249 research outputs found
Topologically protected entanglement switching around exceptional points
The robust operation of quantum entanglement states are crucial for
applications in quantum information, computing, and communications1-3. However,
it has always been a great challenge to complete such a task because of
decoherence and disorder. Here, we propose theoretically and demonstrate
experimentally an effective scheme to realize robust operation of quantum
entanglement states by designing quadruple degeneracy exceptional points. By
encircling the exceptional points on two overlapping Riemann energy surfaces,
we have realized a chiral switch for entangled states with high fidelity. Owing
to the topological protection conferred by the Riemann surface structure, this
switching of chirality exhibits strong robustness against perturbations in the
encircling path. Furthermore, we have experimentally validated such a scheme on
a quantum walk platform. Our work opens up a new way for the application of
non-Hermitian physics in the field of quantum information
Experimental topological quantum computing with electric circuits
The key obstacle to the realization of a scalable quantum computer is
overcoming environmental and control errors. Topological quantum computation
has attracted great attention because it has emerged as one of the most
promising approaches to solving these problems. Various theoretical schemes for
building topological quantum computation have been proposed. However,
experimental implementation has always been a great challenge because it has
proved to be extremely difficult to create and manipulate topological qubits in
real systems. Therefore, topological quantum computation has not been realized
in experiments yet. Here, we report the first experimental realization of
topological quantum computation with electric circuits. Based on our proposed
new scheme with circuits, Majorana-like edge states are not only observed
experimentally, but also T junctions are constructed for the braiding process.
Furthermore, we demonstrate the feasibility of topological quantum computing
through a set of one- and two-qubit unitary operations. Finally, our
implementation of Grover's search algorithm demonstrates that topological
quantum computation is ideally suited for such tasks
Exploring topological phase transition andWeyl physics in five dimensions with electric circuits
Weyl semimetals are phases of matter with gapless electronic excitations that
are protected by topology and symmetry. Their properties depend on the
dimensions of the systems. It has been theoretically demonstrated that
five-dimensional (5D) Weyl semimetals emerge as novel phases during the
topological phase transition in analogy to the three-dimensional case. However,
experimental observation of such a phenomenon remains a great challenge because
the tunable 5D system is extremely hard to construct in real space. Here, we
construct 5D electric circuit platforms in fully real space and experimentally
observe topological phase transitions in five dimensions. Not only are Yang
monopoles and linked Weyl surfaces observed experimentally, but various phase
transitions in five dimensions are also proved, such as the phase transitions
from a normal insulator to a Hopf link of twoWeyl surfaces and then to a 5D
topological insulator. The demonstrated topological phase transitions in five
dimensions leverage the concept of higher-dimensional Weyl physics to control
electrical signals in the engineered circuits
Flow around an oscillating circular disk at low to moderate Reynolds numbers
Direct numerical simulations of the flow induced by a circular disk oscillating sinusoidally along its axis are performed. The aspect ratio of the disk is 10. The Reynolds number , based on the maximum speed and the diameter of the disk, is in the range of . The Keulegan-Carpenter number is in the range of . Five flow regimes are observed in the considered-space: (I) axisymmetric flow (AS), (II) planar symmetric flow in the low-region (PSL), (III) azimuthally rotating flow in the low-region (ARL), (IV) planar symmetric flow in the high-region (PSH) and (V) azimuthally rotating flow in the high-region (ARH). The critical boundaries between different flow regimes are identified based on the evolutions of the magnitude and direction of transverse force acting on the disk. For the non-axisymmetric flow regimes, the flow is one-sided with respect to the axis of the disk and is associated with a non-zero mean value of the transverse force acting on the disk
The Outbreak Evaluation of COVID-19 in Wuhan District of China
There were 27 novel coronavirus pneumonia cases found in Wuhan, China in
December 2019, named as 2019-nCoV temporarily and COVID-19 formally by WHO on
11 February, 2020. In December 2019 and January 2020, COVID-19 has spread in
large scale among the population, which brought terrible disaster to the life
and property of the Chinese people. In this paper, we will first analyze the
feature and pattern of the virus transmission, and discuss the key impact
factors and uncontrollable factors of epidemic transmission based on public
data. Then the virus transmission can be modelled and used for the inflexion
and extinction period of epidemic development so as to provide theoretical
support for the Chinese government in the decision-making of epidemic
prevention and recovery of economic production. Further, this paper
demonstrates the effectiveness of the prevention methods taken by the Chinese
government such as multi-level administrative region isolation. It is of great
importance and practical significance for the world to deal with public health
emergencies.Comment: 7 pages, 18 figure
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