Superconducting RF nanoelectronic devices exhibit a considerable potential for application in future electronics. Josephson effect based devices allow generation, detection, mixing, and parametric amplification of high-frequency signals up into the terahertz region and exhibit high sensitivity, low energy consumption, and small size. Traveling-wave devices can be realized with distributed Josephson junctions. Nonlinear lumped-element circuits can be realized that are small enough so that the circuit dynamics are governed by quantum mechanics. This allows to generate two-photon coherent states and entangled states and will open the door for quantum information processing. Nanotechnological fabrication techniques and the availability of novel materials give a strong impact on the development of novel Josephson-effect-based devices and systems. An overview over the physical principles and the possible applications of nanoelectronic RF Josephson devices is presented.
Superconducting RF nanoelectronic devices exhibit a considerable potential for application in future electronics. Josephson effect based devices allow generation, detection, mixing, and parametric amplification of high-frequency signals up into the terahertz region and exhibit high sensitivity, low energy consumption, and small size. Traveling-wave devices can be realized with distributed Josephson junctions. Nonlinear lumped-element circuits can be realized that are small enough so that the circuit dynamics are governed by quantum mechanics. This allows to generate two-photon coherent states and entangled states and will open the door for quantum information processing. Nanotechnological fabrication techniques and the availability of novel materials give a strong impact on the development of novel Josephson-effect-based devices and systems. An overview over the physical principles and the possible applications of nanoelectronic RF Josephson devices is presented.
Abstract Terahertz (THz) technology is a rapidly developing field that explores the use of electromagnetic waves in the THz frequency range. The unique properties of THz waves have great application prospects in electromagnetic sensing, security inspection, non-destructive testing, medical diagnostics, biology, high-speed wireless communication, space science and so on. At present, the application of THz technology is still under continuous research and development, and its broad scientific prospects are recognized worldwide. THz frequency falls into the gap on the electromagnetic spectrum of electronics and optics, thus both classic microwave and optical technologies cannot be directly applied to the THz systems. New components, circuits and application systems are being developed for THz technology. Superconductivity is a quantum mechanical phenomenon and offers unique advantages for applications in high-frequency electromagnetic domains. Novel superconducting quantum devices are being exploited for THz wave radiation and detection, and many THz application systems. The high-T c superconducting (HTS) electronic devices have great potential in emerging THz technologies due to its very high-energy bandgap (well into THz regions) and much relaxed cooling requirement, and they offer strong prospect for the development of practical and portable THz systems. This paper provides an overview of the state-of-art development of HTS THz quantum devices and their application for THz sensing, imaging and communication. The review will start with a brief introduction about cutting-edge THz technology, the fundamental of superconductivity, Josephson effects and the HTS Josephson junctions. Then, the research progress and the latest achievement of HTS Josephson THz emitters, detectors and mixers will be reviewed, followed by their application examples in some THz systems. Finally, the conclusion, challenges and outlooks of the HTS technologies in THz applications are discussed.
This article reviews recent progress in superconducting nanodevices, with particular emphasis on fabrication methods developed for superconducting nanowires and nanoscale Josephson junctions based on different barrier materials. It evaluates the future potential of superconducting nanodevices, including nano-superconducting quantum interference devices (nanoSQUIDs), in light of improvements in nanoscale fabrication and manipulation techniques, along with their likely impacts on future quantum technology and measurement. The article first considers efforts to realize devices at the physical scale of 100 nm and below before discussing different types of Josephson junction such as trilayer junctions. It also describes the use of focused ion beam milling and electron beam lithography techniques for junction fabrication at the nanoscale and the improved energy sensitivity detectable with a nanoSQUID. Finally, it looks at a range of applications for nanoSQUIDs, superconducting single photon detectors, and other superconducting nanodevices.
Detecting single-photon level signals—carriers of both classical and quantum information—is particularly challenging for low-energy microwave frequency excitations. Here we introduce a superconducting amplifier based on a Josephson junction transmission line. Unlike current standing-wave parametric amplifiers, this traveling wave architecture robustly achieves high gain over a bandwidth of several gigahertz with sufficient dynamic range to read out 20 superconducting qubits. To achieve this performance, we introduce a subwavelength resonant phase-matching technique that enables the creation of nonlinear microwave devices with unique dispersion relations. We benchmark the amplifier with weak measurements, obtaining a high quantum efficiency of 75% (70% including noise added by amplifiers following the Josephson amplifier). With a flexible design based on compact lumped elements, this Josephson amplifier has broad applicability to microwave metrology and quantum optics.
The work involves a study of physical phenomena that take place at very small length scales, below one micro-meter. At temperatures roughly below one degree Kelvin, quantum-mechanical effects may rule in electronic transport. Macroscopic quantum-coherent effects that occur in metallic superconducting microstructures, are particularly intriguing. Large-scale quantum information processing is widely believed to be attainable utilizing such physical systems. This work concentrates on answering the question of how the described quantum-mechanical systems may be used as sensitive measuring devices. Considerable attention is paid to energy-storing metallic microstructures whose electrical properties resemble those of the familiar inductor or capacitor. This research involves primarily experimental investigations conducted around temperatures of 0.1 Kelvin. Methods both at low and at radio frequencies have been used. The experimental findings have been modelled theoretically, and theoretical concepts for new physical phenomena have been introduced. An inductively measured radio-frequency Cooper-pair transistor, the L-SET, has been developed and experimentally verified in this work. Being highly sensitive, fast, and non-invasive, the L-SET appears to be the most promising method for measuring electric charge. Sensitivity in charge measurements of 20 millionths of the electron charge (micro-e) within one second, and an input bandwidth of 100 MHz, have been demonstrated. It has been shown theoretically that the ultimate measurement accuracy is about 0.1 micro-e within a second. A new phase detector based on the Cooper-pair transistor has been proposed. This system has also been shown to be potentially usable as a quantum bit. A new type of radio-frequency single-electron transistor built using a multi-walled carbon nanotube has been fabricated and operated. Technologies have been developed in order to make the physical nano- or microstructures. A method has been presented to fabricate non-superconducting tunnel junctions. Consequences of the inverse superconducting proximity effect on the studied superconducting structures were considered. Measurement procedures were investigated for a new low-noise nanoamplifier, the Bloch-oscillating transistor. Single superconducting tunnel junctions were tested as detectors of energy states of the environment, or of noise.
Superconducting circuits incorporating Josephson elements represent a promising hardware platform for quantum technologies. Potential applications include scalable quantum computing, microwave quantum networks, and quantum-limited amplifiers. However, progress in Josephson junction–based quantum technologies is facing the ongoing challenge of minimizing loss channels. This is also true for parametric superconducting devices based on nonlinear Josephson resonators. In this work, we report on the fabrication and characterization of low-loss Josephson parametric devices operated in the GHz frequency range, showing record internal quality factors. Specifically, we achieve internal quality factors Q int significantly exceeding 10 5 for both Josephson parametric converters and Josephson parametric amplifiers in the single-photon regime by fitting the scattering data. We confirm the extracted Q int values by analyzing purity of squeezed vacuum states generated by these devices. These low-loss devices mark a significant step forward in realizing high-performance quantum circuits, enabling further advancements in superconducting quantum technologies.
With a large portfolio of elemental quantum components, superconducting quantum circuits have contributed to dramatic advances in microwave quantum optics. Of these elements, quantum-limited parametric amplifiers have proven to be essential for low noise readout of quantum systems whose energy range is intrinsically low (tens of µeV). They are also used to generate non classical states of light that can be a resource for quantum enhanced detection. Superconducting parametric amplifiers, like quantum bits, typically utilize a Josephson junction as a source of magnetically tunable and dissipation-free nonlinearity. The magnetic control is not an industry standard for devices and starts already to be an issue in large scale circuits. In recent years, efforts have been made to introduce semiconductor weak links as electrically tunable nonlinear elements, with demonstrations of microwave resonators and quantum bits using semiconductor nanowires, a two dimensional electron gas, carbon nanotubes and graphene. However, given the challenge of balancing nonlinearity, dissipation, participation, and energy scale, parametric amplifiers have not yet been implemented with a semiconductor weak link. The work presented in this PhD thesis demonstrates the design, fabrication and performances of a parametric amplifier leveraging a graphene Josephson junction.The graphene is encapsulated in between hBN flakes in order to improve its quality. Using such high quality junctions, we demonstrate amplification with 20 dB gain which is the milestone for overcoming noise of the classical amplifiers in the rest of the amplification chain. The Josephson parametric amplifier being based on a resonant structure (around 6 GHz) suffers from the gain bandwidth product limiting the amplification to a few MegaHertz frequency range. The use of a side gate to electrically tune the graphene gives control of the Josephson junction inductance and thus the resonant frequency of the amplifier. We demonstrate a near 1 GHz tunability of the amplification frequency with the use of a side gate which is as good as the tunability offered by using a magnetic flux on a SQUID for similar amplifier designs. Moreover, graphene has shown to exhibit nonlinear loss under a strong microwave irradiation arising because of dynamics in the Andreev states. Dissipation is known to add intrinsic noise on quantum amplifiers and could be a problem for quantum limited parametric amplification. We demonstrate that despite the presence of nonlinear loss, graphene based Josephson parametric amplifiers can reach near quantum limited amplification. A two photon loss model was used to describe the behaviour of the device but we show that a more complex model is required in order to take into account the nonlinear dissipation and the non-sinusoidal current phase relation. We also studied the dynamic range and showed that the graphene based Josephson parametric amplifier can reach a 1 dB compression point of -123 dBm which is as good as single tunnel junctions based parametric amplifiers. Our results expand the toolset for electrically tunable superconducting quantum circuits and offer new opportunities for the development of quantum technologies such as quantum computing, quantum sensing and fundamental science.