5,052 research outputs found
Fast Characterization of Dispersion and Dispersion Slope of Optical Fiber Links using Spectral Interferometry with Frequency Combs
We demonstrate fast characterization (~1.4 microseconds) of both the
dispersion and dispersion slope of long optical fiber links (~25 km) using dual
quadrature spectral interferometry with an optical frequency comb. Compared to
previous spectral interferometry experiments limited to fiber lengths of
meters, the long coherence length and the periodic delay properties of
frequency combs, coupled with fast data acquisition, enable spectral
interferometric characterization of fibers longer by several orders of
magnitude. We expect that our method will be useful to recently proposed
lightwave techniques like coherent WDM and to coherent modulation formats by
providing a real time monitoring capability for the link dispersion. Another
area of application would be in stabilization of systems which perform
frequency and timing distribution over long fiber links using stabilized
optical frequency combs.Comment: 3 pages, 3 figures, Minor changes to tex
BSE versus StarTrack: implementations of new wind, remnant-formation, and natal-kick schemes in NBODY7 and their astrophysical consequences
The masses of stellar-remnant black holes (BH), as a result of their
formation via massive single- and binary-stellar evolution, is of high interest
in this era of gravitational-wave detection from binary black hole (BBH) and
binary neutron star (BNS) mergers. Here we present new developments in the
N-body evolution program NBODY7 in regards to its stellar-remnant formation and
related schemes. We demonstrate that the newly-implemented stellar-wind and
remnant-formation schemes in the NBODY7 code's BSE sector, such as the 'rapid'
and the 'delayed' supernova (SN) schemes along with an implementation of
pulsational-pair-instability and pair-instability supernova (PPSN/PSN), now
produces neutron star (NS) and BH masses that agree nearly perfectly, over
large ranges of zero-age-main sequence (ZAMS) mass and metallicity, with those
from the StarTrack population-synthesis program. We also demonstrate the new
implementations of various natal-kick mechanisms on NSs and BHs such as the
'convection-asymmetry-driven', 'collapse-asymmetry-driven', and
'neutrino-emission-driven' kicks, in addition to a fully consistent
implementation of the standard, fallback-dependent, momentum-conserving natal
kick. We find that the SN material fallback causes the convection-asymmetry
kick to effectively retain similar number and mass of BHs in clusters as for
the standard, momentum-conserving kick. The collapse-asymmetry kick would cause
nearly all BHs to retain in clusters irrespective of remnant formation model
and metallicity, whereas the inference of a large number of BHs in GCs would
potentially rule out the neutrino-driven kick mechanism. Pre-SN mergers of
massive primordial binaries would cause BH masses to deviate from the
single-star ZAMS mass-remnant mass relation. Such mergers, at low
metallicities, can produce low-spinning BHs within the PSN mass gap that can be
retained in a stellar cluster.Comment: 27 pages, 15 figures, 2 tables. Accepted for publication in Astronomy
and Astrophysic
Gaussian-shaped Optical Frequency Comb Generation for Microwave Photonic Filtering
Using only electro-optic modulators, we generate a 41-line 10-GHz
Gaussian-shaped optical frequency comb. We use this comb to demonstrate
apodized microwave photonic filters with greater than 43-dB sidelobe
suppression without the need for a pulse shaper.Comment: 3 pages, 4 figure
Recommended from our members
Phase Coexistence of Ferroelectric Vortices and Classical a1/a2 Domains in PbTiO3/SrTiO3 Superlattices.
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dose-response.12-001.Nascarella A SPECIAL ISSUE ON NANOMATERIAL REGULATIONS AND HEALTH EFFECTS
Dynamic-ADAPT-QAOA: An algorithm with shallow and noise-resilient circuits
The quantum approximate optimization algorithm (QAOA) is an appealing
proposal to solve NP problems on noisy intermediate-scale quantum (NISQ)
hardware. Making NISQ implementations of the QAOA resilient to noise requires
short ansatz circuits with as few CNOT gates as possible. Here, we present
Dynamic-ADAPT-QAOA. Our algorithm significantly reduces the circuit depth and
the CNOT count of standard ADAPT-QAOA, a leading proposal for near-term
implementations of the QAOA. Throughout our algorithm, the decision to apply
CNOT-intensive operations is made dynamically, based on algorithmic benefits.
Using density-matrix simulations, we benchmark the noise resilience of
ADAPT-QAOA and Dynamic-ADAPT-QAOA. We compute the gate-error probability
below which these algorithms provide, on average, more
accurate solutions than the classical, polynomial-time approximation algorithm
by Goemans and Williamson. For small systems with qubits, we show that
for Dynamic-ADAPT-QAOA. Compared to standard
ADAPT-QAOA, this constitutes an order-of-magnitude improvement in noise
resilience. This improvement should make Dynamic-ADAPT-QAOA viable for
implementations on superconducting NISQ hardware, even in the absence of error
mitigation.Comment: 15 pages, 9 figure
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