11,998 research outputs found

### New Constraints on Anisotropic Rotation of CMB Polarization

The coupling of a scalar field to electromagnetic field via the Chern-Simons
term will rotate the polarization directions of the cosmic microwave background
radiation. The rotation angle which relies on the distribution of the scalar
field on the CMB sky is direction dependent. Such anisotropies will give rise
to new distortions to the power spectra of CMB polarization and it can be used
to probe the detailed physics of the scalar field. In this paper we use the
updated observational data to constrain the anisotropic rotation angle in a
model independent way. We find that the dominant effect of the anisotropic
rotation on CMB comes from its variance and it is constrained tightly by the
current data.Comment: 9 pages, 2 figures, presentations are improved to match the version
to appear in JCA

### One Password: An Encryption Scheme for Hiding Users' Register Information

In recent years, the attack which leverages register information (e.g.
accounts and passwords) leaked from 3rd party applications to try other
applications is popular and serious. We call this attack "database collision".
Traditionally, people have to keep dozens of accounts and passwords for
different applications to prevent this attack. In this paper, we propose a
novel encryption scheme for hiding users' register information and preventing
this attack. Specifically, we first hash the register information using
existing safe hash function. Then the hash string is hidden, instead a
coefficient vector is stored for verification. Coefficient vectors of the same
register information are generated randomly for different applications. Hence,
the original information is hardly cracked by dictionary based attack or
database collision in practice. Using our encryption scheme, each user only
needs to keep one password for dozens of applications

### $q$-Deformed Chern Characters for Quantum Groups $SU_{q}(N)$

In this paper, we introduce an $N\times N$ matrix $\epsilon^{a\bar{b}}$ in
the quantum groups $SU_{q}(N)$ to transform the conjugate representation into
the standard form so that we are able to compute the explicit forms of the
important quantities in the bicovariant differential calculus on $SU_{q}(N)$,
such as the $q$-deformed structure constant ${\bf C}_{IJ}^{~K}$ and the
$q$-deformed transposition operator $\Lambda$. From the $q$-gauge covariant
condition we define the generalized $q$-deformed Killing form and the $m$-th
$q$-deformed Chern class $P_{m}$ for the quantum groups $SU_{q}(N)$. Some
useful relations of the generalized $q$-deformed Killing form are presented. In
terms of the $q$-deformed homotopy operator we are able to compute the
$q$-deformed Chern-Simons $Q_{2m-1}$ by the condition $dQ_{2m-1}=P_{m}$,
Furthermore, the $q$-deformed cocycle hierarchy, the $q$-deformed gauge
covariant Lagrangian, and the $q$-deformed Yang-Mills equation are derived

### Dark matter self-interactions from the internal dynamics of dwarf spheroidals

Dwarf spheroidal galaxies provide well-known challenges to the standard cold
and collisionless dark matter scenario: The too-big-to-fail problem, namely the
mismatch between the observed mass enclosed within the half-light radius of
dwarf spheroidals and cold dark matter N-body predictions; The hints for inner
constant-density cores. While these controversies may be alleviated by baryonic
physics and environmental effects, revisiting the standard lore of cold and
collisionless dark matter remains an intriguing possibility. Self-interacting
dark matter may be the successful proposal to such a small-scale crisis.
Self-interactions correlate dark matter and baryon distributions, allowing for
constant-density cores in low surface brightness galaxies. Here we report the
first data-driven study of the too-big-to-fail of Milky Way dwarf spheroidals
within the self-interacting dark matter paradigm. We find good description of
stellar kinematics and compatibility with the concentration-mass relation from
recent pure cold dark matter simulations. Within this concentration-mass
relation, a subset of Milky Way dwarfs are well fitted by cross sections of
0.5-3 cm$^2$/g, while others point to values greater than 10 cm$^2$/g.Comment: 19 pages, 3 figures, 1 table. SharedIt at https://rdcu.be/5iT

### Efficient entanglement concentration for arbitrary less-entangled NOON state assisted with single photon

We put forward two efficient entanglement concentration protocols (ECPs) for
distilling the maximally entangled NOON state from arbitrary less-entangled
NOON state with only an auxiliary single photon. With the help of the weak
cross-Kerr nonlinearities, both the two ECPs can be used repeatedly to get a
high success probability. In the first ECP, the auxiliary single photon should
be shared by the two parties say Alice and Bob. In the second ECP, the
auxiliary single photon is only possessed by Bob, which can greatly increase
the practical success probability by avoiding the transmission loss. Moreover,
Bob can operate the whole protocol alone, which makes the protocol more simple.
Therefore, our two ECPs, especially the second ECP may be more useful and
convenient in the current quantum information processing.Comment: 10 pages, 3 figure

### Efficient entanglement purification for polarization logic Bell state with the photonic Faraday rotation

Logic-qubit entanglement is a promising resource in quantum information
processing, especially in future large-scale quantum networks. In the paper, we
put forward an efficient entanglement purification protocol (EPP) for nonlocal
mixed logic entangled states with the bit-flip error in the logic qubits of the
logic Bell state, resorting to the photon-atom interaction in low-quality (Q)
cavity and atomic state measurement. Different from existing EPPs, this
protocol can also purify the logic phase-flip error, and the bit-flip error and
the phase-flip error in physic qubit. During the protocol, we only require to
measure the atom states, and it is useful for improving the entanglement of
photon systems in future large-scale quantum networks.Comment: 14 page, 6 figure

### Distilling and protecting the single-photon entangled state

We propose two efficient entanglement concentration protocols (ECPs) for
arbitrary less-entangled single-photon entanglement (SPE). Different from all
the previous ECPs, these protocols not only can obtain the maximally SPE, but
also can protect the single qubit information encoded in the polarization
degree of freedom. These protocols only require one pair of less-entangled
single-photon entangled state and some auxiliary single photons, which makes
them economical. The first ECP is operated with the linear optical elements,
which can be realized in current experiment. The second ECP adopts the
cross-Kerr nonlinearities. Moreover, the second ECP can be repeated to
concentrate the discard states in some conventional ECPs, so that it can get a
high success probability. Based on above properties, our ECPs may be useful in
current and future quantum communication.Comment: 11 pages, 4 figure

### Generalized entanglement distillation

We present a way for the entanglement distillation of genuine mixed state.
Different from the conventional mixed state in entanglement purification
protocol, each components of the mixed state in our protocol is a
less-entangled state, while it is always a maximally entangled state. With the
help of the weak cross-Kerr nonlinearity, this entanglement distillation
protocol does not require the sophisticated single-photon detectors. Moreover,
the distilled high quality entangled state can be retained to perform the
further distillation. These properties make it more convenient in practical
applications.Comment: 7 pages, 4 figure

### Detection of the nonlocal atomic entanglement assisted with single photons

We present an efficient way for measuring the entanglement of the atoms.
Through the auxiliary single photons input-output process in cavity quantum
electrodynamics (QED), the concurrence of the atomic entanglement can be
obtained according to the success probability of picking up the singlet states
of the atoms. This protocol has three advantages: First, we do not require the
sophisticated controlled-not (CNOT) gates. Second, the distributed atoms are
not required to intact with each other. Third, the atomic entanglement can be
distributed nonlocally, which provides its important applications in
distributed quantum computation.Comment: 5 pages, 3 figure

### Origin of fermion generations from extended noncommutative geometry

We propose a way to understand the 3 fermion generations by the algebraic
structures of noncommutative geometry, which is a promising framework to unify
the standard model and general relativity. We make the tensor product extension
and the quaternion extension on the framework. Each of the two extensions alone
keeps the action invariant, and we consider them as the almost trivial
structures of the geometry. We combine the two extensions, and show the
corresponding physical effects, i.e., the emergence of 3 fermion generations
and the mass relationships among those generations. We define the coordinate
fiber space of the bundle of the manifold as the space in which the classical
noncommutative geometry is expressed, then the tensor product extension
explicitly shows the contribution of structures in the non-coordinate base
space of the bundle to the action. The quaternion extension plays an essential
role to reveal the physical effect of the structure in the non-coordinate base
space.Comment: 17 latex pages, no figure. Final version for publicatio

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