Coherent spin dynamics of rare-earth doped crystals in the high-cooperativity regime

Abstract

Rare-earth doped crystals have long coherence times and the potential to provide quantum interfaces between microwave and optical photons. Such applications benefit from a high cooperativity between the spin ensemble and a microwave cavity-this motivates an increase in the rare-earth ion concentration which in turn impacts the spin coherence lifetime. We measure spin dynamics of two rare-earth spin species, 145 Nd and Yb, doped into Y 2 SiO 5 , coupled to a planar microwave resonator in the high-cooperativity regime, in the temperature range 1.2 K to 14 mK. We identify relevant decoherence mechanisms, including instantaneous diffusion arising from resonant spins and temperature-dependent spectral diffusion from impurity electron and nuclear spins in the environment. We explore two methods to mitigate the effects of spectral diffusion in the Yb system in the low-temperature limit, first, using magnetic fields of up to 1 T to suppress impurity spin dynamics and, second, using transitions with low effective g factors to reduce sensitivity to such dynamics. Finally, we demonstrate how the "clock transition" present in the 171 Yb system at zero field can be used to increase coherence times up to T 2 = 6(1) ms.

Coherent optical-microwave interface for manipulation of low-field electronic clock transitions in 171Yb3+:Y2SiO5

“…4c. This can be compared to the T 2 = (6 ± 1) ms obtained in a parallel study by Alexander et al 49 in a Y 2 SiO 5 crystal doped with 5 ppm of 171 Yb 3+ . In this context, it is also worth noting that we measured the optical coherence time in both crystals, and found a similar relative difference of (0.610 ± 0.050) ms and (1.05 ± 0.130) ms for the 5 and 2 ppm doping, respectively (see Supplementary Note 3).…”

Strain-mediated ion-ion interaction in rare-earth-doped solids

“…In these light-matter interfaces, the optical depth of the medium is an important figure of merit since it enables high storage and retrieval efficiency [10,11,5]. However, reaching large optical depths usually comes with working with large atomic concentrations, leading to reinforced ion-ion interactions and thereby enhanced decoherence [12,13,14,15,16,17].…”

Strain-mediated ion–ion interaction in rare-earth-doped solids

“…In these light-matter interfaces, the optical depth of the medium is an important figure of merit since it enables high storage and retrieval efficiency [5,10,11]. However, reaching large optical depths usually comes with working with large atomic concentrations, leading to reinforced ion-ion interactions and thereby enhanced decoherence [12][13][14][15][16][17]. * Author to whom any correspondence should be addressed.…”