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Coherent coupling of a superconducting flux-qubit to an electron spin ensemble in diamond
Xiaobo Zhu, Shiro Saito, Alexander Kemp, Kosuke Kakuyanagi, Shin-ichi Karimoto, Hayato Nakano, William J. Munro, Yasuhiro Tokura, Mark S. Everitt, Kae Nemoto, Makoto Kasu, Norikazu Mizuochi, Kouichi Semba
TL;DR
Superconducting-qubit coherence may be insufficient for large-scale computation, motivating quantum memories based on atomic or molecular systems. This paper couples a flux qubit to an NV− ensemble in diamond and observes strong coupling with coherent single-quantum energy exchange through vacuum Rabi oscillations.
Problem
Reported superconducting-qubit coherence times may be insufficient for future large-scale quantum computation, motivating engineered quantum memories based on atomic or molecular systems.
Method
The experiment attaches an implanted NV−-diamond sample to a gap-tunable flux qubit and measures the coupled system spectroscopically and through time-domain vacuum Rabi oscillations.
Results
A vacuum Rabi splitting of approximately 70 MHz and coherent exchange of a single quantum of energy were observed between the flux qubit and an ensemble of approximately 3×10^7 NV− centers.
Takeaways & Limitations
The demonstration is a first step toward a long-lived condensed-matter quantum memory and a possible microwave–optical interface.
Takeaways & Limitations
Near resonance, the vacuum Rabi oscillations decay in approximately 20 ns, with strong dephasing likely associated with P1 centers in the diamond.
Abstract
from arXiv · showhide
Electron-spin nitrogen-vacancy color centers in diamond are a natural candidate to act as a quantum memory for superconducting qubits because of their large collective coupling and long coherence times. We report here the first demonstration of strong coupling and coherent exchange of a single quantum of energy between a flux-qubit and an ensemble of nitrogen-vacancy color centers.