In this talk I will review the foundational ingredients of modern superconducting quantum circuit theory. Starting from a mesoscopic theory of superconductivity and lossless circuits, I will review how quantum degrees of freedom emerge, creating both linear circuits (photons) and nonlinear circuits (qubits) that simulate the behavior of low-dimensional quantum light and matter. I will also briefly discuss the applications of those circuits in fundamental research and applied quantum information processing.

In a superconducting quantum device, one uses pulsed-microwave to access and control the qubits and with increased number of qubits in such circuits, minimization of crosstalk becomes vital. It would be severely difficult to operate a multi-qubit system if qubit frequencies do not agree with the design, if the signal meant for one qubit excites other qubits, or if the frequencies shift over time. Since variation in the Josephson inductance is the major cause of qubit frequency variation in transmon qubits, it is essential to develop robust fabrication processes that consistently deliver qubits that match the design parameters. It is also crucial to set up a procedure to monitor the fabrication process and measure and characterize the devices, to tune the process parameters and indicate possible shortcomings or drifts. After reviewing different available fabrication techniques, this talk discusses the work at the Quantum Technology Laboratory, Chalmers University in developing a reliable process of fabricating Josephson junctions.

The proper functioning of some micro-fabricated novel quantum devices, such as superconducting resonators and qubits, is severely affected by the presence of parasitic structural material defects known as tunneling two-level-systems (TLS). Recent experiments have reported unambiguous evidence of the strong interaction between individual (coherent) TLS using strain-assisted spectroscopy. In this talk, we provide an alternative and simple theoretical insight that illustrates how to obtain the spectral response of such strongly interacting defects residing inside the amorphous tunnel barrier of a qubit's Josephson junction. Moreover, the corresponding spectral signatures obtained here may serve to quickly and efficiently elucidate the actual state of these interacting TLS in experiments based on strain- or electric-field spectroscopy.

Quantum technologies is an emerging market that is expected to grow in the tens of billions in the medium term. We may imagine its importance and impact by how it is permeating mains stream media and retail investment. In this session, we will take a look at the non-technical aspects of the second quantum revolution and discuss the state of the quantum ecosystem.

Quantum computing appears to be on the cusp of a major technology disruption, and the race to scale-up to a universally programmable quantum computer for real world application has gathered significant pace recently. Amongst various priorities, increasing the number of qubits whilst maintaining a manageable error rate is paramount. This a multi-disciplinary problem requiring scientific and engineering breakthroughs in materials, processes, multi-qubit architectures, and quantum measurement techniques in the least. In this talk, I will introduce our recent efforts to develop spin-valley qubits in 2D semiconductors. The unique spin-valley coupling in such materials is expected to suppress decoherence since a spin flip requires the concomitant change of valley. In addition, the inherent spin-orbit interaction provides for fast gate operations, and the compatibility with electrostatically gated planar qubit architectures can be advantageous for reducing system complexity and hence scalability. I shall present our recent progress in materials engineering and quantum dot devices toward this goal.

At the Millimeter Wavelength Instrumentation Laboratory at INAOE we have several cryogenic instrumentation available which have been used to characterize filters and materials, millimeter wavelength detectors, Low Noise Amplifiers to CMOS transistors among other applications. Our systems are closed cycle pulse tube coolers which includes He-3/He-4 and dilution fridges to reach temperatures as low as 100 mK. One of our systems has been upgraded in the last couple of years to include a CDIP mounting to characterize different CMOS technologies which are potentially suitable to be used in electronics readout stage for quantum computing applications. In this talk we describe the different subsystems and control stages of our cryogenic equipment, as well as some of the results we have experimentally obtained in the laboratory.

As technology evolves, more and more functions and applications are readily implemented using CMOS circuitry; wireless electronics have become commonplace in our daily life. The development of these circuits involves extensive research leading to accurate models for simulation, which have to include all the effects associated with the circuit, which is embedded in the substrate. As frequency of operation increases, many more effects, which are negligible at lower frequencies, become apparent, up to the point that some can become dominant in this range. RF modeling of the MOS transistor has thus been the object of extensive research over the last few decades, and a continuous field of endeavor since higher operating frequencies can be reached as the devices become smaller, and hence, faster, and better models – electrical, physical, mathematical and for simulation, have to be developed on an almost daily basis. But ICs are not made solely of transistors; many passive structures have to be built on the same chip to attain the desired function of the circuit, such as resistors, capacitors, inductors, transformers and interconnects. Throughout the years, many articles have also been published in reference to the parasitic effects associated with these components, as well as forms to ameliorate them, as they can lead to catastrophic failure if they are not adequately taken into account at the design and simulation stages.

In this talk, we present the models of an integrated inductor and that of a coplanar waveguide (CPW), compared to measurements up to 60 GHz. These are common structures now present in almost all modern ICs, and an important effect associated with them are the losses due to the ground shields that are built underneath these structures to reduce electromagnetic interference. These shields are generally made of metal or poly silicon, and they can be solid, meshed or patterned. The response of the device is highly influenced by the type of shield over which it is built, and there is no clear-cut distinction as to which is better, the answer varying according to the application. All the structures were fabricated at IMEC. Identical structures were built using different types of ground shields, in order to be able to compare their response. Octagonal and circular devices were available. Several CPWs were also fabricated on the same chip. In both cases, the models herein developed compare very well to experimental data up to 60 GHz. They are simple and easily implemented at the design and simulation stages of wireless ICs.

Resonators are devices that have been studied in microwave engineering applications for a long time. However, their applications cover other areas, including quantum computing. In this area they are used as a fundamental element for the measurement of the quantum states of superconducting qubits (Josephson junctions) and they are considered as the most useful devices for the study of superconducting materials. In order to explain the relevance and usefulness of microwave resonators in this area, this talk will present an introduction to the microwave resonators: their electrical characteristics, geometry, and fabrication. Furthermore, their main applications in quantum engineering will be addressed and discussed.

The experimental development of superconducting qubits, mainly based on integrated Josephson junctions, has been long benefited from many advances already obtained from the semiconductor industry. These advances have come in the way of state-of-the-art fabrication processes, nanoscaled electron materials, advanced characterization techniques for semiconductor materials and devices as well as important reliability studies that enable long-term high performance of the final integrated devices. Given that one of the main parameters for reliable qubit development has been long coherence times (thus enabling two important quantum effects of superposition and entanglement), the development of defect-free processes and materials is of the outmost importance. In the Josephson junction for instance (consisting of a thin Metal/ Insulator/Metal structure), an ultra-thin insulator layer like Al2O3 is located in between two superconducting films of aluminum. Since the Al2O3 presents two interfaces with the bottom and top superconducting aluminum films, this device is prone to lots of electronic defects that could negatively impact on the final quantum performance of the qubit itself. It is therefore important to know the basics of the integrated circuit fabrication technology with emphasis in those processes leading to defect-free electron materials and ultimately, to longer coherence times for reliable superconducting qubits.

The talk will focus on the application of advanced physical and electrical analysis techniques, such as in-situ transmission electron microscopy (TEM), conductive atomic force microscopy (CAFM) techniques and electrical acceleration stress technique for in-depth study and characterization of nanoscale semiconductor devices and circuits. These include FINFET technology, emerging non-volatile memory technologies such as RRAM and STT-MRAM, and 2D materials and its potential applications. New understanding of some of the mechanisms responsible for the fundamental device reliability and lifetime projection will be discussed. Potential opportunities in using such findings for state-of-the-art electronics application will be shared.

Graphene and emerging 2D layered semiconductor materials have gathered enormous research interest for wide range of novel applications including optoelectronics and flexible nanoelectronics. These ultra-thin 2D semiconductor materials are highly sought after as a channel material in flexible transistors, given its intrinsic carrier mobilities are much higher than silicon. While a lot of efforts have been directed towards growth of these materials on wafer scale, recent findings have shown that conventional dielectrics (e.g., SiO2, HfO2) are not compatible with 2D layered semiconductors. 2D hexagonal boron nitride (h-BN) have emerged as a potential dielectric material which could seamlessly integrate with almost all the 2D semiconductor materials reported so far. Hence, the reliability of h-BN as a gate dielectric is crucial for its successful commercialization. Interestingly, conduction AFM (CAFM) has been very successful to measure localized electrical properties of gate dielectrics and emerging nanoscale devices. In this talk, I will present our recent works where we extensively use CAFM to probe the electrical defects and understand mechanisms of dielectric breakdown in h-BN.

We have developed a method designed to assemble vertical layers composed of ultra-dense arrays (1Tb/inch2) of Ni and Co nanorods. The fabrication scheme allows total control of the nanorod’s dimensions (diameter and length) by using porous anodic aluminum oxide (AAO) membranes. A two-step anodization process is employed for the fabrication of AAO using Oxalic and Sulfuric electrolytes. The resulting porous network consists of nanopores with 40 and 80 nm diameters respectively. The AAO is used as a mask to nanopattern large areas (cm2) of solid substrates following a two-polymer transfer process. Initially, a sulfuric AAO was used for template assisted electrodeposition to assemble the first layer of Ni nanorods with an overgrown thin film. Subsequently, an oxalic AAO was transferred upon the Ni film. The electrodeposition was repeated using the Ni film as the working electrode to assemble the second vertical layer. Additionally, the nanorod’s elemental composition was controlled by varying the electroplating solution (Ni, Co, Au). Repeating the same transfer procedure, segmented nanorods of Ni-Au and Co-Au were assembled into vertical layers. Cross sectional cuts were prepared using a milling procedure in a Zeiss Crossbeam 340 Focused Ion Beam combined with Scanning Electron Microscopy. The elemental composition of the segmented nanorods was evaluated using energy dispersive spectroscopy. In this way, nanostructures with high complexity can be tailored to have desired aspect ratios and varying chemical compositions for distinct functionalities and applications. Magnetic analysis performed using off axis electron holography will be included in the presentation.

A quantitative study of the surface composition of clean metallic and oxidized chromium exposed to atmospheric conditions was carried out employing X-ray photoelectron spectroscopy (XPS). Advanced tools were used for the fitting process and surface composition analysis. We found that, in contrast with most metals, the oxidation does not come about through the formation of an oxide layer. State of the art analysis showed that, even at long exposures, a fraction of the chromium surface retains its metallic nature even at the top layers. Depth profile of XPS spectra shows no shape modulation from angle to angle which strongly suggest both Cr3+ and Cr6+ species coexist with the metallic species throughout the probing depth of XPS. The oxidation mechanism of metallic chromium exposed to ambient is through the partial oxidation of surface regions. This surface oxidation mechanism, i.e., the oxidation by regions, explains the lustrous look of chromated surfaces even when they are exposed to ambient.

Superconducting qubits are coherent artificial atoms assembled from electrical circuit elements. Their lithographic scalability, compatibility with microwave control, and operability at nanosecond time scales all converge to make the superconducting qubit a highly attractive candidate for the constituent logical elements of a quantum information processor. How do they actually work? And, what makes quantum computers potentially powerful? In this talk, we will address these questions as we present the progress, challenges, and opportunities ahead in the engineering superconducting quantum processors.