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High-sensitivity mass sensors under ambient conditions are essential in various fields such as biological research, gas sensing and environmental monitoring. In the current work, a phonon lasing enhanced mass sensor was proposed based on an optomechanical crystal cavity under ambient conditions. The phonon lasing was harnessed to achieve ultra-high resolution since it resulted in an extremely narrow mechanical linewidth (less than 10 kHz). Masses with different weights were deposited on the cavity, it is predicted that the maximum resolution for mass sensing can be 65 ± 19 zg, which approaches the mass order of a protein and an oligonucleotide. This implies the potential application of the proposed method in the biomedical fields such as oligonucleotide drug delivery area and the Human Proteome Project.

Cryogenic electronics refers to the devices and circuits operated at cryogenic temperatures (below 123.15 K), which are made from a variety of materials such as insulators, conductors, semiconductors, superconductors and topological materials. The cryogenic electronics are endowed with some unique advantages that cannot be realized in room temperature, including high computing speed, high power performance and so on. Choosing the appropriate refrigeration technology is critical for achieving the best performance of the cryogenic electronics. In this review, the cryogenic technology was divided into non-optical refrigeration and optical refrigeration, where non-optical refrigeration technologies are relatively conventional refrigeration technologies, while optical refrigeration is an emerging research field for the cooling of the chips. In the current work, the fundamental principles, applications and development prospects of the non-optical refrigeration was introduced, also the research history, fundamental principles, existing problems and application prospects of the optical refrigeration was thoroughly reviewed.

In the past few decades, circuits based on gallium nitride high electron mobility transistor (GaN HEMT) have demonstrated exceptional potential in a wide range of high-power and high-frequency applications, such as the new generation mobile communications, object detection and consumer electronics, etc. As a critical intermediary between GaN HEMT devices and circuit-level applications, GaN HEMT large-signal models play a pivotal role in the design, application and development of GaN HEMT devices and circuits. This review provides an in-depth examination of the advancements in GaN HEMT large-signal modeling in recent decades. Detailed and comprehensive coverage of various aspects of GaN HEMT large-signal model was offered, including large-signal measurement setups, classical formulation methods, model classification and non-ideal effects, etc. In order to better serve follow-up researches, this review also explored potential future directions for the development of GaN HEMT large-signal modeling.

In recent years, Internet of Things (IoT) has become more and more important owing to the rapid expansion of the number of computing devices and data sizes. The evolution of IoT requires low-power and self-operating devices to expand the coverage area of computing resources. The main components of IoT are the large-scale integration (LSI) chips, which take the function of implementing the energy harvesters, control units and applications. They exhibit different physics or phenomena, making it difficult to understand and design the entire system. The current work reviews the various methods for IoT applications by CMOS LSI chips, from the power components by energy harvesting to realistic applications with future outlooks.

A non-classical light source is essential for implementing a wide range of quantum information processing protocols, including quantum computing, networking, communication and metrology. In the microwave regime, propagating photonic qubits, which transfer quantum information between multiple superconducting quantum chips, serve as building blocks for large-scale quantum computers. In this context, spectral control of propagating single photons is crucial for interfacing different quantum nodes with varied frequencies and bandwidths. Here a deterministic microwave quantum light source was demonstrated based on superconducting quantum circuits that can generate propagating single photons, time-bin encoded photonic qubits and qudits. In particular, the frequency of the emitted photons can be tuned in situ as large as 200 MHz. Even though the internal quantum efficiency of the light source is sensitive to the working frequency, it is shown that the fidelity of the propagating photonic qubit can be well preserved with the time-bin encoding scheme. This work thus demonstrates a versatile approach to realizing a practical quantum light source for future distributed quantum computing.

Investigation into the structural and magnetic properties of organic molecules at cryogenic temperature is beneficial for reducing molecular vibration and stabilizing magnetization, and is of great importance for constructing novel spintronics devices of better performance and scaling the device size down to nanoscale. In order to explore the possibility of fabricating molecule-based memory chips of ultrahigh density, two-dimensional close-packed molecular arrays with carboxylic acid molecules were constructed in the current work and the magnetic properties in a low-temperature scanning tunneling microscope were also investigated. The results demonstrated that each nonmagnetic molecule can be controllably and independently switched into a stable spin-carrying state at 4 K by applying a voltage pulse with atomic resolution. Benefiting from the small size of a single molecule as the basic storage bit, the two-dimensional molecular arrays allowing controllable electrical manipulations on each molecule can behave as a platform of memory chip with an ultrahigh storage density of ∼320 terabytes (Tb) (or ∼2500 terabits) per square inch. This work highlights the potential and advantage of employing organic molecules in developing future cryogenic information storage techniques and devices at nanoscale.

In the current work, we explored a new knowledge amalgamation problem, termed Federated Selective Aggregation for on-device knowledge amalgamation (FedSA). FedSA aims to train an on-device student model for a new task with the help of several decentralized teachers whose pre-training tasks and data are different and agnostic. The motivation to investigate such a problem setup stems from a recent dilemma of model sharing. Due to privacy, security or intellectual property issues, the pre-trained models are, however, not able to be shared, and the resources of devices are usually limited. The proposed FedSA offers a solution to this dilemma and makes it one step further, again, the method can be employed on low-power and resource-limited devices. To this end, a dedicated strategy was proposed to handle the knowledge amalgamation. Specifically, the student-training process in the current work was driven by a novel saliency-based approach which adaptively selects teachers as the participants and integrated their representative capabilities into the student. To evaluate the effectiveness of FedSA, experiments on both single-task and multi-task settings were conducted. The experimental results demonstrate that FedSA could effectively amalgamate knowledge from decentralized models and achieve competitive performance to centralized baselines.

The design and preparation of quantum states free from environmental decohering effects is critically important for the development of on-chip quantum systems with robustness. One promising strategy is to harness quantum state superposition to construct decoherence-free subspace (DFS), which is termed dark state. Typically, the excitation of dark states relies on anti-phase-matching on two qubits and the inter-qubit distance is of wavelength scale, which limits the development of compact quantum chips. In the current work, a hybrid plasmonic quantum emitter was proposed, which was composed of strongly correlated quantum emitters intermediated by a plasmonic nanocavity. Through turning the plasmonic loss from drawback into advantage, the anti-phase-matching rule was broken by rapidly decaying the superposed bright state and preparing a sub-100 nm dark state with decay rate reduced by 3 orders of magnitudes. More interestingly, the dark state could be optically switched to a single-photon emitter with enhanced brightness through photon-blockade, with the quantum second order correlation function at zero delay showing a wide range of tunability down to 0.02.

The rise of quantum computing has prompted the interest in the field of cryogenic electronics. Carbon-based materials hold great promise in the area of cryogenic electronics due to their excellent material properties and emergent quantum effects. This paper introduces the advantages of carbon-based materials for cryogenic applications and reviews recent progress in carbon nanotubes and graphene for logic devices, sensors and novel quantum devices at cryogenic temperatures. Finally, the main challenges and extensive prospects for the further development of carbon-based cryoelectronics are summarized.

A matrix-vector multiplication (MVM) optical signal processor based on mode division multiplexing (MDM) was proposed and demonstrated in the current work, which is composed of a mode multiplexer, a multimode beam splitter, a mode demultiplexer, a modulator array and combiners. In addition, the characteristics of MDM obviate the need for multiple wavelengths and therefore multiple laser light sources are unneeded, which greatly reduces the complexity and cost. A 4 × 4 MDM-MVM was realized on a standard silicon-on-insulator (SOI) platform. Combined with the off-chip light source and photodetectors (PDs), 4-level modulation has been demonstrated, and each level of the output signal could represent 2 bits of information.