Coherent properties of single rare-earth spin qubits

TL;DR

This paper demonstrates the coherent control and readout of single Ce$^{3+}$ electron spins in YAG crystals, highlighting their potential for integrated quantum photonics and long-lived quantum memory applications.

Contribution

It provides the first experimental demonstration of high-fidelity optical initialization, manipulation, and readout of single rare-earth electron spins with long coherence times.

Findings

Spin coherence lifetime reaches 2 ms under dynamic decoupling.

Strong hyperfine coupling to aluminium nuclear spins observed.

Ce$^{3+}$ spins are promising for integrated quantum photonics.

Abstract

Rare-earth-doped crystals are excellent hardware for quantum storage of optical information. Additional functionality of these materials is added by their waveguiding properties allowing for on-chip photonic networks. However, detection and coherent properties of rare-earth single-spin qubits have not been demonstrated so far. Here, we present experimental results on high-fidelity optical initialization, effcient coherent manipulation, and optical readout of a single electron spin of Ce$^{3+}$ ion in a YAG crystal. Under dynamic decoupling, spin coherence lifetime reaches $T_2$=2 ms and is almost limited by the measured spin-lattice relaxation time $T_1$=3.8 ms. Strong hyperfine coupling to aluminium nuclear spins suggests that cerium electron spins can be exploited as an interface between photons and long-lived nuclear spin memory. Combined with high brightness of Ce$^{3+}$ emission and a possibility of creating photonic circuits out of the host material, this makes cerium spins an interesting option for integrated quantum photonics.