Bonn 2025 – scientific programme

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QI: Fachverband Quanteninformation

QI 36: Poster – Quantum Information (joint session QI/Q)

QI 36.2: Poster

Thursday, March 13, 2025, 17:00–19:00, Tent

Intensity Stabilization in Fiber Amplifiers: Effects on Phase Noise, Linewidth, and Qubit Coherence — •Jia-Yang Gao, Jasper Phua Sing Cheng, Morteza Ahmadi, and Manas Mukherjee — Centre for Quantum Technologies, National University of Singapore

Intensity noise is a factor limiting the coherence time of qubits in trapped ion quantum systems. Previously, we observed that using a Thulium-doped fiber amplifier (TDFA) introduces intensity fluctuations to the input seed laser, thus limiting the coherence time. To address this issue, we developed an intensity stabilization setup for a 1762 nm laser used for quadrupole transition, employing an acousto-optic modulator (AOM) with an electrical feedback servo. Our results demonstrate that this setup can reduce intensity noise by up to 20 dB from DC to 10 kHz without introducing additional phase noise and broadening the linewidth to the input signal. The phase noise and linewidth of the laser was analyzed using delayed self-heterodyne interferometry (DSHI). We also cross-check the stabilized beam using a single ion in our ion trap setup. Based on the Rabi oscillation results at different power levels, we observe an improvement in coherence time.

Keywords: Intensity stabilization; Delayed self-heterodyne interferometry; Thulium-doped fiber amplifier; Phase noise and Linewidth; Rabi Oscillation