2,885 research outputs found
Continuous Authentication for Voice Assistants
Voice has become an increasingly popular User Interaction (UI) channel,
mainly contributing to the ongoing trend of wearables, smart vehicles, and home
automation systems. Voice assistants such as Siri, Google Now and Cortana, have
become our everyday fixtures, especially in scenarios where touch interfaces
are inconvenient or even dangerous to use, such as driving or exercising.
Nevertheless, the open nature of the voice channel makes voice assistants
difficult to secure and exposed to various attacks as demonstrated by security
researchers. In this paper, we present VAuth, the first system that provides
continuous and usable authentication for voice assistants. We design VAuth to
fit in various widely-adopted wearable devices, such as eyeglasses,
earphones/buds and necklaces, where it collects the body-surface vibrations of
the user and matches it with the speech signal received by the voice
assistant's microphone. VAuth guarantees that the voice assistant executes only
the commands that originate from the voice of the owner. We have evaluated
VAuth with 18 users and 30 voice commands and find it to achieve an almost
perfect matching accuracy with less than 0.1% false positive rate, regardless
of VAuth's position on the body and the user's language, accent or mobility.
VAuth successfully thwarts different practical attacks, such as replayed
attacks, mangled voice attacks, or impersonation attacks. It also has low
energy and latency overheads and is compatible with most existing voice
assistants
Entangling a series of trapped ions by moving cavity bus
Entangling multiple qubits is one of the central tasks for quantum
information processings. Here, we propose an approach to entangle a number of
cold ions (individually trapped in a string of microtraps) by a moved cavity.
The cavity is pushed to include the ions one by one with an uniform velocity,
and thus the information stored in former ions could be transferred to the
latter ones by such a moving cavity bus. Since the positions of the trapped
ions are precisely located, the strengths and durations of the ion-cavity
interactions can be exactly controlled. As a consequence, by properly setting
the relevant parameters typical multi-ion entangled states, e.g., state for
10 ions, could be deterministically generated. The feasibility of the proposal
is also discussed.Comment: 8 pages, 2 figures, 1 tabl
Valence Bond Entanglement and Fluctuations in Random Singlet Phases
The ground state of the uniform antiferromagnetic spin-1/2 Heisenberg chain
can be viewed as a strongly fluctuating liquid of valence bonds, while in
disordered chains these bonds lock into random singlet states on long length
scales. We show that this phenomenon can be studied numerically, even in the
case of weak disorder, by calculating the mean value of the number of valence
bonds leaving a block of contiguous spins (the valence-bond entanglement
entropy) as well as the fluctuations in this number. These fluctuations show a
clear crossover from a small regime, in which they behave similar to those
of the uniform model, to a large regime in which they saturate in a way
consistent with the formation of a random singlet state on long length scales.
A scaling analysis of these fluctuations is used to study the dependence on
disorder strength of the length scale characterizing the crossover between
these two regimes. Results are obtained for a class of models which include, in
addition to the spin-1/2 Heisenberg chain, the uniform and disordered critical
1D transverse-field Ising model and chains of interacting non-Abelian anyons.Comment: 8 pages, 6 figure
Atomic radius and charge parameter uncertainty in biomolecular solvation energy calculations
Atomic radii and charges are two major parameters used in implicit solvent
electrostatics and energy calculations. The optimization problem for charges
and radii is under-determined, leading to uncertainty in the values of these
parameters and in the results of solvation energy calculations using these
parameters. This paper presents a new method for quantifying this uncertainty
in implicit solvation calculations of small molecules using surrogate models
based on generalized polynomial chaos (gPC) expansions. There are relatively
few atom types used to specify radii parameters in implicit solvation
calculations; therefore, surrogate models for these low-dimensional spaces
could be constructed using least-squares fitting. However, there are many more
types of atomic charges; therefore, construction of surrogate models for the
charge parameter space requires compressed sensing combined with an iterative
rotation method to enhance problem sparsity. We demonstrate the application of
the method by presenting results for the uncertainties in small molecule
solvation energies based on these approaches. The method presented in this
paper is a promising approach for efficiently quantifying uncertainty in a wide
range of force field parameterization problems, including those beyond
continuum solvation calculations.The intent of this study is to provide a way
for developers of implicit solvent model parameter sets to understand the
sensitivity of their target properties (solvation energy) on underlying choices
for solute radius and charge parameters
Chiral condensate and dressed Polyakov loop in the Nambu--Jona-Lasinio model
We investigate the chiral condensate and the dressed Polyakov loop or dual
chiral condensate at finite temperature and density in two-flavor
Nambu--Jona-Lasinio model. The dressed Polyakov loop is regarded as an
equivalent order parameter of deconfinement phase transition in a confining
theory. We find the behavior of dressed Polyakov loop in absence of any
confinement mechanism is quite interesting, with only quark degrees of freedom
present, it still shows an order parameter like behavior. It is found that in
the chiral limit, the critical temperature for chiral phase transition
coincides with that of the dressed Polyakov loop in the whole plane.
In the case of explicit chiral symmetry breaking, it is found that the
transition temperature for chiral restoration is smaller than that
of the dressed Polyakov loop in the low baryon density region
where the transition is a crossover. With the increase of current quark mass
the difference between the two transition temperatures is found to be
increasing. However, the two critical temperatures coincide in the high baryon
density region where the phase transition is of first order. We give an
explanation on the feature of in the case of 1st and
2nd order phase transitions, and in the case of
crossover, and expect this feature is general and can be extended to full QCD
theory. Our result might indicate that in the case of crossover, there exists a
small region where chiral symmetry is restored but the color degrees of freedom
are still confined.Comment: 7 pages, 10 figure
Control and single-shot readout of an ion embedded in a nanophotonic cavity
Distributing entanglement over long distances using optical networks is an intriguing macroscopic quantum phenomenon with applications in quantum systems for advanced computing and secure communication. Building quantum networks requires scalable quantum lightâmatter interfaces based on atoms, ions or other optically addressable qubits. Solid-state emitters5, such as quantum dots and defects in diamond or silicon carbide , have emerged as promising candidates for such interfaces. So far, it has not been possible to scale up these systems, motivating the development of alternative platforms. A central challenge is identifying emitters that exhibit coherent optical and spin transitions while coupled to photonic cavities that enhance the lightâmatter interaction and channel emission into optical fibres. Rare-earth ions in crystals are known to have highly coherent 4fâ4f optical and spin transitions suited to quantum storage and transduction, but only recently have single rare-earth ions been isolated and coupled to nanocavities. The crucial next steps towards using single rare-earth ions for quantum networks are realizing long spin coherence and single-shot readout in photonic resonators. Here we demonstrate spin initialization, coherent optical and spin manipulation, and high-fidelity single-shot optical readout of the hyperfine spin state of single Âčâ·ÂčYbÂłâș ions coupled to a nanophotonic cavity fabricated in an yttrium orthovanadate host crystal. These ions have optical and spin transitions that are first-order insensitive to magnetic field fluctuations, enabling optical linewidths of less than one megahertz and spin coherence times exceeding thirty milliseconds for cavity-coupled ions, even at temperatures greater than one kelvin. The cavity-enhanced optical emission rate facilitates efficient spin initialization and single-shot readout with conditional fidelity greater than 95 per cent. These results showcase a solid-state platform based on single coherent rare-earth ions for the future quantum internet
Quantum phase transitions in a two-dimensional quantum XYX model: Ground-state fidelity and entanglement
A systematic analysis is performed for quantum phase transitions in a
two-dimensional anisotropic spin 1/2 anti-ferromagnetic XYX model in an
external magnetic field. With the help of an innovative tensor network
algorithm, we compute the fidelity per lattice site to demonstrate that the
field-induced quantum phase transition is unambiguously characterized by a
pinch point on the fidelity surface, marking a continuous phase transition. We
also compute an entanglement estimator, defined as a ratio between the
one-tangle and the sum of squared concurrences, to identify both the
factorizing field and the critical point, resulting in a quantitative agreement
with quantum Monte Carlo simulation. In addition, the local order parameter is
"derived" from the tensor network representation of the system's ground state
wave functions.Comment: 4+ pages, 3 figure
Compressive sensing adaptation for polynomial chaos expansions
Basis adaptation in Homogeneous Chaos spaces rely on a suitable rotation of
the underlying Gaussian germ. Several rotations have been proposed in the
literature resulting in adaptations with different convergence properties. In
this paper we present a new adaptation mechanism that builds on compressive
sensing algorithms, resulting in a reduced polynomial chaos approximation with
optimal sparsity. The developed adaptation algorithm consists of a two-step
optimization procedure that computes the optimal coefficients and the input
projection matrix of a low dimensional chaos expansion with respect to an
optimally rotated basis. We demonstrate the attractive features of our
algorithm through several numerical examples including the application on
Large-Eddy Simulation (LES) calculations of turbulent combustion in a HIFiRE
scramjet engine.Comment: Submitted to Journal of Computational Physic
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