Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:1402.5242 · Physical Review B

Strong coupling of an Er3+ -doped YAlO3 crystal to a superconducting resonator

A. Tkalčec, S. Probst, D. Rieger, Hannes Rotzinger, S. Wünsch, Nadezhda Kukharchyk, Andreas Dirk Wieck, M. Siegel, Alexey Vladimirovich Ustinov, Pavel A. Bushev

Published Aug 8, 2014• 38 citations
arXivHTMLPDF

Abstract

Quantum memories are integral parts of both quantum computers and quantum communication networks. Naturally, such a memory is embedded into a hybrid quantum architecture, which has to meet the requirements of fast gates, long coherence times, and long distance communication. Erbium-doped crystals are well suited as a microwave quantum memory for superconducting circuits with additional access to the optical telecom $C$ band around 1.55 $\ensuremath{\mu}\mathrm{m}$. Here, we report on circuit QED experiments with an ${\mathrm{Er}}^{3+}$:${\mathrm{YAlO}}_{3}$ crystal and demonstrate strong coupling to a superconducting lumped element resonator. The low magnetic anisotropy of the host crystal allows for attaining the strong coupling regime at relatively low magnetic fields, which are compatible with superconducting circuits. In addition, ${\mathrm{Ce}}^{3+}$ impurities were detected in the crystal, which showed strong coupling as well.

DOI
10.1103/physrevb.90.075112

Related papers

Realization of strong coupling between Er3+: CaWO4 crystal and the loop-gap resonator for a hybrid quantum system

Q. Li, Miaomiao Ren, Shuping Liu +2 more

Erbium-doped crystals provide a promising platform for integration with other quantum systems, offering telecom-band optical and microwave spin transitions with long coherence times for quantum memory and transduction applications. In order to construct efficient hybrid quantum systems, it is challenging but necessary to realize strong coupling between erbium spins and other microwave photons. Here, we design and construct a high-quality-factor three-dimensional loop-gap microwave resonator for wide-range electron spin resonance detection. We achieved strong coupling with a strength of 85.1 MHz at 100 mK. Our results demonstrate a viable hybrid quantum system, paving the way for integrated networks that combine optical communication with microwave quantum computing.

Applied Physics Letters•Sep 15, 2025•1 citation

Anisotropic Rare-Earth Spin Ensemble Strongly Coupled to a Superconducting Resonator

S. Probst, Hannes Rotzinger, S. Wünsch +5 more

Interfacing photonic and solid-state qubits within a hybrid quantum architecture offers a promising route towards large scale distributed quantum computing. Ideal candidates for coherent qubit interconversion are optically active spins, magnetically coupled to a superconducting resonator. We report on an on-chip cavity QED experiment with magnetically anisotropic Er(3+)∶Y2SiO5 crystals and demonstrate collective strong coupling of rare-earth spins to a lumped element resonator. Moreover, the electron spin resonance and relaxation dynamics of the erbium spins are detected via direct microwave absorption, without the aid of a cavity.

arXiv:1212.2856•Physical Review Letters•Apr 8, 2013•206 citations

Hybrid quantum circuit with implanted erbium ions

S. Probst, Nadezhda Kukharchyk, Hannes Rotzinger +6 more

We report on hybrid circuit quantum electrodynamics experiments with focused ion beam implanted Er3+ ions in Y2SiO5 coupled to an array of superconducting lumped element microwave resonators. The Y2SiO5 crystal is divided into several areas with distinct erbium doping concentrations, each coupled to a separate resonator. The coupling strength is varied from 5 MHz to 18.7 MHz, while the linewidth ranges between 50 MHz and 130 MHz. We confirm the paramagnetic properties of the implanted spin ensemble by evaluating the temperature dependence of the coupling. The efficiency of the implantation process is analyzed and the results are compared to a bulk doped Er:Y2SiO5 sample. We demonstrate the integration of these engineered erbium spin ensembles with superconducting circuits.

arXiv:1409.7667•Applied Physics Letters•Oct 20, 2014•24 citations

Microwave multimode memory with an erbium spin ensemble

S. Probst, Hannes Rotzinger, Alexey Vladimirovich Ustinov +1 more

Hybrid quantum systems combining circuit QED with spin-doped solids are an attractive platform for distributed quantum information processing. There, the magnetic ions serve as coherent memory elements and reversible conversion elements of microwave to optical qubits. Among many possible spin-doped solids, erbium ions offer the unique opportunity for a coherent conversion of microwave photons into the telecom C band at $1.54\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{m}$ employed for long distance communication. In our work, we perform a time-resolved electron spin resonance study of an ${\mathrm{Er}}^{3+}:{\mathrm{Y}}_{2}{\mathrm{SiO}}_{5}$ spin ensemble at millidegrees Kelvin temperatures and demonstrate multimode storage and retrieval of up to 16 coherent microwave pulses. The memory efficiency is measured to be ${10}^{\ensuremath{-}4}$ at a coherence time of ${T}_{2}=5.6\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{s}$. We observe a saturation of the spin coherence time below 50 mK due to full polarization of the surrounding electronic spin bath.

arXiv:1501.01499•Physical Review B•Jul 23, 2015•69 citations

On-chip optical quantum memory at telecom wavelengths (Conference Presentation)

Ioana Craiciu, Jake Rochman, Mi Lei +5 more

Optical quantum memories will enable technologies including long distance quantum communication and modular quantum computing. Rare earth ion doped crystals provide an excellent solid state platform for optical quantum memories. Among rare earths, erbium is particularly appealing due to its long-lived telecom-wavelength resonance, allowing integration with silicon photonics and with existing optical communication technology and infrastructure. We present an on-chip all-optical quantum memory at telecom wavelengths using a nanobeam photonic crystal cavity fabricated directly in erbium-167 doped yttrium orthosilicate. Using an atomic frequency comb protocol, we store coherent pulses for memory times as long as 10 µs, albeit with low efficiency. For shorter memory times, we achieve a memory efficiency of 0.4%, which is limited by the coupling rate between the resonator and the ensemble of ions. By working at dilution refrigerator temperatures, we are able to access a regime where the ions have long optical coherence times and good spectral holeburning properties using only a moderate magnetic field applied with permanent magnets. We characterize the multimode properties and fidelity of the quantum memory in this device, and outline a path toward higher efficiency.

Advances in Photonics of Quantum Computing, Memory, and Communication•Mar 4, 2019•1 citation

Hybrid microring resonator devices for rare-earth quantum-light matter interfaces

Ioana Craiciu, Evan Miyazono, Tian Zhong +2 more

Rare earth quantum light-matter interfaces (QLMIs) are uniquely suited for various quantum communication applications, including quantum memories and quantum optical to microwave transducers. Among rare earths, erbium QLMIs are particularly appealing due to erbium’s long lived telecom wavelength resonance, allowing integration with existing optical communication technology and infrastructure. Micro-resonator QLMIs have various advantages over bulk rare earth crystal memories. They provide the opportunity for on-chip integration; for example, optical resonators can be integrated with microwave resonators for quantum optical-microwave transduction. For spectral hole-burning based quantum memories, coupling rare earth ions to a resonator can provide improved memory initialization via Purcell enhancement of optical lifetimes, while impedance matching the resonator to the ions can raise the theoretical memory efficiency to 100%. We present hybrid nanoscale quantum light matter interfaces in the form of amorphous silicon ring resonators on yttrium orthosilicate (YSO) substrate doped with erbium ions. While working with rare earth crystal hosts can be challenging, the fabrication process for these devices is simple and robust, using traditional thin film fabrication technologies. Our devices have measured quality factors of over 105 in the 11 µm diameter rings, and evanescent coupling to an ensemble of erbium ions characterized by a cooperativity of 0.54. We present simulation and experimental results of the optical properties of these cavities, and their coupling to erbium ions, including a demonstration of Purcell enhancement of the erbium telecom transition. We then analyze their potential as quantum memories and in optical to microwave transducers.

•Jun 2, 2017•0 citations
Quantum memories are integral parts of both quantum computers and quantum communication networks. Naturally, such a memory is embedded into a hybrid quantum architecture, which has to meet the requirements of fast gates, long coherence times, and long distance communication. Erbium-doped crystals are well suited as a microwave quantum memory for superconducting circuits with additional access to the optical telecom CCC band around 1.55 \ensuremathμm\ensuremath{\mu}\mathrm{m}\ensuremathμm. Here, we report on circuit QED experiments with an Er3+{\mathrm{Er}}^{3+}Er3+:YAlO3{\mathrm{YAlO}}_{3}YAlO3​ crystal and demonstrate strong coupling to a superconducting lumped element resonator. The low magnetic anisotropy of the host crystal allows for attaining the strong coupling regime at relatively low magnetic fields, which are compatible with superconducting circuits. In addition, Ce3+{\mathrm{Ce}}^{3+}Ce3+ impurities were detected in the crystal, which showed strong coupling as well.
Erbium-doped crystals provide a promising platform for integration with other quantum systems, offering telecom-band optical and microwave spin transitions with long coherence times for quantum memory and transduction applications. In order to construct efficient hybrid quantum systems, it is challenging but necessary to realize strong coupling between erbium spins and other microwave photons. Here, we design and construct a high-quality-factor three-dimensional loop-gap microwave resonator for wide-range electron spin resonance detection. We achieved strong coupling with a strength of 85.1 MHz at 100 mK. Our results demonstrate a viable hybrid quantum system, paving the way for integrated networks that combine optical communication with microwave quantum computing.
Interfacing photonic and solid-state qubits within a hybrid quantum architecture offers a promising route towards large scale distributed quantum computing. Ideal candidates for coherent qubit interconversion are optically active spins, magnetically coupled to a superconducting resonator. We report on an on-chip cavity QED experiment with magnetically anisotropic Er(3+)∶Y2SiO5 crystals and demonstrate collective strong coupling of rare-earth spins to a lumped element resonator. Moreover, the electron spin resonance and relaxation dynamics of the erbium spins are detected via direct microwave absorption, without the aid of a cavity.
We report on hybrid circuit quantum electrodynamics experiments with focused ion beam implanted Er3+ ions in Y2SiO5 coupled to an array of superconducting lumped element microwave resonators. The Y2SiO5 crystal is divided into several areas with distinct erbium doping concentrations, each coupled to a separate resonator. The coupling strength is varied from 5 MHz to 18.7 MHz, while the linewidth ranges between 50 MHz and 130 MHz. We confirm the paramagnetic properties of the implanted spin ensemble by evaluating the temperature dependence of the coupling. The efficiency of the implantation process is analyzed and the results are compared to a bulk doped Er:Y2SiO5 sample. We demonstrate the integration of these engineered erbium spin ensembles with superconducting circuits.
Hybrid quantum systems combining circuit QED with spin-doped solids are an attractive platform for distributed quantum information processing. There, the magnetic ions serve as coherent memory elements and reversible conversion elements of microwave to optical qubits. Among many possible spin-doped solids, erbium ions offer the unique opportunity for a coherent conversion of microwave photons into the telecom C band at $1.54\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{m}$ employed for long distance communication. In our work, we perform a time-resolved electron spin resonance study of an Er3+:Y2SiO5{\mathrm{Er}}^{3+}:{\mathrm{Y}}_{2}{\mathrm{SiO}}_{5}Er3+:Y2​SiO5​ spin ensemble at millidegrees Kelvin temperatures and demonstrate multimode storage and retrieval of up to 16 coherent microwave pulses. The memory efficiency is measured to be ${10}^{\ensuremath{-}4}$ at a coherence time of ${T}_{2}=5.6\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{s}$. We observe a saturation of the spin coherence time below 50 mK due to full polarization of the surrounding electronic spin bath.
Optical quantum memories will enable technologies including long distance quantum communication and modular quantum computing. Rare earth ion doped crystals provide an excellent solid state platform for optical quantum memories. Among rare earths, erbium is particularly appealing due to its long-lived telecom-wavelength resonance, allowing integration with silicon photonics and with existing optical communication technology and infrastructure. We present an on-chip all-optical quantum memory at telecom wavelengths using a nanobeam photonic crystal cavity fabricated directly in erbium-167 doped yttrium orthosilicate. Using an atomic frequency comb protocol, we store coherent pulses for memory times as long as 10 µs, albeit with low efficiency. For shorter memory times, we achieve a memory efficiency of 0.4%, which is limited by the coupling rate between the resonator and the ensemble of ions. By working at dilution refrigerator temperatures, we are able to access a regime where the ions have long optical coherence times and good spectral holeburning properties using only a moderate magnetic field applied with permanent magnets. We characterize the multimode properties and fidelity of the quantum memory in this device, and outline a path toward higher efficiency.
Rare earth quantum light-matter interfaces (QLMIs) are uniquely suited for various quantum communication applications, including quantum memories and quantum optical to microwave transducers. Among rare earths, erbium QLMIs are particularly appealing due to erbium’s long lived telecom wavelength resonance, allowing integration with existing optical communication technology and infrastructure. Micro-resonator QLMIs have various advantages over bulk rare earth crystal memories. They provide the opportunity for on-chip integration; for example, optical resonators can be integrated with microwave resonators for quantum optical-microwave transduction. For spectral hole-burning based quantum memories, coupling rare earth ions to a resonator can provide improved memory initialization via Purcell enhancement of optical lifetimes, while impedance matching the resonator to the ions can raise the theoretical memory efficiency to 100%. We present hybrid nanoscale quantum light matter interfaces in the form of amorphous silicon ring resonators on yttrium orthosilicate (YSO) substrate doped with erbium ions. While working with rare earth crystal hosts can be challenging, the fabrication process for these devices is simple and robust, using traditional thin film fabrication technologies. Our devices have measured quality factors of over 105 in the 11 µm diameter rings, and evanescent coupling to an ensemble of erbium ions characterized by a cooperativity of 0.54. We present simulation and experimental results of the optical properties of these cavities, and their coupling to erbium ions, including a demonstration of Purcell enhancement of the erbium telecom transition. We then analyze their potential as quantum memories and in optical to microwave transducers.