4,218 publications from this institution
Schr\odinger's cat originates from the famous thought experiment querying the counterintuitive quantum superposition of macroscopic objects. As a natural extension, several cats (quasi-classical objects) can be prepared into coherent quantum superposition states, which is known as multipartite cat states demonstrating quantum entanglement among macroscopically distinct objects. Here we present a highly scalable approach to deterministically create flying multipartite Schr\odinger cat states, by reflecting coherent state photons from a microwave cavity containing a superconducting qubit. We perform full quantum state tomography on the cat states with up to four photonic modes and confirm the existence of quantum entanglement among them. We also witness the hybrid entanglement between discrete-variable states (the qubit) and continuous-variable states (the flying multipartite cat) through a joint quantum state tomography. Our work demonstrates an important experimental control method in the microwave region and provides an enabling step for implementing a series of quantum metrology and quantum information processing protocols based on cat states.
<p indent="0mm">In classical electrodynamics, by motion for either the observer or the media, it always naturally assumed that the relative moving velocity is a constant along a straight line (e.g., in an inertia reference frame), so that the electromagnetic behavior of charged particles in vacuum space can be easily described using special relativity. However, for engineering applications, the media have shapes and sizes and may move with acceleration, and recent experimental signs of progress in triboelectric nanogenerators have revealed pieces of evidence for expanding Maxwell’s equations to include media motion that could be time and even space dependent. Therefore, we have developed the expanded Maxwell’s equations for a mechano-driven media system (MEs-f-MDMS) by neglecting relativistic effect. This article first presents the updated progresses made in the field. Secondly, we extensively investigated Faraday’s law of electromagnetic induction for a media system that moves with an acceleration. We found that, the “anti-flux rule” examples outlined by Feynman in his book are just caused by the accelerated motion of the media, which were not included in Maxwell’s equations, but disregarded. This is a typical example that Maxwell’s equations have to be expanded for moving media. Therefore, the charged moving media are confirmed to be the sources of generating electromagnetic radiation (a motion-generated electromagnetic field); and the generated electromagnetic wave within the medium can be described using the expanded Maxwell’s equations. Most importantly, in comparison to the existing classical electrodynamics, the newly developed MEs-f-MDMS marks four unique advances, which have been summarized and the near field electrodynamics vs. the far field electrodynamics are proposed.
Photonic crystal with periodic dielectric constant distribution has become the focus of theoretical and applied research in recent years because of their bandgap structure similar to the electronic states in semiconductors. It is also a promising method for creating a stable low power microplasma. This area of research makes it possible to explore plasma science using microplasmas driven by millimeter wave bands. The dispersive and dissipative properties of plasma make plasma photonic crystals have properties that conventional dielectric photonic crystals do not have. The properties and parameters of plasma photonic crystal can be artificially controlled by changing the parameters of the plasma. To further investigate the influence of photonic crystals on electromagnetic wave transmission, a waveguide model with a plasma photonic crystal array structure was proposed in order to achieve modulation of electromagnetic wave transmission. This proposed model structure can achieve multiple frequency transmission points, making up for the shortcoming of single frequency point transmission in the W-band. Meanwhile, adding a plasma column to the center of defect vacancy in the gradient structure can limit the amplitude of electromagnetic waves and regulate the transmission of electromagnetic waves at different resonant frequencies. The results show that electromagnetic wave can achieve efficient transmission at multiple frequency points such as 85.2 GHz, 92.1 GHz, 98.5 GHz, 102.4 GHz, and 106 GHz without plasma interference, and transmission coefficients are greater than -0.42 dB. The construction of gradient structure can form different strong electric fields around the defect vacancy at the resonance frequency, resulting in gas breakdown and the generation of high-concentration microwave plasma, achieving effective control of the reflected power, transmitted power and absorbed power of electromagnetic wave. When the plasma concentration reaches the plasma frequency equivalent to the incident wave frequency, the electromagnetic wave can be transmitted with less loss during this period. When it reaches a considerable degree or higher, the electromagnetic wave will be rapidly absorbed or reflected by the high concentration plasma, and the transmission power will decrease rapidly, and finally stabilize at a low level. In addition, changing the size of the plasma column can further adjust the transmission characteristics of electromagnetic waves at different frequency points. This study can provide support for the transmission of high-frequency electromagnetic waves and the design of microwave devices.
Nanoenergy is a field of studying the small-scale, highly efficient energy harvesting, storage, and applications by using nanomaterials and nanodevices. Nanogenerators are developed to harvest these small-scale energies in the ambient environment, which were first invented in our group in 2006. In the past decade, we have developed nanogenerators based on piezoelectric and triboelectric effects for mechanical energy harvesting, and those based on pyroelectric and thermoelectric effects for thermal energy harvesting. We also explored other novel nanogenerators such as that based on ion streams. The proposed nanogenerators will facilitate the development of self-powered systems, which enables efficient energy utilization and sustainable operations of mobile devices for “smart” wearable technology, health monitoring, biomedical sensing, environmental protection, and even security.
