A Critical Overview on Quantum Computing

Quantum Computing and Quantum Information Science seem very promising and developing rapidly since its inception in early 1980s by Paul Benioff with the proposal of quantum mechanical model of the Turing machine and later By Richard Feynman and Yuri Manin for the proposal of a quantum computers for simulating various problems that classical computer could not.Quantum computers have a computational advantage for some problems,over classical computers and most applications are trying to use an efficient combination of classical and quantum computers like Shor’s factoring algorithm.Other areas that are expected to be benefitted from quantum computing are Machine Learning and deep learning,molecular biology,genomics and cancer research,space exploration,atomic and nuclear research and macro-economic forecasting.This paper represents a brief overview of the state of art of quantum computing and quantum information science with discussions of various theoretical and experimental aspects adopted by the researchers.

Entanglement Purification for Mixed Entangled Quantum Dot States via Superconducing Transmission Line Resonators

An entanglement purification protocol for mixed entangled states is presented via double quantum dot molecules inside a superconducing transmission line resonator （TLR）. In the current scenario, coupling for arbitrary double quantum dot molecules can be tuned via the TLR in the large detuning region by controlling the qubit level splitting. The TLR is always empty and only virtually excited, so the interaction is insensitive to both the TLR decay and thermal field. Discussion about the feasibility of our scheme shows that the entanglement purification can be implemented with high fidelity and successful probability.

Population Swap of a Pair of Quantum Dots Coupling to a Plasmonic Nanocavity

We theoretically design a single-mode plasmonic ring nanocavity. Based on the plasmonic cavity, the exciton dynamics between two identical quantum dots （QD-p, QD-q） coupled to the nanocavity are investigated. It is shown that the coupling factors gi （i = p, q） between QD-i and surface plasmons are both equal to 12.53meV in our model and exeiton population swap between the two QDs can be realized. The periods and amplitudes of population oscillations can be modified by the coupling factors. Our results may have potential applications in quantum information and quantum computation on a chip.

Coherent Addressing of Single Molecular Electron Spin Qubits

With rational designability,versatile tunability,and quantum coherence,molecular electron spin qubits could offer new opportunities for quantum information science,enabling simplified implementation of quantum algorithms and chemical-specific quantum sensing.The development of these transformative technologies relies on coherent addressing of single molecular electron spin qubits with high initialization,manipulation,and readout fidelities.This is unfeasible to conventional electron spin resonance spectroscopy,which is widely used for coherent addressing of ensemble electron spins,due to its low initialization efficiency and readout sensitivity.Taking advantage of single spin detectability of single-molecule spectroscopy,scanning tunneling microscopy,atomic force microscopy,and quantum metrology,several strategies have been developed to empower electron spin resonance spectroscopy with single qubit addressability.In this Emerging Topic,we introduce principles and technical implementation of strategies for coherent addressing of single molecular electron spin qubits,discuss their potential applicability in quantum technologies,and point out their challenges in terms of scalability,molecular design,and/or decoherence suppression.We discuss future directions to overcome these challenges and to improve single qubit addressing technologies,which will facilitate the advancement of molecular quantum information science.