# Highly coherent spin states in carbon nanotubes coupled to cavity photons

## TL;DR

This paper demonstrates highly coherent spin states in carbon nanotubes coupled to cavity photons, highlighting their potential for scalable quantum information processing and coherent spin-spin interactions.

## Contribution

It introduces a circuit QED spin-photon interface with tunable coherence in carbon nanotube quantum dots, advancing spin qubit coupling via cavity photons.

## Key findings

- Identified electrically controlled spin transition with low decoherence rate
- Coherence properties consistent with hyperfine coupling in nanotubes
- Comparable to coherence in silicon-based circuit QED systems

## Abstract

Spins confined in quantum dots are considered as a promising platform for quantum information processing. While many advanced quantum operations have been demonstrated, experimental as well as theoretical efforts are now focusing on the development of scalable spin quantum bit architectures. One particularly promising method relies on the coupling of spin quantum bits to microwave cavity photons. This would enable the coupling of distant spins via the exchange of virtual photons for two qubit gate applications, which still remains to be demonstrated with spin qubits. Here, we use a circuit QED spin-photon interface to drive a single electronic spin in a carbon nanotube based double quantum dot using cavity photons. The microwave spectroscopy allows us to identify an electrically controlled spin transition with a decoherence rate which can be tuned to be as low as $250kHz$. We show that this value is consistent with the expected hyperfine coupling in carbon nanotubes. These coherence properties, which can be attributed to the use of pristine carbon nanotubes stapled inside the cavity, should enable coherent spin-spin interaction via cavity photons and compare favourably to the ones recently demonstrated in Si-based circuit QED experiments.