分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The portal connecting the invisible and visible sectors is one of the most natural explanations of the dark world. However, the early-time dark matter production via the portal faces extremely stringent late-time constraints. To solve such tension, we construct the scalar-controlled kinetic mixing varying with the ultralight CP-even scalar's cosmological evolution. To realize this and eliminate the constant mixing, we couple the ultralight scalar within the mass range $10^{-33}\text{eV} \lesssim m_0 \ll \text{eV}$ with the heavy doubly charged messengers and impose the $\mathbb{Z}_2$ symmetry under the dark charge conjugation. Via the varying mixing, the $\text{keV}-\text{MeV}$ dark photon dark matter is produced through the early-time freeze-in when the scalar is misaligned from the origin and free from the late-time exclusions when the scalar does the damped oscillation and dynamically sets the kinetic mixing. We also find that the scalar-photon coupling emerges from the underlying physics, which changes the cosmological history and provides the experimental targets based on the fine-structure constant variation and the equivalence principle violation. To protect the scalar naturalness, we discretely re-establish the broken shift symmetry by embedding the minimal model into the $\mathbb{Z}_N$-protected model. When $N \sim 10$, the scalar's mass quantum correction can be suppressed much below $10^{-33}\text{eV}$. Moreover, utilizing two different methods, we precisely calculate the $\mathbb{Z}_N$-invariant Coleman-Weinberg potential to arbitrary orders. Finally, we explore the varying kinetic mixing in the Dirac gaugino model and the dark matter models via other varying portals.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Lan-Tian Feng
Ming Zhang
Xiao Xiong
Di Liu
Yu-Jie Cheng
Fang-Ming Jing
Xiao-Zhuo Qi
Yang Chen
De-Yong He
Guo-Ping Guo
Guang-Can Guo
Dao-Xin Dai
Xi-Feng Ren
摘要： As an important degree of freedom (DoF) in integrated photonic circuits, the orthogonal transverse mode provides a promising and flexible way to increasing communication capability, for both classical and quantum information processing. To construct large-scale on-chip multimode multi-DoF quantum systems, a transverse mode-encoded controlled-NOT (CNOT) gate is necessary. Here, through design and integrate transverse mode-dependent directional coupler and attenuators on a silicon photonic chip, we demonstrate the first multimode implementation of a two-qubit quantum gate. With the aid of state preparation and analysis parts, we show the ability of the gate to entangle two separated transverse mode qubits with an average fidelity of $0.89\pm0.02$ and the achievement of 10 standard deviations of violations in the quantum nonlocality verification. In addition, a fidelity of $0.82\pm0.01$ was obtained from quantum process tomography used to completely characterize the CNOT gate. Our work paves the way for universal transverse mode-encoded quantum operations and large-scale multimode multi-DoF quantum systems.
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