A Novel Metric for Assessing National Strength in Scientific Research:Understanding China’s Research Output in Quantum Technology through Collaboration

Purpose:The 5th Plenary Session of the 19th Communist Party of China(CPC)Central Committee clearly states that developing science and technology through self-reliance and self-strengthening provides the strategic underpinning for China’s development.Based on this background,this paper explores a metric model for assessing national scientific research strength through collaboration on research papers.Design/methodology/approach:We propose a novel metric model for assessing national scientific research strength,which sets two indicators,national scientific self-reliance(SR)and national academic contribution(CT),to reflect“self-reliance”and“self-strengthening”respectively.Taking the research papers in quantum technology as an example,this study analyzes the scientific research strength of various countries around the world,especially China in quantum technology.Findings:The results show that the research of quantum technology in China has always been relatively independent with fewer international collaboration papers and located in a more marginal position in cooperation networks.China’s academic contribution(CT)to global quantum technology research is increasing and has been greater than that of the United States in 2020.Combining the two indicators,CT and SR,China’s research strength in the quantum field closely follows the United States,and the United States is the most powerful with high research autonomy.Research limitations:This paper only reflects China’s scientific research strength in quantum technology from collaboration on research papers and doesn’t consider the segmentation of quantum technology and the industrial upstream and downstream aspects,which need further study.Practical implications:The model is helpful to better understand the national scientific research strength in a certain field from“self-reliance”and“self-strengthening”.ScienceOriginality/value:We propose a novel metric model to measure the national scientific research strength from the perspective of“self-reliance”and“self-strengthening”,which provides a solid basis for the assessment of the strength level of scientific research in countries/regions and institutions.

The Influence of Quantum Technology on the Development of Metrology and Measuring Science

In the new century, quantum technology has developed rapidly and has been applied in many fields. As an important aspect of the aerospace science, metrology and measuring science is a field which is influenced by the quantum technology dramatically. The new generation of the International System of Units will be redefined on the basis of the quantum theory. More and more new sensing techniques are developed taking into account quantum principles. In this paper, the influence of quantum technology on metrology and measuring science is introduced.

Influence of Quantum Information Technology on International Security

Humanity is currently undergoing the fourth industrial revolution,characterized by advancements in artificial intelligence,clean energy,quantum information technology,virtual reality,and biotechnology.This technological revolution is poised to have a profound impact on the world.Quantum information technology encompasses both quantum computing and the transmission of quantum information.This article aims to integrate quantum information technology with international security concerns,exploring its implications for international security and envisioning its groundbreaking significance.

Twin-Field Quantum Key Distribution Protocol Based on Wavelength-Division-Multiplexing Technology

Quantum key distribution(QKD) generates information-theoretical secret keys between two parties based on the physical laws of quantum mechanics. Following the advancement in quantum communication networks, it becomes feasible and economical to combine QKD with classical optical communication through the same fiber using dense wavelength division multiplexing(DWDM) technology. This study proposes a detailed scheme of TF-QKD protocol with DWDM technology and analyzes its performance, considering the influence of quantum channel number and adjacent quantum crosstalk on the secret key rates. The simulation results show that the scheme further increases the secret key rate of TF-QKD and its variants. Therefore, this scheme provides a method for improving the secret key rate for practical quantum networks.

Quantum simulation and quantum computation of noisy-intermediate scale

In the past years, great progresses have been made on quantum computation and quantum simulation. Increasing the number of qubits in the quantum processors is expected to be one of the main motivations in the next years, while noises in manipulation of quantum states may still be inevitable even the precision will improve. For research in this direction, it is necessary to review the available results about noisy multiqubit quantum computation and quantum simulation. The review focuses on multiqubit state generations, quantum computational advantage, and simulating physics of quantum many-body systems. Perspectives of near term noisy intermediate-quantum processors will be discussed.

Application of Quantum Dots in Display:The Milestones of Quantum Dots Light Emitting Displays

We reviewed the key advantages and development of the QD-display and other light applications based on their color purity,stability,and solution processisibility.Analysis of quantum dot based LEDs and the main challenges facing in this field,such as QD luminescence quenching,QD charging in thin films,and the external quantum efficiency was presented in detail.The description about how different optical down-conversion and structures enabled researchers to overcome these challenges and to commercialize the products to achieve the desirable CRI and color temperature was presented.The recent developments about how to overcome these difficulties have also been discussed in this article.

Experimental quantum state compression from two identical qubits to a qutrit

In the realm of modern information technology,data compression technology occupies a pivotal position.With advancements in quantum information technology,the need to compress large-scale qubits ensembles has become urgent,aiming to reduce the demand on quantum storage resources.However,existing quantum state compression schemes generally face a limitation:the particles before and after compression must reside in the same dimensional space.In specific scenarios,compressing qubits into particles of higher dimensions not only enhances the efficiency of quantum state compression but also further reduces the usage of quantum storage resources.Here we experimentally demonstrated a quantum state compression between particles of different dimensions,successfully compressing two qubits into a single qutrit.The average fidelity of the resulting qutrit with the ideal quantum state is 0.8835.Our study may have potential applications in future quantum information,such as increasing quantum communication bandwidth and reducing storage resource consumption in quantum computing.

On the Directivity of Radiating Quantum Electromagnetic Systems

We explore the spatial directivity of radiating quantum source systems,which are defined as any generic source capable of producing photon emission and directing it to specific regions in space.We present a comprehensive definition of quantum directivity,inspired by both classical antenna theory and photon detection theory.Through an in-depth conceptual and mathematical analysis,we identify and address several critical challenges associated with characterizing the directive properties of a general quantum source system.Our approach essentially presents a computational model that relies solely on the density operator of the radiation field as input.

Widely tunable single-photon source with high spectral-purity from telecom wavelength to mid-infrared wavelength based on MgO:PPLN

By utilizing the extended phase-matching(EPM)method,we investigate the generation of single photons with high spectral-purity in a magnesium-doped periodically-poled lithium niobate(MgO:PPLN)crystal via the spontaneous parametric down-conversion(SPDC)process.By adjusting the temperature and pump wavelength,the wavelength of the single photons can be tuned from telecom to mid-infrared(MIR)wavelengths,for which the spectral-purity can be above 0.95 with high transmission filters.In experiments,we engineer a MgO:PPLN with poling period of 20.35µm which emits the EPM photon pair centered at 1496.6 nm and 1644.0 nm and carry out the joint spectral intensity(JSI)and Glauber’s second-order self-correlation measurements to characterize the spectral purity.The results are in good agreement with the numerical simulations.Our work may provide a valuable approach for the generation of spectrally pure single photons at a wide range of wavelengths which is competent for various photonic quantum technologies.

A Quantum of Technology

Scientific breakthrough offers prospect of highly secure information transfer

Experimental demonstration of deterministic quantum search algorithms on a programmable silicon photonic chip

The Grover quantum search algorithm is a landmark quantum computing application, which has a speed advantage over classical algorithms for searching an unsorted database. For an√ unsorted database of N items, the classical algorithm needs to search O(N) times, while the Grover algorithm only needs O(√N) times. However, except for the special case of N = 4, the traditional Grover algorithm always has some probability of failure. To solve this problem, several schemes for deterministically performing quantum search have been proposed, but they all impose additional requirements on the query Oracle and cannot be implemented in many practical scenarios. Recently, Roy et al. [Phys. Rev. Res. 4, L022013(2022)] proposed a new deterministic quantum search scheme with no additional requirements on the query Oracle, which has the potential to perfectly replace the traditional Grover algorithm. In this study, we experimentally implement on a programmable silicon quantum photonic chip four deterministic quantum search algorithms, including the Roy algorithm, all of which obtained an average search success rate of over0.93, exceeding the theoretical maximum of 0.9074 that the traditional Grover algorithm can achieve. Our results demonstrate the feasibility and superiority of the deterministic quantum search algorithms and are expected to facilitate the wider application of these algorithms in future quantum information processing.

The modelling of quantum control systems

High-performance control of quantum dynamics is key to the development of quantum technologies.From quantum-state engineering to quantum metrology,theory and practice of quantum control enable robust and cheaper technologies for future industrial applications.Starting from fundamental matter–field interactions, we overview various approaches to modelling quantum control systems, in which control can be implemented by either changing field or material properties. These models are built in time or frequency domain and can be interconnected to form quantum feedback networks. This review can be taken as a useful reference for engineers to understand the quantum physics behind, or for physicists to resolve control problems from a control engineering point of view.

Quantum correlated imaging is a promising new technique in medical imaging

Cardio-cerebral vascular diseases are common and frequently occurring serious diseases that threaten humans. In recent years, Digital Subtraction Angiography(DSA) has played a vital role in the diagnosis and treatment of cardio-cerebral vascular diseases. However, DSA is not able to visualize intravascular structures in real time,and it is especially difficult to evaluate each layer of the vascular wall and the composition of atherosclerotic plaques with DSA. Quantum correlated imaging is a new technique that can be used to perform real-time online imaging of intravascular flow, vascular wall structure, and atherosclerotic plaque composition. Quantum correlated imaging is a promising new technique that will soon be used in the diagnosis and treatment of cardio-cerebral vascular diseases.

Optical studies of semiconductor perovskite nanocrystals for classical optoelectronic applications and quantum information technologies: a review

Semiconductor perovskite films are now being widely investigated as light harvesters in solar cells with ever-increasing power conversion efficiencies,which have motivated the fabrication of other optoelectronic devices,such as light-emitting diodes,lasers,and photodetectors.Their superior material and optical properties are shared by the counterpart colloidal nanocrystals(NCs),with the additional advantage of quantum confinement that can yield size-dependent optical emission ranging from the near-UV to near-infrared wavelengths.So far,intensive research efforts have been devoted to the optical characterization of perovskite NC ensembles,revealing not only fundamental exciton relaxation and recombination dynamics but also lowthreshold amplified spontaneous emission and novel superfluorescence effects.Meanwhile,the application of single-particle spectroscopy techniques to perovskite NCs has helped to resolve a variety of optical properties for which there are few equivalents in traditional colloidal NCs,mainly including nonblinking photoluminescence,suppressed spectral diffusion,stable exciton fine structures,and coherent singlephoton emission.While the main purpose of ensemble optical studies is to guide the smooth development of perovskite NCs in classical optoelectronic applications,the rich observations from single-particle optical studies mark the emergence of a potential platform that can be exploited for quantum information technologies.

Full-color quantum dots active matrix display fabricated by ink-jet printing

Making full-color active matrix display based on quantum dot light emitting diodes(AM-QLEDs) via ink-jet printing is attractive in display industry due to QLEDs' wide color gamut and their potential manufacturing advantages of large screen size and low cost. The challenges for realizing AM-QLED display are how to achieve high quality films through ink-jet printing, multi-color patterning, electroluminescence(EL) color purity, and high efficiency. Herein, a 2-inch diagonal full-color AM-QLEDs display with pixel density of 120 pixels per inch(PPI) fabricated by ink-jet printing technique is presented. Driven by a metal oxide TFT(MOTFT) back-panel, the display exhibits a maximum brightness of 400 cd m.2, and a color gamut of 109%(NTSC 1931). The red, green, and blue(RGB) monochrome QLEDs passive matrix panels fabricated by ink-jet printing technique have a current efficiency(CE) of 2.5, 13.9, and 0.30 cd A.1, respectively. To the best of our knowledge, the efficiencies are the highest among passive matrix QLEDs panels made by ink-jet printing technique. The ink-jet printed QDs films show good thickness uniformity due to high viscosity and low volatility of the printable inks, and no cross-contamination between adjacent pixels resulting from the hydrophobic pixel defining layer.