120 research outputs found
Remote Sensing and Control of Phase Qubits
We demonstrate a remote sensing design of phase qubits by separating the
control and readout circuits from the qubit loop. This design improves
measurement reliability because the control readout chip can be fabricated
using more robust materials and can be reused to test different qubit chips.
Typical qubit measurements such as Rabi oscillations, spectroscopy, and
excited-state energy relaxation are presented.Comment: 3 pages, 4 figure
A Chandra Proper Motion for PSR J1809-2332
We report on a new Chandra exposure of PSR J1809-2332, the recently
discovered pulsar powering the bright EGRET source 3EG J1809-2328. By
registration of field X-ray sources in an archival exposure, we measure a
significant proper motion for the pulsar point source over an ~11 year
baseline. The shift of 0.30+/-0.06" (at PA= 153.3+/-18.4) supports an
association with proposed SNR parent G7.5-1.7. Spectral analysis of diffuse
emission in the region also supports the interpretation as a hard wind nebula
trail pointing back toward the SNR.Comment: To Appear in the Astrophysical Journal, Sept 1 (v. 756
Chandra Imaging of the Gamma-Ray Source GeV J1809-2327
We report on Chandra imaging observations of the Galactic Unidentified
-ray source GEV J1809-2327, comparing the X-ray images with new VLA
1.46 GHz and 4.86 GHz maps. The X-ray images reveal a point source connected to
a non-thermal X-ray/radio nebula, supporting a pulsar/wind model for the
-ray emitter. We also detect numerous X-ray sources from the young
stellar association in the adjacent HII region S32.Comment: to appear in ApJ letter
Light Curves of Rapidly Rotating Neutron Stars
We consider the effect of rapid rotation on the light curves of neutron stars
with hot polar caps. For ms spin periods, the pulse fractions can
be as much as an order of magnitude larger than with simple slowly-rotating
(Schwarzschild) estimates. Doppler boosting, in particular, leads to
characteristic distortion and ``soft lags'' in the pulse profiles, which are
easily measurable in light curves with moderate energy resolution. With photons it should also be possible to isolate the more subtle distortions
of light travel time variations and frame dragging. Detailed analysis of high
quality millisecond pulsar data from upcoming X-ray missions must include these
effects
Emulated nuclear spin gyroscope with NV centers in diamond
Nuclear spins in solid-state platforms are promising for building rotation
sensors due to their long coherence times. Among these platforms,
nitrogen-vacancy centers have attracted considerable attention with ambient
operating conditions. However, the current performance of NV gyroscopes remains
limited by the degraded coherence when operating with large spin ensembles.
Protecting the coherence of these systems requires a systematic study of the
coherence decay mechanism. Here we present the use of nitrogen-15 nuclear spins
of NV centers in building gyroscopes, benefiting from its simpler energy
structure and vanishing nuclear quadrupole term compared with nitrogen-14
nuclear spins, though suffering from different challenges in coherence
protection. We systematically reveal the coherence decay mechanism of the
nuclear spin in different NV electronic spin manifolds and further develop a
robust coherence protection protocol based on controlling the NV electronic
spin only, achieving a 15-fold dephasing time improvement. With the developed
coherence protection, we demonstrate an emulated gyroscope by measuring a
designed rotation rate pattern, showing an order-of-magnitude sensitivity
improvement
Thermal emission from low-field neutron stars
We present a new grid of LTE model atmospheres for weakly magnetic
(B<=10e10G) neutron stars, using opacity and equation of state data from the
OPAL project and employing a fully frequency- and angle-dependent radiation
transfer. We discuss the differences from earlier models, including a
comparison with a detailed NLTE calculation. We suggest heating of the outer
layers of the neutron star atmosphere as an explanation for the featureless
X-ray spectra of RX J1856.5-3754 and RX J0720.4-3125 recently observed with
Chandra and XMM.Comment: 8 pages A&A(5)-Latex, 6 Figures, A&A in press. The model spectra
presented here are available as XSPEC tables at
http://www.astro.soton.ac.uk/~btg/outgoing/nsspec
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