Kavli Affiliate: Irfan Siddiqi
| First 5 Authors: D. Dominic Briseño-Colunga, Bibek Bhandari, Debmalya Das, Long B. Nguyen, Yosep Kim
| Summary:
Modern superconducting and semiconducting quantum hardware use external
charge and microwave flux drives to both tune and operate devices. However,
each external drive is susceptible to low-frequency (e.g., $1/f$) noise that
can drastically reduce the decoherence lifetime of the device unless the drive
is placed at specific operating points that minimize the sensitivity to
fluctuations. We show that operating a qubit in a driven frame using two
periodic drives of distinct commensurate frequencies can have advantages over
both monochromatically driven frames and static frames with constant offset
drives. Employing Floquet theory, we analyze the spectral and lifetime
characteristics of a two-level system under weak and strong bichromatic drives,
identifying drive-parameter regions with high coherence (sweet spots) and
highlighting regions where coherence is limited by additional sensitivity to
noise at the drive frequencies (sour spots). We present analytical expressions
for quasienergy gaps and dephasing rates, demonstrating that bichromatic
driving can alleviate the trade-off between DC and AC noise robustness observed
in monochromatic drives. This approach reveals continuous manifolds of doubly
dynamical sweet spots, along which drive parameters can be varied without
compromising coherence. Our results motivate further study of bichromatic
Floquet engineering as a powerful strategy for maintaining tunability in
high-coherence quantum systems.
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