order parameter,the fermion condensation in the unquenched approximation decreases when 0≤ξ5,while it increases when ξ5.However,nothing like this is observed in the quenched approximation,which indicates that there may be flaws in the quenched approximations.

基于腔量子电动力学的两原子远程态制备方案

提出了一个以两原子纠缠态和三原子W类纠缠态作为量子通道,在腔量子电动力学(QED)体系中实现两原子纠缠态的远程制备方案。借助于另一位接收者帮助,发送者通过控制原子与腔相互作用时间,可以概率地将被传送的两原子纠缠态远程制备到2位接收者中的任何一位的手中,而无需借助于辅助系统。

中子星辐射引力红移的量子真空极化修正

测量中子星表面辐射谱的引力红移被认为是探究这类致密天体基本物理特性最为直接有效的手段.但是,脉冲星、磁星这些强磁化中子星表面的辐射红移不仅源于引力的作用,还需要考虑星体表面的磁化等离子体以及由超强磁场所诱导的量子电动力学(quantum electrodynamics,QED)真空极化效应对辐射的电磁作用.运用Gordon有效度规理论研究磁化等离子体以及QED真空极化效应对星体辐射的影响.计算结果表明,一般情况下对辐射引力红移的修正起主要作用的是星体表面的磁化等离子体,但在某些特定情况下,还必须考虑QED真空极化效应的作用.

极强激光场驱动超亮伽马辐射和正负电子对产生的研究进展

高功率超短超强激光脉冲的诞生开启了相对论非线性光学、高强场物理、新型激光聚变、实验室天体物理等前沿领域.近年来,随着数拍瓦级乃至更高峰值功率激光装置的建成,超强激光与等离子体相互作用进入到一个全新的高强场范畴.这种极强激光场与等离子体相互作用蕴含着丰富的物理过程,除了经典的波与粒子作用、相对论效应、有质动力效应等非线性物理过程外,量子电动力学(QED)效应变得格外重要,例如辐射阻尼效应、正负电子对产生、强伽马射线辐射、QED级联、真空极化等.本文主要介绍我们近年来在极端强激光场与等离子体相互作用中激发的QED效应以及伴随的超亮强伽马射线辐射和稠密正负电子对产生等方面的研究进展.