Cryogenic sensor enabling broad-band and traceable power measurements

Funding Information: We acknowledge the provision of facilities and technical support by Aalto University at OtaNano–Micronova Nanofabrication Center and LTL infrastructure, which is part of the European Microkelvin Platform (EMP, Grant No. 824109 EU Horizon 2020). We have received funding from the European Research Council under Consolidator Grant No. 681311 (QUESS) and under Advanced Grant Nos. 670743 (QuDeT) and 101053801 (ConceptQ), the European Commission through H2020 program projects QMiCS (Grant Agreement No. 820505, Quantum Flagship), the Quantum Flagship funding by the European Commission through Project No. 101113946 (OpenSuperQPlus100), the Academy of Finland through its Centers of Excellence Program (project Nos. 312300, 312059, and 312295) and grants (Nos. 336810, 314447, 314448, 314449, 305237, 316551, 308161, 335460, and 314302), the Finnish Cultural Foundation, the Vilho, Yrjö, and Kalle Väisälä Foundation of the Finnish Academy of Science and Letters, the Jane and Aatos Erkko Foundation, and the Technology Industries of Finland Centennial Foundation. | openaire: EC/H2020/681311/EU//QUESS | openaire: EC/H2020/101053801/EU//ConceptQ | openaire: EC/H2020/670743/EU//QuDeT | openaire: EC/H2020/820505/EU//QMiCS | openaire: EC/H2020/681311/EU//QUESSRecently, great progress has been made in the field of ultrasensitive microwave detectors, reaching even the threshold for utilization in circuit quantum electrodynamics. However, cryogenic sensors lack the compatibility with broad-band metrologically traceable power absorption measurements at ultralow powers, which restricts their range of applications. Here, we demonstrate such measurements using an ultralow-noise nanobolometer, which we extend by an additional direct-current (dc) heater input. The tracing of the absorbed power relies on comparing the response of the bolometer between radio frequency and dc-heating powers traced to the Josephson voltage and quantum Hall resistance. To illustrate this technique, we demonstrate two different methods of dc-substitution to calibrate the power that is delivered to the base temperature stage of a dilution refrigerator using our in situ power sensor. As an example, we demonstrate the ability to accurately measure the attenuation of a coaxial input line between thefrequencies of 50 MHz and 7 GHz with an uncertainty down to 0.1 dB at a typical input power of −114 dBm.Peer reviewe

Wireless Nanosensor Network with Flying Gateway

Part 5: Aerial NetworksInternational audienceThe use of unmanned aerial vehicles (UAVs) with a nano communication networks can significantly expand the network’s capabilities. In addition, UAVs can automate the process of data collection and reduce its cost. This article expands the application that uses UAV to collect data from passive nanosensor devices. The article considers the specifics of the THz frequency range for the energy supply of nanodevices, as well as for communication with them. The paper presents a mathematical model of these processes and simulation results

Channel estimation and hybrid architectures for RIS-assisted communications

Abstract Reconfigurable intelligent surfaces (RISs) are considered as potential technologies for the upcoming sixth-generation (6G) wireless communication system. Various benefits brought by deploying one or multiple RISs include increased spectrum and energy efficiency, enhanced connectivity, extended communication coverage, reduced complexity at transceivers, and even improved localization accuracy. However, to unleash their full potential, fundamentals related to RISs, ranging from physical-layer (PHY) modelling to RIS phase control, need to be addressed thoroughly. In this paper, we provide an overview of some timely research problems related to the RIS technology, i.e., PHY modelling (including also physics), channel estimation, potential RIS architectures, and RIS phase control (via both model-based and data-driven approaches), along with recent numerical results. We envision that more efforts will be devoted towards intelligent wireless environments, enabled by RISs

Bolometer operating at the threshold for circuit quantum electrodynamics

| openaire: EC/H2020/824109/EU//EMP | openaire: EC/H2020/681311/EU//QUESS | openaire: EC/H2020/670743/EU//QuDeT | openaire: EC/H2020/820505/EU//QMiCSRadiation sensors based on the heating effect of absorbed radiation are typically simple to operate and flexible in terms of input frequency, so they are widely used in gas detection, security, terahertz imaging, astrophysical observations and medical applications. Several important applications are currently emerging from quantum technology and especially from electrical circuits that behave quantum mechanically, that is, circuit quantum electrodynamics. This field has given rise to single-photon microwave detectors and a quantum computer that is superior to classical supercomputers for certain tasks. Thermal sensors hold potential for enhancing such devices because they do not add quantum noise and they are smaller, simpler and consume about six orders of magnitude less power than the frequently used travelling-wave parametric amplifiers. However, despite great progress in the speed and noise levels of thermal sensors, no bolometer has previously met the threshold for circuit quantum electrodynamics, which lies at a time constant of a few hundred nanoseconds and a simultaneous energy resolution of the order of 10h gigahertz (where h is the Planck constant). Here we experimentally demonstrate a bolometer that operates at this threshold, with a noise-equivalent power of 30 zeptowatts per square-root hertz, comparable to the lowest value reported so far, at a thermal time constant two orders of magnitude shorter, at 500 nanoseconds. Both of these values are measured directly on the same device, giving an accurate estimation of 30h gigahertz for the calorimetric energy resolution. These improvements stem from the use of a graphene monolayer with extremely low specific heat as the active material. The minimum observed time constant of 200 nanoseconds is well below the dephasing times of roughly 100 microseconds reported for superconducting qubits and matches the timescales of currently used readout schemes, thus enabling circuit quantum electrodynamics applications for bolometers.Peer reviewe

Exceptional points in tunable superconducting resonators

Abstract Superconducting quantum circuits are potential candidates to realize a large-scale quantum computer. The envisioned large density of integrated components, however, requires a proper thermal management and control of dissipation. To this end, it is advantageous to utilize tunable dissipation channels and to exploit the optimized heat flow at exceptional points (EPs). Here, we experimentally realize an EP in a superconducting microwave circuit consisting of two resonators. The EP is a singularity point of the effective Hamiltonian, and corresponds to critical damping with the most efficient heat transfer between the resonators without back and forth oscillation of energy. We observe a crossover from underdamped to overdamped coupling across the EP by utilizing photon-assisted tunneling as an in situ tunable dissipative element in one of the resonators. These methods can be used to obtain fast dissipation, for example, for initializing qubits to their ground states. In addition, these results pave the way for thorough investigation of parity-time symmetry and the spontaneous symmetry breaking at the EP in superconducting quantum circuits operating at the level of single energy quanta

Terahertz technologies to deliver optical network quality of experience in wireless systems beyond 5G

Abstract This article discusses the basic system architecture for THz wireless links with bandwidths of more than 50 GHz into optical networks. New design principles and breakthrough technologies are required in order to demonstrate terabit- per-second data rates at near zero latency using the proposed system concept. Specifically, we present the concept of designing the baseband signal processing for both the optical and wireless links and using an E2E error correction approach for the combined link. We provide two possible electro-optical baseband interface architectures, namely transparent optical-link and digital- link architectures, which are currently under investigation. THz wireless link requirements are given as well as the main principles and research directions for the development of a new generation of transceiver front-ends that will be capable of operating at ultra-high spectral efficiency by employing higher-order modulation schemes. Moreover, we discuss the need for developing a novel THz network information theory framework, which will take into account the channel characteristics and the nature of interference in the THz band. Finally, we highlight the role of PBF, which is required in order to overcome the propagation losses, as well as the physical layer and medium access control challenges