8,596 research outputs found

### Quantum phase estimation using path-symmetric entangled states

We study the sensitivity of phase estimation using a generic class of
path-symmetric entangled states
$|\varphi\rangle|0\rangle+|0\rangle|\varphi\rangle$, where an arbitrary state
$|\varphi\rangle$ occupies one of two modes in quantum superposition. This
class of states includes the previously considered states, i.e. $NOON$ states
and entangled coherent states, as special cases. With its generalization, we
identify the practical limit of phase estimation under energy constraint that
is characterized by the photon statistics of the component state
$|\varphi\rangle$. We first show that quantum Cramer-Rao bound (QCRB) can be
lowered with super-Poissonianity of the state $|\varphi\rangle$. By introducing
a component state of the form
$|\varphi\rangle=\sqrt{q}|1\rangle+\sqrt{1-q}|N\rangle$, we particularly show
that an arbitrarily small QCRB can be achieved even with a finite energy in an
ideal situation. For practical measurement schemes, we consider a parity
measurement and a full photon-counting method to obtain phase-sensitivity.
Without photon loss, the latter scheme employing any path-symmetric states
$|\varphi\rangle|0\rangle+|0\rangle|\varphi\rangle$ achieves the QCRB over the
entire range $[0,2\pi]$ of unknown phase shift $\phi$ whereas the former does
so in a certain confined range of $\phi$. We find that the case of
$|\varphi\rangle=\sqrt{q}|1\rangle+\sqrt{1-q}|N\rangle$ provides the most
robust resource against loss among the considered entangled states over the
whole range of input energy. Finally we also propose experimental schemes to
generate these path-symmetric entangled states.Comment: 10 pages, 5 figures, published versio

### Increasing and decreasing entanglement characteristics for continuous variables by a local photon subtraction

We investigate how the entanglement characteristics of a non-Gaussian
entangled state are increased or decreased by a local photon subtraction
operation. The non-Gaussian entangled state is generated by injecting a
single-mode non-Gaussian state and a vacuum state into a 50:50 beam splitter.
We consider a photon-added coherent state and an odd coherent state as a
single-mode non-Gaussian state. In the regime of small amplitude, we show that
the performance of quantum teleportation and the second-order
Einstein-Podolsky- Rosen-type correlation can both be enhanced, whereas the
degree of entanglement decreases, for the output state when a local photon
subtraction operation is applied to the non-Gaussian entangled state. The
counterintuitive effect is more prominent in the limit of nearly zero
amplitude.Comment: Published version, 7 pages, 3 figure

### Statistical Self-Similar Properties of Complex Networks

It has been shown that many complex networks shared distinctive features,
which differ in many ways from the random and the regular networks. Although
these features capture important characteristics of complex networks, their
applicability depends on the type of networks. To unravel ubiquitous
characteristics that complex networks may have in common, we adopt the
clustering coefficient as the probability measure, and present a systematic
analysis of various types of complex networks from the perspective of
statistical self-similarity. We find that the probability distribution of the
clustering coefficient is best characterized by the multifractal; moreover, the
support of the measure had a fractal dimension. These two features enable us to
describe complex networks in a unified way; at the same time, offer unforeseen
possibilities to comprehend complex networks.Comment: 11 pages, 4 figure

### Comparative Effects of Dehydration Processes on Physico-Chemical Changes in Fruits

Drying with the help of sun and wind is one of the oldest methods of food preservation known to man, but artificial drying, or dehydration, has been developed and used extensively only during the last two decades. The problem in dehydration is that the water content must be decreased sufficiently to maintain the stability of the product by retarding the rates of deteriorative biochemical, microbiological, and enzymatic reactions during subsequent storage. At the same time irreversible changes should not be brought about

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