Magnetic strong coupling in a spin-photon system and transition to classical regime

Abstract

We study the energy level structure of the Tavis-Cumming model applied to an ensemble of independent magnetic spins $s=1/2$ coupled to a variable number of photons. Rabi splittings are calculated and their distribution is analyzed as a functin of photon number $n_{\max }$ and spin system size $N$. A sharp transition in the distribution of the Rabi frequency is found at $n_{\max }\approx N$. The width of the Rabi frequency spectrum diverges as $\sqrt{N}$ at this point. For increased number of photons $n_{\max }>N$, the Rabi frequencies converge to a value proportional to $\sqrt{n_{\max }}$. This behavior is interpreted as analogous to the classical spin resonance mechanism where the photon is treated as a classical field and one resonance peak is expected. We also present experimental data demonstrating cooperative, magnetic strong coupling between a spin system and photons, measured at room temperature. This points towards quantum computing implementation with magnetic spins, using cavity quantum-electrodynamics techniques.

Received 8 April 2010; revised manuscript received 17 June 2010; published 14 July 2010

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Cited by in corpus (3)

• Strong Coupling of a Spin Ensemble to a Superconducting Resonator
• Electron spin ensemble strongly coupled to a three-dimensional microwave cavity
• Spectroscopic properties of inhomogeneously broadened spin ensembles in a cavity