The nitrogen-vacancy (NV) center in diamond has been developed as a promising platform for quantum sensing, especially for magnetic field measurements in the nano-tesla range with a nano-meter resolution. Optical spin readout performance has a direct effect on the signal-to-noise ratio (SNR) of experiments. In this work, we introduce an online optimization method to customize the laser waveform for readout. Both simulations and experiments reveal that our new scheme optimizes the optically detected magnetic resonance in NV center. The SNR of optical spin readout has been witnessed a 44.1% increase in experiments. In addition, we applied the scheme to the Rabi oscillation experiment, which shows an improvement of 46.0% in contrast and a reduction of 12.1% in mean deviation compared to traditional constant laser power SNR optimization. This scheme is promising to improve sensitivities for a wide range of NV-based applications in the future.

In quantum computing, the computation is achieved by linear operators in or between Hilbert spaces. In this work, we explore a new computation scheme, in which the linear operators in quantum computing are replaced by (higher) functors between two (higher) categories. If from Turing computing to quantum computing is the first quantization of computation, then this new scheme can be viewed as the second quantization of computation. The fundamental problem in realizing this idea is how to realize a (higher) functor physically. We provide a theoretical idea of realizing (higher) functors physically based on the physics of topological orders.

Rare-earth doped crystals carry great prospect in developing ensemble-based solid state quantum memories for remote quantum communication and fast quantum processing applications. In recent years, with this system, remarkable quantum storage performances have been realized, and more exciting applications have been exploited, while the technical challenges are also significant. In this paper, we outlined the status quo in the development of rare-earth-based quantum memories from the point of view of different storage protocols, with a focus on the experimental demonstrations. We also analyzed the challenges and provided feasible solutions.

Topological states of matter possess bulk electronic structures categorized by topological invariants and edge/surface states due to the bulk-boundary correspondence. Topological materials hold great potential in the development of dissipationless spintronics, information storage and quantum computation, particularly if combined with magnetic order intrinsically or extrinsically. Here, we review the recent progress in the exploration of intrinsic magnetic topological materials, including but not limited to magnetic topological insulators, magnetic topological metals, and magnetic Weyl semimetals. We pay special attention to their characteristic band features such as the gap of topological surface state, gapped Dirac cone induced by magnetization (either bulk or surface), Weyl nodal point/line and Fermi arc, as well as the exotic transport responses resulting from such band features. We conclude with a brief envision for experimental explorations of new physics or effects by incorporating other orders in intrinsic magnetic topological materials.

The stabilization and manipulation of laser frequency by means of an external cavity are nearly ubiquitously used in fundamental research and laser applications. While most of the laser light transmits through the cavity, in the presence of some back-scattered light from the cavity to the laser, the self-injection locking effect can take place, which locks the laser emission frequency to the cavity mode of similar frequency. The self-injection locking leads to dramatic reduction of laser linewidth and noise. Using this approach, a common semiconductor laser locked to an ultrahigh-Q microresonator can obtain sub-Hertz linewidth, on par with state-of-the-art fiber lasers. Therefore it paves the way to manufacture high-performance semiconductor lasers with reduced footprint and cost. Moreover, with high laser power, the optical nonlinearity of the microresonator drastically changes the laser dynamics, offering routes for simultaneous pulse and frequency comb generation in the same microresonator. Particularly, integrated photonics technology, enabling components fabricated via semiconductor CMOS process, has brought increasing and extending interest to laser manufacturing using this method. In this article, we present a comprehensive tutorial on analytical and numerical methods of laser self-injection locking, as well a review of most recent theoretical and experimental achievements.

We review our most recent research on quantum transport, organizing the review according to the intensity of the magnetic field and focus mostly on topological semimetals and topological insulators. We first describe the phenomenon of quantum transport when a magnetic field is not present. We introduce the nonlinear Hall effect and its theoretical descriptions. Then, we discuss Coulomb instabilities in 3D higher-order topological insulators. Next, we pay close attention to the surface states and find a function to identify the axion insulator in the antiferromagnetic topological insulator MnBi₂Te₄. Under weak magnetic fields, we focus on the decaying Majorana oscillations which has the correlation with spin−orbit coupling. In the section on strong magnetic fields, we study the helical edge states and the one-sided hinge states of the Fermi-arc mechanism, which are relevant to the quantum Hall effect. Under extremely large magnetic fields, we derive a theoretical explanation of the negative magnetoresistance without a chiral anomaly. Then, we show how magnetic responses can be used to detect relativistic quasiparticles. Additionally, we introduce the 3D quantum Hall effect’s charge-density wave mechanism and compare it with the theory of 3D transitions between metal and insulator driven by magnetic fields.

Quantum computers have made extraordinary progress over the past decade, and significant milestones have been achieved along the path of pursuing universal fault-tolerant quantum computers. Quantum advantage, the tipping point heralding the quantum era, has been accomplished along with several waves of breakthroughs. Quantum hardware has become more integrated and architectural compared to its toddler days. The controlling precision of various physical systems is pushed beyond the fault-tolerant threshold. Meanwhile, quantum computation research has established a new norm by embracing industrialization and commercialization. The joint power of governments, private investors, and tech companies has significantly shaped a new vibrant environment that accelerates the development of this field, now at the beginning of the noisy intermediate-scale quantum era. Here, we first discuss the progress achieved in the field of quantum computation by reviewing the most important algorithms and advances in the most promising technical routes, and then summarizing the next-stage challenges. Furthermore, we illustrate our confidence that solid foundations have been built for the fault-tolerant quantum computer and our optimism that the emergence of quantum killer applications essential for human society shall happen in the future.

Lee–Yang (LY) zeros play a fundamental role in the formulation of statistical physics in terms of (grand) partition functions, and assume theoretical significance for the phenomenon of phase transitions. In this paper, motivated by recent progress in cold Rydberg atom experiments, we explore the LY zeros in classical Rydberg blockade models. We find that the distribution of zeros of partition functions for these models in one dimension (1d) can be obtained analytically. We prove that all the LY zeros are real and negative for such models with arbitrary blockade radii. Therefore, no phase transitions happen in 1d classical Rydberg chains. We investigate how the zeros redistribute as one interpolates between different blockade radii. We also discuss possible experimental measurements of these zeros.

InP solar cell is promising for space application due to its strong space radiation resistance and high power conversion efficient (PCE). Graphene/InP heterostructure solar cell is expected to have a higher PCE because strong near-infrared light can also be absorbed and converted additionally by graphene in this heterostructure. However, a low PCE was reported experimentally for Graphene/InP heterostructures. In this paper, electronic properties of graphene/InP heterostructures are calculated using density functional theory to understand the origin of the low PCE and propose possible improving ways. Our calculation results reveal that graphene contact with InP form a p-type Schottky heterostructure with a low Schottky barrier height (SBH). It is the low SBH that leads to the low PCE of graphene/InP heterostructure solar cells. A new heterostructure, graphene/insulating layer/InP solar cells, is proposed to raise SBH and PCE. Moreover, we also find that the opened bandgap of graphene and SBH in graphene/InP heterostructures can be tuned by exerting an electric field, which is useful for photodetector of graphene/InP heterostructures.

We numerically study the general valley polarization and anomalous Hall effect in van der Waals (vdW) heterostructures based on monolayer jacutingaite family materials Pt₂AX₃ (A = Hg, Cd, Zn; X = S, Se, Te). We perform a systematic study on the atomic, electronic, and topological properties of vdW heterostructures composed of monolayer Pt₂AX₃ and two-dimensional ferromagnetic insulators. We show that four kinds of vdW heterostructures exhibit valley-polarized quantum anomalous Hall phase, i.e., Pt₂HgS₃/NiBr₂, Pt₂HgSe₃/CoBr₂, Pt₂HgSe₃/NiBr₂, and Pt₂ZnS₃/CoBr₂, with a maximum valley splitting of 134.2 meV in Pt₂HgSe₃/NiBr₂ and sizable global band gap of 58.8 meV in Pt₂HgS₃/NiBr₂. Our findings demonstrate an ideal platform to implement applications on topological valleytronics.

In our study, we constructed a series of inorganic nonmetallic ternary hydrides PSH₆ by first-principles structural screening under pressure of 200 GPa. The structural stability under lower pressure are examined. Focusing on the structural stability, electronic and phonon properties, as well as the possible superconducting properties within the framework of Bardeen−Cooper−Schrieffer (BCS) theory, we show that PSH₆ with space group \text{textcolor}[RGB]12,108,100Pm\overline{3}m possesses a superconducting transition temperature of 146 K at 130 GPa. In the pressure range of 100−200 GPa, our work suggests that the ternary phosphorus-sulfur-hydrogen would act as a promising compositional and elemental space for achieving high-temperature superconductivity.