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Multi-Mode Bus Coupling Architecture of Superconducting Quantum Processor
Changhao Zhao, Yongcheng He, Xiao Geng, Kaiyong He, Genting Dai, Jianshe Liu, and Wei Chen
Chin. Phys. Lett. 2023, 40 (1):
010301
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DOI: 10.1088/0256-307X/40/1/010301
Resonators in circuit quantum electrodynamics systems naturally carry multiple modes, which may have non-negligible influence on qubit parameters and device performance. While new theories and techniques are under investigation to deal with the multi-mode effects in circuit quantum electrodynamics systems, researchers have proposed novel engineering designs featuring multi-mode resonators to achieve enhanced functionalities of superconducting quantum processors. Here, we propose multi-mode bus coupling architecture, in which superconducting qubits are coupled to multiple bus resonators to gain larger coupling strength. Applications of multi-mode bus couplers can be helpful for improving iSWAP gate fidelity and gate speed beyond the limit of single-mode scenario. The proposed multi-mode bus coupling architecture is compatible with a scalable variation of the traditional bus coupling architecture. It opens up new possibilities for realization of scalable superconducting quantum computation with circuit quantum electrodynamics systems.
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Flat Top Optical Frequency Combs Based on a Single-Core Quantum Cascade Laser at Wavelength of $\sim$ 8.7 μm
Yu Ma, Wei-Jiang Li Yun-Fei, Xu, Jun-Qi Liu, Ning Zhuo, Ke Yang, Jin-Chuan Zhang, Shen-Qiang Zhai, Shu-Man Liu, Li-Jun Wang, and Feng-Qi Liu
Chin. Phys. Lett. 2023, 40 (1):
014201
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DOI: 10.1088/0256-307X/40/1/014201
We present optical frequency combs with a spectral emission of 48 cm$^{-1}$ and an output power of 420 mW based on a single-core quantum cascade laser at $\lambda \sim 8.7$ µm. A flat top spectrum sustains up to 130 comb modes delivering $\sim$ 3.2 mW of optical power per mode, making it a valuable tool for dual comb spectroscopy. The homogeneous gain medium, relying on a slightly diagonal bound-to-continuum structure, promises to provide a broad and stable gain for comb operating. Remarkably, the dispersion of this device is measured within 300 fs$^{2}$/mm to ensure stable comb operation over 90% of the total current range. The comb is observed with a narrow beatnote linewidth around 2 kHz and has weak dependence on the applied current for stable comb operation.
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Superscattering of Underwater Sound via Deep Learning Approach
Wenjie Miao, Zhiang Linghu, Qiujiao Du, Pai Peng, and Fengming Liu
Chin. Phys. Lett. 2023, 40 (1):
014301
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DOI: 10.1088/0256-307X/40/1/014301
We design a multilayer cylindrical structure to realize superscattering of underwater sound. Because of the near degeneracy of resonances in multiple channels of the structure, the scattering contributions from these resonances can overlap to break the single-channel limit of subwavelength objects. However, tuning the design parameters to achieve the target response is an optimization process that is tedious and time-consuming. Here, we demonstrate that a well-trained tandem neural network can deal with this problem efficiently, which can not only forwardly predict the scattering spectra of the multilayer structure with high precision, but also inversely design the required structural parameters efficiently.
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Observation of Charge Density Wave in Layered Hexagonal Cu$_{1.89}$Te Single Crystal
Wenshuai Gao, Zheng Chen, Wensen Wei, Chao Yan, Shasha Wang, Jin Tang, Ranran Zhang, Lixun Cheng, Pengfei Nan, Jie Wang, Yuyan Han, Chuanying Xi, Binghui Ge, Lin He, Haifeng Du, Wei Ning, Xiangde Zhu, and Mingliang Tian
Chin. Phys. Lett. 2023, 40 (1):
017101
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DOI: 10.1088/0256-307X/40/1/017101
We report comprehensive transport, electron microscopy and Raman spectroscopy studies on transition-metal chalcogenides Cu$_{1.89}$Te single crystals. The metallic Cu$_{1.89}$Te displays successive metal-semiconductor transitions at low temperatures and almost ideal linear MR when magnetic field up to 33 T. Through the electron diffraction patterns, the stable room-temperature phase is identified as a $3 \times 3\times 2$ modulated superstructure based on the Nowotny hexagonal structure. The superlattice spots of transmission electron microscopy and scanning tunneling microscopy clearly show the structural transitions from the room-temperature commensurate I phase, named as C-I phase, to the low temperature commensurate II (C-II) phase. All the results can be understood in terms of charge density wave (CDW) instability, yielding intuitive evidences for the CDW formations in Cu$_{1.89}$Te. The additional Raman modes below room temperature further reveal that the zone-folded phonon modes may play an important role on the CDW transitions. Our research sheds light on the novel electron features of Cu$_{1.89}$Te at low temperature, and may provide potential applications for future nano-devices.
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Fe$_{1+y}$Te$_{x}$Se$_{1-x}$: A Delicate and Tunable Majorana Material
Fazhi Yang, Giao Ngoc Phan, Renjie Zhang, Jin Zhao, Jiajun Li, Zouyouwei Lu, John Schneeloch, Ruidan Zhong, Mingwei Ma, Genda Gu, Xiaoli Dong, Tian Qian, and Hong Ding
Chin. Phys. Lett. 2023, 40 (1):
017401
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DOI: 10.1088/0256-307X/40/1/017401
We report the observation for the $p_{z}$ electron band and the band inversion in Fe$_{1+y}$Te$_{x}$Se$_{1-x}$ with angle-resolved photoemission spectroscopy. Furthermore, we found that excess Fe ($y> 0$) inhibits the topological band inversion in Fe$_{1+y}$Te$_{x}$Se$_{1-x}$, which explains the absence of Majorana zero modes in previous reports for Fe$_{1+y}$Te$_{x}$Se$_{1-x}$ with excess Fe. Based on our analysis of different amounts of Te doping and excess Fe, we propose a delicate topological phase in this material. Thanks to this delicate phase, one may be able to tune the topological transition via applying lattice strain or carrier doping.
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Theoretical Prediction of Superconductivity in Boron Kagome Monolayer: $M$B$_{3}$ ($M$ = Be, Ca, Sr) and the Hydrogenated CaB$_{3}$
Liu Yang, Ya-Ping Li, Hao-Dong Liu, Na Jiao, Mei-Yan Ni, Hong-Yan Lu, Ping Zhang, and C. S. Ting
Chin. Phys. Lett. 2023, 40 (1):
017402
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DOI: 10.1088/0256-307X/40/1/017402
Using first-principles calculations, we predict a new type of two-dimensional (2D) boride $M$B$_{3}$ ($M$ = Be, Ca, Sr), constituted by boron kagome monolayer and the metal atoms adsorbed above the center of the boron hexagons. The band structures show that the three $M$B$_{3}$ compounds are metallic, thus the possible phonon-mediated superconductivity is explored. Based on the Eliashberg equation, for BeB$_{3}$, CaB$_{3}$, and SrB$_{3}$, the calculated electron–phonon coupling constants $\lambda $ are 0.46, 1.09, and 1.33, and the corresponding superconducting transition temperatures $T_{\rm c}$ are 3.2, 22.4, and 20.9 K, respectively. To explore superconductivity with higher transition temperature, hydrogenation and charge doping are further considered. The hydrogenated CaB$_{3}$, i.e., HCaB$_{3}$, is stable, with the enhanced $\lambda $ of 1.39 and a higher $T_{\rm c}$ of 39.3 K. Moreover, with further hole doping at the concentration of $5.8\times 10^{11}$ hole/cm$^{2}$, the $T_{\rm c}$ of HCaB$_{3}$ can be further increased to 44.2 K, exceeding the McMillan limit. The predicted $M$B$_{3}$ and HCaB$_{3}$ provide new platforms for investigating 2D superconductivity in boron kagome lattice since superconductivity based on monolayer boron kagome lattice has not been studied before.
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Growth and Characterization of a New Superconductor GaBa$_{2}$Ca$_{3}$Cu$_{4}$O$_{11+\delta}$
Xue Ming, Chengping He, Xiyu Zhu, Huiyang Gou, and Hai-Hu Wen
Chin. Phys. Lett. 2023, 40 (1):
017403
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DOI: 10.1088/0256-307X/40/1/017403
We successfully grow a new superconductor GaBa$_{2}$Ca$_{3}$Cu$_{4}$O$_{11+ \delta}$ (Ga-1234) with a transition temperature of 113 K, using the Walker-type high-pressure synthesis apparatus. X-ray diffraction measurements on the powderized samples show a mixture of the Ga-1234 phase and the Ca$_{0.85}$CuO$_{2}$ phase, and the former is dominant. Under the scanning electron microscope, plate-like crystals of the Ga-based 1234 phase with shiny surfaces can be seen. The obtained local chemical compositions revealed by energy dispersion x-ray spectroscopy are very close to the stoichiometric values. On some sub-millimeter crystal-like samples of the 1234 phase, we obtain a full Meissner shielding volume. From the temperature-dependent magnetizations, we determine the irreversibility fields and find that the system exhibits a highly anisotropic behavior.
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Strain-Enabled Control of Chiral Magnetic Structures in MnSeTe Monolayer
Zhiwen Wang, Jinghua Liang, and Hongxin Yang
Chin. Phys. Lett. 2023, 40 (1):
017501
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DOI: 10.1088/0256-307X/40/1/017501
Chiral magnetic states are promising for future spintronic applications. Recent progress of chiral spin textures in two-dimensional magnets, such as chiral domain walls, skyrmions, and bimerons, have been drawing extensive attention. Here, via first-principles calculations, we show that biaxial strain can effectively manipulate the magnetic parameters of the Janus MnSeTe monolayer. Interestingly, we find that both the magnitude and the sign of the magnetic constants of the Heisenberg exchange coupling, Dzyaloshinskii–Moriya interaction and magnetocrystalline anisotropy can be tuned by strain. Moreover, using micromagnetic simulations, we obtain the distinct phase diagram of chiral spin texture under different strains. Especially, we demonstrate that abundant chiral magnetic structures including ferromagnetic skyrmion, skyrmionium, bimeron, and antiferromagnetic spin spiral can be induced in the MnSeTe monolayer. We also discuss the effect of temperature on these magnetic structures. The findings highlight the Janus MnSeTe monolayer as a good candidate for spintronic nanodevices.
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Latest Data Constraint of Some Parameterized Dark Energy Models
Jing Yang, Xin-Yan Fan, Chao-Jun Feng, and Xiang-Hua Zhai
Chin. Phys. Lett. 2023, 40 (1):
019801
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DOI: 10.1088/0256-307X/40/1/019801
Using various latest cosmological datasets including type-Ia supernovae, cosmic microwave background radiation, baryon acoustic oscillations, and estimations of the Hubble parameter, we test some dark-energy models with parameterized equations of state and try to distinguish or select observation-preferred models. We obtain the best fitting results of the six models and calculate their values of the Akaike information criteria and Bayes information criterion. We can distinguish these dark energy models from each other by using these two information criterions. However, the $\varLambda $CDM model remains the best fit model. Furthermore, we perform geometric diagnostics including statefinder and $Om$ diagnostics to understand the geometric behavior of the dark energy models. We find that the six dark-energy models can be distinguished from each other and from $\varLambda $CDM, Chaplygin gas, quintessence models after the statefinder and $Om$ diagnostics are performed. Finally, we consider the growth factor of the dark-energy models with comparison to the $\varLambda $CDM model. Still, we find the models can be distinguished from each other and from the $\varLambda $CDM model through the growth factor approximation.
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15 articles
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