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1. Erasure conversion in a high-fidelity Rydberg quantum simulator

   https://doi.org/10.1038/s41586-023-06516-4  

   Scholl, Pascal; Shaw, Adam L.; Tsai, Richard Bing-Shiun; Finkelstein, Ran; Choi, Joonhee; Endres, Manuel (October 2023, Nature)

   Abstract Minimizing and understanding errors is critical for quantum science, both in noisy intermediate scale quantum (NISQ) devices¹and for the quest towards fault-tolerant quantum computation^2,3. Rydberg arrays have emerged as a prominent platform in this context⁴with impressive system sizes^5,6and proposals suggesting how error-correction thresholds could be significantly improved by detecting leakage errors with single-atom resolution^7,8, a form of erasure error conversion^9–12. However, two-qubit entanglement fidelities in Rydberg atom arrays^13,14have lagged behind competitors^15,16and this type of erasure conversion is yet to be realized for matter-based qubits in general. Here we demonstrate both erasure conversion and high-fidelity Bell state generation using a Rydberg quantum simulator^5,6,17,18. When excising data with erasure errors observed via fast imaging of alkaline-earth atoms^19–22, we achieve a Bell state fidelity of$$\ge 0.997{1}_{-13}^{+10}$$ $\ge 0.9971_{-13}^{+10}$, which improves to$$\ge 0.998{5}_{-12}^{+7}$$ $\ge 0.9985_{-12}^{+7}$when correcting for remaining state-preparation errors. We further apply erasure conversion in a quantum simulation experiment for quasi-adiabatic preparation of long-range order across a quantum phase transition, and reveal the otherwise hidden impact of these errors on the simulation outcome. Our work demonstrates the capability for Rydberg-based entanglement to reach fidelities in the 0.999 regime, with higher fidelities a question of technical improvements, and shows how erasure conversion can be utilized in NISQ devices. These techniques could be translated directly to quantum-error-correction codes with the addition of long-lived qubits^7,22–24. 

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2. Error-detected quantum operations with neutral atoms mediated by an optical cavity

   https://doi.org/10.1126/science.adr7075  

   Grinkemeyer, Brandon; Guardado-Sanchez, Elmer; Dimitrova, Ivana; Shchepanovich, Danilo; Mandopoulou, G Eirini; Borregaard, Johannes; Vuletić, Vladan; Lukin, Mikhail D (March 2025, Science)

   Neutral-atom quantum processors are a promising platform for large-scale quantum computing. Integrating them with optical cavities enables fast nondestructive qubit readout and access to fast remote entanglement generation for quantum networking. In this work, we introduce a platform for coupling single atoms in optical tweezers to a Fabry-Perot fiber cavity. Leveraging the strong atom-cavity coupling, we demonstrated fast qubit-state readout with ${99.960}_{-24}^{+14}\%$fidelity and two methods for cavity-mediated entanglement generation with integrated error detection. First, we used cavity-carving to generate a Bell state with 91(4)% fidelity and a 32(1)% success rate (the number in parentheses is the standard deviation). Second, we performed a cavity-mediated gate with a deterministic entanglement fidelity of 52.5(18)%, increased to 76(2)% with error detection. Our approach provides a route toward modular quantum computing and networking. 

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3. Spectroscopy and Modeling of ${}^{171}\mathrm{Yb}$ Rydberg States for High-Fidelity Two-Qubit Gates

   https://doi.org/10.1103/PhysRevX.15.011009  

   Peper, Michael; Li, Yiyi; Knapp, Daniel Y; Bileska, Mila; Ma, Shuo; Liu, Genyue; Peng, Pai; Zhang, Bichen; Horvath, Sebastian P; Burgers, Alex P; et al (January 2025, Physical Review X)

   Highly excited Rydberg states and their interactions play an important role in quantum computing and simulation. These properties can be predicted accurately for alkali atoms with simple Rydberg level structures. However, an extension of these methods to more complex atoms such as alkaline-earth atoms has not been demonstrated or experimentally validated. Here, we present multichannel quantum defect models for highly excited ${}^{174}\mathrm{Yb}$and ${}^{171}\mathrm{Yb}$Rydberg states with $L\le 2$. The models are developed using a combination of existing literature data and new, high-precision laser and microwave spectroscopy in an atomic beam, and validated by detailed comparison with experimentally measured Stark shifts and magnetic moments. We then use these models to compute interaction potentials between two Yb atoms, and find excellent agreement with direct measurements in an optical tweezer array. From the computed interaction potential, we identify an anomalous Förster resonance that likely degraded the fidelity of previous entangling gates in ${}^{171}\mathrm{Yb}$using $F=3/2$Rydberg states. We then identify a more suitable $F=1/2$state, and achieve a state-of-the-art controlled- gate fidelity of $\mathcal{F}=0.994\left(1\right)$, with the remaining error fully explained by known sources. This work establishes a solid foundation for the continued development of quantum computing, simulation, and entanglement-enhanced metrology with Yb neutral atom arrays. Published by the American Physical Society2025 

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4. Highly-excited Rydberg excitons in synthetic thin-film cuprous oxide

   https://doi.org/10.1038/s41598-023-41465-y  

   DeLange, Jacob; Barua, Kinjol; Paul, Anindya Sundar; Ohadi, Hamid; Zwiller, Val; Steinhauer, Stephan; Alaeian, Hadiseh (December 2023, Scientific Reports)

   Abstract Cuprous oxide ($$\hbox {Cu}{}_2\hbox {O}$$ $\text{Cu}{}_2\text{O}$) has recently emerged as a promising material in solid-state quantum technology, specifically for its excitonic Rydberg states characterized by large principal quantum numbers (n). The significant wavefunction size of these highly-excited states (proportional to$$n^2$$ $n^2$) enables strong long-range dipole-dipole (proportional to$$n^4$$ $n^4$) and van der Waals interactions (proportional to$$n^{11}$$ $n^{11}$). Currently, the highest-lying Rydberg states are found in naturally occurring$$\hbox {Cu}_2\hbox {O}$$ ${\text{Cu}}_2\text{O}$. However, for technological applications, the ability to grow high-quality synthetic samples is essential. The fabrication of thin-film$$\hbox {Cu}{}_2\hbox {O}$$ $\text{Cu}{}_2\text{O}$samples is of particular interest as they hold potential for observing extreme single-photon nonlinearities through the Rydberg blockade. Nevertheless, due to the susceptibility of high-lying states to charged impurities, growing synthetic samples of sufficient quality poses a substantial challenge. This study successfully demonstrates the CMOS-compatible synthesis of a$$\hbox {Cu}{}_2\hbox {O}$$ $\text{Cu}{}_2\text{O}$thin film on a transparent substrate that showcases Rydberg excitons up to$$n = 8$$ $n=8$which is readily suitable for photonic device fabrications. These findings mark a significant advancement towards the realization of scalable and on-chip integrable Rydberg quantum technologies. 

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5. Widely tunable cavity-enhanced frequency combs

   https://doi.org/10.1364/OL.389412  

   Silfies, Myles_C; Kowzan, Grzegorz; Chen, Yuning; Lewis, Neomi; Hou, Ryan; Baehre, Robin; Gross, Tobias; Allison, Thomas_K (April 2020, Optics Letters)

   We describe the cavity enhancement of frequency combs over a wide tuning range of 450–700 nm ( $><\#comment/>7900{\mathrm{c}\mathrm{m}}^{-<\#comment/>1}$), covering nearly the entire visible spectrum. Tunable visible frequency combs from a synchronously pumped optical parametric oscillator are coupled into a four-mirror, dispersion-managed cavity with a finesse of 600–1400. An intracavity absorption path length enhancement greater than 190 is obtained over the entire tuning range, while preserving intracavity spectral bandwidths capable of supporting sub-200 fs pulse durations. These tunable cavity-enhanced frequency combs can find many applications in nonlinear optics and spectroscopy. 

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