arXiv subjects

Qian Liu

Publications and source records attributed to Qian Liu.

305 records · Page 17Linked to original sources

arXiv2016

Complete nondestructive analysis of two-photon six-qubit hyperentangled Bell states assisted by cross-Kerr nonlinearity

Hyperentanglement, the entanglement in several degrees of freedom (DOFs) of a quantum system, has attracted much attention as it can be used to increase both the channel capacity of quantum communication and its security largely. Here, we present the first scheme to completely distinguish the hyperentangled Bell states of two-photon systems in three DOFs with the help of cross-Kerr nonlinearity without destruction, including two longitudinal momentum DOFs and the polarization DOF. We use cross-Kerr nonlinearity to construct quantum nondemolition detectors which can be used to make a parity-check measurement and analyze Bell states of two-photon systems in different DOFs. Our complete scheme for two-photon six-qubit hyperentangled Bell-state analysis may be useful for the practical applications in quantum information, especially in long-distance high-capacity quantum communication.

quant-ph↗

arXiv2015

Three-dimensional graphene skeletons supported nickel molybdate nanowire composite as novel ultralight electrode for supercapacitors

Nickel molybdate (NiMoO$_{4}$) nanowires were prepared on chemical-vapor-deposition-grown three-dimensional graphene skeletons by hydrothermal method. The X-ray diffraction and Raman results show that NiMoO$_{4}$ is $α$ phase. This binder-free and ultralight graphene/ NiMoO$_{4}$ composite was used as a positive electrode for supercapacitors. This electrode presents a high specific capacitance of 1194 F g$^{-1}$ at 12 mA cm$^{-2}$ and the good stability with a cycling efficiency of 97.3% after 1000 cycles. Further, the energy density reaches an energy density of 41 Wh kg$^{-1}$ at a steady power density of 1319 W kg$^{-1}$. These results demonstrate the potential of the designed composite for the future flexible and lightweight energy storage.

cond-mat.mtrl-sci↗

arXiv2015

Implementation of PFC and RCM for RoCEv2 Simulation in OMNeT++

As traffic patterns and network topologies become more and more complicated in current enterprise data centers and TOP500 supercomputers, the probability of network congestion increases. If no countermeasures are taken, network congestion causes long communication delays and degrades network performance. A congestion control mechanism is often provided to reduce the consequences of congestion. However, it is usually difficult to configure and activate a congestion control mechanism in production clusters and supercomputers due to concerns that it may negatively impact jobs if the mechanism is not appropriately configured. Therefore, simulations for these situations are necessary to identify congestion points and sources, and more importantly, to determine optimal settings that can be utilized to reduce congestion in those complicated networks. In this paper, we use OMNeT++ to implement the IEEE 802.1Qbb Priority-based Flow Control (PFC) and RoCEv2 Congestion Management (RCM) in order to simulate clusters with RoCEv2 interconnects.

cs.NI↗

arXiv2015

Rayleigh scattering of linear alkylbenzene in large liquid scintillator detectors

Rayleigh scattering poses an intrinsic limit for the transparency of organic liquid scintillators. This work focuses on the Rayleigh scattering length of linear alkylbenzene (LAB), which will be used as the solvent of the liquid scintillator in the central detector of the Jiangmen Underground Neutrino Observatory. We investigate the anisotropy of the Rayleigh scattering in LAB, showing that the resulting Rayleigh scattering length will be significantly shorter than reported before. Given the same overall light attenuation, this will result in a more efficient transmission of photons through the scintillator, increasing the amount of light collected by the photosensors and thereby the energy resolution of the detector.

physics.ins-det↗

arXiv2015

Generation and complete nondestructive analysis of hyperentanglement assisted by nitrogen-vacancy centers in resonators

We present two efficient schemes for the deterministic generation and the complete nondestructive analysis of hyperentangled Bell states in both the polarization and spatial-mode degrees of freedom (DOFs) of two-photon systems, assisted by the nitrogen-vacancy (NV) centers in diamonds coupled to microtoroidal resonators as a result of cavity quantum electrodynamics (QED). With the input-output process of photons, two-photon polarization-spatial hyperentangled Bell states can be generated in a deterministic way and their complete nondestructive analysis can be achieved. These schemes can be generalized to generate and analyze hyperentangled Greenberger-Horne-Zeilinger states of multi-photon systems as well. Compared with previous works, these two schemes relax the difficulty of their implementation in experiment as it is not difficult to obtain the $π$ phase shift in single-sided NV-cavity systems. Moreover, our schemes do not require that the transmission for the uncoupled cavity is balanceable with the reflectance for the coupled cavity. Our calculations show that these schemes can reach a high fidelity and efficiency with current technology, which may be a benefit to long-distance high-capacity quantum communication with two DOFs of photon systems.

quant-ph↗

arXiv2015

Spectroscopic study of light scattering in linear alkylbenzene for liquid scintillator neutrino detectors

We has set up a light scattering spectrometer to study the depolarization of light scattering in linear alkylbenzene. From the scattering spectra it can be unambiguously shown that the depolarized part of light scattering belongs to Rayleigh scattering. The additional depolarized Rayleigh scattering can make the effective transparency of linear alkylbenzene much better than it was expected. Therefore sufficient scintillation photons can transmit through the large liquid scintillator detector of JUNO. Our study is crucial to achieving the unprecedented energy resolution 3\%/$\sqrt{E\mathrm{(MeV)}}$ for JUNO experiment to determine the neutrino mass hierarchy. The spectroscopic method can also be used to judge the attribution of the depolarization of other organic solvents used in neutrino experiments.

physics.chem-ph↗

arXiv2015

Rayleigh scattering and depolarization ratio in linear alkylbenzene

Linear alkylbenzene (LAB) is adopted to be the organic solvent for the Jiangmen Underground Neutrino Observatory (JUNO) liquid scintillator detectors due to the ultra-transparency. However the current Rayleigh scattering length calculation disagrees with the measurement. The present paper for the first time reports the Rayleigh scattering of LAB being anisotropic and the depolarization ratio being 0.31+-0.01(stat.)+-0.01(sys.). We proposed an indirectly method for Rayleigh scattering measurement with Einstein-Smoluchowski-Cabannes formula, and the Rayleigh scattering length of LAB is determined to be 28.2+-1.0 m at 430 nm.

physics.ins-det↗

arXiv2015

Densities, isobaric thermal expansion coefficients and isothermal compressibilities of linear alkylbenzene

We report the measurements of the densities of linear alkylbenzene at three temperatures over 4 to 23 Celsius degree with pressures up to 10 MPa. The measurements have been analysed to yield the isobaric thermal expansion coefficients and, so far for the first time, isothermal compressibilities of linear alkylbenzene. Relevance of results for current generation (i.e. Daya Bay) and next generation (i.e. JUNO) large liquid scintillator neutrino detectors are discussed.

physics.ins-det↗

arXiv2015

Scintillation efficiency measurement of Na recoils in NaI(Tl) below the DAMA/LIBRA energy threshold

The dark matter interpretation of the DAMA modulation signal depends on the NaI(Tl) scintillation efficiency of nuclear recoils. Previous measurements for Na recoils have large discrepancies, especially in the DAMA/LIBRA modulation energy region. We report a quenching effect measurement of Na recoils in NaI(Tl) from 3keV$_{\text{nr}}$ to 52keV$_{\text{nr}}$, covering the whole DAMA/LIBRA energy region for light WIMP interpretations. By using a low-energy, pulsed neutron beam, a double time-of-flight technique, and pulse-shape discrimination methods, we obtained the most accurate measurement of this kind for NaI(Tl) to date. The results differ significantly from the DAMA reported values at low energies, but fall between the other previous measurements. We present the implications of the new quenching results for the dark matter interpretation of the DAMA modulation signal.

physics.ins-det↗

arXiv2015

p/${π^+}$ response of single layer THGEM detector in Ar/3%iC$_4$H$_{10}$

In this work, we study the response of single layer Thick GEM (THGEM) detector to p/${π^+}$ at E3 line of Beijing Test Beam Facility. In our experiment, the drift gap of THGEM Detector is 4mm, and the working gas is Ar/3% iso. Result shows at the momentum 500MeV/c to 1000MeV/c, detection efficiency for p is from 93% to 99% in a relatively lower gain($\sim$2000), while the detection efficiency for ${π^+}$ is slightly lower than that for p, which is from 82% to 88%. Meanwhile, simple Geant4 simulations have been done, and results of beam test are almost consistent with it. We preliminarily study the feasibility of THGEM detectors as sampling elements for Digital Hadronic Calorimeter(DHCAL), which may provide related reference for THGEM possibly applied in Circular Electron Positron Collider(CEPC) HCAL.

physics.ins-det↗

arXiv2015

The combined equilibrium of business land-use and its congestion pricing principles (working paper)

This working paper is divided into two parts. Firstly, we develop a new combined equilibrium model of business land-use, which puts travelers' traffic equilibrium and business companies' competitive location equilibrium into a unified framework. A variational inequality is presented for the combined equilibrium and the properties of equilibrium solution are investigated. Secondly, the congestion pricing principles associated with the combined equilibrium are studied. From the mathematical point of view, we prove that there exists an optimal road pricing scheme that can minimize the social cost of travelers. This road pricing scheme generalizes the traditional link-based optimal road pricing scheme. Furthermore, when simultaneously imposing charges on travelers and companies is allowed, we prove that there exists an optimal congestion pricing scheme that can derive a combined equilibrium toward an overall system optimum. The economic meaning of every pricing scheme proposed in this paper is discussed in detail. At last, a simple numerical example is used to demonstrate that the optimal congestion pricing scheme may indeed reduce the social cost.

math.OC↗

arXiv2014

Biclustering Via Sparse Clustering

In many situations it is desirable to identify clusters that differ with respect to only a subset of features. Such clusters may represent homogeneous subgroups of patients with a disease, such as cancer or chronic pain. We define a bicluster to be a submatrix U of a larger data matrix X such that the features and observations in U differ from those not contained in U. For example, the observations in U could have different means or variances with respect to the features in U. We propose a general framework for biclustering based on the sparse clustering method of Witten and Tibshirani (2010). We develop a method for identifying features that belong to biclusters. This framework can be used to identify biclusters that differ with respect to the means of the features, the variance of the features, or more general differences. We apply these methods to several simulated and real-world data sets and compare the results of our method with several previously published methods. The results of our method compare favorably with existing methods with respect to both predictive accuracy and computing time.

stat.ME↗

arXiv2013

Experimental studies of THGEM in different Ar/CO2 mixtures

In this paper, the performances of a type of the domestic THGEM (THick Gaseous Electron Multiplier) working in the Ar/CO2 mixtures are reported in details. This kind of single THGEM can provide the gain range from 100 to 1000, which is very suitable for the application in the neutron detection. In order to study its basic characteristics as the references for the development of THGEM based neutron detector, the counting rate plateau, the energy resolution and the gain of the THGEM have been measured in the different Ar/CO2 mixtures with the change of the electrical fields. For the Ar/CO2(90%/10%) gas mixture, a wide counting rate plateau is got from 720V to 770V with the plateau slope of 2.4% / 100 V and the excellent energy resolution about 22% is obtained at the 5.9keV full energy peak of the 55Fe X-ray source.

physics.ins-det↗

arXiv2013

The Reactive Volatility Model

We present a new volatility model, simple to implement, that includes a leverage effect whose return-volatility correlation function fits to empirical observations. This model is able to capture both the "retarded effect" induced by the specific risk, and the "panic effect", which occurs whenever systematic risk becomes the dominant factor. Consequently, in contrast to a GARCH model and a standard volatility estimate from the squared returns, this new model is as reactive as the implied volatility: the model adjusts itself in an instantaneous way to each variation of the single stock price or the stock index price and the adjustment is highly correlated to implied volatility changes. We also test the reactivity of our model using extreme events taken from the 470 most liquid European stocks over the last decade. We show that the reactive volatility model is more robust to extreme events, and it allows for the identification of precursors and replicas of extreme events.

q-fin.ST↗

arXiv2009

Arbitrary-order lensless ghost imaging with thermal light

Arbitrary Nth-order ($N\geq2$) lensless ghost imaging with thermal light has been performed for the first time by only recording the intensities in two optical paths. It is shown that the image visibility can be dramatically enhanced as the order N increases. It is also found that longer integration times are required for higher-order correlation measurements as N increases, due to the increased fluctuations of higher-order intensity correlation functions.

quant-ph↗

arXiv2009

The Second-Order Talbot Effect with Entangled Photon Pairs

The second-order Talbot effect is analyzed for a periodic object illuminated by entangled photon pairs in both the quantum imaging and quantum lithography configurations. The Klyshko picture is applied to describe the quantum imaging scheme, in which self-images of the object that may or may not be magnified can be observed nonlocally in the photon coincidences but not in the singles count rate. In the quantum lithography setup, we find that the second-order Talbot length is half that of the classical first-order case, thus the resolution may be improved by a factor of two.

quant-ph↗

arXiv2009

Lensless ghost imaging with true thermal light

We report the first (to our knowledge) experimental demonstration of lensless ghost imaging with true thermal light. Although there is no magnification, the method is suitable for all wavelengths and so may find special applications in cases where it is not possible to use lenses, such as with x-rays or gamma-rays. We also show numerically that some magnification may be realized away from the focal plane, but the image will always be somewhat blurred.

quant-ph↗