Thermal-fluctuator driven decoherence of an oscillator resonantly coupled to a two-level system
Thomas J. Antolin, Jonas Glatthard, Andrew D. Armour
TLDR
This paper details how thermal fluctuators degrade oscillator coherence when coupled to a two-level system, causing complex decay patterns.
Key contributions
- Explores how thermal fluctuators (TLFs) degrade oscillator coherence via a coupled two-level system (TLS).
- Shows single TLFs can induce coherence oscillations, sometimes replacing Rabi oscillations.
- Identifies bath-driven TLF transitions causing irreversible, coupling-sensitive coherence decay.
- Characterizes non-exponential coherence decay for TLF ensembles, comparing few vs. many TLFs.
Why it matters
This work offers a theoretical framework to understand how thermal fluctuators cause dephasing in quantum devices. It's crucial for designing more robust quantum technologies, such as superconducting and phononic resonators, by addressing a key source of decoherence.
Original Abstract
Recent experiments on a range of engineered quantum systems have highlighted the important role of interacting two-level systems (TLSs) in modifying device properties and generating fluctuations. Focusing on the case of an oscillator coupled to a single near-resonant TLS, we explore how interactions between the TLS and lower-frequency thermally activated two-level fluctuators (TLFs) degrade the oscillator's coherence. Depending on the strength of the couplings, a single TLF can give rise to coherence oscillations that appear alongside, or supplant, Rabi oscillations of the oscillator-TLS system. Bath-driven transitions in the TLF cause irreversible coherence decay at a rate that is highly sensitive to both the couplings and the transition rate. For an ensemble of TLFs, we identify and characterise the different regimes of non-exponential phase-averaging-driven coherence decay that the oscillator can display. Using numerical calculations, we examine the extent to which systems with just a few TLFs differ from the limit of a large (continuum) TLF ensemble. Our work provides a theoretical framework for understanding the interplay of coherent TLS interactions and TLF-induced dephasing in quantum devices such as superconducting and phononic resonators.
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