Particle swarm optimization for a variational quantum eigensolver.

In the field of finding ground and excited states, where quantum computation holds significant promise, using a variational quantum eigensolver (VQE) is a typical approach. However, the success of this approach is vulnerable to two factors: classical optimization for the ansätz parameters and noise from quantum devices. To address these challenges, we adopted particle swarm optimization (PSO) based on swarm intelligence for VQE and presented its performance.

Highly Tunable 2D Silicon Quantum Dot Array with Coupling beyond Nearest Neighbors.

Scaling up quantum dots to two-dimensional (2D) arrays is a crucial step for advancing semiconductor quantum computation. However, maintaining excellent tunability of quantum dot parameters, including both nearest-neighbor and next-nearest-neighbor couplings, during 2D scaling is challenging, particularly for silicon quantum dots due to their relatively small size. Here, we present a highly controllable and interconnected 2D quantum dot array in planar silicon, demonstrating independent control over electron fillings and the tunnel couplings of nearest-neighbor dots.

Quantum Interference and Coherent Population Trapping in a Double Quantum Dot.

Quantum interference is a natural consequence of wave-particle duality in quantum mechanics, and is widely observed at the atomic scale. One interesting manifestation of quantum interference is coherent population trapping (CPT), first proposed in three-level driven atomic systems and observed in quantum optical experiments. Here, we demonstrate CPT in a gate-defined semiconductor double quantum dot (DQD), with some unique twists as compared to the atomic systems.

Simulating chemical reaction dynamics on quantum computer.

The electronic energies of molecules have been successfully evaluated on quantum computers. However, more attention is paid to the dynamics simulation of molecules in practical applications. Based on the variational quantum eigensolver (VQE) algorithm, Fedorov et al.

The cell-centered Finite-Volume self-consistent approach for heterostructures: 1D electron gas at the Si-SiOinterface.

Achieving self-consistent convergence with the conventional effective-mass approach at ultra-low temperatures (below 4.2 K) is a challenging task, which mostly lies in the discontinuities in material properties (e.g.

SoK: Benchmarking the Performance of a Quantum Computer.

The quantum computer has been claimed to show more quantum advantage than the classical computer in solving some specific problems. Many companies and research institutes try to develop quantum computers with different physical implementations. Currently, most people only focus on the number of qubits in a quantum computer and consider it as a standard to evaluate the performance of the quantum computer intuitively.

Probing Two Driven Double Quantum Dots Strongly Coupled to a Cavity.

We experimentally and theoretically study a driven hybrid circuit quantum electrodynamics (cQED) system beyond the dispersive coupling regime. Treating the cavity as part of the driven system, we develop a theory applicable to such strongly coupled and to multiqubit systems. The fringes measured for a single driven double quantum dot (DQD)-cavity setting and the enlarged splittings of the hybrid Floquet states in the presence of a second DQD are well reproduced with our model.

Undoped Strained Ge Quantum Well with Ultrahigh Mobility of Two Million.

We develop a method to fabricate an undoped Ge quantum well (QW) under a 32 nm relaxed SiGe shallow barrier. The bottom barrier contains SiGe (650 °C) and SiGe (800 °C) such that variation of Ge content forms a sharp interface that can suppress the threading dislocation density (TDD) penetrating into the undoped Ge quantum well. The SiGe barrier introduces enough in-plane parallel strain (ε strain -0.

Collective Microwave Response for Multiple Gate-Defined Double Quantum Dots.

We fabricate and characterize a hybrid quantum device that consists of five gate-defined double quantum dots (DQDs) and a high-impedance NbTiN transmission resonator. The controllable interactions between DQDs and the resonator are spectroscopically explored by measuring the microwave transmission through the resonator in the detuning parameter space. Utilizing the high tunability of the system parameters and the high cooperativity ( > 17.

Ultrafast and Electrically Tunable Rabi Frequency in a Germanium Hut Wire Hole Spin Qubit.

Hole spin qubits based on germanium (Ge) have strong tunable spin-orbit interaction (SOI) and ultrafast qubit operation speed. Here we report that the Rabi frequency () of a hole spin qubit in a Ge hut wire (HW) double quantum dot (DQD) is electrically tuned through the detuning energy (ϵ) and middle gate voltage (). gradually decreases with increasing ϵ; on the contrary, is positively correlated with .

Coupling of Photon Emitters in Monolayer WS with a Photonic Waveguide Based on Bound States in the Continuum.

On-chip light sources are an essential component of scalable photonic integrated circuits (PICs), and coupling between light sources and waveguides has attracted a great deal of attention. Photonic waveguides based on bound states in the continuum (BICs) allow optical confinement in a low-refractive-index waveguide on a high-refractive-index substrate and thus can be employed for constructing PICs. In this work, we experimentally demonstrated that the photoluminescence (PL) from a monolayer of tungsten sulfide (WS) could be coupled into a BIC waveguide on a lithium-niobate-on-insulator (LNOI) substrate.

Sliding nanomechanical resonators.

The motion of a vibrating object is determined by the way it is held. This simple observation has long inspired string instrument makers to create new sounds by devising elegant string clamping mechanisms, whereby the distance between the clamping points is modulated as the string vibrates. At the nanoscale, the simplest way to emulate this principle would be to controllably make nanoresonators slide across their clamping points, which would effectively modulate their vibrating length.

A unified framework of transformations based on the Jordan-Wigner transformation.

Quantum simulation of chemical Hamiltonians enables the efficient calculation of chemical properties. Mapping is one of the essential steps in simulating fermionic systems on quantum computers. In this work, a unified framework of transformations mapping fermionic systems to qubit systems is presented and many existing transformations-such as Jordan-Wigner, Bravyi-Kitaev, and parity transformations-are included in this framework.

Room-temperature coherent manipulation of single-spin qubits in silicon carbide with a high readout contrast.

Spin defects in silicon carbide (SiC) with mature wafer-scale fabrication and micro/nano-processing technologies have recently drawn considerable attention. Although room-temperature single-spin manipulation of colour centres in SiC has been demonstrated, the typically detected contrast is less than 2[Formula: see text], and the photon count rate is also low. Here, we present the coherent manipulation of single divacancy spins in 4H-SiC with a high readout contrast ([Formula: see text]) and a high photon count rate (150 kilo counts per second) under ambient conditions, which are competitive with the nitrogen-vacancy centres in diamond.

Near-Field Modulation of Differently Oriented Single Photon Emitters with A Plasmonic Probe.

Single photon emitters (SPEs) are critical components of photon-based quantum technology. Recently, the interaction between surface plasmons and emitters has attracted increasing attention because of its potential to improve the quality of single-photon sources through stronger light-matter interactions. In this work, we use a hybrid plasmonic probe composed of a fiber taper and silver nanowire to controllably modulate the radiation properties of SPEs with differently oriented polarization.

Transverse Mode-Encoded Quantum Gate on a Silicon Photonic Chip.

As an important degree of freedom (d.o.f.

Ultrafast coherent control of a hole spin qubit in a germanium quantum dot.

Operation speed and coherence time are two core measures for the viability of a qubit. Strong spin-orbit interaction (SOI) and relatively weak hyperfine interaction make holes in germanium (Ge) intriguing candidates for spin qubits with rapid, all-electrical coherent control. Here we report ultrafast single-spin manipulation in a hole-based double quantum dot in a germanium hut wire (GHW).

An Operation Guide of Si-MOS Quantum Dots for Spin Qubits.

In the last 20 years, silicon quantum dots have received considerable attention from academic and industrial communities for research on readout, manipulation, storage, near-neighbor and long-range coupling of spin qubits. In this paper, we introduce how to realize a single spin qubit from Si-MOS quantum dots. First, we introduce the structure of a typical Si-MOS quantum dot and the experimental setup.

Graphene-Based Nanoelectromechanical Periodic Array with Tunable Frequency.

Phononic crystals (PnCs) have attracted much attention due to their great potential for dissipation engineering and propagation manipulation of phonons. Notably, the excellent electrical and mechanical properties of graphene make it a promising material for nanoelectromechanical resonators. Transferring a graphene flake to a prepatterned periodic mechanical structure enables the realization of a PnC with on-chip scale.

High Performance p-i-n Photodetectors on Ge-on-Insulator Platform.

In this article, we demonstrated novel methods to improve the performance of p-i-n photodetectors (PDs) on a germanium-on-insulator (GOI). For GOI photodetectors with a mesa diameter of 10 μm, the dark current at -1 V is 2.5 nA, which is 2.

Anisotropic -Factor and Spin-Orbit Field in a Germanium Hut Wire Double Quantum Dot.

Holes in nanowires have drawn significant attention in recent years because of the strong spin-orbit interaction, which plays an important role in constructing Majorana zero modes and manipulating spin-orbit qubits. Here, from the strongly anisotropic leakage current in the spin blockade regime for a double dot, we extract the full -tensor and find that the spin-orbit field is in plane with an azimuthal angle of 59° to the axis of the nanowire. The direction of the spin-orbit field indicates a strong spin-orbit interaction along the nanowire, which may have originated from the interface inversion asymmetry in Ge hut wires.

Supercompact Photonic Quantum Logic Gate on a Silicon Chip.

To build universal quantum computers, an essential step is to realize the so-called controlled-NOT (CNOT) gate. Quantum photonic integrated circuits are well recognized as an attractive technology offering great promise for achieving large-scale quantum information processing, due to the potential for high fidelity, high efficiency, and compact footprints. Here, we demonstrate a supercompact integrated quantum CNOT gate on silicon by using the concept of symmetry breaking of a six-channel waveguide superlattice.

Growth of h-BN/graphene heterostructure using proximity catalysis.

In this study, a proximity catalysis route was developed for the fast growth of graphene/h-BN vertical heterostructures on Cu foils, which shows much improved synthesis efficiency (500 times faster than other routes) and good crystalline quality graphene (large single crystalline length up to 10m). The key advantage of our synthesis route is the introduction of fresh Cu foil (or Cu foam) into the high-temperature zone using a turntable. At high temperatures, Cu vapor acts as a gaseous catalyst, which can reduce the energy barrier of graphene growth and promote the decomposition of carbon sources.

Correlated spectrum of distant semiconductor qubits coupled by microwave photons.

We develop a new spectroscopic method to quickly and intuitively characterize the coupling of two microwave-photon-coupled semiconductor qubits via a high-impedance resonator. Highly distinctive and unique geometric patterns are revealed as we tune the qubit tunnel couplings relative to the frequency of the mediating photons. These patterns are in excellent agreement with a simulation using the Tavis-Cummings model, and allow us to readily identify different parameter regimes for both qubits in the detuning space.

A quantum circuit simulator and its applications on Sunway TaihuLight supercomputer.

Classical simulation of quantum computation is vital for verifying quantum devices and assessing quantum algorithms. We present a new quantum circuit simulator developed on the Sunway TaihuLight supercomputer. Compared with other simulators, the present one is distinguished in two aspects.