Of Ghostly Holograms
Traditionally, an image is formed when photons carry information from an object to a detection plane. However, the strong position correlations found in entangled photons allow one to construct an image by querying an object with one photon, while measuring the position of its entangled partner. As more and more photons pairs are used, a "ghost image" is formed. In a recent experiment researchers carried out a ghost imaging experiment in which only a few photons were needed in order to identify an object. The experiment employed a new method in which a hologram is used to sort single photons based on what image they are carrying. In this case, the hologram was used to sort single photons carrying "ghost image" information, i.e., photons that had not directly interacted with the object being queried. Such a technique overcomes the limitations of using slow optical detectors such as CCDs and could be very useful when querying a small set of objects using only a very small number of photons.
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LP11872
Guiding current pathway through Ag–SnPc–Ag junctions
Single atoms and molecules on surfaces are being explored for their
potential of leading to small electronic devices. One challenge in this
field is to understand how an electrical current flows through a single
atom or molecule. Over the last 2 decades, tremendous effort has been made
to investigate this issue. In the present Letter, we use single molecule
chemistry to demonstrate that the current in a molecular junction, which
is comprised of atomically controlled Ag electrodes and a single
Sn-Phthalocyanine molecule, can be directionally guided along particular
pathways by selectively modifying the bonds between the molecule and an
electrode.
SnPc molecules adsorbed on Ag(111) were contacted with the tip of a
cryogenic scanning tunneling microscope. By systematically manipulating
the chemical bonding between SnPc and Ag(111) through selective cutting
hydrogen atoms from SnPc together with an single atom manipulation
technique, the conductance of single molecule junctions was controllably
varied from 1 to 25 micro-Siemens. Ab initio calculations using density
functional methods and non-equilibrium Green’s function techniques enable
a quantitative analysis of electron transport through Ag-SnPc-Ag junctions
and a visualization of the guided current flow.
