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Quantification of Single-Qubit Gates Performance

Kajsa Williams and Louis-S. Bouchard, researchers at the University of California, Los Angeles’ Center for Quantum Science and Engineering, developed and tested single-qubit gate performance with specially designed composite and adiabatic pulses.

While they discovered no significant improvements in gate leakage and seepage compared to normal gates, their ability to manage field error was considerably enhanced. Their findings were published on February 19th, 2024, in Intelligent Computing, a Science Partner Journal.

Quantum computing on modern noisy intermediate-scale quantum devices remains beneficial for specific applications. Attempting to extend the time and complexity of computations conducted on these devices rapidly results in an unsustainable quantity of inaccuracy.

Improving the resilience of the gates used to regulate system drift will reduce the buildup of errors, expanding the spectrum of feasible quantum computing applications. Williams and Bouchard's approaches for composite and adiabatic pulses that implement single-qubit gates increased robustness by roughly an order of magnitude.

Williams and Bouchard utilized Qiskit, a software tool, and the IBM Quantum Experience (IBM-QE) platform to construct and evaluate composite and adiabatic pulses for superconducting qubit control. They used calibration processes to find a carrier frequency for the pulses that would enable them to show improvement over the default pulse.

After determining the parameters for the composite pulses, they used Python to simulate their impact. Python was also utilized to look for parameters for the adiabatic pulses they created before they were implemented and validated on IBM-QE.

They employed specially designed pulses, including Gaussian, DRAG, and HS1 pulses, to operate a transmon qubit on the IBM-QE platform and Lima superconducting quantum processor. Performance evaluation was conducted using randomized benchmarking. Adiabatic full passage pulses were the most powerful of the pulses studied.

The study authors added, “The successful implementation of [adiabatic full passage] pulses only 2.8 to 5 times longer than single pulses makes composite [adiabatic full passage] schemes possible; otherwise, such pulses would consume an untenable proportion of the intrinsic coherence time.

Future research could focus on controlling leakage and seepage to reduce errors. The phenomenon known as leakage occurs when a qubit moves into higher energy levels that are not involved in the computation from the states that are intended for processing. Imperfections in control pulses or interactions with the environment might cause this.

Leakage is a concern because it can result in errors that are hard for conventional quantum error correction methods to fix. A similar idea is seepage, which describes the speed at which qubits emerge from the leakage state.

Seepage is also an issue, since certain qubits return to the incorrect states. Both leakage and seepage are essential concerns for determining the accuracy and robustness of quantum operations on NISQ devices.

Journal Reference:

Williams, K., et. al. (2024) Quantification of Robustness, Leakage, and Seepage for Composite and Adiabatic Gates on Modern NISQ Systems. Intelligent Computing. doi:10.34133/icomputing.0069


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