43 research outputs found
Quantum limit in continuous quantum measurement
An inequality about quantum noise is presented with the imprecise measurement
theory, which is used to analyse the quantum limit in continuous quantum
measurement. Different from the linear-response approach based on the quantum
relation between noise and susceptibilities of the detector, we provide an
explicit functional relation between quantum noise and reduction operator, and
show a rigorous result: The minimum noise added by the detector in quantum
measurement is precisely equal to the zero-point noise. This conclusion
generalizes the standard Haus-Caves quantum limit for a linear amplifier. We
also discuss the statistic characters of the back-action force in quantum
measurement and show on how to reach the quantum limit.Comment: 18 page
Students’ Ability Evaluation Structure Model of Local Finance and Economic Universities
The students’ ability evaluation of local finance and economic universities is conducive to the cultivation of talents, and to promote local economic development. In order to objectively evaluate the students’ ability of local finance and economic universities, this paper divides the ability of college students into three dimensions, including basic quality and ability, professional competence, the ability of innovation and practice. This paper builds the students’ ability evaluation indicator system of local finance and economic universities, and designs evaluation indicator system scale tables. Collecting data from high school students, teachers and the employers through paper questionnaires and web-based survey, this paper uses principal component analysis to extract ability factors, and establishes the students’ ability evaluation structure model of local finance and economic universities. This study provides a theoretical reference for the objective evaluation of students’ ability and training students’ ability purposefully
Searching for scalar field dark matter with short-range gravity experiments
The nature of dark matter remains a mystery, although enormous efforts have
been made to search for dark matter candidate particles. Scalar field dark
matter is one of the most prominent options that is being explored by the
various precision experiments, such as gravitational-wave detectors, atomic
clocks and gravity experiments. We describe a direct search for scalar field
dark matter using the short-range gravity experiments, in which we investigate
the possible influences of scalar field dark matter as a function of its mass.
By analyzing the torque signals in the torsion pendulum experiments of the
HUST-18 and HUST-20, we set new constraints on the large mass regions of scalar
field dark matter parameter space. Based on the maximum reach analysis (MRA)
method, the constraints on the photon coupling parameter and
electron coupling parameter improve on limits from
previous direct searches in interferometer experiments by more than four orders
of magnitude. Further combining the HUST-18 and HUST-20 experiments, we also
present the exclusion limits that are not dependent on MRA approximation. This
work paves the way for dark-matter search in future HUST experiments, and the
projected constraints can be competitive with those limits produced by the MRA
method.Comment: 13 pages, 5 fiure
The morphological dependent Tully-Fisher relation of spiral galaxies
The Tully-Fisher relation of spiral galaxies shows notable dependence on
morphological types, with earlier type spirals having systematically lower
luminosity at fixed maximum rotation velocity . This decrement of
luminosity is more significant in shorter wavelengths. By modeling the rotation
curve and stellar population of different morphological type spiral galaxies in
combination, we find the of spiral galaxies is weakly dependent on
the morphological type, whereas the difference of the stellar population
originating from the bulge disk composition effect mainly account for the
morphological type dependence of the Tully-Fisher relation.Comment: 8 pages, 3 figures, ApJ accepte
Influence of EOM sideband modulation noise on space-borne gravitational wave detection
Clock noise is one of the dominant noises in the space-borne gravitational
wave (GW) detection. To suppress this noise, the clock noise-calibrated
time-delay-interferometry (TDI) technique is proposed. In this technique, an
inter-spacecraft clock tone transfer chain is necessary to obtain the
comparison information of the clock noises in two spacecraft, during which an
electro-optic-modulator (EOM) is critical and used to modulate the clock noise
to the laser phase. Since the EOM sideband modulation process introduces
modulation noise, it is significant to put forward the corresponding
requirements and assess whether the commercial EOM meets. In this work, based
on the typical Michelson TDI algorithm and the fundamental noise requirement of
GW detectors, the analytic expression of the modulation noise requirement is
strictly derived, which relax the component indicator need compared to the
existing commonly used rough assessments. Furthermore, a commercial EOM
(iXblue-NIR-10 GHz) is tested, and the experimental results show that it can
meet the requirement of the typical GW detection mission LISA in whole
scientific bandwidth by taking the optimal combination of the data stream. Even
when the displacement measurement accuracy of LISA is improved to 1 pm/
in the future, it still meets the demand
Experimental demonstration of picometer level signal extraction with time-delay interferometry technique
In this work, we have built an experimental setup to simulate the clock noise
transmission with two spacecrafts and two optical links, and further
demonstrated the extraction of picometer level signal drowned by the large
laser frequency noise and clock noise with the data post-processing method.
Laser frequency noise is almost eliminated by using the idea of time-delay
interferometry (TDI) to construct an equal arm interferometer. Clock
asynchronism and clock jitter noise are significantly suppressed by laser
sideband transmitting the clock noise using an electro-optic modulator (EOM).
Experimental results show a reduction in laser frequency noise by approximately
10^5 and clock noise by 10^2, recovering a weak displacement signal with an
average amplitude about 60 picometer and period 1 second. This work has
achieved the principle verification of the noise reduction function of TDI
technique to some extent, serving the data processing research of space-borne
gravitational wave detection