We introduce a method for high-fidelity quantum state transduction between a superconducting microwave qubit and the ground state spin system of a solid-state artificial atom, mediated via an acoustic bus connected by piezoelectric transducers. Applied to present-day experimental parameters for superconducting circuit qubits and diamond silicon-vacancy centers in an optimized phononic cavity, we estimate quantum state transduction with fidelity exceeding 99% at a MHz-scale bandwidth. By combining the complementary strengths of superconducting circuit quantum computing and artificial atoms, the hybrid architecture provides high-fidelity qubit gates with long-lived quantum memory, high-fidelity measurement, large qubit number, reconfigurable qubit connectivity, and high-fidelity state and gate teleportation through optical quantum networks.

The development of high performing and accessible sensors is crucial to future point-of-care diagnostic sensing systems. Here, we report on a gold-titanium dioxide-gold metal-insulator-metal plasmonic nanocup array device for spectrometer-free refractometric sensing with a performance exceeding conventional surface plasmon resonance sensors. This device shows distinct spectral properties such that a superstrate refractive index increase causes a transmission intensity increase at the peak resonance wavelength. There is no spectral shift at this peak and there are spectral regions with no transmission intensity change, which can be used as internal device references. The sensing mechanism, plasmon-cavity coupling optimization, and material properties are studied using electromagnetic simulations. The optimal device structure is determined using simulation and experimental parameter sweeps to tune the cavity confinement and the resonance coupling. An experimental sensitivity of 800 ΔT%/RIU is demonstrated. Spectrometer-free, imaged-based detection is also carried out for the cancer biomarker carcinoembryonic antigen with a 10 ng/mL limit of detection. The high performance and distinct spectral features of this metal-insulator-metal plasmonic nanocup array make this device promising for future portable optical sensing systems with minimal instrumentation requirements.

The addition of active, nonlinear, and nonreciprocal functionalities to passive piezoelectric acoustic wave technologies could enable all-acoustic and therefore ultra-compact radiofrequency signal processors. Toward this goal, we present a heterogeneously integrated acoustoelectric material platform consisting of a 50 nm indium gallium arsenide epitaxial semiconductor film in direct contact with a 41° YX lithium niobate piezoelectric substrate. We then demonstrate three of the main components of an all-acoustic radiofrequency signal processor: passive delay line filters, amplifiers, and circulators. Heterogeneous integration allows for simultaneous, independent optimization of the piezoelectric-acoustic and electronic properties, leading to the highest performing surface acoustic wave amplifiers ever developed in terms of gain per unit length and DC power dissipation, as well as the first-ever demonstrated acoustoelectric circulator with an isolation of 46 dB with a pulsed DC bias. Finally, we describe how the remaining components of an all-acoustic radiofrequency signal processor are an extension of this work.

Active surface acoustic wave components have the potential to transform RF front ends by consolidating functionalities that currently occur across multiple chip technologies, leading to reduced insertion loss from converting back and forth between acoustic and electronic domains in addition to improved size and power efficiency. This letter demonstrates a significant advance in these active devices with a compact, high-gain, and low-power leaky surface acoustic wave amplifier based on the acoustoelectric effect. Devices use an acoustically thin semi-insulating InGaAs surface film on a YX lithium niobate substrate to achieve exceptionally high acoustoelectric interaction strength via an epitaxial In0.53Ga0.47As(P)/InP quaternary layer structure and wafer-scale bonding. We demonstrate 1.9 dB of gain per acoustic wavelength and power consumption of 90 mW for 30 dB of electronic gain. Despite the strong intrinsic leaky propagation loss, 5 dB of terminal gain is obtained for a semiconductor that is only 338 μm long due to state-of-the-art heterogenous integration and an improved material platform.

of surface plasmons with an incoherent light source and the detection with a portable spectrometer; however, the sensitivity of these devices is an order of magnitude lower than conventional SPR sensors. [7] Here, we report a new nanoplasmonic resonance sensor design that shows a unique interactive plasmonic-photonic resonance effect: only resonance peak intensity variation, not a plasmon resonance wavelength shift, is observed in the far field as a function of the optical refractive index (RI) on the superstrate when a periodic plasmonic nanostructure and a multilayer nanocavity are combined. Multilayer plasmonic structures have been investigated for on-chip photonic devices, such as multilayered plasmonic waveguides. [8] Metal-insulator-metal (MIM) surface plasmon waveguides have been studied for refractometric detection. [9] In addition, the localized surface plasmon resonance (LSPR) effect has been used with multilayered geometries to increase light-induced catalytic activity of materials such as palladium. [10] The study of dielectric films and MIM structures combined with an EOT substrate has been reported previously. [11] However, these prior works focused on surface enhanced Raman spectroscopy applications or on the plasmon resonance peak shift of nanohole arrays and the sensitivity of these structures to superstrate RI changes was lower than conventional EOT devices.The new hybrid nanoplasmonic-nanocavity sensor that we utilize here is based on a 3D plasmonic nanocup resonator structure, which consists of a nanostructured polymer substrate with a deposited gold (Au) layer. [12] To form a nanocavity A sensor design and sensing method based on plasmonic-photonic interactions that occur when a nanocavity array is embedded in a 3D tapered nanocup plasmonic substrate are reported. This device enables highly sensitive detection of refractive index changes based on changes to the transmission peak intensity without shift in the resonance wavelength. Unlike conventional plasmonic sensors, there is a consistent and selective change in the transmission intensity at the resonance peak wavelength with no spectral shift. In addition, there are wavelength ranges that show no intensity change, which can be used as reference regions. The fabrication and characterization of the plasmonic nanocavity sensor are described and also advanced biosensing is demonstrated. Simulations are carried out to better understand the plasmon-photonic coupling mechanism. This nanocavity plasmonic sensor design has a limit of detection of 1 ng mL −1 (5 × 10 −12 m) for the cancer biomarker carcinoembryonic antigen (CEA), which is a significant improvement over current surface plasmon resonance systems, and a dynamic range that is clinically relevant for human CEA levels.