4,429 research outputs found
Positive noise cross-correlations in superconducting hybrids: Roles of interfaces and interactions
Shot noise cross-correlations in normal metal-superconductor-normal metal
structures are discussed at arbitrary interface transparencies using both the
scattering approach of Blonder, Tinkham and Klapwik and a microscopic Green's
function approach. Surprisingly, negative crossed conductance in such set-ups
[R. Melin and D. Feinberg, Phys. Rev. B 70, 174509 (2004)] does not preclude
the possibility of positive noise cross-correlations for almost transparent
contacts. We conclude with a phenomenological discussion of interactions in the
one dimensional leads connected to the superconductor, which induce sign
changes in the noise cross-correlations.Comment: 15 pages, 9 figure
Quantum optical signal processing in diamond
Controlling the properties of single photons is essential for a wide array of
emerging optical quantum technologies spanning quantum sensing, quantum
computing, and quantum communications. Essential components for these
technologies include single photon sources, quantum memories, waveguides, and
detectors. The ideal spectral operating parameters (wavelength and bandwidth)
of these components are rarely similar; thus, frequency conversion and spectral
control are key enabling steps for component hybridization. Here we perform
signal processing of single photons by coherently manipulating their spectra
via a modified quantum memory. We store 723.5 nm photons, with 4.1 nm
bandwidth, in a room-temperature diamond crystal; upon retrieval we demonstrate
centre frequency tunability over 4.2 times the input bandwidth, and bandwidth
modulation between 0.5 to 1.9 times the input bandwidth. Our results
demonstrate the potential for diamond, and Raman memories in general, to be an
integrated platform for photon storage and spectral conversion.Comment: 6 pages, 4 figure
Storage and retrieval of ultrafast single photons using a room-temperature diamond quantum memory
We report the storage and retrieval of single photons, via a quantum memory,
in the optical phonons of room-temperature bulk diamond. The THz-bandwidth
heralded photons are generated by spontaneous parametric downconversion and
mapped to phonons via a Raman transition, stored for a variable delay, and
released on demand. The second-order correlation of the memory output is
, demonstrating preservation of non-classical
photon statistics throughout storage and retrieval. The memory is low-noise,
high-speed and broadly tunable; it therefore promises to be a versatile
light-matter interface for local quantum processing applications.Comment: 6 pages, 4 figure
Storage of polarization-entangled THz-bandwidth photons in a diamond quantum memory
Bulk diamond phonons have been shown to be a versatile platform for the
generation, storage, and manipulation of high-bandwidth quantum states of
light. Here we demonstrate a diamond quantum memory that stores, and releases
on demand, an arbitrarily polarized 250 fs duration photonic qubit. The
single-mode nature of the memory is overcome by mapping the two degrees of
polarization of the qubit, via Raman transitions, onto two spatially distinct
optical phonon modes located in the same diamond crystal. The two modes are
coherently recombined upon retrieval and quantum process tomography confirms
that the memory faithfully reproduces the input state with average fidelity
with a total memory efficiency of . In an
additional demonstration, one photon of a polarization-entangled pair is stored
in the memory. We report that entanglement persists in the retrieved state for
up to 1.3 ps of storage time. These results demonstrate that the diamond phonon
platform can be used in concert with polarization qubits, a key requirement for
polarization-encoded photonic processing
Resolving the order parameter of High-T Superconductors through quantum pumping spectroscopy
The order parameter of High-T superconductors through a series of
experiments has been quite conclusively demonstrated to not be of the normal
type. It is either a pure -wave type or a mixture of
a with a small imaginary or
component. In this work a distinction is brought out among the four types,
i.e., , , and
types with the help of quantum pumping
spectroscopy. This involves a normal metal double barrier structure in contact
with a High-T superconductor. The pumped current, heat and noise show
different characteristics with change in order parameter revealing quite easily
the differences among these.Comment: 11 pages, 3 figures, 1 table, Manuscript revised with new material on
d+id' cas
State Legislative Update
Senate Bill 1970 was introduced in the Florida Senate on March 2, 2004. It was initially referred to the Senate Judiciary Committee where it passed on April 19 with an 8-0 vote. Senate Bill 1970 was read for the first time in the Senate on April 21. The bill passed the full Senate on April 24 with a 39-0 vote. It was then sent to the full House on April 26 where it was substituted for House Bill 1765. Senate Bill 1970 was read and passed in the House on April 27 with a 114-0 vote. The bill was presented to Govenor Bush for signature on June 9 and signed into law on June 10, 2004
Ginzburg Criterion for Coulombic Criticality
To understand the range of close-to-classical critical behavior seen in
various electrolytes, generalized Debye-Hueckel theories (that yield density
correlation functions) are applied to the restricted primitive model of
equisized hard spheres. The results yield a Landau-Ginzburg free-energy
functional for which the Ginzburg criterion can be explicitly evaluated. The
predicted scale of crossover from classical to Ising character is found to be
similar in magnitude to that derived for simple fluids in comparable fashion.
The consequences in relation to experiments are discussed briefly.Comment: 4 pages, revtex, 2 tables (latex2.09 required due to revtex's
incompatibility with latex2e tables
Hypervelocity Stars III. The Space Density and Ejection History of Main Sequence Stars from the Galactic Center
We report the discovery of 3 new unbound hypervelocity stars (HVSs), stars
traveling with such extreme velocities that dynamical ejection from a massive
black hole (MBH) is their only suggested origin. We also detect a population of
possibly bound HVSs. The significant asymmetry we observe in the velocity
distribution -- we find 26 stars with v_rf > 275 km/s and 1 star with v_rf <
-275 km/s -- shows that the HVSs must be short-lived, probably 3 - 4 Msun main
sequence stars. Any population of hypervelocity post-main sequence stars should
contain stars falling back onto the Galaxy, contrary to the observations. The
spatial distribution of HVSs also supports the main sequence interpretation:
longer-lived 3 Msun HVSs fill our survey volume; shorter-lived 4 Msun HVSs are
missing at faint magnitudes. We infer that there are 96 +- 10 HVSs of mass 3 -
4 Msun within R < 100 kpc, possibly enough HVSs to constrain ejection
mechanisms and potential models. Depending on the mass function of HVSs, we
predict that SEGUE may find up to 5 - 15 new HVSs. The travel times of our HVSs
favor a continuous ejection process, although a ~120 Myr-old burst of HVSs is
also allowed.Comment: 10 pages, 8 figures, accepted to ApJ, minor revision
1,4-Di-n-heptyloxy-2,5-dinitrobenzene
The complete molecule of the title compound, C20H32N2O6, is generated by crystallographic inversion symmetry. The two mutually trans nitro substituents are hence in fully eclipsed conformation and also twisted by 43.2 (2)° with respect to the phenyl ring plane. The benzene-connected portions of the alkoxy substituents lie almost coplanar with the ring [C—O—C—C torsion angle = 2.0 (2)°]. In the crystal, weak C—H⋯O interactions link the molecules
- …