Superconducting transmon qubits with fixed frequencies are widely used in many applications due to their advantages of better coherence and less control lines compared to the frequency tunable qubits.However,any uncon...Superconducting transmon qubits with fixed frequencies are widely used in many applications due to their advantages of better coherence and less control lines compared to the frequency tunable qubits.However,any uncontrolled interactions with the qubits such as the two-level systems could lead to adverse impacts,degrading the qubit coherence and inducing crosstalk.To mitigate the detrimental effect from uncontrolled interactions between qubits and defect modes in fixed-frequency transmon qubits,we propose and demonstrate an active approach using an off-resonance microwave drive to dress the qubit and to induce the ac-Stark shift on the qubit frequency.We show experimentally that the qubit frequency can be tuned well away from the defect mode so that the impact on qubit coherence is greatly reduced while maintaining the universal controls of the qubit initialization,readout,and single-qubit gate operations.Our approach provides an effective way for tuning the qubit frequency and suppressing the detrimental effect from the defect modes that happen to be located close to the qubit frequency.展开更多
Dielectric properties offerrite ceramics have been less reported than their magnetic properties.Ourrecent study indicated that ferrite ceramics with very low dielectric loss tangent can be developed byusing appropriat...Dielectric properties offerrite ceramics have been less reported than their magnetic properties.Ourrecent study indicated that ferrite ceramics with very low dielectric loss tangent can be developed byusing appropriate sintering aids,together with the optimization of other sintering parameters suchas sintering temperature and time duration.Among various candidates of sintering aids,Bi_(2)O_(3)isthe most promising one.It is important to find that the optimized concentration of sintering aid forfull densification is not sufficient to achieve lowest dielectric loss tangent.This short review was aimed to summarize the understanding in microstructural evolution,grain growth,densificationand dielectric properties offerrite ceramics as a function of sintering aid concentration and sinteringparameters,which could be used as a guidance to develop ferrite ceramics with low dielectric losstangents for various applications.展开更多
We report the high-purity identification of cosmic-ray(CR)protons and a precise measurement of their energy spectrum from 0.15 to 12 PeV using the Large High Altitude Air Shower Observatory(LHAASO).Abundant event stat...We report the high-purity identification of cosmic-ray(CR)protons and a precise measurement of their energy spectrum from 0.15 to 12 PeV using the Large High Altitude Air Shower Observatory(LHAASO).Abundant event statistics,combined with the simultaneous detection of electrons/photons,muons,and Cherenkov light in air showers,enable spectroscopic measurements with statistical and systematic precision comparable to satellite data at lower energies.The proton spectrum shows significant hardening relative to low-energy extrapolations,culminating at 3 PeV,followed by sharp softening.This distinct spectral structure closely aligned with the knee in the all-particle spectrum points to the emergence of a new CR component at PeV energies that might be linked to the dozens of PeVatrons recently discovered by LHAASO,and offers crucial clues to the origin of Galactic cosmic rays.展开更多
基金partly supported by the National Natural Science Foundation of China(Grant Nos.12204050,11890704,and 12004042)the Beijing Natural Science Foundation(Grant No.Z190012)the Key-Area Research and Development Program of Guang Dong Province(Grant No.2018B030326001)。
文摘Superconducting transmon qubits with fixed frequencies are widely used in many applications due to their advantages of better coherence and less control lines compared to the frequency tunable qubits.However,any uncontrolled interactions with the qubits such as the two-level systems could lead to adverse impacts,degrading the qubit coherence and inducing crosstalk.To mitigate the detrimental effect from uncontrolled interactions between qubits and defect modes in fixed-frequency transmon qubits,we propose and demonstrate an active approach using an off-resonance microwave drive to dress the qubit and to induce the ac-Stark shift on the qubit frequency.We show experimentally that the qubit frequency can be tuned well away from the defect mode so that the impact on qubit coherence is greatly reduced while maintaining the universal controls of the qubit initialization,readout,and single-qubit gate operations.Our approach provides an effective way for tuning the qubit frequency and suppressing the detrimental effect from the defect modes that happen to be located close to the qubit frequency.
文摘Dielectric properties offerrite ceramics have been less reported than their magnetic properties.Ourrecent study indicated that ferrite ceramics with very low dielectric loss tangent can be developed byusing appropriate sintering aids,together with the optimization of other sintering parameters suchas sintering temperature and time duration.Among various candidates of sintering aids,Bi_(2)O_(3)isthe most promising one.It is important to find that the optimized concentration of sintering aid forfull densification is not sufficient to achieve lowest dielectric loss tangent.This short review was aimed to summarize the understanding in microstructural evolution,grain growth,densificationand dielectric properties offerrite ceramics as a function of sintering aid concentration and sinteringparameters,which could be used as a guidance to develop ferrite ceramics with low dielectric losstangents for various applications.
基金supported by the National Key R&D Program of China(2024YFA1611401,2024YFA1611402,2024YFA1611403,and 2024YFA1611404)the National Natural Science Foundation of China(12393851,12393852,12393853,12393854,12205314,12105301,12305120,12261160362,12105294,U1931201,12375107,12275280,12105293,11905240,12375106,and 12261141691)+3 种基金Innovation Project of IHEP(E25451U2)Sichuan Province Science Foundation for Distinguished Young Scholars(2022JDJQ0043)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(CAS YIPA)(2023019)the Institute of Plateau Meteorology,CMA Chengdu to maintain meteorological data,and Thailand’s National Science and Technology Development Agency(NSTDA)and National Research Council of Thailand(NRCT)under the High-Potential Research Team Grant Program(N42A650868)。
文摘We report the high-purity identification of cosmic-ray(CR)protons and a precise measurement of their energy spectrum from 0.15 to 12 PeV using the Large High Altitude Air Shower Observatory(LHAASO).Abundant event statistics,combined with the simultaneous detection of electrons/photons,muons,and Cherenkov light in air showers,enable spectroscopic measurements with statistical and systematic precision comparable to satellite data at lower energies.The proton spectrum shows significant hardening relative to low-energy extrapolations,culminating at 3 PeV,followed by sharp softening.This distinct spectral structure closely aligned with the knee in the all-particle spectrum points to the emergence of a new CR component at PeV energies that might be linked to the dozens of PeVatrons recently discovered by LHAASO,and offers crucial clues to the origin of Galactic cosmic rays.
