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All-optical control of long-lived nuclear spins in rare-earth doped nanoparticles

Diana Serrano, Jenny Karlsson, Alexandre Fossati, Alban Ferrier, Philippe Goldner

Published Jan 1, 2018• 48 citations
OpenAlex

Abstract

Abstract Nanoscale systems that coherently couple to light and possess spins offer key capabilities for quantum technologies. However, an outstanding challenge is to preserve properties, and especially optical and spin coherence lifetimes, at the nanoscale. Here, we report optically controlled nuclear spins with long coherence lifetimes (T2) in rare-earth-doped nanoparticles. We detect spins echoes and measure a spin coherence lifetime of 2.9 ± 0.3 ms at 5 K under an external magnetic field of 9 mT, a T2 value comparable to those obtained in bulk rare-earth crystals. Moreover, we achieve spin T2 extension using all-optical spin dynamical decoupling and observe high fidelity between excitation and echo phases. Rare-earth-doped nanoparticles are thus the only nano-material in which optically controlled spins with millisecond coherence lifetimes have been reported. These results open the way to providing quantum light-atom-spin interfaces with long storage time within hybrid architectures.

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All-optical control of long-lived nuclear spins in rare-earth doped nanoparticles

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Nanoscale systems possessing long-lived spins and the ability to coherently couple to light are highly demanded for quantum devices implementations. Several approaches, like NV centers in diamond, semiconductor quantum dots are intensively investigated in the field, where an outstanding challenge is to preserve properties, and especially optical and spin coherence lifetimes, at the nanoscale. In this context, chemically synthesized Eu3+ doped Y2O3 nanoparticles have demonstrated great potential for quantum technologies based on their narrow optical homogeneous linewidth, down to the 10 kHz level, and millisecond-long spin coherence time. Here, we investigate an alternative nanoscale material: Pr3+: Y2O3. We first determine the Pr3+ hyperfine structure in Y2O3 by spectral hole burning and then measure photon and spin echoes from nanoparticles down to 150 nm. Spin T2 up to 880 μs was obtained for the ±3/2↔±5/2 hyperfine transition at 10.42 MHz, a value which exceeds that of bulk Pr3+doped crystals so far reported. These promising results confirm nanoscale Pr3+:Y2O3 as a very appealing candidate to integrate quantum devices.

SPIE Quantum Technologies•Mar 30, 2020•0 citations
Abstract Nanoscale systems that coherently couple to light and possess spins offer key capabilities for quantum technologies. However, an outstanding challenge is to preserve properties, and especially optical and spin coherence lifetimes, at the nanoscale. Here, we report optically controlled nuclear spins with long coherence lifetimes (T2) in rare-earth-doped nanoparticles. We detect spins echoes and measure a spin coherence lifetime of 2.9 ± 0.3 ms at 5 K under an external magnetic field of 9 mT, a T2 value comparable to those obtained in bulk rare-earth crystals. Moreover, we achieve spin T2 extension using all-optical spin dynamical decoupling and observe high fidelity between excitation and echo phases. Rare-earth-doped nanoparticles are thus the only nano-material in which optically controlled spins with millisecond coherence lifetimes have been reported. These results open the way to providing quantum light-atom-spin interfaces with long storage time within hybrid architectures.
Abstract Nanoscale systems that coherently couple to light and possess spins offer key capabilities for quantum technologies. However, an outstanding challenge is to preserve properties, and especially optical and spin coherence lifetimes, at the nanoscale. Here, we report optically controlled nuclear spins with long coherence lifetimes ( T 2 ) in rare-earth-doped nanoparticles. We detect spins echoes and measure a spin coherence lifetime of 2.9 ± 0.3 ms at 5 K under an external magnetic field of 9 mT, a T 2 value comparable to those obtained in bulk rare-earth crystals. Moreover, we achieve spin T 2 extension using all-optical spin dynamical decoupling and observe high fidelity between excitation and echo phases. Rare-earth-doped nanoparticles are thus the only nano-material in which optically controlled spins with millisecond coherence lifetimes have been reported. These results open the way to providing quantum light-atom-spin interfaces with long storage time within hybrid architectures.
Quantum memories for light are essential components in quantum technologies like long-distance quantum communication and distributed quantum computing. Recent studies have shown that long optical and spin coherence lifetimes can be observed in rare earth doped nanoparticles, opening exciting possibilities over bulk materials, e.g., for enhancing coupling to light and other quantum systems, and material design. Here, we report on coherent light storage in Eu 3+:Y 2 O 3 nanoparticles using the Stark echo modulation memory (SEMM) quantum protocol. We first measure a nearly constant Stark coefficient of 50 kHz/(V/cm) across a bandwidth of 15 GHz, which is promising for broadband operation. Storage of light is then demonstrated with an effective coherence lifetime of 5 μs. Pulses with two different frequencies are also stored, confirming frequency-multiplexing capability, and are used to demonstrate the memory high phase fidelity. These results open the way to nanoscale optical quantum memories with increased efficiency, bandwidth, and processing capabilities.
Interfacing between various elements of a computer--from memory to processors to long range communication--will be as critical for quantum computers as it is for classical computers today. Paramagnetic rare-earth doped crystals, such as Nd(3+):Y2SiO5(YSO), are excellent candidates for such a quantum interface: they are known to exhibit long optical coherence lifetimes (for communication via optical photons), possess a nuclear spin (memory), and have in addition an electron spin that can offer hybrid coupling with superconducting qubits (processing). Here we study two of these three elements, demonstrating coherent storage and retrieval between electron and (145)Nd nuclear spin states in Nd(3+):YSO. We find nuclear spin coherence times can reach 9 ms at ∼5 K, about 2 orders of magnitude longer than the electron spin coherence, while quantum state and process tomography of the storage or retrieval operation between the electron and nuclear spin reveal an average state fidelity of 0.86. The times and fidelities are expected to further improve at lower temperatures and with more homogeneous radio-frequency excitation.
Dense rare-earth spin ensembles in solids offer strong collective light-matter coupling for scalable quantum technologies but are typically incompatible with long coherence times due to strong dipolar interactions. Here we challenge this paradigm by showing long-lived coherence in such systems. In a stoichiometric EuCl_{3}·6H_{2}O crystal, we achieve hyperfine coherence times T_{2}^{CPMG} of up to 15 s at 4 K, extending the zero-field value T_{2} of 1.28 ms by more than four orders of magnitude using dynamical decoupling at a zero-first-order Zeeman (ZEFOZ) transition. Homogeneous linewidth measurements reveal a substantial suppression of resonant Eu^{3+}-Eu^{3+} spin interactions introduced by the full concentration near the ZEFOZ point. Coherence remains resilient to strong local perturbations, with a 32 ms coherence time for Eu^{3+} ions adjacent to Er^{3+} dopants. These results establish stoichiometric rare-earth crystals as a promising platform for quantum memories and spin-photon interfaces, demonstrating that intrinsically high optical depth and long-lived spin coherence can coexist in a fully concentrated ensemble.
Nanoscale systems possessing long-lived spins and the ability to coherently couple to light are highly demanded for quantum devices implementations. Several approaches, like NV centers in diamond, semiconductor quantum dots are intensively investigated in the field, where an outstanding challenge is to preserve properties, and especially optical and spin coherence lifetimes, at the nanoscale. In this context, chemically synthesized Eu3+ doped Y2O3 nanoparticles have demonstrated great potential for quantum technologies based on their narrow optical homogeneous linewidth, down to the 10 kHz level, and millisecond-long spin coherence time. Here, we investigate an alternative nanoscale material: Pr3+: Y2O3. We first determine the Pr3+ hyperfine structure in Y2O3 by spectral hole burning and then measure photon and spin echoes from nanoparticles down to 150 nm. Spin T2 up to 880 μs was obtained for the ±3/2↔±5/2 hyperfine transition at 10.42 MHz, a value which exceeds that of bulk Pr3+doped crystals so far reported. These promising results confirm nanoscale Pr3+:Y2O3 as a very appealing candidate to integrate quantum devices.