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

Journal of the American Chemical Society

Chiral Polar Eu 2 (SeO 3 ) 2 (SO 4 )(H 2 O) 2 : A Pathway Toward Narrow Optical Line Widths and Microsecond Lifetimes for Quantum Memory Candidates

Uchenna Chinaegbomkpa, Ebube E. Oyeka, Xudong Huai, Ramesh Kumar, Mingli Liang, ByungDo Lee, Jakoah Brgoch, Hugo Sanabria, T. Thao Tran

Published Apr 16, 2026• 1 citation
Publisher

Abstract

Stoichiometric materials of Eu(III) offer a promising platform for quantum memories attributable to their unique capability to display a distinctive, nondegenerate 5 D 0 → 7 F 0 transition, which enables precise mapping of optical quantum states into their energy-level manifold─a prerequisite for reliable storage and retrieval on demand. However, placing Eu(III) into chiral polar structures, which are necessary for achieving narrow spectral line widths and long optical lifetimes, is a daunting task. Here, we discover Eu 2 (SeO 3 ) 2 (SO 4 )(H 2 O) 2, a rare Eu(III) material that exhibits chiral polar symmetries encompassing both local and global structures. This unique structure is shaped by an appropriate combination of asymmetric ligands. Chirality fosters dipole–dipole interactions and J -mixing, as evidenced by second-harmonic generation, photoluminescence, and magnetic susceptibility. The broken inversion symmetry is supported by the phase-matching behavior in second-harmonic generation. The 5 D 0 → 7 F 0 transition is observed at 578 nm (2.145 eV) with 7.42 meV line width and 3.39 μs lifetime at T = 78 K. The analysis of magnetic susceptibility data using Van Vleck’s theory results in an effective magnetic moment of ρ eff = 3.33 μ B /Eu 3+ and J -mixing. Heat capacity data reveal underlying phonon dynamics in the material. This study demonstrates a pathway to realizing new chiral stoichiometric Eu 3+ compounds with potential for optically addressable quantum memory applications.

DOI
10.1021/jacs.6c00793

Related papers

Chiral Polar Eu2(SeO3)2(SO4)(H2O)2: A Pathway Toward Narrow Optical Linewidths and Microsecond Lifetimes for Quantum Memory Candidates

Uchenna Chinaegbomkpa, Ebube E. Oyeka, Xudong Huai +5 more

Stoichiometric materials of Eu(III) offer a promising platform for quantum memories attributable to their unique capability to display a distinctive, nondegenerate J = 0 transition, which enables precise mapping of optical quantum states into their hyperfine structure for reliable storage and retrieval on demand. However, placing Eu(III) into chiral polar structures, which are necessary for achieving narrow spectral linewidths and long optical lifetimes, is a daunting task. Here, we discover Eu2(SeO3)2(SO4)(H2O)2, a rare Eu(III) material that exhibits chiral polar symmetries encompassing both local and global structures. This unique structure is shaped by an appropriate combination of asymmetric ligands. The chirality fosters dipole-dipole interactions and J-mixing, as characterized by second-harmonic generation, photoluminescence, and magnetic susceptibility. The broken inversion symmetry is supported by the phase-matching behavior of second-harmonic generation. The J = 0 transition is observed at 578 nm with a narrow linewidth at 78 K and a microsecond-scale optical lifetime. The analysis of magnetic susceptibility data using Van Vleck theory results in an effective magnetic moment of 3.33 μB/Eu3+ and J-mixing. Heat capacity data reveal underlying phonon dynamics in the material. This study demonstrates a pathway toward realizing new stoichiometric Eu3+ compounds with potential for optically addressable quantum memory applications.

arXiv:2602.09178•Feb 9, 2026•0 citations

LaPO 4 :Eu 3+ Monazite Crystals: A Promising Platform for Optical Quantum Technologies

Valentin Grand d’Esnon, Diana Serrano, Simon Delacroix +4 more

Materials science has an important role to play in the successful establishment of quantum technologies as they are expected to develop suitable material platforms for these highly demanding applications. Among different promising solid-state materials, rare-earth ions embedded in some host crystals show outstandingly narrow optical line widths and long-lived spin states at cryogenic temperatures. In this manuscript, we explore a promising rare-earth (RE)-based material for use in quantum applications: monazite-phase LaPO 4:Eu 3+ crystals, providing the first comprehensive, high-resolution optical coherence and spin lifetime characterization across the full concentration range, starting from 1% Eu 3+ and up to the fully stoichiometric compound EuPO 4 . The results show optical coherence times of the order 100 μs and nuclear spin lifetimes up to 2 h at 4 K, setting this material among the best reported so far, while experimental conditions for its synthesis with appropriate quality consist of a rather simple solid-state reaction. This opens promising perspectives for its use in quantum applications.

The Journal of Physical Chemistry C•Mar 13, 2026•3 citations

Synthesis and Optical Quantum Memory Characterization of α-Eu(IO 3 ) 3 , β-Eu(IO 3 ) 3 , and NaEu(IO 3 ) 4

Jack A. D’Amelio, Nick Kwentus, Amy Tram +6 more

Three phases of stoichiometric europium(III) iodate compounds are probed as candidates for optical quantum memory to determine the impact of reaction conditions on phase formation and to relate crystal structure to their ability to host persistent excited states relevant to quantum memory. Hydrothermal synthesis procedures for growing macroscopic single crystals of rectangular-block α-Eu(IO 3 ) 3 ( P 2 1 / c ), yellow hexagonal plate β-Eu(IO 3 ) 3 ( P 2 1 / n ), and transparent plate NaEu(IO 3 ) 4 ( Cc ) are presented. The ability to burn narrow and long-lived spectral holes on the 7 F 0 → 5 D 0 optical transitions is a necessary condition for implementing optical quantum memory. α-Eu(IO 3 ) 3 was determined to be incapable of hole-burning due to the presence of insufficient asymmetry of the europium site, which forbids the required optical transition. β-Eu(IO 3 ) 3 was determined to be incapable of storing information due to a lack of observed spectral hole burning, likely due to decoherence caused by the closely packed edge-sharing Eu(III) polyhedra. Analysis of each phase’s crystal structure suggests that the Eu–Eu nearest neighbor distance and distortion of europium site symmetry are critical material design parameters for quantum memory applications.

Inorganic Chemistry•Apr 8, 2026•1 citation

Design Rules, Accurate Enthalpy Prediction, and Synthesis of Stoichiometric Eu 3+ Quantum Memory Candidates

Zachary W. Riedel, Daniel P. Shoemaker

Stoichiometric Eu 3+ compounds have recently shown promise for building dense, optically addressable quantum memory as the cations’ long nuclear spin coherence times and shielded 4f electron optical transitions provide reliable memory platforms. Implementing such a system, though, requires ultranarrow, inhomogeneous linewidth compounds. Finding this rare linewidth behavior within a wide range of potential chemical spaces remains difficult, and while exploratory synthesis is often guided by density functional theory (DFT) calculations, lanthanides’ 4f electrons pose unique challenges for stability predictions. Here, we report DFT procedures that reliably reproduce known phase diagrams and correctly predict two experimentally realized quantum memory candidates. We are the first to synthesize the double perovskite halide Cs 2 NaEuF 6 . It is an air-stable compound with a calculated band gap of 5.0 eV that surrounds Eu 3+ with mononuclidic elements, which are desirable for avoiding inhomogeneous linewidth broadening. We also analyze computational database entries to identify phosphates and iodates as the next generation of chemical spaces for stoichiometric quantum memory system studies. This work identifies new candidate platforms for exploring chemical effects on quantum memory candidates’ inhomogeneous linewidth while also providing a framework for screening Eu 3+ compound stability with DFT.

Journal of the American Chemical Society•Jan 12, 2024•8 citations

Molecule-based coherent light-spin interfaces for quantum information processing -- optical spin state polarization in a binuclear Europium complex

Senthil Kumar Kuppusamy, Diana Serrano, Aline M. Nonat +5 more

The success of the emerging field of solid-state optical quantum information processing (QIP) critically depends on the access to resonant optical materials. Rare-earth ions (REIs) are suitable candidates for QIP protocols due to their extraordinary photo-physical and magnetic quantum properties such as long optical and spin coherence lifetimes ($T_2$). However, molecules incorporating REIs, despite having advantageous properties such as atomically exact quantum tunability, inherent scalability, and large portability, have not yet been studied for QIP applications. As a first testimony of the usefulness of REI molecules for optical QIP applications, we demonstrate in this study that narrow spectral holes can be burned in the inhomogeneously broadened $^5$D$_0\to^7$F$_0$ optical transition of a binuclear Eu(III) complex, rendering a homogeneous linewidth ($Γ_h$) = 22 $\pm$ 1 MHz, which translates as $T_2 = 14.5$ $\pm$ 0.7 ns at 1.4 K. Moreover, long-lived spectral holes are observed, demonstrating efficient polarization of Eu(III) ground state nuclear spins, a fundamental requirement for all-optical spin initialization and addressing. These results elucidate the usefulness of REI-based molecular complexes as versatile coherent light-spin interfaces for applications in quantum communications and processing.

arXiv:2006.09831•Jun 17, 2020•0 citations

Evaluation of a stoichiometric rare earth crystal for quantum computing

Rose L. Ahlefeldt

This thesis presents a spectroscopic study of the 7F0 ---t5D0 transition of Eu3+ in EuC13 ·6H2 0, which is used to evaluate the potential performance of a quantum com­ puting system implemented in EuCla·6H2 0 and, more generally, in stoichiometric rare earth crystals. EuC13 ·6H2 0 has one of the narrowest optical inhomogeneous linewidths of any solid but this linewidth is shown to be still much larger than that required for practical quantum computing in a rare earth crystal. To assess the possibility of reducing the linwidth, the contributions of isotopic impurities to both the optical linewidth and line structure were investigated, and ligand isotopes were identified as a major source of both inhomogeneous broadening and structure on the optical transition, suggesting that the linewidth could be substantially reduced by isotopi­ cally purifying EuC13 ·6H20. The effect of ligand isotopes on the optical lifetime and coherence time was also investigated. It was found that fully deuterating the crystal to EuC13·6D20 substantially improves both the lifetime and coherence time. The satellite lines formed in the optical spectrum of a rare earth crystal when it is doped with another rare earth are proposed as qubits. A crucial step in char­ acterising EuCla ·6H20 for quantum computing is associating these satellite lines in EuC13 ·6H2 0 with crystallographic sites. A new method for associating sites with lines, which works for low symmetry crystals such as EuC13·6H20, is presented. This method involves modelling the splitting of the ground state hyperfine levels caused by the magnetic dipole-dipole interaction between a Kramers dopant and the Eu3+ ion. Using this method, most of the outer satellite lines in rare earth doped EuCla·6H2 0 were assigned to crystallographic sites. It has been proposed that the electronic interactions between these satellite lines be used to enact two-qubit gates in a rare earth quantum computer. These interac­ tions were measured between a number of different satellite lines using a new two­ laser spectral holeburning technique. Interactions of up to 46.081±0.005 MHz were observed, and this was the first time that electronic interactions between weakly coupled rare earth ions had been measured. The two most common interactions identified between rare earth ions in solids are electric dipole-dipole and exchange, but the observed interactions are stronger than expected from a electric dipole-dipole model and occur at too large a distance to be superexchange. It is shown that the development of a moderate-sized quantum processor, one with more than 10 qubits, in a stoichiometric rare earth crystal is feasible provided that the optical inhomogeneous linewidth is reduced below 1MHz. Demonstrations of three or four qubit devices should be possible using existing materials.

•Jan 1, 2013•4 citations
Stoichiometric materials of Eu(III) offer a promising platform for quantum memories attributable to their unique capability to display a distinctive, nondegenerate 5 D 0 → 7 F 0 transition, which enables precise mapping of optical quantum states into their energy-level manifold─a prerequisite for reliable storage and retrieval on demand. However, placing Eu(III) into chiral polar structures, which are necessary for achieving narrow spectral line widths and long optical lifetimes, is a daunting task. Here, we discover Eu 2 (SeO 3 ) 2 (SO 4 )(H 2 O) 2, a rare Eu(III) material that exhibits chiral polar symmetries encompassing both local and global structures. This unique structure is shaped by an appropriate combination of asymmetric ligands. Chirality fosters dipole–dipole interactions and J -mixing, as evidenced by second-harmonic generation, photoluminescence, and magnetic susceptibility. The broken inversion symmetry is supported by the phase-matching behavior in second-harmonic generation. The 5 D 0 → 7 F 0 transition is observed at 578 nm (2.145 eV) with 7.42 meV line width and 3.39 μs lifetime at T = 78 K. The analysis of magnetic susceptibility data using Van Vleck’s theory results in an effective magnetic moment of ρ eff = 3.33 μ B /Eu 3+ and J -mixing. Heat capacity data reveal underlying phonon dynamics in the material. This study demonstrates a pathway to realizing new chiral stoichiometric Eu 3+ compounds with potential for optically addressable quantum memory applications.
Stoichiometric materials of Eu(III) offer a promising platform for quantum memories attributable to their unique capability to display a distinctive, nondegenerate J = 0 transition, which enables precise mapping of optical quantum states into their hyperfine structure for reliable storage and retrieval on demand. However, placing Eu(III) into chiral polar structures, which are necessary for achieving narrow spectral linewidths and long optical lifetimes, is a daunting task. Here, we discover Eu2(SeO3)2(SO4)(H2O)2, a rare Eu(III) material that exhibits chiral polar symmetries encompassing both local and global structures. This unique structure is shaped by an appropriate combination of asymmetric ligands. The chirality fosters dipole-dipole interactions and J-mixing, as characterized by second-harmonic generation, photoluminescence, and magnetic susceptibility. The broken inversion symmetry is supported by the phase-matching behavior of second-harmonic generation. The J = 0 transition is observed at 578 nm with a narrow linewidth at 78 K and a microsecond-scale optical lifetime. The analysis of magnetic susceptibility data using Van Vleck theory results in an effective magnetic moment of 3.33 μB/Eu3+ and J-mixing. Heat capacity data reveal underlying phonon dynamics in the material. This study demonstrates a pathway toward realizing new stoichiometric Eu3+ compounds with potential for optically addressable quantum memory applications.
Materials science has an important role to play in the successful establishment of quantum technologies as they are expected to develop suitable material platforms for these highly demanding applications. Among different promising solid-state materials, rare-earth ions embedded in some host crystals show outstandingly narrow optical line widths and long-lived spin states at cryogenic temperatures. In this manuscript, we explore a promising rare-earth (RE)-based material for use in quantum applications: monazite-phase LaPO 4:Eu 3+ crystals, providing the first comprehensive, high-resolution optical coherence and spin lifetime characterization across the full concentration range, starting from 1% Eu 3+ and up to the fully stoichiometric compound EuPO 4 . The results show optical coherence times of the order 100 μs and nuclear spin lifetimes up to 2 h at 4 K, setting this material among the best reported so far, while experimental conditions for its synthesis with appropriate quality consist of a rather simple solid-state reaction. This opens promising perspectives for its use in quantum applications.
Three phases of stoichiometric europium(III) iodate compounds are probed as candidates for optical quantum memory to determine the impact of reaction conditions on phase formation and to relate crystal structure to their ability to host persistent excited states relevant to quantum memory. Hydrothermal synthesis procedures for growing macroscopic single crystals of rectangular-block α-Eu(IO 3 ) 3 ( P 2 1 / c ), yellow hexagonal plate β-Eu(IO 3 ) 3 ( P 2 1 / n ), and transparent plate NaEu(IO 3 ) 4 ( Cc ) are presented. The ability to burn narrow and long-lived spectral holes on the 7 F 0 → 5 D 0 optical transitions is a necessary condition for implementing optical quantum memory. α-Eu(IO 3 ) 3 was determined to be incapable of hole-burning due to the presence of insufficient asymmetry of the europium site, which forbids the required optical transition. β-Eu(IO 3 ) 3 was determined to be incapable of storing information due to a lack of observed spectral hole burning, likely due to decoherence caused by the closely packed edge-sharing Eu(III) polyhedra. Analysis of each phase’s crystal structure suggests that the Eu–Eu nearest neighbor distance and distortion of europium site symmetry are critical material design parameters for quantum memory applications.
Stoichiometric Eu 3+ compounds have recently shown promise for building dense, optically addressable quantum memory as the cations’ long nuclear spin coherence times and shielded 4f electron optical transitions provide reliable memory platforms. Implementing such a system, though, requires ultranarrow, inhomogeneous linewidth compounds. Finding this rare linewidth behavior within a wide range of potential chemical spaces remains difficult, and while exploratory synthesis is often guided by density functional theory (DFT) calculations, lanthanides’ 4f electrons pose unique challenges for stability predictions. Here, we report DFT procedures that reliably reproduce known phase diagrams and correctly predict two experimentally realized quantum memory candidates. We are the first to synthesize the double perovskite halide Cs 2 NaEuF 6 . It is an air-stable compound with a calculated band gap of 5.0 eV that surrounds Eu 3+ with mononuclidic elements, which are desirable for avoiding inhomogeneous linewidth broadening. We also analyze computational database entries to identify phosphates and iodates as the next generation of chemical spaces for stoichiometric quantum memory system studies. This work identifies new candidate platforms for exploring chemical effects on quantum memory candidates’ inhomogeneous linewidth while also providing a framework for screening Eu 3+ compound stability with DFT.
The success of the emerging field of solid-state optical quantum information processing (QIP) critically depends on the access to resonant optical materials. Rare-earth ions (REIs) are suitable candidates for QIP protocols due to their extraordinary photo-physical and magnetic quantum properties such as long optical and spin coherence lifetimes (T2T_2T2​). However, molecules incorporating REIs, despite having advantageous properties such as atomically exact quantum tunability, inherent scalability, and large portability, have not yet been studied for QIP applications. As a first testimony of the usefulness of REI molecules for optical QIP applications, we demonstrate in this study that narrow spectral holes can be burned in the inhomogeneously broadened 5^55D0→7_0\to^70​→7F0_00​ optical transition of a binuclear Eu(III) complex, rendering a homogeneous linewidth (ΓhΓ_hΓh​) = 22 ±\pm± 1 MHz, which translates as T2=14.5T_2 = 14.5T2​=14.5 ±\pm± 0.7 ns at 1.4 K. Moreover, long-lived spectral holes are observed, demonstrating efficient polarization of Eu(III) ground state nuclear spins, a fundamental requirement for all-optical spin initialization and addressing. These results elucidate the usefulness of REI-based molecular complexes as versatile coherent light-spin interfaces for applications in quantum communications and processing.
This thesis presents a spectroscopic study of the 7F0 ---t5D0 transition of Eu3+ in EuC13 ·6H2 0, which is used to evaluate the potential performance of a quantum com­ puting system implemented in EuCla·6H2 0 and, more generally, in stoichiometric rare earth crystals. EuC13 ·6H2 0 has one of the narrowest optical inhomogeneous linewidths of any solid but this linewidth is shown to be still much larger than that required for practical quantum computing in a rare earth crystal. To assess the possibility of reducing the linwidth, the contributions of isotopic impurities to both the optical linewidth and line structure were investigated, and ligand isotopes were identified as a major source of both inhomogeneous broadening and structure on the optical transition, suggesting that the linewidth could be substantially reduced by isotopi­ cally purifying EuC13 ·6H20. The effect of ligand isotopes on the optical lifetime and coherence time was also investigated. It was found that fully deuterating the crystal to EuC13·6D20 substantially improves both the lifetime and coherence time. The satellite lines formed in the optical spectrum of a rare earth crystal when it is doped with another rare earth are proposed as qubits. A crucial step in char­ acterising EuCla ·6H20 for quantum computing is associating these satellite lines in EuC13 ·6H2 0 with crystallographic sites. A new method for associating sites with lines, which works for low symmetry crystals such as EuC13·6H20, is presented. This method involves modelling the splitting of the ground state hyperfine levels caused by the magnetic dipole-dipole interaction between a Kramers dopant and the Eu3+ ion. Using this method, most of the outer satellite lines in rare earth doped EuCla·6H2 0 were assigned to crystallographic sites. It has been proposed that the electronic interactions between these satellite lines be used to enact two-qubit gates in a rare earth quantum computer. These interac­ tions were measured between a number of different satellite lines using a new two­ laser spectral holeburning technique. Interactions of up to 46.081±0.005 MHz were observed, and this was the first time that electronic interactions between weakly coupled rare earth ions had been measured. The two most common interactions identified between rare earth ions in solids are electric dipole-dipole and exchange, but the observed interactions are stronger than expected from a electric dipole-dipole model and occur at too large a distance to be superexchange. It is shown that the development of a moderate-sized quantum processor, one with more than 10 qubits, in a stoichiometric rare earth crystal is feasible provided that the optical inhomogeneous linewidth is reduced below 1MHz. Demonstrations of three or four qubit devices should be possible using existing materials.