Spin ensembles in superconducting nonlinear cavities

Circuit quantum electrodynamics (cQED) provides a modern test bed for exploring the well-established physics of cavity quantum electrodynamics. cQED exploits circuit-based cavities that are fabricated on a chip and interfaced with real or artificial atoms to examine a range of light-matter interactions. It has gained considerable popularity and became one of the most powerful platforms to experimentally explore quantum mechanical effects in the solid state. cQED offers a simple way to couple together distinct quantized degrees of freedom, and this has instigated a new sub-field often referred to as “hybrid quantum systems”. Through combining different quantum systems with superconducting circuits, one can deploy the cQED toolbox to deliver advantages in other fields. Recently, superconducting micro-resonators have been used in conjunction with microwave parametric amplifiers to push the detection sensitivity in Electron Spin Resonance (ESR) spectroscopy to the quantum noise limit. ESR spectroscopy is an important technique for studying the structure and function of materials, broadly utilized throughout chemistry, physics and biology and sensitive enhancement is often a highly prized goal. The superconducting parametric amplifier circuits employed in previous quantum-limited ESR experiments have all been based on Josephson junction technology -- a lossless nonlinear element that enables many important cQED devices -- and are incompatible with the high magnetic fields often required by spins. Spin signals are collected using a linear resonator and must be routed to the amplifier (housed away from any magnetic fields) through various microwave components and cables, which introduce loss and complexity. In this thesis we develop a new type of superconducting parametric amplifier that utilizes a nonlinear kinetic inductance, called the KIPA. The amplifier contains no Josephson junctions and is compatible with the large magnetic fields relevant for ESR spectroscopy. We analyze the key properties of this new amplifier and demonstrate that it has excellent characteristics, including a quantum-limited noise performance and high dynamic range. In a break from previous work, we integrate the spins directly with this parametric amplifier and show that the spin signals can be collected and amplified all within the same device, greatly simplifying the quantum-limited spectrometer design. By adopting analogues from optomechanics, we develop and lay the experimental groundwork for an idea that utilizes the nonlinearity of our KIPA circuit to parametrically cool a spin ensemble coupled to it. We show that we are able to induce a parametric interaction between the fundamental mode and first harmonic of the device, which can in principle be used to cool the lower frequency mode. By coupling the electron spins to the fundamental mode, their polarization can be increased through Purcell relaxation (or radiative cooling), where the spins relax via photon emission into the device and thus thermalize to the photon temperature. This constitutes an active cooling process and can be used to lower the effective spin temperature below that of the cryostat to which the device is thermally anchored. Our proposed active cooling scheme would have application in low-temperature ESR spectroscopy, where the resulting population enhancement directly translates to a sensitivity gain. This thesis presents a novel hybrid architecture that combines spins in a solid-state chip with a new type of high-performance superconducting parametric amplifier, allowing for high-sensitivity detection of the spins through parametric amplification and cooling, where both processes may be performed entirely on-chip. The results are of interest to a range of fields, particularly ESR spectroscopy and superconducting-based quantum information processing (QIP)

Fabrication of 3-D phononic crystals for thermal transport management

Thermal transport is an important physical phenomenon, and it has recently become even more relevant for the reduction of energy losses and the increase of efficiency in novel devices based on thermoelectricity [1]. Significant reduction of thermal conduction was recently achieved by coherent modification of phonon modes [2], with the help of periodic phononic crystal structures. However, currently the experimental studies have only been performed for two-dimensional (2-D) nanostructures. Theoretically, the magnitude of control of thermal transport should be even stronger in three-dimensional (3-D) phononic crystal structures. For that reason, the question arises how to fabricate the desired 3-D phononic crystal nanostructures and to measure its thermal conductivity. [1] Minnich and A. J. et al., Energy Environ. Sci. 2, 466 (2009) [2] N. Zen, T. Puurtinen, T. Isotalo, S Chaudhuri, and I. J. Maasilta, Nature Communications, 5, 3435 (2014

Визначення параметрів кілей внутрішнього контуру гнучкої огорожі СППА

Determination of shape and the tight-strained state of internal circuit keels of flexible skirt of amphibious hovercraft vessels has been considered. A mathematical model which describes the shape and the tight-strained state of the keel of the skirt has been shown. Keel is made from an isotropic, inextensible and perfectly flexible material. It is assumed that the removable element is a rigid structure in the form of a straight rectangular prism.Определены основные параметры облегченных стальных баллонов, которые могут быть применены в грузовой системе CNG-газовозов. Рассмотрены различные варианты компоновки этих баллонов в специальных модулях и определены их некоторые параметры. Освящены вопросы технологии изготовления этих баллонов. Описано созданное авторами оборудование для изготовления облегченных стальных CNG-баллонов.Розглянуто визначення форми і напружено-деформованого стану кілів внутрішнього контуру гнучкої огорожі суден на повітряній подушці амфібійного типу. Наведено математичну модель, що описує форму і напружено-деформований стан кіля внутрішнього контуру гнучної огорожі, виконаної з ізотропного, нерозтяжного й абсолютно гнучкого матеріалу. Прийнято, що знімний елемент є жорсткою конструкцією у вигляді прямої чотирикутної призми

Latched detection of zeptojoule spin echoes with a kinetic inductance parametric oscillator.

When strongly pumped at twice their resonant frequency, nonlinear resonators develop a high-amplitude intracavity field, a phenomenon known as parametric self-oscillations. The boundary over which this instability occurs can be extremely sharp and thereby presents an opportunity for realizing a detector. Here, we operate such a device based on a superconducting microwave resonator whose nonlinearity is engineered from kinetic inductance. The device indicates the absorption of low-power microwave wavepackets by transitioning to a self-oscillating state. Using calibrated pulses, we measure the detection efficiency to zeptojoule energy wavepackets. We then apply it to measurements of electron spin resonance, using an ensemble of 209Bi donors in silicon that are inductively coupled to the resonator. We achieve a latched readout of the spin signal with an amplitude that is five hundred times greater than the underlying spin echoes

In-situ amplification of spin echoes within a kinetic inductance parametric amplifier

The use of superconducting micro-resonators in combination with quantum-limited Josephson parametric amplifiers has in recent years lead to more than four orders of magnitude improvement in the sensitivity of pulsed Electron Spin Resonance (ESR) measurements. So far, the microwave resonators and amplifiers have been designed as separate components, largely due to the incompatibility of Josephson junction-based devices with even moderate magnetic fields. This has led to complex spectrometers that operate under strict environments, creating technical barriers for the widespread adoption of the technique. Here we circumvent this issue by inductively coupling an ensemble of spins directly to a weakly nonlinear microwave resonator, which is engineered from a magnetic field-resilient thin superconducting film. We perform pulsed ESR measurements with a $1$~pL effective mode volume and amplify the resulting spin signal using the same device, ultimately achieving a sensitivity of $2.8 \times 10^3$ spins in a single-shot Hahn echo measurement at a temperature of 400 mK. We demonstrate the combined functionalities at fields as large as 254~mT, highlighting the technique's potential for application under more conventional ESR operating conditions

In situ amplification of spin echoes within a kinetic inductance parametric amplifier

The use of superconducting microresonators together with quantum-limited Josephson parametric amplifiers has enhanced the sensitivity of pulsed electron spin resonance (ESR) measurements by more than four orders of magnitude. So far, the microwave resonators and amplifiers have been designed as separate components due to the incompatibility of Josephson junction-based devices with magnetic fields. This has produced complex spectrometers and raised technical barriers toward adoption of the technique. Here, we circumvent this issue by coupling an ensemble of spins directly to a weakly nonlinear and magnetic field-resilient superconducting microwave resonator. We perform pulsed ESR measurements with a 1-pL mode volume containing 6 × 107 spins and amplify the resulting signals within the device. When considering only those spins that contribute to the detected signals, we find a sensitivity of [Formula: see text] for a Hahn echo sequence at a temperature of 400 mK. In situ amplification is demonstrated at fields up to 254 mT, highlighting the technique's potential for application under conventional ESR operating conditions

Unimon qubit

Funding Information: S.K., A.G., O.K., V.V., and M.M. acknowledge funding from the European Research Council under Consolidator Grant No. 681311 (QUESS) and Advanced Grant No. 101053801 (ConceptQ), European Commission through H2020 program projects QMiCS (grant agreement 820505, Quantum Flagship), the Academy of Finland through its Centers of Excellence Program (project Nos. 312300, and 336810), and Business Finland through its Quantum Technologies Industrial grant No. 41419/31/2020. S.K. and M.M. acknowledge Research Impact Foundation for grant No. 173 (CONSTI). E.H. thanks Emil Aaltonen Foundation (grant No. 220056 K) and Nokia Foundation (grant No. 20230659) for funding. We acknowledge the provision of facilities and technical support by Aalto University at OtaNano - Micronova Nanofabrication Center and LTL infrastructure which is part of European Microkelvin Platform (EMP, No. 824109 EU Horizon 2020). We thank the whole staff at IQM and QCD Labs for their support. Especially, we acknowledge the help withthe experimental setup from Roope Kokkoniemi, code and software support from Joni Ikonen, Tuukka Hiltunen, Shan Jolin, Miikka Koistinen, Jari Rosti, Vasilii Sevriuk, and Natalia Vorobeva, and useful discussions with Brian Tarasinski. | openaire: EC/H2020/681311/EU//QUESS | openaire: EC/H2020/101053801/EU//ConceptQSuperconducting qubits seem promising for useful quantum computers, but the currently wide-spread qubit designs and techniques do not yet provide high enough performance. Here, we introduce a superconducting-qubit type, the unimon, which combines the desired properties of increased anharmonicity, full insensitivity to dc charge noise, reduced sensitivity to flux noise, and a simple structure consisting only of a single Josephson junction in a resonator. In agreement with our quantum models, we measure the qubit frequency, ω01/(2π), and increased anharmonicity α/(2π) at the optimal operation point, yielding, for example, 99.9% and 99.8% fidelity for 13 ns single-qubit gates on two qubits with (ω01, α) = (4.49 GHz, 434 MHz) × 2π and (3.55 GHz, 744 MHz) × 2π, respectively. The energy relaxation seems to be dominated by dielectric losses. Thus, improvements of the design, materials, and gate time may promote the unimon to break the 99.99% fidelity target for efficient quantum error correction and possible useful quantum advantage with noisy systems.Peer reviewe

Long-Distance Transmon Coupler with cz -Gate Fidelity above 99.8 %

Funding Information: We acknowledge Matthew Sarsby, Roope Kokkoniemi, Ali Yurtalan Jean-Luc Orgiazzi, Lucas Ortega, Jorge Santos, Jaakko Jussila, Illari Kuronen, Jaakko Salo, Tiina Naaranoja, Otto Koskinen, and Tero Somppi for supporting the conceptualization, construction, and maintenance of the experimental setup, Ferenc Dósa-Rácz, Janne Mäntylä, Sinan Inel, and Leon Wubben for additional software support, and Olli-Pentti Saira for valuable discussions. We would additionally like to thank the rest of the IQM team for creating the entire infrastructure, laying the foundation of this work. The work was partly supported by the European Innovation Council (EIC) under Prometheus (Grant No. 959521), by Business Finland (Grant No. 7547/31/2021), and by the German Federal Ministry of Education and Research (BMBF) under the projects Q-Exa (Grant No. 13N16062), QSolid (Grant No. 13N16161), and MUNIQC-SC (Grant No. 13N16185). M.M. is partly supported by the Academy of Finland through its Centers of Excellence Program(Project No. 336810) and by the European Research Council under Advanced Grant ConceptQ (Grant No. 101053801). Parts of this work are included in patents applications filed by IQM Finland Oy. This work has used resources from the OtaNano Micronova cleanroom. Publisher Copyright: © 2023 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Tunable coupling of superconducting qubits has been widely studied due to its importance for isolated gate operations in scalable quantum processor architectures. Here, we demonstrate a tunable qubit-qubit coupler based on a floating transmon device, which allows us to place qubits at least 2 mm apart from each other while maintaining over 50-MHz coupling between the coupler and the qubits. In the introduced tunable-coupler design, both the qubit-qubit and the qubit-coupler couplings are mediated by two waveguides instead of relying on direct capacitive couplings between the components, reducing the impact of the qubit-qubit distance on the couplings. This leaves space for each qubit to have an individual readout resonator and a Purcell filter, which is needed for fast high-fidelity readout. In addition, simulations show that the large qubit-qubit distance significantly lowers unwanted non-nearest-neighbor coupling and allows multiple control lines to cross over the structure with minimal crosstalk. Using theproposed flexible and scalable architecture, we demonstrate a controlled-Z gate with (99.81±0.02)% fidelity.Peer reviewe