Ramsey oscillations typically exhibit an exponential decay envelope due to environmental noise. However,recent experiments have observed nonmonotonic Ramsey fringes characterized by beating patterns, which deviate fro...Ramsey oscillations typically exhibit an exponential decay envelope due to environmental noise. However,recent experiments have observed nonmonotonic Ramsey fringes characterized by beating patterns, which deviate from the standard behavior. These beating patterns have primarily been attributed to charge-noise fluctuations.In this paper, we have experimentally observed Ramsey fringe with beating pattern for transmon qubits, and traced the origin to electric instruments induced flux noise.展开更多
We report the implementation of qubit-lubit coupling in a three-dimensional （3D） cavity, using the exchange of virtual photons, to realize logical operations. We measure single photon and multi-photon transitions in...We report the implementation of qubit-lubit coupling in a three-dimensional （3D） cavity, using the exchange of virtual photons, to realize logical operations. We measure single photon and multi-photon transitions in this qubit-qubit coupling system and obtain its energy avoided-crossing spectrum. With ac-Stark effect, fast control of the qubits is achieved to tune the effective coupling on and off and the state-swap gate SWAP is successfully constructed. Moreover, using two-photon transition between the ground state and doubly observed. A quarter period of this oscillation corresponds to states, bSWAP and are the foundations of future gate excited states, a kind of two-photon Rabi-like oscillation is the logical gate bSbSWAP, which is used for generating Bell preparation of two-qubit Bell states and realization of CNOT展开更多
1|Introduction Achieving practical quantum computers(PQCs)each based on millions and even billons of integrated quantum bits(qubits)is essential for tackling real-world computational tasks involving quantum phenomena ...1|Introduction Achieving practical quantum computers(PQCs)each based on millions and even billons of integrated quantum bits(qubits)is essential for tackling real-world computational tasks involving quantum phenomena at atomic and molecular levels[1,2]such as drug discovery[3]and materials design[4];conventional supercomputers based on digital technology are inherently inefficient for such problems.Our recent analysis[5]of dimensional scalability for transmon qubit(i.e.,transmission line shunted plasma oscillation qubit[6]).展开更多
As superconducting quantum processors scale,a key challenge is maintaining high coherence times and fidelity control over numerous qubits.We propose an automatic frequency allocation method for frequency-tunable qubit...As superconducting quantum processors scale,a key challenge is maintaining high coherence times and fidelity control over numerous qubits.We propose an automatic frequency allocation method for frequency-tunable qubits that equally considers coherence-limited fidelity and crosstalk-induced control errors during the allocation process.By employing a weighted average of the objective functions for coherence time and crosstalk,we numerically calculate gate fidelity to establish an open-loop optimization for determining suitable weight factors.This results in an efficient objective function for frequency optimization.We apply our method to frequency-tunable transmon qubits with tunable couplers,both theoretically and experimentally.The numerical results demonstrate significant advantages,including substantial reductions in gate errors and faster operation times,especially at higher qubit counts.Experimentally,our approach successfully achieves approximately 99.9%single-qubit fidelity on a nine-qubit chip.展开更多
Superconducting transmon qubits are the leading platform in solid-state quantum computing and quantum simulation applications.In this work,we develop a fabrication process for the transmon multiqubit device with a nio...Superconducting transmon qubits are the leading platform in solid-state quantum computing and quantum simulation applications.In this work,we develop a fabrication process for the transmon multiqubit device with a niobium base layer,shadow-evaporated Josephson junctions,and airbridges across the qubit control lines to suppress crosstalk.Our results show that these multiqubit devices have well-characterized readout resonators,and that the energy relaxation and Ramsey(spin-echo)dephasing times are up to∼40µs and 14(47)µs,respectively.We perform single-qubit gate operations that demonstrate a maximum gate fidelity of 99.97%.In addition,two-qubit vacuum Rabi oscillations are measured to evaluate the coupling strength between qubits,and the crosstalk among qubits is found to be less than 1%with the fabricated airbridges.Further improvements in qubit coherence performance using this fabrication process are also discussed.展开更多
We propose an effective method to realize the quantum phase gate the system in which the transmon qubits are capacitively coupled to of one qubit simultaneously controlling N qubits. We use a superconducting transmiss...We propose an effective method to realize the quantum phase gate the system in which the transmon qubits are capacitively coupled to of one qubit simultaneously controlling N qubits. We use a superconducting transmission line resonator driven by a strong microwave field. In our scheme, the phase gate can be realized in a time （nanosecond-scale） much shorter than deco herence time （microsecond-scale）, and it is more immune to the l/（charge noise and has longer dephasing time due to the fa vorable properties of the transmon qubits in the system.展开更多
文摘Ramsey oscillations typically exhibit an exponential decay envelope due to environmental noise. However,recent experiments have observed nonmonotonic Ramsey fringes characterized by beating patterns, which deviate from the standard behavior. These beating patterns have primarily been attributed to charge-noise fluctuations.In this paper, we have experimentally observed Ramsey fringe with beating pattern for transmon qubits, and traced the origin to electric instruments induced flux noise.
基金Project supported by the National Basic Research and Development Program of China(Grant No.2011CBA00304)the National Natural Science Foundation of China(Grant Nos.60836001 and 61174084)the Tsinghua University Initiative Scientific Research Program,China(Grant No.20131089314)
文摘We report the implementation of qubit-lubit coupling in a three-dimensional （3D） cavity, using the exchange of virtual photons, to realize logical operations. We measure single photon and multi-photon transitions in this qubit-qubit coupling system and obtain its energy avoided-crossing spectrum. With ac-Stark effect, fast control of the qubits is achieved to tune the effective coupling on and off and the state-swap gate SWAP is successfully constructed. Moreover, using two-photon transition between the ground state and doubly observed. A quarter period of this oscillation corresponds to states, bSWAP and are the foundations of future gate excited states, a kind of two-photon Rabi-like oscillation is the logical gate bSbSWAP, which is used for generating Bell preparation of two-qubit Bell states and realization of CNOT
基金financed by the Swedish Governmental Agency for Innovation Systems(Grant VINNOVA,2024-00436)the European QuantEra II Program(Grant 101017733)via the Swedish Research Council(Grant 2021-06025).
文摘1|Introduction Achieving practical quantum computers(PQCs)each based on millions and even billons of integrated quantum bits(qubits)is essential for tackling real-world computational tasks involving quantum phenomena at atomic and molecular levels[1,2]such as drug discovery[3]and materials design[4];conventional supercomputers based on digital technology are inherently inefficient for such problems.Our recent analysis[5]of dimensional scalability for transmon qubit(i.e.,transmission line shunted plasma oscillation qubit[6]).
文摘As superconducting quantum processors scale,a key challenge is maintaining high coherence times and fidelity control over numerous qubits.We propose an automatic frequency allocation method for frequency-tunable qubits that equally considers coherence-limited fidelity and crosstalk-induced control errors during the allocation process.By employing a weighted average of the objective functions for coherence time and crosstalk,we numerically calculate gate fidelity to establish an open-loop optimization for determining suitable weight factors.This results in an efficient objective function for frequency optimization.We apply our method to frequency-tunable transmon qubits with tunable couplers,both theoretically and experimentally.The numerical results demonstrate significant advantages,including substantial reductions in gate errors and faster operation times,especially at higher qubit counts.Experimentally,our approach successfully achieves approximately 99.9%single-qubit fidelity on a nine-qubit chip.
基金supported by the National Key R&D Program of China(Grant No.2016YFA0300601)the National Natural Science Foundation of China(Grant Nos.11934018 and 11874063)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB28000000)the Key-Area Research and Development Program of GuangDong Province,China(Grant No.2018B030326001)。
文摘Superconducting transmon qubits are the leading platform in solid-state quantum computing and quantum simulation applications.In this work,we develop a fabrication process for the transmon multiqubit device with a niobium base layer,shadow-evaporated Josephson junctions,and airbridges across the qubit control lines to suppress crosstalk.Our results show that these multiqubit devices have well-characterized readout resonators,and that the energy relaxation and Ramsey(spin-echo)dephasing times are up to∼40µs and 14(47)µs,respectively.We perform single-qubit gate operations that demonstrate a maximum gate fidelity of 99.97%.In addition,two-qubit vacuum Rabi oscillations are measured to evaluate the coupling strength between qubits,and the crosstalk among qubits is found to be less than 1%with the fabricated airbridges.Further improvements in qubit coherence performance using this fabrication process are also discussed.
基金supported by the National Natural Science Foundation of China (Grant No. 10947017/A05)the Key Lab of Novel Thin Film Solar Cells (Grant No. KF200912)Graduates’ Innovative Scientific Research Project of Zhejiang Province (Grant No. 2011831)
文摘We propose an effective method to realize the quantum phase gate the system in which the transmon qubits are capacitively coupled to of one qubit simultaneously controlling N qubits. We use a superconducting transmission line resonator driven by a strong microwave field. In our scheme, the phase gate can be realized in a time （nanosecond-scale） much shorter than deco herence time （microsecond-scale）, and it is more immune to the l/（charge noise and has longer dephasing time due to the fa vorable properties of the transmon qubits in the system.
