1,105 research outputs found
Comment on "Far-field microscopy with a nanometer-scale resolution based on the in-plane image magnification by surface plasmon polaritons"
This is a small comment concerning the work by Smolyaninov et al. in Phys.
Rev. Lett.94, 057401 (2005)
On the local unitary equivalence of states of multi-partite systems
Two pure states of a multi-partite system are alway are related by a unitary
transformation acting on the Hilbert space of the whole system. This
transformation involves multi-partite transformations. On the other hand some
quantum information protocols such as the quantum teleportation and quantum
dense coding are based on equivalence of some classes of states of bi-partite
systems under the action of local (one-particle) unitary operations. In this
paper we address the question: ``Under what conditions are the two states
states, and , of a multi-partite system locally unitary
equivalent?'' We present a set of conditions which have to be satisfied in
order that the two states are locally unitary equivalent. In addition, we study
whether it is possible to prepare a state of a multi-qudit system. which is
divided into two parts A and B, by unitary operations acting only on the
systems A and B, separately.Comment: 6 revtex pages, 1 figur
Quantum Zeno tomography
We show that the resolution "per absorbed particle" of standard absorption
tomography can be outperformed by a simple interferometric setup, provided that
the different levels of "gray" in the sample are not uniformly distributed. The
technique hinges upon the quantum Zeno effect and has been tested in numerical
simulations. The scheme we propose could be implemented in experiments with
UV-light, neutrons or X-rays.Comment: 8 pages, 5 figure
Experimental GHZ Entanglement beyond Qubits
The Greenberger-Horne-Zeilinger (GHZ) argument provides an all-or-nothing
contradiction between quantum mechanics and local-realistic theories. In its
original formulation, GHZ investigated three and four particles entangled in
two dimensions only. Very recently, higher dimensional contradictions
especially in three dimensions and three particles have been discovered but it
has remained unclear how to produce such states. In this article we
experimentally show how to generate a three-dimensional GHZ state from
two-photon orbital-angular-momentum entanglement. The first suggestion for a
setup which generates three-dimensional GHZ entanglement from these entangled
pairs came from using the computer algorithm Melvin. The procedure employs
novel concepts significantly beyond the qubit case. Our experiment opens up the
possibility of a truly high-dimensional test of the GHZ-contradiction which,
interestingly, employs non-Hermitian operators.Comment: 6+6 pages, 8 figure
Quantum orbital angular momentum of elliptically-symmetric light
We present a quantum mechanical analysis of the orbital angular momentum of a
class of recently discovered elliptically-symmetric stable light fields --- the
so-called Ince-Gauss modes. We study, in a fully quantum formalism, how the
orbital angular momentum of these beams varies with their ellipticity and
discover several compelling features, including: non-monotonic behavior, stable
beams with real continuous (non-integer) orbital angular momenta, and
orthogonal modes with the same orbital angular momenta. We explore, and explain
in detail, the reasons for this behavior. These features may have application
to quantum key distribution, atom trapping, and quantum informatics in general
--- as the ellipticity opens up a new way of navigating the photonic Hilbert
space.Comment: 9 Pages, 4 Figures, Comments Welcom
Pollen Processing Behavior of Heliconius Butterflies: A Derived Grooming Behavior
Pollen feeding behaviors Heliconius and Laparus (Lepidoptera: Nymphalidae) represent a key innovation that has shaped other life history traits of these neotropical butterflies. Although all flower visiting Lepidoptera regularly come in contact with pollen, only Heliconius and Laparus butterflies actively collect pollen with the proboscis and subsequently take up nutrients from the pollen grains. This study focused on the behavior of pollen processing and compared the movement patterns with proboscis grooming behavior in various nymphalid butterflies using video analysis. The proboscis movements of pollen processing behavior consisted of a lengthy series of repeated coiling and uncoiling movements in a loosely coiled proboscis position combined with up and down movements and the release of saliva. The proboscis-grooming behavior was triggered by contamination of the proboscis in both pollen feeding and non-pollen feeding nymphalid butterflies. Proboscis grooming movements included interrupted series of coiling and uncoiling movements, characteristic sideways movements, proboscis lifting, and occasionally full extension of the proboscis. Discharge of saliva was more pronounced in pollen feeding species than in non-pollen feeding butterfly species. We conclude that the pollen processing behavior of Heliconius and Laparus is a modified proboscis grooming behavior that originally served to clean the proboscis after contamination with particles
The End of the Great Depression 1939-41: Policy Contributions and Fiscal Multipliers
This paper is about the size of fiscal multipliers and the sources of recovery from the Great Depression. Its baseline result is that 89.1 percent of the 1939:Q1-1941:Q4 recovery can be attributed to fiscal policy innovations, 34.1 percent to monetary policy innovations and the remaining -23.2 percent to the combined effect of the basic VAR dynamic forecast and innovations in non-government components of GDP. Traditional Keynesian multipliers assume that there are no capacity constraints to impede a fiscal-driven expansion in aggregate demand. On the contrary, we find ample evidence of capacity constraints in 1941, particularly in the second half of that year. As a result our preferred government spending multiplier is 1.80 when the time period ends in 1941:Q2 but only 0.88 when the time period ends in supply-constrained 1941:Q4. Only the 1.80 multiplier is relevant to situations like 2009-10 when capacity constraints are absent across the economy. Two sets of new insights emerge from a review of contemporary print media. We document that the American economy went to war starting in June 1940, fully 18 months before Pearl Harbor. We also detail the bifurcated nature of the 1941 economy, with excess capacity in its labor market but capacity constraints in many of the key manufacturing industries. By July 1941, the American economy was in a state of perceived national emergency.
Arbitrary d-dimensional Pauli X gates of a flying qudit
High-dimensional degrees of freedom of photons can encode more quantum information than their two-dimensional counterparts. While the increased information capacity has advantages in quantum applications (such as quantum communication), controlling and manipulating these systems has been challenging. Here we show a method to perform deterministic arbitrary high-dimensional Pauli X gates for single photons carrying orbital angular momentum. The X gate consists of a cyclic permutation of qudit basis vectors and, together with the Z gate, forms the basis for performing arbitrary transformations. The proposed experimental setups only use two basic optical elements such as mode sorters and mode shifters and thus could be implemented in any system where these experimental tools are available. Furthermore the number of involved interferometers scales logarithmically with the dimension, which is important for practical implementation
- …