Fast superconducting qubit control with subharmonic drives

Area of Science:

• Quantum Computing
• Superconducting Qubits
• Quantum Control

Background:

• High-fidelity single-qubit gates require fast pulses and long qubit coherence times, which are often contradictory.
• Increased drive power for faster gates can lead to environmental heating and reduced qubit coherence.

Purpose of the Study:

• To develop a method for achieving rapid single-qubit gates without compromising qubit coherence.
• To address the challenge of contradictory requirements for gate speed and coherence in superconducting qubits.

Main Methods:

• Utilized subharmonic pumping of a transmon qubit's native Kerr nonlinearity at one-third of the resonant frequency.
• Employed filtering techniques to protect qubit coherence during rapid gate operations.
• Performed theoretical calculations on drive-induced multi-photon decay and power absorption.

Main Results:

• Demonstrated single-qubit gates as short as 37.4 ns with a fidelity of 99.91%.
• Showcased that the subharmonic Rabi rate is proportional to the applied drive amplitude cubed, enabling rapid gate operations.
• Theoretical analysis indicated that multi-photon decay does not limit qubit lifetime and the technique could reduce cryostat heating.

Conclusions:

• The subharmonic pumping technique effectively enables rapid, high-fidelity single-qubit gates.
• This method circumvents the trade-off between gate speed and coherence by mitigating environmental heating.
• The findings are vital for the development of large-scale quantum computers.