First-in-man clinical implantation and acute pacing performance of a novel subxiphoidal pacemaker system.

BACKGROUND: Intravascular cardiac pacemakers are an established therapy for bradycardic indications. Recently, a new class of leadless pacemakers have mitigated some of the complications related to pacemaker leads. In this study, we evaluate the implantation and performance of a novel extravascular technology that delivers epicardial pacing through a subxiphoidal approach. METHODS: Fifteen patients undergoing non-emergent open-heart surgery were enrolled. A midline incision was made just below the xiphoid process, and substernal tunneling was used to create a pocket for the device and to access the anterior pericardium over the right ventricle. The test device (Calyan Technologies, Oakdale, MN) was temporarily inserted underneath the ribcage and clipped to the xiphoid process. The sensing and pacing electrode (FlexArm) was positioned on the anterior pericardium. Ventricular sensing and pacing capture thresholds were measured. RESULTS: The test device was successfully implanted in all 15 patients. There were no device or procedure-related adverse events. The first five implanted patients had no pacing capture at maximum stimulation intensity. Design changes were made to the device, including different electrode size and shape, and successful ventricular capture was achieved in 9 of the subsequent 10 patients. In these patients, pacing threshold was 3.8 ± 1.6 mA with a pulse width of 0.5 ms. All devices were successfully explanted at the end of the procedure. CONCLUSIONS: In a first-in-human experience with a novel extravascular pacemaker, this study demonstrated the feasibility of pericardial ventricular pacing via a subxiphoidal approach. Further chronic studies are required to evaluate the safety and performance of this novel pacing technology.

A 64-pixel mid-infrared single-photon imager based on superconducting nanowire detectors.

A large-format mid-infrared single-photon imager with very low dark count rates would enable a broad range of applications in fields like astronomy and chemistry. Superconducting nanowire single-photon detectors (SNSPDs) are a mature photon-counting technology as demonstrated by their figures of merit such as high detection efficiencies and very low dark count rates. However, scaling SNSPDs to large array sizes for mid-infrared applications requires sophisticated readout architectures in addition to superconducting materials development. In this work, an SNSPD array design that combines a thermally coupled row-column multiplexing architecture with a thermally coupled time-of-flight transmission line was developed for mid-infrared applications. The design requires only six cables and can be scaled to larger array sizes. The demonstration of a 64-pixel array shows promising results for wavelengths between 3.4 µm and 10 µm, which will enable the use of this single-photon detector technology for a broad range of new applications.

Safety and performance of a novel subxiphoidal pacemaker system.

BACKGROUND: Traditional cardiac pacemakers commonly have a range of complications related to the presence of intracardiac leads. A new class of extravascular and leadless pacemakers has recently emerged with the potential to mitigate these complications and expand access to cardiac pacing. The objective of this study is to evaluate the implantation, short-term chronic safety, and performance of a novel subxiphoidal extracardiac pacemaker. METHODS: Normal Yorkshire Cross swine (n = 16) were implanted with the subxiphoidal pacemaker. The pacemaker was inserted through a midline chest incision and clipped to the underside of the sternum, with the stimulation electrode placed on the anterior pericardium. Animals were chronically paced and followed for 90 days post-implant, with periodic measurement of pacing capture threshold (PCT) and electrode impedance. RESULTS: All 16 animals were successfully implanted with the study device. At implant, a consistent average PCT of 2.2 ± 0.4 V at a pulse width of 1.0 ms was observed in all animals, with an average implant impedance of 648 ± 44 Ω. Chronic pacing was programmed at a rate of 60 bpm, an amplitude of 3.4 ± 0.7 V, and a pulse width of 1.0 ms. PCT rose to 4.6 ± 0.8 V at 14 days and stabilized; at 90 days, PCT was 3.8 ± 1.2 V and electrode impedance was 533 ± 105 Ω. All implanted animals completed the study with no clinically significant findings, no clinically significant abnormalities, and with no adverse events that affected animal welfare. CONCLUSIONS: This study demonstrated the safety and feasibility of a novel subxiphoidal extracardiac pacemaker to deliver short-term chronic extravascular therapy. Further studies are required to assess the safety, feasibility, and long-term chronic pacing performance in human subjects.

Trap-Integrated Superconducting Nanowire Single-Photon Detectors with Improved RF Tolerance for Trapped-Ion Qubit State Readout.

State readout of trapped-ion qubits with trap-integrated detectors can address important challenges for scalable quantum computing, but the strong rf electric fields used for trapping can impact detector performance. Here, we report on NbTiN superconducting nanowire single-photon detectors (SNSPDs) employing grounded aluminum mirrors as electrical shielding that are integrated into linear surface-electrode rf ion traps. The shielded SNSPDs can be operated at applied rf trapping potentials of up to 54 Vpeak at 70 MHz and temperatures of up to 6 K, with a maximum system detection efficiency of 68 %. This performance should be sufficient to enable parallel high-fidelity state readout of a wide range of trapped ion species in typical cryogenic apparatus.

Superconducting single-photon detectors in the mid-infrared for physical chemistry and spectroscopy.

Applications of vibrational spectroscopy throughout the field of physical chemistry are limited by detectors with poor temporal resolution, low detection efficiency, and high background levels. Up to now, the field has relied upon detectors based on semiconducting materials with small bandgaps, which unavoidably leads to a compromise between good spectral response and noise at long wavelengths. However, a revolution in mid-infrared light detection is underway based on the interactions of photons with superconducting materials, which function under fundamentally different operating principles. Superconducting detectors were first used to detect light at shorter wavelengths. However, recent developments in their sensitivity toward mid-infrared wavelengths up to 10 µm provide new opportunities for applications in molecular science, such as infrared emission experiments, exoplanet spectroscopy and single molecule microscopy. In this tutorial review, we provide background information needed for the non-expert in superconducting light detection to apply these devices in the field of mid-infrared molecular spectroscopy. We present and compare the detection mechanisms and current developments of three types of superconducting detectors: superconducting nanowire single-photon detectors (SNSPDs), transition edge sensors (TESs), and microwave kinetic inductance detectors (MKIDs). We also highlight existing applications of SNSPDs for laser-induced infrared fluorescence experiments and discuss their potential for other molecular spectroscopy applications. Ultimately, superconducting infrared detectors have the potential to approach the sensitivity and characteristics of established single-photon detectors operating in the UV/Vis region, which have existed for almost a century and become an indispensable tool within the field of physical chemistry.

Quantum channel correction outperforming direct transmission.

Long-distance optical quantum channels are necessarily lossy, leading to errors in transmitted quantum information, entanglement degradation and, ultimately, poor protocol performance. Quantum states carrying information in the channel can be probabilistically amplified to compensate for loss, but are destroyed when amplification fails. Quantum correction of the channel itself is therefore required, but break-even performance-where arbitrary states can be better transmitted through a corrected channel than an uncorrected one-has so far remained out of reach. Here we perform distillation by heralded amplification to improve a noisy entanglement channel. We subsequently employ entanglement swapping to demonstrate that arbitrary quantum information transmission is unconditionally improved-i.e., without relying on postselection or post-processing of data-compared to the uncorrected channel. In this way, it represents realization of a genuine quantum relay. Our channel correction for single-mode quantum states will find use in quantum repeater, communication and metrology applications.

Transporting and concentrating vibrational energy to promote isomerization.

Visible-light absorption and transport of the resultant electronic excitations to a reaction centre through Förster resonance energy transfer1-3 (FRET) are critical to the operation of biological light-harvesting systems4, and are used in various artificial systems made of synthetic dyes5, polymers6 or nanodots7,8. The fundamental equations describing FRET are similar to those describing vibration-to-vibration (V-V) energy transfer9, and suggest that transport and localization of vibrational energy should, in principle, also be possible. Although it is known that vibrational excitation can promote reactions10-16, transporting and concentrating vibrational energy has not yet been reported. We have recently demonstrated orientational isomerization enabled by vibrational energy pooling in a CO adsorbate layer on a NaCl(100) surface17. Here we build on that work to show that the isomerization reaction proceeds more efficiently with a thick 12C16O overlayer that absorbs more mid-infrared photons and transports the resultant vibrational excitations by V-V energy transfer to a 13C18O-NaCl interface. The vibrational energy density achieved at the interface is 30 times higher than that obtained with direct excitation of the interfacial CO. We anticipate that with careful system design, these concepts could be used to drive other chemical transformations, providing new approaches to condensed phase chemistry.

Demonstration of a polarization-entangled photon-pair source based on phase-modulated PPLN.

We develop and demonstrate a source of polarization-entangled photon pairs using spontaneous parametric down-conversion (SPDC) in domain-engineered, periodically poled lithium niobate (PPLN) at telecom wavelengths. Pumped at 775 nm, this domain-engineered type-II SPDC source produces non-degenerate signal and idler pairs at 1530 nm and 1569 nm. Because of birefringence, the photon pair with horizontally polarized signal and vertically polarized idler has a different phasematching condition than the pair with vertically polarized signal and horizontally polarized idler. Using phase-modulation of the domain structure, we produced a crystal that can simultaneously generate both states in a distributed fashion throughout a single crystal. Performing SPDC using this aperiodically poled crystal, we observed polarization entanglement visibility above 93%. We compare the phase-modulated crystal to other aperiodic structures, including dual-periodically-poled and interlaced biperiodic structures.

Connecting heterogeneous quantum networks by hybrid entanglement swapping.

Recent advances in quantum technologies are rapidly stimulating the building of quantum networks. With the parallel development of multiple physical platforms and different types of encodings, a challenge for present and future networks is to uphold a heterogeneous structure for full functionality and therefore support modular systems that are not necessarily compatible with one another. Central to this endeavor is the capability to distribute and interconnect optical entangled states relying on different discrete and continuous quantum variables. Here, we report an entanglement swapping protocol connecting such entangled states. We generate single-photon entanglement and hybrid entanglement between particle- and wave-like optical qubits and then demonstrate the heralded creation of hybrid entanglement at a distance by using a specific Bell-state measurement. This ability opens up the prospect of connecting heterogeneous nodes of a network, with the promise of increased integration and novel functionalities.

Observation of an isomerizing double-well quantum system in the condensed phase.

Molecular isomerization fundamentally involves quantum states bound within a potential energy function with multiple minima. For isolated gas-phase molecules, eigenstates well above the isomerization saddle points have been characterized. However, to observe the quantum nature of isomerization, systems in which transitions between the eigenstates occur-such as condensed-phase systems-must be studied. Efforts to resolve quantum states with spectroscopic tools are typically unsuccessful for such systems. An exception is CO adsorbed on NaCl(100), which is bound with the well-known OC-Na+ structure. We observe an unexpected upside-down isomer (CO-Na+) produced by infrared laser excitation and obtain well-resolved infrared fluorescence spectra from highly energetic vibrational states of both orientational isomers. This distinctive condensed-phase system is ideally suited to spectroscopic investigations of the quantum nature of isomerization.

Kilopixel array of superconducting nanowire single-photon detectors.

We present a 1024-element near-infrared imaging array of superconducting nanowire single photon detectors (SNSPDs) using a 32×32 row-column multiplexing architecture. The array has an active area of 0.96 × 0.96 mm, making it the largest SNSPD array reported to date in terms of both active area and pixel count. Using a 64-channel time-tagging readout, we have characterized the array's yield, efficiency, and timing resolution. Large arrays of SNSPDs are desirable for applications such as imaging, spectroscopy, or particle detection.

Detecting Sub-GeV Dark Matter with Superconducting Nanowires.

We propose the use of superconducting nanowires as both target and sensor for direct detection of sub-GeV dark matter. With excellent sensitivity to small energy deposits on electrons and demonstrated low dark counts, such devices could be used to probe electron recoils from dark matter scattering and absorption processes. We demonstrate the feasibility of this idea using measurements of an existing fabricated tungsten-silicide nanowire prototype with 0.8-eV energy threshold and 4.3 ng with 10 000 s of exposure, which showed no dark counts. The results from this device already place meaningful bounds on dark matter-electron interactions, including the strongest terrestrial bounds on sub-eV dark photon absorption to date. Future expected fabrication on larger scales and with lower thresholds should enable probing of new territory in the direct detection landscape, establishing the complementarity of this approach to other existing proposals.

Tunable quantum beat of single photons enabled by nonlinear nanophotonics.

We demonstrate the tunable quantum beat of single photons through the co-development of core nonlinear nanophotonic technologies for frequency-domain manipulation of quantum states in a common physical platform. Spontaneous four-wave mixing in a nonlinear resonator is used to produce non-degenerate, quantum-correlated photon pairs. One photon from each pair is then frequency shifted, without degradation of photon statistics, using four-wave mixing Bragg scattering in a second nonlinear resonator. Fine tuning of the applied frequency shift enables tunable quantum interference of the two photons as they are impinged on a beamsplitter, with an oscillating signature that depends on their frequency difference. Our work showcases the potential of nonlinear nanophotonic devices as a valuable resource for photonic quantum information science.

The Sommerfeld ground-wave limit for a molecule adsorbed at a surface.

Using a mid-infrared emission spectrometer based on a superconducting nanowire single-photon detector, we observed the dynamics of vibrational energy pooling of carbon monoxide (CO) adsorbed at the surface of a sodium chloride (NaCl) crystal. After exciting a majority of the CO molecules to their first vibrationally excited state (v = 1), we observed infrared emission from states up to v = 27. Kinetic Monte Carlo simulations showed that vibrational energy collects in a few CO molecules at the expense of those up to eight lattice sites away by selective excitation of NaCl's transverse phonons. The vibrating CO molecules behave like classical oscillating dipoles, losing their energy to NaCl lattice vibrations via the electromagnetic near-field. This is analogous to Sommerfeld's description of radio transmission along Earth's surface by ground waves.

Quantum Frequency Conversion of a Quantum Dot Single-Photon Source on a Nanophotonic Chip.

Single self-assembled InAs/GaAs quantum dots are promising bright sources of indistinguishable photons for quantum information science. However, their distribution in emission wavelength, due to inhomogeneous broadening inherent to their growth, has limited the ability to create multiple identical sources. Quantum frequency conversion can overcome this issue, particularly if implemented using scalable chip-integrated technologies. Here, we report the first demonstration of quantum frequency conversion of a quantum dot single-photon source on a silicon nanophotonic chip. Single photons from a quantum dot in a micropillar cavity are shifted in wavelength with an on-chip conversion efficiency ≈ 12 %, limited by the linewidth of the quantum dot photons. The intensity autocorrelation function g(2)(τ) for the frequency-converted light is antibunched with g(2)(0)=0.290±0.030, compared to the before-conversion value g(2)(0)=0.080±0.003. We demonstrate the suitability of our frequency conversion interface as a resource for quantum dot sources by characterizing its effectiveness across a wide span of input wavelengths (840 nm to 980 nm), and its ability to achieve tunable wavelength shifts difficult to obtain by other approaches.

Optically Addressing Single Rare-Earth Ions in a Nanophotonic Cavity.

We demonstrate optical probing of spectrally resolved single Nd^{3+} rare-earth ions in yttrium orthovanadate. The ions are coupled to a photonic crystal resonator and show strong enhancement of the optical emission rate via the Purcell effect, resulting in near radiatively limited single photon emission. The measured high coupling cooperativity between a single photon and the ion allows for the observation of coherent optical Rabi oscillations. This could enable optically controlled spin qubits, quantum logic gates, and spin-photon interfaces for future quantum networks.

Conclusive Experimental Demonstration of One-Way Einstein-Podolsky-Rosen Steering.

Einstein-Podolsky-Rosen steering is a quantum phenomenon wherein one party influences, or steers, the state of a distant party's particle beyond what could be achieved with a separable state, by making measurements on one-half of an entangled state. This type of quantum nonlocality stands out through its asymmetric setting and even allows for cases where one party can steer the other but where the reverse is not true. A series of experiments have demonstrated one-way steering in the past, but all were based on significant limiting assumptions. These consisted either of restrictions on the type of allowed measurements or of assumptions about the quantum state at hand, by mapping to a specific family of states and analyzing the ideal target state rather than the real experimental state. Here, we present the first experimental demonstration of one-way steering free of such assumptions. We achieve this using a new sufficient condition for nonsteerability and, although not required by our analysis, using a novel source of extremely high-quality photonic Werner states.

Ultra-sensitive mid-infrared emission spectrometer with sub-ns temporal resolution.

We evaluate the performance of a mid-infrared emission spectrometer operating at wavelengths between 1.5 and 6 µm based on an amorphous tungsten silicide (a-WSi) superconducting nanowire single-photon detector (SNSPD). We performed laser induced fluorescence spectroscopy of surface adsorbates with sub-monolayer sensitivity and sub-nanosecond temporal resolution. We discuss possible future improvements of the SNSPD-based infrared emission spectrometer and its potential applications in molecular science.

Short-wave infrared compressive imaging of single photons.

We present a short-wave infrared (SWIR) single photon camera based on a single superconducting nanowire single photon detector (SNSPD) and compressive imaging. We show SWIR single photon imaging at a megapixel resolution with a low signal-to-background ratio around 0.6, show SWIR video acquisition at 20 frames per second and 64x64 pixel video resolution, and demonstrate sub-nanosecond resolution time-of-flight imaging. All scenes were sampled by detecting only a small number of photons for each compressive sampling matrix. In principle, our technique can be used for imaging faint objects in the mid-IR regime.

Handlebar Hernia with Triple Herniation and Perforation: A Case Report and Literature Review.

Blunt trauma abdomen is a very common entity but traumatic abdominal wall hernia is not that common. Herniation through abdominal wall usually occurs following trauma with seat belt, motor cycle, bicycle handle bar etc. Handlebar hernia is a less known variety of traumatic abdominal wall hernia as a consequence of injury with handlebar of a bicycle. It is difficult to diagnose and one should have high index of suspicion. Management in traumatic abdominal wall hernia is individualized based on various factors. We herein present an interesting case of a14-year-old boy, who sustained blunt trauma abdomen from bicycle handlebar leading to triple herniation and perforation of the small bowel and hematoma of the mesentery. Patient was resuscitated and operated with a favorable outcome. Blunt trauma abdomen is a very common and the possibility of traumatic abdominal wall hernia should always be borne in mind.