分类： 物理学 >> 核物理学 提交时间： 2024-01-18
摘要： The elliptic azimuthal anisotropy coefficient ($v_{2}$) of the identified particles at midrapidity ($ eta <0.8$) was investigated in p--Pb collisions at $ sqrt{s_ mathrm{NN}}=$ 5.02 TeV using a multi-phase transport model (AMPT). The calculations of differential $v_{2}$ based on the advanced flow extraction method of light flavor hadrons (pions, kaons, protons, and $ Lambda$) in small collision systems were extended to a wider transverse momentum ($p_{ mathrm{T}}$) range of up to 8 GeV/$c$ for the first time. The string- melting version of the AMPT model provides a good description of the measured $p_{ mathrm{T}}$-differential $v_{2}$ of the mesons but exhibits a slight deviation from the baryon $v_{2}$. In addition, we observed the features of mass ordering at low $p_{ mathrm{T}}$ and the approximate number of constituent quarks (NCQ) scaled at intermediate $p_{ mathrm{T}}$. Moreover, we demonstrate that hadronic rescattering does not have a significant impact on $v_{2}$ in p--Pb collisions for different centrality selections, whereas partonic scattering dominates in generating the elliptic anisotropy of the final particles. This study provides further insight into the origin of collective-like behavior in small collision systems and has referential value for future measurements of azimuthal anisotropy.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： A crucial subroutine for various quantum computing and communication algorithms is to efficiently extract different classical properties of quantum states. In a notable recent theoretical work by Huang, Kueng, and Preskill [Nat. Phys. 16, 1050 (2020)], a thrifty scheme showed how to project the quantum state into classical shadows and simultaneously predict $M$ different functions of a state with only $\mathcal{O}(\log_2 M)$ measurements, independent of the system size and saturating the information-theoretical limit. Here, we experimentally explore the feasibility of the scheme in the realistic scenario with a finite number of measurements and noisy operations. We prepare a four-qubit GHZ state and show how to estimate expectation values of multiple observables and Hamiltonians. We compare the measurement strategies with uniform, biased, and derandomized classical shadows to conventional ones that sequentially measure each state function exploiting either importance sampling or observable grouping. We next demonstrate the estimation of nonlinear functions using classical shadows and analyze the entanglement of the prepared quantum state. Our experiment verifies the efficacy of exploiting (derandomized) classical shadows and sheds light on efficient quantum computing with noisy intermediate-scale quantum hardware.
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