32,376 research outputs found
Exotic Topological States with Raman-Induced Spin-Orbit Coupling
We propose a simple experimental scheme to realize simultaneously the
one-dimensional spin-orbit coupling and the staggered spin-flip in ultracold
pseudospin- atomic Fermi gases trapped in square optical lattices. In the
absence of interspecies interactions, the system supports gapped Chern
insulators and gapless topological semimetal states. By turning on the -wave
interactions, a rich variety of gapped and gapless inhomogeneous topological
superfluids can emerge. In particular, a gapped topological Fulde-Ferrell
superfluid, in which the chiral edge states at opposite boundaries possess the
same chirality, is predicted.Comment: 11 pages, 6 figure
Period halving of Persistent Currents in Mesoscopic Mobius ladders
We investigate the period halving of persistent currents(PCs) of
non-interacting electrons in isolated mesoscopic M\"{o}bius ladders without
disorder, pierced by Aharonov-Bhom flux. The mechanisms of the period halving
effect depend on the parity of the number of electrons as well as on the
interchain hopping. Although the data of PCs in mesoscopic systems are
sample-specific, some simple rules are found in the canonical ensemble average,
such as all the odd harmonics of the PCs disappear, and the signals of even
harmonics are non-negative. {PACS number(s): 73.23.Ra, 73.23.-b, 68.65.-k}Comment: 6 Pages with 3 EPS figure
High-Fidelity Archeointensity Results for the Late Neolithic Period From Central China
Archeomagnetism focuses on exploring high-resolution variations of the geomagnetic field over hundreds to thousands of years. In this study, we carried out a comprehensive study of chronology, absolute and relative paleointensity on a late Neolithic site in central China. Ages of the samples are constrained to be ~3,500–3,000 BCE, a period when available paleointensity data are sparse. We present a total of 64 high-fidelity absolute paleointensities, demonstrating the field varied quickly from ~55 to ~90 ZAm2 between ~3,500–3,000 BCE. Our results record a new archeomagnetic jerk around 3,300 BCE, which is probably non-dipolar origin. The new results provide robust constraints on global geomagnetic models. We calculated a revised Chinese archeointensity reference curve for future application. The variations of absolute and relative paleointensity versus depth show good consistency, reinforcing the reliability of our results. This new attempt of combining absolute and relative paleointenstiy provides a useful tool for future archeomagnetic research
Universal Quantum Degeneracy Point for Superconducting Qubits
The quantum degeneracy point approach [D. Vion et al., Science 296, 886
(2002)] effectively protects superconducting qubits from low-frequency noise
that couples with the qubits as transverse noise. However, low-frequency noise
in superconducting qubits can originate from various mechanisms and can couple
with the qubits either as transverse or as longitudinal noise. Here, we present
a quantum circuit containing a universal quantum degeneracy point that protects
an encoded qubit from arbitrary low-frequency noise. We further show that
universal quantum logic gates can be performed on the encoded qubit with high
gate fidelity. The proposed scheme is robust against small parameter spreads
due to fabrication errors in the superconducting qubits.Comment: 7 pages, 4 figure
A Probabilistic Embedding Clustering Method for Urban Structure Detection
Urban structure detection is a basic task in urban geography. Clustering is a
core technology to detect the patterns of urban spatial structure, urban
functional region, and so on. In big data era, diverse urban sensing datasets
recording information like human behaviour and human social activity, suffer
from complexity in high dimension and high noise. And unfortunately, the
state-of-the-art clustering methods does not handle the problem with high
dimension and high noise issues concurrently. In this paper, a probabilistic
embedding clustering method is proposed. Firstly, we come up with a
Probabilistic Embedding Model (PEM) to find latent features from high
dimensional urban sensing data by learning via probabilistic model. By latent
features, we could catch essential features hidden in high dimensional data
known as patterns; with the probabilistic model, we can also reduce uncertainty
caused by high noise. Secondly, through tuning the parameters, our model could
discover two kinds of urban structure, the homophily and structural
equivalence, which means communities with intensive interaction or in the same
roles in urban structure. We evaluated the performance of our model by
conducting experiments on real-world data and experiments with real data in
Shanghai (China) proved that our method could discover two kinds of urban
structure, the homophily and structural equivalence, which means clustering
community with intensive interaction or under the same roles in urban space.Comment: 6 pages, 7 figures, ICSDM201
Probing the Melting of a Two-dimensional Quantum Wigner Crystal via its Screening Efficiency
One of the most fundamental and yet elusive collective phases of an
interacting electron system is the quantum Wigner crystal (WC), an ordered
array of electrons expected to form when the electrons' Coulomb repulsion
energy eclipses their kinetic (Fermi) energy. In low-disorder, two-dimensional
(2D) electron systems, the quantum WC is known to be favored at very low
temperatures () and small Landau level filling factors (), near the
termination of the fractional quantum Hall states. This WC phase exhibits an
insulating behavior, reflecting its pinning by the small but finite disorder
potential. An experimental determination of a vs phase diagram for
the melting of the WC, however, has proved to be challenging. Here we use
capacitance measurements to probe the 2D WC through its effective screening as
a function of and . We find that, as expected, the screening
efficiency of the pinned WC is very poor at very low and improves at higher
once the WC melts. Surprisingly, however, rather than monotonically
changing with increasing , the screening efficiency shows a well-defined
maximum at a which is close to the previously-reported melting temperature
of the WC. Our experimental results suggest a new method to map out a vs
phase diagram of the magnetic-field-induced WC precisely.Comment: The formal version is published on Phys. Rev. Lett. 122, 116601
(2019
Quantum secret sharing between m-party and n-party with six states
We propose a quantum secret sharing scheme between -party and -party
using three conjugate bases, i.e. six states. A sequence of single photons,
each of which is prepared in one of the six states, is used directly to encode
classical information in the quantum secret sharing process. In this scheme,
each of all members in group 1 choose randomly their own secret key
individually and independently, and then directly encode their respective
secret information on the states of single photons via unitary operations, then
the last one (the th member of group 1) sends of the resulting qubits
to each of group 2. By measuring their respective qubits, all members in group
2 share the secret information shared by all members in group 1. The secret
message shared by group 1 and group 2 in such a way that neither subset of each
group nor the union of a subset of group 1 and a subset of group 2 can extract
the secret message, but each whole group (all the members of each group) can.
The scheme is asymptotically 100% in efficiency. It makes the Trojan horse
attack with a multi-photon signal, the fake-signal attack with EPR pairs, the
attack with single photons, and the attack with invisible photons to be
nullification. We show that it is secure and has an advantage over the one
based on two conjugate bases. We also give the upper bounds of the average
success probabilities for dishonest agent eavesdropping encryption using the
fake-signal attack with any two-particle entangled states. This protocol is
feasible with present-day technique.Comment: 7 page
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