13,605 research outputs found
Symmetric Extension of Two-Qubit States
Quantum key distribution uses public discussion protocols to establish shared
secret keys. In the exploration of ultimate limits to such protocols, the
property of symmetric extendibility of underlying bipartite states
plays an important role. A bipartite state is symmetric extendible
if there exits a tripartite state , such that the marginal
state is identical to the marginal state, i.e. .
For a symmetric extendible state , the first task of the public
discussion protocol is to break this symmetric extendibility. Therefore to
characterize all bi-partite quantum states that possess symmetric extensions is
of vital importance. We prove a simple analytical formula that a two-qubit
state admits a symmetric extension if and only if
\tr(\rho_B^2)\geq \tr(\rho_{AB}^2)-4\sqrt{\det{\rho_{AB}}}. Given the
intimate relationship between the symmetric extension problem and the quantum
marginal problem, our result also provides the first analytical necessary and
sufficient condition for the quantum marginal problem with overlapping
marginals.Comment: 10 pages, no figure. comments are welcome. Version 2: introduction
rewritte
Minimum Entangling Power is Close to Its Maximum
Given a quantum gate acting on a bipartite quantum system, its maximum
(average, minimum) entangling power is the maximum (average, minimum)
entanglement generation with respect to certain entanglement measure when the
inputs are restricted to be product states. In this paper, we mainly focus on
the 'weakest' one, i.e., the minimum entangling power, among all these
entangling powers. We show that, by choosing von Neumann entropy of reduced
density operator or Schmidt rank as entanglement measure, even the 'weakest'
entangling power is generically very close to its maximal possible entanglement
generation. In other words, maximum, average and minimum entangling powers are
generically close. We then study minimum entangling power with respect to other
Lipschitiz-continuous entanglement measures and generalize our results to
multipartite quantum systems.
As a straightforward application, a random quantum gate will almost surely be
an intrinsically fault-tolerant entangling device that will always transform
every low-entangled state to near-maximally entangled state.Comment: 26 pages, subsection III.A.2 revised, authors list updated, comments
are welcom
A zinc finger protein array for the visual detection of specific DNA sequences for diagnostic applications.
The visual detection of specific double-stranded DNA sequences possesses great potential for the development of diagnostics. Zinc finger domains provide a powerful scaffold for creating custom DNA-binding proteins that recognize specific DNA sequences. We previously demonstrated sequence-enabled reassembly of TEM-1 Ī²-lactamase (SEER-LAC), a system consisting of two inactive fragments of Ī²-lactamase each linked to engineered zinc finger proteins (ZFPs). Here the SEER-LAC system was applied to develop ZFP arrays that function as simple devices to identify bacterial double-stranded DNA sequences. The ZFP arrays provided a quantitative assay with a detection limit of 50āfmol of target DNA. The method could distinguish target DNA from non-target DNA within 5āmin. The ZFP arrays provided sufficient sensitivity and high specificity to recognize specific DNA sequences. These results suggest that ZFP arrays have the potential to be developed into a simple and rapid point-of-care (POC) diagnostic for the multiplexed detection of pathogens
Water-based Recreation and Water Quality Indices: A Revealed Preference Approach
Benefit estimates of water pollution control policies rely heavily on water quality indices. Since the 1970s, these measures of water quality have been used extensively in stated preference surveys to estimate willingness to pay for water quality that is suitable for recreational use. However, there is little empirical evidence of how well these indices correspond to observed recreational behavior. This paper utilizes a unique micro-dataset of individual household recreational use and water quality in a revealed preference framework to explore how well several major water quality indices explain water-based recreational use
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