28,528 research outputs found
Automatic collision avoidance of ships
One of the key elements in automatic simulation of ship manoeuvring in confined waterways is route finding and collision avoidance. This paper presents a new practical method of automatic trajectory planning and collision avoidance based on an artificial potential field and speed vector. Collision prevention regulations and international navigational rules have been incorporated into the algorithm. The algorithm is fairly straightforward and simple to implement, but has been shown to be effective in finding safe paths for all ships concerned in complex situations. The method has been applied to some typical test cases and the results are very encouraging
Simple unconventional geometric scenario of one-way quantum computation with superconducting qubits inside a cavity
We propose a simple unconventional geometric scenario to achieve a kind of
nontrivial multi-qubit operations with superconducting charge qubits placed in
a microwave cavity. The proposed quantum operations are insensitive not only to
the thermal state of cavity mode but also to certain random operation errors,
and thus may lead to high-fidelity quantum information processing. Executing
the designated quantum operations, a class of highly entangled cluster states
may be generated efficiently in the present scalable solid-state system,
enabling one to achieve one-way quantum computation.Comment: Accepted version with minor amendments. To appear in Phys. Rev.
Engineering graphene by oxidation: a first principles study
Graphene epoxide, with oxygen atoms lining up on pristine graphene sheets, is
investigated theoretically in this Letter. Two distinct phases: metastable
clamped and unzipped structures are unveiled in consistence with experiments.
In the stable (unzipped) phase, epoxy group breaks underneath sp2 bond and
modifies the mechanical and electronic properties of graphene remarkably. The
foldable epoxy ring structure reduces its Young's modulus by 42.4%, while
leaves the tensile strength almost unchanged. Epoxidation also perturbs the pi
state and opens semiconducting gap for both phases, with dependence on the
density of epoxidation. In the unzipped structures, localized states revealed
near the Fermi level resembles the edge states in graphene nanoribbons. The
study reported here paves the way for oxidation-based functionalization of
graphene-related materials.Comment: 17 pages (4 figures, 1 table
Universal holonomic quantum gates in decoherence-free subspace on superconducting circuits
To implement a set of universal quantum logic gates based on non-Abelian
geometric phases, it is a conventional wisdom that quantum systems beyond two
levels are required, which is extremely difficult to fulfil for superconducting
qubits, appearing to be a main reason why only single qubit gates was
implemented in a recent experiment [A. A. Abdumalikov Jr \emph{et al}., Nature
496, 482 (2013)]. Here we propose to realize non-adiabatic holonomic quantum
computation in decoherence-free subspace on circuit QED, where one can use only
the two levels in transmon qubits, a usual interaction, and a minimal resource
for the decoherence-free subspace encoding. In particular, our scheme not only
overcomes the difficulties encountered in previous studies, but also can still
achieve considerably large effective coupling strength, such that high fidelity
quantum gates can be achieved. Therefore, the present scheme makes it very
promising way to realize robust holonomic quantum computation with
superconducting circuits.Comment: V4: published version; V1: submitted on April
Short note on two output-dependent hidden Markov models
The purpose of this note is to study the assumption of mutual information independence", which is used by Zhou (2005) for deriving an output-dependent hidden Markov model, the so-called discriminative HMM (D-HMM), in the context of determining a stochastic optimal sequence of hidden states. The assumption is extended to derive its generative counterpart, the G-HMM. In addition, state-dependent representations for two output-dependent HMMs, namely HMMSDO (Li, 2005) and D-HMM, are presented
- …