Radio-frequency Resonator Research Articles

Simultaneous cooling of high-frequency difference resonators through voltage modulation and intracavity-squeezed light

We propose a scheme to achieve simultaneous cooling of the mechanical and radio-frequency resonators in a hybrid optoelectromechanical system. By introducing the voltage modulation switch and intracavity-squeezed light, the high-frequency difference resonators can be successfully cooled to their quantum ground states by eliminating cavity mode dissipation through precise phase and amplitude matching of the squeezed pump field and the cooling optical field. More significantly, ground-state cooling can be achieved even in the highly unresolved sideband regime, and the quantum backaction heating can be effectively suppressed, leading to a significant improvement in cooling performance. Our work provides an alternative approach for quantum coherent manipulation of multiple mechanical systems with different resonant frequencies.

Direct measurement of microwave loss in Nb films for superconducting qubits

Niobium films are a key component in modern two-dimensional superconducting qubits, yet their contribution to the total qubit decay rate is not fully understood. The presence of different layers of materials and interfaces makes it difficult to identify the dominant loss channels in present two-dimensional qubit designs. In this paper, we present the study that directly correlates measurements of RF losses in such films to material parameters by investigating a high-power impulse magnetron sputtered (HiPIMS) film atop a three-dimensional niobium superconducting radio frequency (SRF) resonator. By using a 3D SRF structure, we are able to isolate the niobium film loss from other contributions. Our findings indicate that microwave dissipation in the HiPIMS-prepared niobium films, within the quantum regime, resembles that of record-high intrinsic quality factor of bulk niobium SRF cavities, with lifetimes extending into seconds. Microstructure and impurity level of the niobium film do not significantly affect the losses. These results set the scale of microwave losses in niobium films and show that niobium losses do not dominate the observed coherence times in present two-dimensional superconducting qubit designs, instead highlighting the dominant role of the dielectric oxide in limiting the performance. We can also set a bound for when niobium film losses will become a limitation for qubit lifetimes.

Towards shorter composite 180° refocusing pulses for NMR

Novel composite 180° pulses are designed for use in nuclear magnetic resonance (NMR) and verified experimentally using solution-state 1H NMR spectroscopy. Rather than being constructed from 180° pulses (as in much recent work), the new composite pulses are constructed from 90° pulses, with the aim of finding sequences that are shorter overall than existing equivalents. The primary (but not exclusive) focus is on composite pulses that are dual compensated – simultaneously broadband with respect to both inhomogeneity of the radiofrequency field and resonance offset – and have antisymmetric phase schemes, such that they can be used to form spin echoes without the introduction of a phase error. In particular, a new antisymmetric dual-compensated refocusing pulse is presented that is constructed from ten 90° pulses, equivalent to just five 180° pulses.

Moiré patterns of space-filling curves

It is shown on the examples of Moore and Gosper curves that two spatially shifted or twisted, preasymptotic space-filling curves can produce large-scale superstructures akin to moiré patterns. To study physical phenomena emerging from these patterns, a geometrical coupling coefficient based on the Neumann integral is introduced. It is found that moiré patterns appear most defined at the peaks of those coefficients. A physical interpretation of these coefficients as a measure for inductive coupling between radiofrequency resonators leads to a design principle for strongly overlapping resonators with vanishing mutual inductance, which might be interesting for applications in MRI. These findings are demonstrated in graphical, numerical, and physical experiments. Published by the American Physical Society 2024

All-Electrical Driving and Probing of Dressed States in a Single Spin.

The subnanometer distance between tip and sample in a scanning tunneling microscope (STM) enables the application of very large electric fields with a strength as high as ∼1 GV/m. This has allowed for efficient electrical driving of Rabi oscillations of a single spin on a surface at a moderate radiofrequency (RF) voltage on the order of tens of millivolts. Here, we demonstrate the creation of dressed states of a single electron spin localized in the STM tunnel junction by using resonant RF driving voltages. The read-out of these dressed states was achieved all electrically by a weakly coupled probe spin. Our work highlights the strength of the atomic-scale geometry inherent to the STM that facilitates the creation and control of dressed states, which are promising for the design of atomic scale quantum devices using individual spins on surfaces.

Superconducting NbTi Radiofrequency Resonator for Surface ion Traps

Superconducting NbTi Radiofrequency Resonator for Surface ion Traps

3D Woven Liquid Metals for Radio‐Frequency Stretchable Circuits

AbstractMechanically flexible and stretchable inductive coils are critical for enabling communication, sensing, and wireless power transfer capabilities in wearable electronics that conform to the body for healthcare and Internet of Things (IoT) applications. Leading stretchable conductors such as liquid metals (LMs) offer conformability but sacrifice electromagnetic performance compared with Cu wires, leading to lossy radio‐frequency (RF) characteristics. Here, a strategy leveraging multistranded 3D woven ‘litz’ transmission lines is presented to amplify the resonant RF performance of LM inductors. Through comprehensive simulations and experiments, it is discovered that interwoven LM litz wires boost the Quality Factor (Q) by 80% compared to standard liquid metal wires. A fabrication methodology is also demonstrated for stretchable coils that retain high Q (>30), outperforming the previously reported LM coils and maintaining 98% of their wireless transmission efficiency under up to 30% biaxial strain. Moreover, the versatility of this approach is showcased by 3D printing four‐terminal ‘choke’ inductors optimized for RF filtering and inductance tunability, overcoming the fabrication limitations of traditional planar printed electronics. These results offer valuable insights into the design and implementation of 3D‐printed inductors for a diverse suite of electromagnetic device applications.

Unilateral Magnetic Resonance Imaging-Guided Laser Interstitial Thermal Therapy Thalamotomy for Essential Tremor.

Essential tremor (ET) affects numerous adults, impacting quality of life (QOL) and often defying pharmacological treatment. Surgical interventions like deep brain stimulation (DBS) and lesional approaches, including radiofrequency, gamma-knife radiosurgery, and magnetic resonance imaging (MRI)-guided focused ultrasound, offer solutions but are not devoid of limitations. This retrospective, single-center, single-blinded pilot study aimed to assess the safety and efficacy of unilateral MRI-guided laser interstitial thermal therapy (MRIg-LITT) thalamotomy for medically intractable ET. Nine patients with ET, unresponsive to medications and unsuitable for DBS, underwent unilateral MRIg-LITT thalamotomy. We assessed tremor severity, QOL, cognitive function, and adverse events (AE) over a 12-month period. Tremor severity significantly improved, with a reduction of 83.37% at 12 months post-procedure. QOL scores improved by 74.60% at 12 months. Reported AEs predominantly included transient dysarthria, proprioceptive disturbances, and gait balance issues, which largely resolved within a month. At 3 months, 2 patients (22%) exhibited contralateral hemiparesis requiring physiotherapy, with 1 patient (11%) exhibiting persistent hemiparesis at 12 months. No significant cognitive impairment was detected post-procedure. Unilateral MRIg-LITT thalamotomy yielded substantial and enduring tremor alleviation and enhanced QOL in patients with ET that is resistant to medication. The AE profile was acceptable. Our findings support the need for additional research with expanded patient cohorts and extended follow-up to corroborate these outcomes and to refine the role of MRIg-LITT as a targeted and minimally invasive approach for ET management. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Confirmatory study of the usefulness of quantum molecular resonance and microdissectomy for the treatment of lumbar radiculopathy in a prospective cohort at 6 months follow-up.

Low back pain is a common musculoskeletal complaint and while prognosis is usually favorable, some patients experience persistent pain despite conservative treatment and invasive treatment to target the root cause of the pain may be necessary. The aim of this study is to evaluate patient outcomes after treatment of lumbar radiculopathy (LR) with quantum molecular resonance radiofrequency coblation disc decompression and percutaneous microdiscectomy with grasper forceps (QMRG). This prospective cohort study was carried out in two Spanish hospitals on 58 patients with LR secondary to a contained hydrated lumbar disc hernia or lumbar disc protrusion of more than 6 months of evolution, which persisted despite conservative treatment with analgesia, rehabilitation, and physiotherapy, and/or epidural block, in the previous 2 years. Patients were treated with QMRG and the outcomes were measured mainly using the Douleur Neuropathique en 4 Questions, Numeric Rating Scale, Oswestry Disability Index, SF12: Short Form 12 Health Survey, Patient Global Impression of Improvement, Clinical Global Impression of Improvement, and Medical Outcomes Study Sleep Scale. Patients who received QMRG showed significant improvement in their baseline scores at 6 months post-treatment. The minimal clinically important difference (MCID) threshold was met by 26-98% of patients, depending on the outcome measure, for non-sleep-related outcomes, and between 17 and 62% for sleep-related outcome measures. Of the 14 outcome measures studied, at least 50% of the patients met the MCID threshold in 8 of them. Treatment of LR with QMRG appears to be effective at 6 months post-intervention.

Quantum Molecular Resonance Radiofrequency Disc Decompression and Percutaneous Microdiscectomy for Lumbar Radiculopathy.

Within the practice of pain management, one of the most commonly encountered events is low back pain. Lumbar radiculopathy (LR) is a pain syndrome caused by the compression or irritation of the nerve roots in the lower back due to lumbar disc herniation, vertebra degeneration, or foramen narrowing. Symptoms of LR include low back pain that propagates toward the legs, numbness, weakness, and loss of reflexes. The aim of this study is to assess the long-term effectiveness of quantum molecular resonance disc decompression and its combination with a percutaneous microdiscectomy using Grasper© forceps (QMRG) in patients with persistent lumbar radiculopathy (LR) in relation to patient physical stress status. The main outcome measures of this prospective observational study were DN4, NRS, ODI, SF12, PGI, CGI, and MOS Sleep Scale. An improvement 12 months post-intervention was observed in patients without physical stress, presenting better overall results. The mean change was over the minimal clinically important difference in 64.3% of outcome measures studied for the whole sample. QMRG appears to be an effective treatment option for LR, but a reduction in physical stress is needed to ensure long-term effectiveness.

Evaluation of Lumbar Adhesiolysis Using a Radiofrequency Catheter During Epiduroscopy in the Treatment of Failed Back Surgery Syndrome (FBSS).

Failed back surgery syndrome (FBSS) is a complication of spinal surgery that results in severe and disabling back/leg pain. Epiduroscopy is a percutaneous minimally invasive surgical technique used in the treatment of lumbar radicular pain that enables both direct visualization of epidural adhesions in patients with FBSS and the mechanical release of fibrotic scars in the epidural space. Although the use of a balloon catheter during epiduroscopy can usually remove adhesions between the dura and the vertebrae, in the thickest areas of fibrosis, the use of a catheter with a molecular quantum resonance radiofrequency generator may resect hard epidural fibrotic obstructions. The aim of this study was to evaluate the efficacy and safety of this radiofrequency catheter in the treatment of severe epidural fibrotic scars. Ninety-three patients with FBSS were enrolled in this study. In 49 cases, a thick area of fibrosis was visualized during epiduroscopy and the use of a balloon catheter could not remove the fibrotic scars. In all of these cases, we used a molecular quantum resonance radiofrequency catheter to remove dense fibrotic areas. Intraoperatively during epiduroscopy, we could directly visualize lysis of the fibrotic scars. Immediately after the procedure and at 1-month and 6-month follow-up, the patients reported significant pain reduction. Pain reduction and patient satisfaction were also reported at 12 months in all but 5 cases. This study found a clinically relevant reduction of pain at 1 and 6 months after epiduroscopy in patients with FBSS. The use of a radiofrequency catheter is safe and effective in resection of hard and thick epidural scars.

Wireless Detection of Trace Ammonia: A Chronic Kidney Disease Biomarker.

Elevated levels of ammonia in breath can be linked to medical complications, such as chronic kidney disease (CKD), that disturb the urea balance in the body. However, early stage CKD is usually asymptomatic, and mass screening is hindered by high instrumentation and operation requirements and accessible and reliable detection methods for CKD biomarkers, such as trace ammonia in breath. Enabling methods would have significance in population screening for early stage CKD patients. We herein report a method to effectively immobilize transition metal selectors in close proximity to a single-walled carbon nanotube (SWCNT) surface using pentiptycene polymers containing metal-chelating backbone structures. The robust and modular nature of the pentiptycene metallopolymer/SWCNT complexes creates a platform that accelerates sensor discovery and optimization. Using these methods, we have identified sensitive, selective, and robust copper-based chemiresistive ammonia sensors that display low parts per billion detection limits. We have added these hybrid materials to the resonant radio frequency circuits of commercial near-field communication (NFC) tags to achieve robust wireless detection of ammonia at physiologically relevant levels. The integrated devices offer a noninvasive and cost-effective approach for early detection and monitoring of CKD.

Shaped Magnetogel Microparticles for Multispectral Magnetic Resonance Contrast and Sensing.

Multispectral magnetic resonance imaging (MRI) contrast agents are microfabricated three-dimensional magnetic structures that encode nearby water protons with discrete frequencies. The agents have a unique radiofrequency (RF) resonance that can be tuned by engineering the geometric parameters of these microstructures. Multispectral contrast agents can be used as sensors by incorporating a stimulus-driven shape-changing response into their structure. These geometrically encoded magnetic sensors (GEMS) enable MRI-based sensing via environmentally induced changes to their geometry and their corresponding RF resonance. Previously, GEMS have been made using thin-film lithography techniques in a cleanroom environment. While these approaches offer precise control of the microstructure, they can be a limitation for researchers who do not have cleanroom access or microfabrication expertise. Here, an alternative approach for GEMS fabrication based on soft lithography is introduced. The fabrication scheme uses cheap, accessible materials and simple chemistry to produce shaped magnetic hydrogel microparticles with multispectral MRI contrast properties. The microparticles can be used as sensors by fabricating them out of shape-reconfigurable, "smart" hydrogels. The change in shape causes a corresponding shift in the resonance of the GEMS, producing an MRI-addressable readout of the microenvironment. Proof-of-principle experiments showing a multispectral response to pH change with cylindrical shell-shaped magnetogel GEMS are presented.

Precision Spectroscopy of Radiation Transitions between Singlet Rydberg States of the Group IIb and Yb Atoms

The measurements of microwave (μw) and radio-frequency (RF) radiation quantitative parameters may be based on the quantum–optical approach to determine the spectral characteristics of radiation transitions between the Rydberg states of atoms. Frequencies and matrix elements are calculated for dipole transitions between opposite-parity Rydberg states nL 1L and n′L±1 1L±1 (where n′= n,n±1,n±2) of the singlet series in the alkaline–earth–metal-like atoms of group IIb (Zn, Cd, Hg) and Yb. The matrix elements determine the shifts of Rydberg-state energy levels in the field of resonance μw or RF radiation, splitting the resonance of electromagnetically induced transparency (EIT) for intensely absorbed probe radiation. Numerical computations based on the single-electron quantum defect method (QDM) and the Fues’ model potential (FMP) approach with the use of the most reliable data from the current literature on quantum defect values are performed for frequencies and matrix elements of transitions between singlet Rydberg states of 1S0-, 1P1-, 1D2-, and 1F3-series in Zn, Cd, Hg, and Yb atoms. The calculated data are approximated by polynomials in the powers of the principal quantum numbers. The polynomial coefficients are determined with the use of a standard curve-fitting interpolation polynomial procedure for numerically calculated functions. These approximation expressions provide new possibilities for accurately evaluating the frequencies and matrix elements of dipole transitions between Rydberg states over a wide range of quantum numbers n >> 1, accompanied by the emission and absorption of μw and RF photons.

Simultaneous cooling and synchronization of the mechanical and the radio-frequency resonators via voltage modulation

We explore the ground state cooling and quantum synchronization of the mechanical and low-frequency inductor-capacitor (LC) resonators in a hybrid three-mode optoelectromechanical system, in which the mechanical resonator is optically and capacitively coupled to the optical cavity and the LC circuit, respectively. We find that when the bias voltage modulation switch is incorporated into the direct current (DC) bias voltage, ground state cooling and quantum synchronization can be simultaneously achieved regardless of whether the mechanical resonator and the low-frequency LC resonator have the identical frequency. Furthermore, we elucidate the relationship between quantum synchronization and ground state cooling of the two resonators, that is, the simultaneous ground state cooling of the resonators must be accompanied by quantum synchronization. Our work may open up an alternative approach to the simultaneous ground state cooling and quantum synchronization of multiple resonators, which has fewer parametric limitations.

Sympathetically cooled highly charged ions in a radio-frequency trap with superconducting magnetic shielding

We sympathetically cool highly charged ions (HCI) in Coulomb crystals of Doppler-cooled Be+ ions confined in a cryogenic linear Paul trap that is integrated into a fully enclosing radio-frequency resonator manufactured from superconducting niobium. By preparing a single Be+ cooling ion and a single HCI, quantum logic spectroscopy toward frequency metrology and qubit operations with a great variety of species are enabled. While cooling down the assembly through its transition temperature into the superconducting state, an applied quantization magnetic field becomes persistent, and the trap becomes shielded from subsequent external electromagnetic fluctuations. Using a magnetically sensitive hyperfine transition of Be+ as a qubit, we measure the fractional decay rate of the stored magnetic field to be at the 10−10 s−1 level. Ramsey interferometry and spin-echo measurements yield coherence times of >400 ms, demonstrating excellent passive magnetic shielding at frequencies down to DC.

Additive Influence of Top Metal Contact and Alumina Deposition on the Threshold Voltage of Suspended Carbon Nanotube Field-Effect Transistors.

One-dimensional nanostructures such as carbon nanotubes offer excellent properties useful for applications in gas sensors, piezoresistive devices, and radio frequency resonators. Considering their nanoscale form factor, carbon nanotubes (CNTs) are highly sensitive to surface adsorbents. This study presents the fabrication flow of CNT devices with extended passivated areas around electrical contacts between the CNT and source and drain electrodes. These types of structures could help in understanding the intrinsic CNT response by eliminating the analyte impact on the Schottky barrier regions of the CNT field-effect transistors (CNTFETs). The influence of multiple processing conditions on the electronic properties of CNTFETs with a suspended individual CNT used as the CNTFET channel is presented. Our findings show a threshold voltage shift in CNT ISD-Vg characteristics following the metal deposition and alumina atomic layer deposition.

Parallel Contactless Transmission of Power and Rotor Temperature of Electrical Machines via Magnetically-Coupled Resonance and Capacitive Radio Frequency

Over-temperature of the rotor may cause a series of insulation deterioration of electrical machines. In severe cases, it can lead to insulation failure and even faults, such as broken rotor bars and end ring fracture. The temperature online monitoring can effectively avoid the aforementioned insulation failure; however, the conventional temperature measurement by embedded sensors is difficult to utilize due to the power and data transmission of sensors at the rotor side. This paper proposes a contactless strategy to supply power and send rotor temperature data between the stator and rotor sides of electrical machines. With the proposed method, contactless power transfer is realized by means of magnetically-coupled resonance, while the data signal is transferred by capacitive radio frequency (RF) technology. An experimental prototype was developed and installed on a 22-kW induction motor. The results show that the embedded sensors are contactless powered effectively. At the same time clear temperature data signal can be received on the stator side without filtering, and rotor temperature can be monitored in real-time accurately.

Electromechanically Functionalized Ureteral Stents for Wireless Obstruction Monitoring.

While millions of ureteral stents are placed in patients with urinary tract issues around the world every year, hydronephrosis still poses great danger to these patients as a common complication. In the present work, an intelligent double-J ureteral stent equipped with a micro pressure sensor and antenna circuitry is investigated and prototyped toward enabling continuous wireless monitoring of kidney pressure to detect a ureteral obstruction and the resultant hydronephrosis via the indwelling stent. This electromechanically functionalized "intelligent" ureteral stent acts as a radiofrequency resonator with a pressure-sensitive resonant frequency that can be interrogated using an external antenna to track the local pressure. The prototype passes mechanical bending tests of up to 15 cm radius of curvature and shows wireless sensing with a sensitivity of 3.1 kHz/mmHg in artificial urine, which represents 25× enhancement over the preceding design, using an in vitro model with test tissue layers and a pressure range that functions within the conditions found in hydronephrotic conditions. These promising results are expected to propel intelligent ureteral stent technology into further clinical research.

Clustering into Three Groups on a Quantum Processor of Five Spins S = 1, Controlled by Pulses of Resonant RF Fields

We consider a quantum processor based on five qutrits represented by spins S = 1, which is driven by radio frequency (RF) pulses selective in transitions between adjacent levels. Numerical simulation of the implementation of the quantum-adiabatic clustering algorithm was performed on the example of partitioning a set of six points into three groups. We find the amplitudes and durations of rectangular RF pulses, as well as the durations of free evolution intervals in the control pulse sequence, which made it possible to engineer a time-dependent effective Hamiltonian in the discrete-time approximation. Also we studied the dependence of the implementation fidelity on the parameters. We took quadrupole nuclei as qutrits, but the results obtained will be useful for controlling quantum processors based on qutrits represented by other systems.