Spectator-transition crosstalk in a spin-3/2 silicon vacancy qudit in silicon carbide revealed by broadband Ramsey interferometry

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Main Authors: Choi, Jun-Jae, Hwang, Seung-Jae, Paik, Seoyoung, Kim, Juhwan, UI-Hassan, Jawad, Son, Nguyen Tien, Abe, Hiroshi, Ohshima, Takeshi, Suk, Jaekwon, Jeong, Hyeon-Ho, Kim, Dong-Hee, Lee, Sang-Yun
Format: Preprint
Published: 2026
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author Choi, Jun-Jae
Hwang, Seung-Jae
Paik, Seoyoung
Kim, Juhwan
UI-Hassan, Jawad
Son, Nguyen Tien
Abe, Hiroshi
Ohshima, Takeshi
Suk, Jaekwon
Jeong, Hyeon-Ho
Kim, Dong-Hee
Lee, Sang-Yun
author_facet Choi, Jun-Jae
Hwang, Seung-Jae
Paik, Seoyoung
Kim, Juhwan
UI-Hassan, Jawad
Son, Nguyen Tien
Abe, Hiroshi
Ohshima, Takeshi
Suk, Jaekwon
Jeong, Hyeon-Ho
Kim, Dong-Hee
Lee, Sang-Yun
contents Color center spins in 4H-SiC offer a rare combination of wafer-scale materials maturity with long spin coherence and chip-level photonics, making them promising building blocks for scalable quantum technologies. In particular, the silicon vacancy hosts an S=3/2 ground state, a native qudit that enables compact encodings and subspace-selective control, but also introduces spectator transitions: short, detuned pulses can coherently drive non-addressed level pairs and create crosstalk. Here we use broadband Ramsey interferometry to reveal and quantify such spectator-transition crosstalk. Experimentally, the Ramsey Fourier spectra display multiple lines beyond the addressed single-quantum transition. Analytically, we map each line to a pairwise energy difference between qudit levels of the rotating-frame Hamiltonian and assign its weight via compact amplitudes set by the prepared state and the microwave pulse parameters, predicting a deterministic six-branch structure. Numerical time-domain propagation with the experimental sampling reproduces the detuning map, and the measured peak positions coincide with the analytic branch lines without frequency fitting. Together these results provide a practical, spectator-aware framework for multilevel control in the silicon vacancy qudit. The approach offers clear guidance to suppress crosstalk or, conversely, to exploit spectator lines, for example as additional constraints for in situ pulse calibration and for phase-sensitive quantum state and process estimation.
format Preprint
id arxiv_https___arxiv_org_abs_2601_15559
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Spectator-transition crosstalk in a spin-3/2 silicon vacancy qudit in silicon carbide revealed by broadband Ramsey interferometry
Choi, Jun-Jae
Hwang, Seung-Jae
Paik, Seoyoung
Kim, Juhwan
UI-Hassan, Jawad
Son, Nguyen Tien
Abe, Hiroshi
Ohshima, Takeshi
Suk, Jaekwon
Jeong, Hyeon-Ho
Kim, Dong-Hee
Lee, Sang-Yun
Quantum Physics
Color center spins in 4H-SiC offer a rare combination of wafer-scale materials maturity with long spin coherence and chip-level photonics, making them promising building blocks for scalable quantum technologies. In particular, the silicon vacancy hosts an S=3/2 ground state, a native qudit that enables compact encodings and subspace-selective control, but also introduces spectator transitions: short, detuned pulses can coherently drive non-addressed level pairs and create crosstalk. Here we use broadband Ramsey interferometry to reveal and quantify such spectator-transition crosstalk. Experimentally, the Ramsey Fourier spectra display multiple lines beyond the addressed single-quantum transition. Analytically, we map each line to a pairwise energy difference between qudit levels of the rotating-frame Hamiltonian and assign its weight via compact amplitudes set by the prepared state and the microwave pulse parameters, predicting a deterministic six-branch structure. Numerical time-domain propagation with the experimental sampling reproduces the detuning map, and the measured peak positions coincide with the analytic branch lines without frequency fitting. Together these results provide a practical, spectator-aware framework for multilevel control in the silicon vacancy qudit. The approach offers clear guidance to suppress crosstalk or, conversely, to exploit spectator lines, for example as additional constraints for in situ pulse calibration and for phase-sensitive quantum state and process estimation.
title Spectator-transition crosstalk in a spin-3/2 silicon vacancy qudit in silicon carbide revealed by broadband Ramsey interferometry
topic Quantum Physics
url https://arxiv.org/abs/2601.15559