Coherence Time Extension by Large-Scale Optical Spin Polarization in a Rare-Earth Doped Crystal

Abstract

Optically addressable spins are actively investigated in quantum communication, processing, and sensing. Optical and spin coherence lifetimes, which determine quantum operation fidelity and storage time, are often limited by spin-spin interactions, which can be decreased by polarizing spins. Spin polarization can be achieved using optical pumping, large magnetic fields, or mK-range temperatures. Here, we show that optical pumping of a small fraction of ions with a fixed-frequency laser, coupled with spin-spin interactions and spin diffusion, leads to substantial spin polarization in a paramagnetic rare-earth doped crystal, 171 Yb 3þ ∶Y 2 SiO 5. Indeed, more than 90% spin polarization has been achieved at 2 K and zero magnetic field. Using this spin polarization mechanism, we further demonstrate an increase in optical coherence lifetime from 0.3 ms to 0.8 ms, due to a strong decrease in spin-spin interactions. This effect opens the way to new schemes for obtaining long optical and spin coherence lifetimes in various solid-state systems such as ensembles of rare-earth ions or color centers in diamond, which are of interest for a broad range of quantum technologies.

Remote distribution of non-classical correlations over 1250 modes between a telecom photon and a $^{171}$Yb$^{3+}$:Y$_2$SiO$_{5}$ crystal

“…In comparison, up to T AFC 2 = 92(9) µs has been measured in Pr 3+ :Y 2 SiO 5 [14], while the longest AFC coherence time of T AFC 2 = 300(30) µs was reached in 151 Eu 3+ :Y 2 SiO 5 [16]. Ultimately, the AFC coherence time is limited by the coherence time measured by photon echo, where in 171 Yb 3+ :Y 2 SiO 5 up to 800 µs was measured [32]. In the current experiment, we believe the laser linewidth to be the main limitation of the observed T AFC 2 value.…”

“…1(a). At zero magnetic field, these states have zero first-order Zeeman (ZEFOZ) effect, resulting in spin and optical coherence times comparable to those of non-Kramer ions [31,32]. At the same time, hyperfine splittings range from 288 MHz to 2.623 GHz (for 171 Yb 3+ in site II), typical of Kramer ions, and should therefore also allow high-bandwidth quantum memories [33].…”

Однородные и неоднородные ширины линий в оптических спектрах кристалла Y-=SUB=-2-=/SUB=-SiO-=SUB=-5-=/SUB=- : -=SUP=-171-=/SUP=-Yb-=SUP=-3+-=/SUP=-

“…4), все образцы обладают очень большими временами когерентности из-за эффекта ZEFOZ. В образце с концентрацией Yb 10 ppm затухание амплитуды эха хорошо аппроксимируется простой экспонентой, при этом получаем T 2 = 285 ± 6 µs (Ŵ h = 1.12 ± 0.02 kHz), что согласуется со значениями, измеренными на переходе 4g−1e при 2 K [9]. Образец с концентрацией 5 ppm обладает гораздо более длительным затуханием, которое также хорошо описывается простой экспонентой при значении T 2 = 685 ± 20 µs (Ŵ h = 465 ± 13 Hz), что близко к значению, приведенному в [5].…”

Erbium-Implanted Materials for Quantum Communication Applications

“…The prominent hyperfine-split transitions are a result of the large transverse component of the hyperfine tensor [38]; this acts in the same manner as a large off-axis magnetic field, giving rise to optical transitions which flip the electron or nuclear spin. Well-resolved hyperfine transitions may find use in optical manipulation of the nuclear spin [43], potentially serving as an ancilla qubit.…”