High-Fidelity Control, Detection, and Entanglement of Alkaline-Earth Rydberg Atoms

Trapped neutral atoms have become a prominent platform for quantum science, where entanglement fidelity records have been set using highly excited Rydberg states. However, controlled two-qubit entanglement generation has so far been limited to alkali species, leaving the exploitation of more complex electronic structures as an open frontier that could lead to improved fidelities and fundamentally different applications such as quantum-enhanced optical clocks. Here, we demonstrate a novel approach utilizing the two-valence electron structure of individual alkaline-earth Rydberg atoms. We find fidelities for Rydberg state detection, single-atom Rabi operations and two-atom entanglement that surpass previously published values. Our results pave the way for novel applications, including programmable quantum metrology and hybrid atom–ion systems, and set the stage for alkaline-earth based quantum computing architectures

Many-body cavity quantum electrodynamics with driven inhomogeneous emitters

Quantum emitters coupled to optical resonators are quintessential systems for exploring fundamental phenomena in cavity quantum electrodynamics (cQED) and are commonly used in quantum devices acting as qubits, memories and transducers. Many previous experimental cQED studies have focused on regimes in which a small number of identical emitters interact with a weak external drive, such that the system can be described with simple, effective models. However, the dynamics of a disordered, many-body quantum system subject to a strong drive have not been fully explored, despite its importance and potential in quantum applications. Here we study how a large, inhomogeneously broadened ensemble of solid-state emitters coupled with high cooperativity to a nanophotonic resonator behaves under strong excitation. We discover a sharp, collectively induced transparency (CIT) in the cavity reflection spectrum, resulting from quantum interference and collective response induced by the interplay between driven inhomogeneous emitters and cavity photons. Furthermore, coherent excitation within the CIT window leads to highly nonlinear optical emission, spanning from fast superradiance to slow subradiance. These phenomena in the many-body cQED regime enable new mechanisms for achieving slow light and frequency referencing, pave a way towards solid-state superradiant lasers and inform the development of ensemble-based quantum interconnects.Comment: ML and RF contributed equally to this wor

Thermal Effects of Microwave Reduced-Graphene-Oxide Coated Polyester Fabric on a Simulated Human Skin in Cool and Neutral Air Temperatures

Batteryless wearable technology has wide applications. In particular, human body surface temperature controlling fabrics can help regulate skin temperature in heat or cold. This study investigated surface temperature distribution of the fabrics coated with reduced graphene oxide (rGO) on simulated human body skin conditions at 18 degrees C (cool) and 27 degrees C (neutral) ambient air temperatures. Polyester fabrics were spin-coated with a graphene-oxide (GO) solution of 0.2 wt%. Preparation of rGO was processed by using a microwave oven (MW-rGO). Non-treated fabric (CON) was compared to GO and MW-rGO. The surface temperature of a hot plate was maintained at 35 degrees C or 40 degrees C. The test fabrics were put on the heated hot plate or non-heated-outer portions of the hot plate. Surface temperatures of MW-rGO on the heated hot plate at an air temperature of 18 degrees C (cool) were higher than those of non-treated fabric (CON) under the same conditions (p < 0.01). No effects from the graphene treatment were found on non-heated portions of the graphene oxide fabric (GO) or the reduced graphene oxide fabric (MW-rGO). On the non-heated portions, surface temperatures were higher at the location closer to the hot plate compared to the location farther from the hot plate (p < 0.05). These results partially represent thermal effects of MW-rGO under a specific environment and heat source. Our findings enable an application of reduced graphene oxide to body temperature regulating clothing.

Erasure conversion in a high-fidelity Rydberg quantum simulator

Minimizing and understanding errors is critical for quantum science, both in noisy intermediate scale quantum (NISQ) devices and for the quest towards fault-tolerant quantum computation. Rydberg arrays have emerged as a prominent platform in this context with impressive system sizes and proposals suggesting how error-correction thresholds could be significantly improved by detecting leakage errors with single-atom resolution, a form of erasure error conversion. However, two-qubit entanglement fidelities in Rydberg atom arrays have lagged behind competitors and 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. We implement erasure conversion via fast imaging of alkaline-earth atoms, which leaves atoms in a metastable state unperturbed and yields additional information independent of the final qubit readout. When excising data with observed erasure errors, we achieve a lower-bound for the Bell state generation fidelity of ${\geq} 0.9971^{+10}_{-13}$, which improves to ${\geq}0.9985^{+7}_{-12}$ when correcting for remaining state preparation errors. We further demonstrate erasure conversion in a quantum simulation experiment for quasi-adiabatic preparation of long-range order across a quantum phase transition, where we explicitly differentiate erasure conversion of preparation and Rydberg decay errors. We unveil the otherwise hidden impact of these errors on the simulation outcome by evaluating correlations between erasures and the final readout as well as between erasures themselves. Our work demonstrates the capability for Rydberg-based entanglement to reach fidelities in the ${\sim} 0.999$ regime, with higher fidelities a question of technical improvements, and shows how erasure conversion can be utilized in NISQ devices.Comment: PS and ALS contributed equally to this wor

Emergent quantum state designs from individual many-body wavefunctions

Quantum chaos in many-body systems provides a bridge between statistical and quantum physics with strong predictive power. This framework is valuable for analyzing properties of complex quantum systems such as energy spectra and the dynamics of thermalization. While contemporary methods in quantum chaos often rely on random ensembles of quantum states and Hamiltonians, this is not reflective of most real-world systems. In this paper, we introduce a new perspective: across a wide range of examples, a single non-random quantum state is shown to encode universal and highly random quantum state ensembles. We characterize these ensembles using the notion of quantum state $k$-designs from quantum information theory and investigate their universality using a combination of analytic and numerical techniques. In particular, we establish that $k$-designs arise naturally from generic states as well as individual states associated with strongly interacting, time-independent Hamiltonian dynamics. Our results offer a new approach for studying quantum chaos and provide a practical method for sampling approximately uniformly random states; the latter has wide-ranging applications in quantum information science from tomography to benchmarking.Comment: 7+19 pages, 6 figure

Benchmarking highly entangled states on a 60-atom analog quantum simulator

Quantum systems have entered a competitive regime where classical computers must make approximations to represent highly entangled quantum states. However, in this beyond-classically-exact regime, fidelity comparisons between quantum and classical systems have so far been limited to digital quantum devices, and it remains unsolved how to estimate the actual entanglement content of experiments. Here we perform fidelity benchmarking and mixed-state entanglement estimation with a 60-atom analog Rydberg quantum simulator, reaching a high entanglement entropy regime where exact classical simulation becomes impractical. Our benchmarking protocol involves extrapolation from comparisons against many approximate classical algorithms with varying entanglement limits. We then develop and demonstrate an estimator of the experimental mixed-state entanglement, finding our experiment is competitive with state-of-the-art digital quantum devices performing random circuit evolution. Finally, we compare the experimental fidelity against that achieved by various approximate classical algorithms, and find that only one, which we introduce here, is able to keep pace with the experiment on the classical hardware we employ. Our results enable a new paradigm for evaluating the performance of both analog and digital quantum devices in the beyond-classically-exact regime, and highlight the evolving divide between quantum and classical systems.Comment: ALS, ZC, and JC contributed equall

Multi-ensemble metrology by programming local rotations with atom movements

Current optical atomic clocks do not utilize their resources optimally. In particular, an exponential gain could be achieved if multiple atomic ensembles were to be controlled or read-out individually, even without entanglement. However, controlling optical transitions locally remains an outstanding challenge for neutral atom based clocks and quantum computing platforms. Here we show arbitrary, single-site addressing for an optical transition via sub-wavelength controlled moves of tweezer-trapped atoms, which we perform with $99.84(5)\%$ fidelity and with $0.1(2)\%$ crosstalk to non-addressed atoms. The scheme is highly robust as it relies only on relative position changes of tweezers and requires no additional addressing beams. Using this technique, we implement single-shot, dual-quadrature readout of Ramsey interferometry using two atomic ensembles simultaneously, and show an enhancement of the usable interrogation time at a given phase-slip error probability, yielding a 2.55(9) dB gain over standard, single-ensemble methods. Finally, we program a sequence which performs local dynamical decoupling during Ramsey evolution to evolve three ensembles with variable phase sensitivities, a key ingredient of optimal clock interrogation. Our results demonstrate the potential of fully programmable quantum optical clocks even without entanglement and could be combined with metrologically useful entangled states in the future