A high-fidelity controlled-$Z$ (CZ) gate utilizing a double-transmon coupler (DTC) has recently been demonstrated as a building block for superconducting quantum processors. Like many other kinds of tunable couplers, however, the DTC requires a finite dc current for flux biasing the coupler at the idling point to turn off the coupling, necessitating extra care for wiring and heat-load management. To address this issue, we theoretically propose and experimentally realize a coupling scheme by introducing a shunt capacitance between the two transmons of the DTC at zero-flux bias, which demonstrates high-fidelity CZ-gate performance comparable to the previous DTC. Through a comprehensive error budget analysis using multiple randomized benchmarking methods, we also identify that the current fidelity is limited by the decoherence through the coupler. Moreover, we experimentally demonstrate the wide operational flux range of the capacitively shunted DTC, which solves the challenging issue of remnant flux existing even with careful magnetic shielding.

Due to the high penetrating power of cosmic-ray muons, they can be used to probe very thick and dense objects. As muons are charged particles, they can be tracked by ionization detectors, determining the position and direction of the muons. With detectors on either side of an object to measure particle direction change, scattering information within the object can be found. This can be used to produce a scattering-intensity image within the object related to density and atomic number. Such imaging is typically performed with a single detector-object orientation, taking advantage of the more intense downward flux of muons, producing planar imaging with some depth-of-field information in the third dimension. Several simulation studies were published with multiorientation tomography, which can form a three-dimensional representation faster than a single-orientation view. In this study, experimental muon-scatter-based tomography was performed using a concrete filled steel drum with several different metal wedges inside, with the drum between detector planes. Data were collected from different detector-object orientations by rotating the steel drum. The data collected from each orientation were combined using two different tomographic methods. A traditional inverse Radon transform approach used for computed tomography and a combination of multiple depth-of-field reconstructions were applied to the data. As cosmic-ray muon flux imaging is rate limited, the imaging techniques were compared for sparse data. Using the combined depth-of-field reconstruction technique, fewer detector-object orientations were needed to reconstruct images that could be used to differentiate the metal wedges.

Classical broadband ventilated insulation metamaterials (BVSIMs) usually have a trade-off between bandwidth, efficiency, and thickness. In this paper, we propose a different design method of BVSIM based on dual-mode Fano resonance (DMFR) with a simple structure and fine performance. The bandwidth of a unit cell (ventilation rate exceeds 30%) can be adjusted arbitrarily within 1/3–1 octave by changing structural parameters based on the DMFR. The broadband sound insulation and filtering effects can be achieved by connecting different BVSIM units in series. Through the nonlocal coupling resonance (NCR) of the four-unit Fano resonance and Fabry-Pérot (FP) resonances, the supercell with NCR can achieve ultrabroadband sound insulation within 400–2450 Hz (i.e., >2.5 octaves). The thickness of the low-frequency unit is only 0.0776λ of the minimum working frequency. Our findings are demonstrated via theoretical derivation, numerical simulation, and experimental measurement, which could have a variety of practical application scenarios such as noise control, acoustic communication, and sound detection.

Nodal line semimetals exhibit band degeneracies that manifest themselves as one-dimensional ring structures in the momentum space. Here we experimentally demonstrate the existence of both gapless and gapped nodal rings in a two-dimensional photonic crystal composed of all-dielectric material. Breaking mirror symmetry that introduces a mass term causes the nodal ring degeneracies to transition into gapped states. By stacking two photonic crystals with opposite mass terms, we observe the emergence of Jackiw-Rebbi-like interface states within the gapped nodal rings. These interface states exhibit flat band dispersion, which is used to realize slow-light waveguides with low propagation loss. Additionally, a mode-tapering waveguide is designed by our modulating both the size of the gapless nodal ring structure and the bandwidth of the gapped nodal rings. Our results provide a simple two-dimensional platform for investigating nodal ring physics and exploring the potential applications of nodal rings in photonic devices.

High-sensitivity laser spectroscopy is integral to applications such as atomic clocks, quantum computers, and chemical sensing. Lowering the atomic temperature decreases spectral Doppler broadening and increases the transit time across the excitation laser. We find that a polydimethylsiloxane (PDMS)-coated surface can cool iron atoms from approximately $1400$ K to room temperature by surface scattering. It is also apparent that a single scattering event is enough for atoms to equilibrate with the surface temperature of the PDMS. Further, we reveal the very low adsorption of iron and ytterbium atoms on PDMS, an effect that persists at surface temperatures down to 200 K. Through numerical simulations, we demonstrate the potential use of surface scattering in creating a room-temperature source of collimated atoms with enhanced flux and reduced velocity compared to one without surface scattering.

Amorphous-oxide layers in thin-film capacitors are linked to reduced transmon-qubit $T_1$ coherence times. $\mathrm{Ta}$-based capacitors outperform $\mathrm{Nb}$-based ones, suggesting that amorphous $\mathrm{Ta}$${}_2$$\mathrm{O}$${}_{5-x}$ is less lossy than $\mathrm{Nb}$${}_2$$\mathrm{O}$${}_{5-x}$. We investigate the microscopic features of these amorphous oxides using ab initio molecular dynamics and density functional theory, revealing the origins of the superior performance of $\mathrm{Ta}$${}_2$$\mathrm{O}$${}_{5-x}$. We establish that oxygen deficiency is less likely to occur in amorphous $\mathrm{Ta}$${}_2$$\mathrm{O}$${}_{5-x}$ than in $\mathrm{Nb}$${}_2$$\mathrm{O}$${}_{5-x}$ for $0\le x\le 0.25$ and that for a given oxygen deficiency $x$, metal $\mathrm{Ta}$—$\mathrm{Ta}$ bond formation is enhanced. Such bonds, which are accommodated by structural flaws in the amorphous network, capture electrons better than in amorphous $\mathrm{Nb}$${}_2$$\mathrm{O}$${}_{5-x}$. These thermochemical differences quench or highly suppress magnetic moments in amorphous $\mathrm{Ta}$${}_2$$\mathrm{O}$${}_{5-x}$ and eliminate a potential source of quasiparticles and magnetic flux noise. We also show that hyperfine couplings between $\mathrm{Nb}$ nuclei and local magnetic moments in $\mathrm{Nb}$${}_2$$\mathrm{O}$${}_{5-x}$ can form “two-level systems” (TLSs) or “two-level fluctuators” with energy splittings of 100–1000 MHz or higher. This reveals a TLS mechanism in amorphous $\mathrm{Nb}$${}_2$$\mathrm{O}$${}_{5-x}$ oxide layers that is likely inactive in $\mathrm{Ta}$${}_2$$\mathrm{O}$${}_{5-x}$. Our work provides a fundamental understanding of the materials chemistry and limitations imposed by native oxides of superconducting qubits that can be used to guide materials selection and processing.

We phenomenologically formulate and experimentally observe an adiabatic transverse thermoelectric conversion enhanced by a heat current reorientation in artificially tilted multilayers (ATMLs). By alternately stacking two materials with different thermal conductivities and rotating the multilayered structure with respect to a longitudinal temperature gradient, we induce off-diagonal components in the thermal conductivity tensor. This off-diagonal thermal conduction (ODTC) generates a finite transverse temperature gradient and Seebeck effect–induced thermopower in the adiabatic condition, which is superposed on the isothermal transverse thermopower driven by the off-diagonal Seebeck effect. In this study, we calculate and observe the two-dimensional temperature distribution and the resultant transverse thermoelectric conversion in ATMLs comprising thermoelectric ${\mathrm{Co}}_2\mathrm{Mn}\mathrm{Ga}$ Heusler alloys and ${\mathrm{Bi}}_{2-a}{\mathrm{Sb}}_a{\mathrm{Te}}_3$ compounds. By our changing the tilt angle from 0° to 90°, the transverse temperature gradient obviously appeared in the middle angles and the transverse thermopower increases up to −121.9 µV/K in the ${\mathrm{Co}}_2\mathrm{Mn}\mathrm{Ga}/{\mathrm{Bi}}_{0.2}{\mathrm{Sb}}_{1.8}{\mathrm{Te}}_3$-based ATML at a tilt angle of 45° whereas the isothermal contribution is estimated to be −82.6 µV/K from the analytical calculation. This hybrid action derived from ODTC results in a significant increase of the maximum reduced conversion efficiency from 3.1% to 8.1% in calculations and from 2.3% to 4.4% in experiments.

The intricate interplay between Laguerre-Gauss beams (LGBs) carrying orbital angular momentum (OAM) and atomic systems has emerged as a fascinating area of research in quantum optics and quantum information science. These LGBs have proven to be invaluable tools for advancing optical manipulation, information processing, imaging technologies, and communication systems. In the present investigation, we explore two near-infrared pump vortex beams of Laguerre-Gaussian mode, each characterized by distinct azimuthal indices $l_1$ and $l_2$, representing their respective topological charges. Through meticulous observation of the blue vortex beam generated under dual-wavelength condition in the four-wave-mixing process, we successfully demonstrate and verify OAM conversions, thereby providing compelling evidence for the conservation of OAM. The findings from this study hold significant promise for applications in spatial optical communication multiplexing technology, potentially revolutionizing transmission capacity in future communication systems.

The rapid growth of digital technology has driven the need for efficient storage solutions, positioning memristors as promising candidates for next-generation nonvolatile memory (NVM) due to their superior electrical properties. Organic and inorganic materials each offer distinct advantages for resistive-switching performance, while hybrid materials such as metal-organic frameworks (MOFs) combine the strengths of both. In this study, we present a resistive random-access memory (ReRAM) device using zeolitic imidazolate framework (ZIF-8), an MOF material, as the resistive-switching layer. The ZIF-8 film is synthesized via a simple solution process method at room temperature and subsequently characterized. The $\mathrm{Al}$/ZIF-8/ITO device demonstrates bipolar resistive-switching behavior with an on-off resistance ratio of approximately ${10}^2$, stable retention up to ${10}^4$ s, and consistent performance across 60 cycles while exhibiting robust thermal stability from $-20{}^{\circ }\mathrm{C}$ to $100{}^{\circ }\mathrm{C}$. Low-frequency noise and impedance spectroscopy measurements suggest a filamentary switching mechanism. Additionally, the memory state can be tuned by adjusting the reset voltage, pointing to its potential as multilevel memory. Potentiation and depression experiments further highlight the device’s promise for neuromorphic applications. With high stability, tunability, and strong performance, ZIF-8 based ReRAM shows great promise for advanced NVM and neuromorphic computing applications.

Correlated noise across multiqubit architectures is known to be highly detrimental to the operation of error-correcting codes and the long-term feasibility of quantum processors. The recent discovery of spatially dependent correlated noise in multiqubit architectures of superconducting qubits arising from the impact of cosmic radiation and high-energy particles giving rise to quasiparticle poisoning within the substrate has led to intense investigations of mitigation strategies to address this. Correlated noise in semiconductor spin qubits is also now receiving attention, as this platform begins to scale. Here we report the magnitude, frequency, and spatial dependence of noise correlations between four silicon quantum dot pairs as a function of interdot distance at frequencies from 0.3 to 1 mHz. We find the magnitude of charge-noise correlations, quantified by the magnitude square coherence $C_{xy}$, are significantly suppressed from $>0.5$ to $<0.1$ as the interdot distance increases from 75 to 300 nm. Using an analytical model we confirm that, in contrast to superconducting qubits, the dominant source of correlated noise arises from low-frequency charge noise from the presence of two level fluctuators (TLFs) at the native silicon-silicon dioxide surface. Knowing this, we conclude with a timely discussion of charge-noise mitigation strategies.

Gradient-index lenses, enabled by meta-atoms, have demonstrated effective focusing capabilities in both airborne and submerged environments. However, the current focusing capabilities remain constrained primarily to two-dimensional systems. Here we introduce a quasi-3D gradient-index lens designed for underwater sound focusing. This lens, characterized by a simple yet effective design, features an additional degree of freedom along the axial direction, enabling controlled wave refraction in longitudinal and lateral directions. To achieve this, eigenfrequency analysis and a scattering parameter retrieval method are used to calculate the band structure and characterize the effective material properties. Numerical simulations and experimental validation confirm the efficacy of the lens in focusing underwater sound and highlight its potential for high-resolution sensing, advanced biomedical imaging, and efficient energy harvesting.

Building a scalable, universal, high-performance quantum processor is a formidable challenge. In particular, the problem of realizing fast, high-performance two-qubit gates of high fidelity has yet to be addressed. Here, we propose a building block for a scalable quantum processor consisting of two transmons and a tunable three-mode coupler allowing for $ZZ$ interaction control. We experimentally demonstrate a native cz gate with a pulse duration of 60 ns, achieving a two-qubit gate fidelity above $98\mathrm{\%}$, limited mostly by the qubit coherence time. Numerical simulations show that by optimizing the gate duration, the fidelity can be pushed over $99.97\mathrm{\%}$.

Lithium niobate (LN) is a promising material for building acoustic resonators used in quantum applications, but its performance is limited by poorly understood material defects called two-level systems (TLSs). In this work, we fabricate high-performance acoustic resonators from LN with quality factors up to $6\times {10}^7$ and use them to separate bulk and surface contributions to TLS loss. By comparing these bulk acoustic wave (BAW) resonators with previous surface-acoustic-wave and phononic-crystal studies, we show that devices with high surface-participation ratios are limited by surface TLSs, while our BAW devices reveal an intrinsic bulk TLS limit. Through systematic surface treatments and microscopy, we demonstrate that BAW resonator performance remains unchanged despite surface modifications, confirming operation in a bulk-limited regime. Our work establishes quantitative bounds on both surface and bulk TLS losses in LN within the context of the material growth and fabrication approaches we have pursued, and it provides guidance for future device engineering and materials development.

Acoustic-wave devices in the microwave regime are pivotal to next-generation wireless communications, the Internet of Things, and burgeoning quantum technologies. Here, we present a lithium niobate on a silicon carbide (${\mathrm{Li}\mathrm{Nb}\mathrm{O}}_3$-$\mathrm{on}$-$\mathrm{Si}\mathrm{C}$) ridge waveguide platform engineered to harness quasi-Love-mode surface acoustic waves with strong lateral confinement and low propagation loss. By leveraging the velocity mismatch between ${\mathrm{Li}\mathrm{Nb}\mathrm{O}}_3$ and $\mathrm{Si}\mathrm{C}$, acoustic waves are steered efficiently along the ridge. To surmount persistent limitations in bandwidth (BW) and insertion loss (IL), we integrate single-phase unidirectional transducers (SPUDTs) and tapered waveguide structures. Experimental data reveal that, compared to conventional interdigital transducers, SPUDTs markedly extend the passband and lower IL, achieving a minimum of 2.81 dB. Further introducing taper structures reduces IL to 2.53 dB over a BW exceeding 150 MHz, all while preserving favorable propagation characteristics. In addition, we demonstrate bent waveguides and Y-shaped splitters that maintain robust performance, underscoring the quasi-Love-mode resilience to curvature. Altogether, this SPUDT-based ridge waveguide platform delivers low-loss, wideband acoustic-transmission lines poised for advanced phononic-integrated circuits, spanning both classical signal processing and hybrid quantum applications.

Traveling-wave parametric amplifiers (TWPAs) have become an essential tool for the readout of quantum circuits and the search for dark matter. We report on the implementation of an rf-superconducting quantum interference device (SQUID)-based Josephson TWPA with an average saturation power of −84 dBm while providing an average power gain of 20 dB from 3.5 to 8.5 GHz. This wide bandwidth is enabled by reducing the curvature of the dispersion in the signal band while suppressing detrimental mixing processes. With 2393 rf-SQUIDs, our device has a comparable number of nonlinear elements but achieves ten times higher saturation power than previously reported devices. This shows that using rf-SQUIDs results in a more favorable trade-off between device length and saturation power. Harnessing wideband characterization techniques, we determine the TWPA’s excess noise above the quantum limit to be 0.8 to 1.5 photons. In addition, we validate the signal-to-noise ratio improvement as a practical measure for tuning the TWPA to minimize the total system noise and demonstrate that its optimum does not coincide with the highest gain.

In the noisy intermediate-scale quantum era, one of the most crucial bottlenecks for the realization of universal quantum computation is error correction. Stabilizer code is the most recognizable type of quantum error-correction code. A scalable efficient decoder is most desired for the application of the quantum error-correction codes. In this work, we propose a self-attention U-Net quantum decoder (SU-NetQD) for toric code, which outperforms the minimum-weight perfect-matching decoder, especially in the circuit-level noise environments. Specifically, with our SU-NetQD, we achieve lower logical error rates compared with MWPM and discover an increased trend of code threshold as the increase of noise bias. We obtain a high threshold of 0.231 for the extremely biased noise environment. The combination of low-level decoder and high-level decoder is the key innovation for the high accuracy of our decoder. With transfer learning mechanics, our decoder is scalable for cases with different code distances. Our decoder provides a practical tool for quantum noise analysis and promotes the practicality of quantum error-correction codes and quantum computing.