4,427 research outputs found
Wavevector Selective Metasurfaces and Tunnel Vision Filters
Metasurfaces offer unprecedented flexibility in the design and control of
light propagation, replacing bulk optical components and exhibiting exotic
optical effects. One of the basic properties of the metasurfaces, which renders
them as frequency selective surfaces, is the ability to transmit or reflect
radiation within a narrow spectral band that can be engineered on demand. Here
we introduce and demonstrate experimentally in the THz domain the concept of
wavevector selective surfaces -- metasurfaces transparent only within a narrow
range of light propagation directions operating effectively as tunnel vision
filters. Practical implementations of the new concept include applications in
wavefront manipulation, observational instruments, vision and free-space
communication in light-scattering environments, as well as passive camouflage
Full characterization of a three-photon GHZ state using quantum state tomography
We have performed the first experimental tomographic reconstruction of a
three-photon polarization state. Quantum state tomography is a powerful tool
for fully describing the density matrix of a quantum system. We measured 64
three-photon polarization correlations and used a "maximum-likelihood"
reconstruction method to reconstruct the GHZ state. The entanglement class has
been characterized using an entanglement witness operator and the maximum
predicted values for the Mermin inequality was extracted.Comment: 3 pages, 3 figure
Sequential Generation of Matrix-Product States in Cavity QED
We study the sequential generation of entangled photonic and atomic
multi-qubit states in the realm of cavity QED. We extend the work of C. Schoen
et al. [Phys. Rev. Lett. 95, 110503 (2005)], where it was shown that all states
generated in a sequential manner can be classified efficiently in terms of
matrix-product states. In particular, we consider two scenarios: photonic
multi-qubit states sequentially generated at the cavity output of a
single-photon source and atomic multi-qubit states generated by their
sequential interaction with the same cavity mode.Comment: 11 page
Target Zones in History and Theory: Lessons from an Austro-Hungarian Experiment (1896-1914)
The first known experiment with an exchange rate band took place in Austria-
Hungary between 1896 and 1914. The rationale for introducing this policy rested
on precisely those intuitions that the modern literature has emphasized: the band
was designed to secure both exchange rate stability and monetary policy
autonomy. However, unlike more recent experiences, such as the ERM, this
policy was not undermined by credibility problems. The episode provides an ideal
testing ground for some important ideas in modern macroeconomics: specifically,
can formal rules, when faithfully adhered to, provide policy makers with some
advantages such as short term autonomy? First, we find that a credible band has a
"microeconomic" influence on exchange rate stability. By reducing uncertainty, a
credible fluctuation band improves the quality of expectations, a channel that has been neglected in the modern literature. Second, we show that the standard test of the basic target zone model is flawed and develop an alternative methodology. We believe that these findings shed a new light on the economics of exchange rate bands
Measure of phonon-number moments and motional quadratures through infinitesimal-time probing of trapped ions
A method for gaining information about the phonon-number moments and the
generalized nonlinear and linear quadratures in the motion of trapped ions (in
particular, position and momentum) is proposed, valid inside and outside the
Lamb-Dicke regime. It is based on the measurement of first time derivatives of
electronic populations, evaluated at the motion-probe interaction time t=0. In
contrast to other state-reconstruction proposals, based on measuring Rabi
oscillations or dispersive interactions, the present scheme can be performed
resonantly at infinitesimal short motion-probe interaction times, remaining
thus insensitive to decoherence processes.Comment: 10 pages. Accepted in JPhys
Evidence of terbium and oxygen co-segregation in annealed AlN:Tb
Analytical scanning transmission electron microscopy has been applied to study aluminium nitride (AlN) doped with terbium (Tb) and annealed at 800 ºC. The correlation of the maps of Tb and oxygen (O) from electron energy-loss spectrum (EELS) imaging proves that these two elements co-segregate, replacing aluminium (Al) and nitrogen (N) atoms, respectively. This agrees well with modelling which predicted the existence of Tb–O complexes needed to fit all lines in the rather complicated cathodoluminescence emission spectrum of the sample
Uptake, biodistribution, and time course of naked plasmid DNA trafficking after intratumoral in vivo jet injection
Nonviral jet injection is an applicable technology for in vivo gene transfer of naked DNA. However, little is known about the biodistribution and clearance of jet-injected DNA, or about its localization within tissue and cells. Therefore, in this study we analyzed the intratumoral and systemic biodistribution of jet-injected naked DNA in human colon carcinoma-bearing NCr-nu/nu mice, which were jet-injected with the pCMVbeta plasmid DNA. Intratumoral and systemic plasmid DNA biodistribution was analyzed 5, 10, 20, and 40 min and 3, 6, 24, 48, and 72 hr after jet injection, using quantitative real-time polymerase chain reaction. In the tumors, a rapid drop in naked DNA load within 24 hr of jet injection was shown. Detailed analysis of intratumoral distribution of rhodamine-labeled DNA revealed the presence of plasmid DNA within tumor cells 5 min after jet injection and further accumulation of significant DNA amounts in the cell nuclei 30 to 60 min after jet injection. In the blood, DNA amounts rapidly dropped within 10 to 40 min of jet injection to less than 0.001 pg of plasmid per 250 ng of tissue DNA and only minimal plasmid DNA dissemination was detected in liver, lung, spleen, kidney, and ovaries, which was cleared 3 to 6 hr after jet injection. By contrast, in heart, bone marrow, and brain almost no plasmid DNA was detectable
Towards an eficient atomic frequency comb quantum memory
We present an efficient photon-echo experiment based on atomic frequency
combs [Phys. Rev. A 79, 052329 (2009)]. Echoes containing an energy of up to
35% of that of the input pulse are observed in a Pr3+-doped Y2SiO5 crystal.
This material allows for the precise spectral holeburning needed to make a
sharp and highly absorbing comb structure. We compare our results with a simple
theoretical model with satisfactory agreement. Our results show that atomic
frequency combs has the potential for high-efficiency storage of single photons
as required in future long-distance communication based on quantum repeaters.Comment: 10 pages, 5 figure
- …