Reliable coherent optical memory based on a laser-written waveguide

Abstract

151 Eu 3+ -doped yttrium silicate ( 151 Eu 3+ : Y 2 SiO 5 ) crystal is a unique material that possesses hyperfine states with coherence time up to 6 h. Many efforts have been devoted to the development of this material as optical quantum memories based on the bulk crystals, but integrable structures (such as optical waveguides) that can promote 151 Eu 3+ : Y 2 SiO 5 -based quantum memories to practical applications, have not been demonstrated so far. Here we report the fabrication of type II waveguides in a 151 Eu 3+ : Y 2 SiO 5 crystal using femtosecond-laser micromachining. The resulting waveguides are compatible with single-mode fibers and have the smallest insertion loss of 4.95 dB. On-demand light storage is demonstrated in a waveguide by employing the spinwave atomic frequency comb (AFC) scheme and the revival of silenced echo (ROSE) scheme. We implement a series of interference experiments based on these two schemes to characterize the storage fidelity. Interference visibility of the readout pulse is 0.99 ± 0.03 for the spin-wave AFC scheme and 0.97 ± 0.02 for the ROSE scheme, demonstrating the reliability of the integrated optical memory.

On-Demand Quantum Storage of Photonic Qubits in an On-Chip Waveguide

“…For more flexible applications, much longer storage times [9] could be obtained with spin-wave storage protocols such as spinwave AFC [31] or the noiseless photon echo protocol [32]. Our waveguide structure strongly confines the light field so that much larger Rabi frequencies can be obtained [34] to apply the optical π pulses required for spin-wave memories [15]. The close-to-surface optical waveguides can further enable efficient interface with on-chip electric waveguides to facilitate spin decoherence control through dynamical decoupling.…”

Towards real-world quantum networks: a review

“…Excellent progresses has been made, such as a storage time of greater than one second [184], high storage efficiency of 56% [185], high storage fidelity of 0.999 [186] and simultaneous storage of up to 1060 temporal modes [187]. In addition, REIDSs have been shown to function as on-chip waveguide based quantum memory [188][189][190][191][192][193][194], which is favorable for the construction of integrated quantum network. In the following we will focus on the atomic frequency comb (AFC) protocol [79,80], which distinguishes itself by it's high-multimode storage capacity and use in most practical demonstrations using REIDS for quantum network applications.…”

Quantum memory and manipulation based on erbium doped crystals

“…aquy"OŽÅEâÚ&E äEâé8¤>´ •6 §™5 þf äA^[ 32,33] •I ‡?n [35−37] !-1 † [38,39] Úà lfå•¡ [40,41] §Xã4 (a)-(c)¤«"2011 c §\<OEk \pOEAE ïÄ ||^l f*ÑEâ §3•OE ¬Ná þ› ÑÅ ( §¢y éÅ 1f þf•; [36] ¶2019c §{I\ ²nó ïÄ |ÏL3Er , YSO ¬Nþ † ^à lfå•¡ •{\óÑ ˜'1f¬Nn( §¢y ü1f þf•; [40] [38,39] " ù« † 3¬Nþ?1\ó…”

“…(b) Nanophotonic quantum memory by using focued-ion-beam to fabricate a one-dimensional photonic cavity in a YVO crystal [41] . (c) Waveguide memory fabricated by femtosecond-laser micromachining on the surface of a YSO crystal [38] . (d) Quantum memory comprised of an amorphous silicon (öSi) waveguide on a YSO crystal [42] .…”