Correction to probing the quantum states of a single atom transistor at microwave frequencies

Abstract not availableGiuseppe Carlo Tettamanzi, Samuel James Hile, Matthew Gregory House, Martin Fuechsle, Sven Rogge, and Michelle Y. Simmon

Investigation of the mechanisms for wireless nerve stimulation without active electrodes

First published: 01 November 2023. OnlinePublElectric‐field stimulation of neuronal activity can be used to improve the speed of regeneration for severed and damaged nerves. Most techniques, however, require invasive electronic circuitry which can be uncomfortable for the patient and can damage surrounding tissue. A recently suggested technique uses a graft‐antenna—a metal ring wrapped around the damaged nerve—powered by an external magnetic stimulation device. This technique requires no electrodes and internal circuitry with leads across the skin boundary or internal power, since all power is provided wirelessly. This paper examines the microscopic basic mechanisms that allow the magnetic stimulation device to cause neural activation via the graft‐antenna. A computational model of the system was created and used to find that under magnetic stimulation, diverging electric fields appear at the metal ring's edges. If the magnetic stimulation is sufficient, the gradients of these fields can trigger neural activation in the nerve. In‐vivo measurements were also performed on rat sciatic nerves to support the modeling finding that direct contact between the antenna and the nerve ensures neural activation given sufficient magnetic stimulation. Simulations also showed that the presence of a thin gap between the graft‐antenna and the nerve does not preclude neural activation but does reduce its efficacy.Luke A. Smith, Jaedon D. Bem, Xiaojing Lv, Antonio Lauto, Ashour Sliow, Zhiyuan Ma, David A. Mahns, Carolyn Berryman, Mark R. Hutchinson, Christophe Fumeaux, Giuseppe C. Tettamanz

Mass Production of Silicon MOS-SETs: Can We Live with Nano-Devices’ Variability?

AbstractIt is very important to study variability of nanodevices because the inability to produce large amounts of identical nanostructures is eventually a bottleneck for any application. In fact variability is already a major concern for CMOS circuits. In this work we report on the variability of dozens of silicon single-electron transistors (SETs). At room temperature their variability is compared with the variability of the most advanced CMOS FET i.e. the ultra thin Silicon-on-Insulator Multiple gate FET (UT SOI MuGFET). We found that dopants diffused from Source –Drain into the edge of the undoped channel are the main source of variability. This emphasizes the role of extrinsic factors like the contact junctions for variability of any nanodevice

Nonadiabatic quantum control of valley states in silicon

Published 7 February 2022Nonadiabatic quantum effects, often experimentally observed in semiconductor nanodevices such as singleelectron pumps operating at high frequencies, can result in undesirable and uncontrollable behavior. However, when combined with the valley degree of freedom inherent to silicon, these unfavourable effects may be leveraged for quantum information processing schemes. By using an explicit time evolution of the Schrödinger equation, we study numerically nonadiabatic transitions between the two lowest valley states of an electron in a quantum dot formed in a SiGe/Si heterostructure. The presence of a single-atomic layer step at the top SiGe/Si interface opens an anticrossing in the electronic spectrum as the center of the quantum dot is varied. We show that an electric field applied perpendicularly to the interface allows tuning of the anticrossing energy gap. As a result, by moving the electron through this anticrossing, and by electrically varying the energy gap, it is possible to electrically control the probabilities of the two lowest valley states.Alan Gardin, Ross D. Monaghan, Tyler Whittaker, Rajib Rahman, and Giuseppe C. Tettamanz

Ultrahigh Linearity of the Magnetic-Flux-to-Voltage Response of Proximity-Based Mesoscopic Bi-SQUIDs

Superconducting double-loop interferometers (bi-SQUIDs) have been introduced to produce magnetic flux sensors specifically designed to exhibit an ultrahighly linear voltage response as a function of the magnetic flux. These devices are very important for quantum sensing and for signal processing of signals oscillating in the radio-frequency range of the electromagnetic spectrum. Here, we report an Al doubleloop bi-SQUID based on proximitized mesoscopic Cu Josephson junctions. Such a scheme provides an alternative fabrication approach to conventional tunnel-junction-based interferometers, where the junction characteristics and, consequently, the magnetic-flux-to-voltage and magnetic-flux-to-critical-current device responses can be largely and easily tailored by the geometry of the metallic weak links. We discuss the performance of such sensors by showing a full characterization of the device switching current and voltage drop versus the magnetic flux for operation temperatures ranging from 30 mK to approximately 1 K. The figures of merit of the transfer function and of the total harmonic distortion are also discussed. The latter provides an estimate of the linearity of the flux-to-voltage device response, which attains values as large as 45 dB. Such a result lets us foresee a performance already on par with that achieved in conventional tunnel-junction-based bi-SQUIDs arrays composed of hundreds of interferometers.Giorgio De Simoni, Nadia Ligato, Francesco Giazotto, Lorenzo Cassola, and Giuseppe C. Tettamanz

Manifestation of the coupling phase in microwave cavity magnonics

The interaction between microwave photons and magnons is well understood and originates from the Zeeman coupling between spins and a magnetic field. Interestingly, the magnon-photon interaction is accompanied by a phase factor, which can usually be neglected. However, under the rotating wave approximation, if two magnon modes simultaneously couple with two cavity resonances, this phase cannot be ignored as it changes the physics of the system. We consider two such systems, each differing by the sign of one of the magnon-photon coupling strengths. This simple difference, originating from the various coupling phases in the system, is shown to preserve, or destroy, two potential applications of hybrid photon-magnon systems, namely dark-mode memories and cavity-mediated coupling. The observable consequences of the coupling phase in this system is akin to the manifestation of a discrete Pancharatnam-Berry phase, which may be useful for quantum information processing and the creation of nonreciprocal devices using proper cavity engineering.Alan Gardin, Jeremy Bourhill, Vincent Vlaminck, Christian Person, Christophe Fumeaux, Vincent Castel, and Giuseppe C. Tettamanz

Coherent transport through a double donor system in silicon

In this letter, we describe the observation of the interference of conduction paths induced by two donors in a nanoscale silicon transistor, resulting in a Fano resonance. This demonstrates the coherent exchange of electrons between two donors. In addition, the phase difference between the two conduction paths can be tuned by means of a magnetic field, in full analogy to the Aharonov–Bohm effect. One of the crucial ingredients for donor based quantum computation is phase coherent manipulation of electrons. This has not been achieved as yet, and this work presents a stepping stone.Kavli Institute of NanoscienceApplied Science

Drain current modulation in a nanoscale field-effect-transistor channel by single dopant implantation

We demonstrate single dopant implantation into the channel of a silicon nanoscale metal-oxide-semiconductor field-effect-transistor. This is achieved by monitoring the drain current modulation during ion irradiation. Deterministic doping is crucial for overcoming dopant number variability in present nanoscale devices and for exploiting single atom degrees of freedom. The two main ion stopping processes that induce drain current modulation are examined. We employ 500 keV He ions, in which electronic stopping is dominant, leading to discrete increases in drain current and 14 keV P dopants for which nuclear stopping is dominant leading to discrete decreases in drain current.Kavli Institute of NanoscienceApplied Science

Single Ion Implantation into Si-Based Devices

Deterministic doping is crucial for overcoming dopant number variability in present nano-scale devices and for exploiting single atom degrees of freedom. The development of determinisitic doping schemes is required. Here, two approaches to the detection of single ion impact events in Si-based devices are reviewed. The first is via specialized PiN structures where ions are directed onto a target area around which a field effect transistor can be formed. The second approach involves monitoring the drain current modulation during ion irradiation. We investigate the detection of both high energy He+ and 14 keV P+ dopants. The stopping of these ions is dominated by ionization and nuclear collisions, respectively. The optimization of the implant energy for a particular device and post-implantation processing are also briefly considered.QN/Quantum NanoscienceApplied Science