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Hardware-Efficient Microwave-Activated Tunable Coupling between Superconducting Qubits.
Bradley K Mitchell1,2, Ravi K Naik1,2, Alexis Morvan1,2
1Quantum Nanoelectronics Laboratory, University of California, Berkeley, Berkeley, California 94720, USA.
Physical Review Letters
|December 3, 2021
Summary
Researchers developed a new method for tunable quantum entanglement in superconducting circuits. This technique uses off-resonant driving to control qubit interactions, improving gate fidelity for quantum computation.
Area of Science:
- Quantum Information Science
- Superconducting Quantum Computing
Background:
- Achieving high-fidelity, tunable entanglement between qubits is essential for gate-based quantum computation.
- Current methods using flux-tunable qubits or coupling elements introduce complexity and noise.
Purpose of the Study:
- To demonstrate a novel method for inducing tunable ZZ interactions between fixed-frequency transmon qubits.
- To explore an alternative approach to controlled interactions in superconducting circuits, reducing reliance on tunable hardware.
Main Methods:
- Utilizing off-resonant microwave driving of two fixed-frequency transmon qubits to create a tunable ZZ interaction.
- Characterizing the tunable coupling strength and sign-flipping capability.
- Implementing a controlled-phase (CZ) gate using the developed interaction.
Main Results:
- Achieved tunable coupling strength over an order of magnitude larger than static coupling.
- Demonstrated the ability to change the sign of the interaction, enabling cancellation of idle coupling.
- Implemented a CZ gate with a fidelity of 99.43(1)%, limited by incoherent errors.
Conclusions:
- The off-resonant driving method provides a robust and scalable approach for tunable qubit interactions in large quantum processors.
- This technique is resilient to microwave crosstalk and allows flexible drive frequency selection.
- The demonstrated CZ gate fidelity highlights the potential of this method for advancing quantum computation.
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