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4 results for au:Ito_R in:cond-mat

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Semiconductor Circuits for Quantum Computing with Electronic Wave Packets
David Pomaranski, Ryo Ito, Ngoc Han Tu, Arne Ludwig, Andreas D. Wieck, Shintaro Takada, Nobu-Hisa Kaneko, Seddik Ouacel, Christopher Bauerle, Michihisa Yamamoto
Oct 23 2024 cond-mat.mes-hall quant-ph arXiv:2410.16244v1

@misc{2410.16244, author = {David Pomaranski and Ryo Ito and Ngoc Han Tu and Arne Ludwig and Andreas D.~Wieck and Shintaro Takada and Nobu-Hisa Kaneko and Seddik Ouacel and Christopher Bauerle and Michihisa Yamamoto}, title = {{S}emiconductor {C}ircuits for {Q}uantum {C}omputing with {E}lectronic {W}ave {P}ackets}, year = {2024}, eprint = {2410.16244}, note = {arXiv:2410.16244v1} }
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Standard approaches to quantum computing require significant overhead to correct for errors. The hardware size for conventional quantum processors in solids often increases linearly with the number of physical qubits, such as for transmon qubits in superconducting circuits or electron spin qubits in quantum dot arrays. While photonic circuits based on flying qubits do not suffer from decoherence or lack of potential scalability, they have encountered significant challenges to overcome photon loss in long delay circuits. Here, we propose an alternative approach that utilizes flying electronic wave packets propagating in solid-state quantum semiconductor circuits. Using a novel time-bin architecture for the electronic wave packets, hardware requirements are drastically reduced because qubits can be created on-demand and manipulated with a common hardware element, unlike the localized approach of wiring each qubit individually. The electronic Coulomb interaction enables reliable coupling and readout of qubits. Improving upon previous devices, we realize electronic interference at the level of a single quantized mode that can be used for manipulation of electronic wavepackets. This important landmark lays the foundation for fault-tolerant quantum computing with a compact and scalable architecture based on electron interferometry in semiconductors.
Electrical control of a Kondo spin screening cloud
Ngoc Han Tu, Donghoon Kim, Minsoo Kim, Jeongmin Shim, Ryo Ito, David Pomaranski, Ivan V. Borzenets, Arne Ludwig, Andreas D. Wieck, Heung-Sun Sim, Michihisa Yamamoto
Apr 19 2024 cond-mat.mes-hall quant-ph arXiv:2404.11955v1

@misc{2404.11955, author = {Ngoc Han Tu and Donghoon Kim and Minsoo Kim and Jeongmin Shim and Ryo Ito and David Pomaranski and Ivan V.~Borzenets and Arne Ludwig and Andreas D.~Wieck and Heung-Sun Sim and Michihisa Yamamoto}, title = {{E}lectrical control of a {K}ondo spin screening cloud}, year = {2024}, eprint = {2404.11955}, note = {arXiv:2404.11955v1} }
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In metals and semiconductors, an impurity spin is quantum entangled with and thereby screened by surrounding conduction electrons at low temperatures, called the Kondo screening cloud. Quantum confinement of the Kondo screening cloud in a region, called a Kondo box, with a length smaller than the original cloud extension length strongly deforms the screening cloud and provides a way of controlling the entanglement. Here we realize such a Kondo box and develop an approach to controlling and monitoring the entanglement. It is based on a spin localized in a semiconductor quantum dot, which is screened by conduction electrons along a quasi-one-dimensional channel. The box is formed between the dot and a quantum point contact placed on a channel. As the quantum point contact is tuned to make the confinement stronger, electron conductance through the dot as a function of temperature starts to deviate from the known universal function of the single energy scale, the Kondo temperature. Nevertheless, the entanglement is monitored by the measured conductance according to our theoretical development. The dependence of the monitored entanglement on the confinement strength and temperature implies that the Kondo screening is controlled by tuning the quantum point contact. Namely, the Kondo cloud is deformed by the Kondo box in the region across the original cloud length. Our findings offer a way of manipulating and detecting spatially extended quantum many-body entanglement in solids by electrical means.
Coherent beam splitting of flying electrons driven by a surface acoustic wave
R. Ito, S. Takada, A. Ludwig, A. D. Wieck, S. Tarucha, M. Yamamoto
Apr 27 2020 cond-mat.mes-hall arXiv:2004.11553v1

@misc{2004.11553, author = {R.~Ito and S.~Takada and A.~Ludwig and A.~D.~Wieck and S.~Tarucha and M.~Yamamoto}, title = {{C}oherent beam splitting of flying electrons driven by a surface acoustic wave}, year = {2020}, eprint = {2004.11553}, note = {arXiv:2004.11553v1} }
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We develop a coherent beam splitter for single electrons driven through two tunnel-coupled quantum wires by surface acoustic waves (SAWs). The output current through each wire oscillates with gate voltages to tune the tunnel-coupling and potential difference between the wires. This oscillation is assigned to coherent electron tunneling motion that can be used to encode a flying qubit and is well reproduced by numerical calculations of time evolution of the SAW-driven single electrons. The oscillation visibility is currently limited to about 3%, but robust against decoherence, indicating that the SAW-electron can serve as a novel platform for a solid-state flying qubit.
Lower critical field measurement of NbN multilayer thin film superconductor at KEK
H. Ito, H. Hayano, T. Kubo, T. Saeki, R. Katayama, Y. Iwashita, H. Tongu, R. Ito, T. Nagata, C. Z. Antoine
Jul 09 2019 physics.acc-ph cond-mat.supr-con arXiv:1907.03410v1

@misc{1907.03410, author = {H.~Ito and H.~Hayano and T.~Kubo and T.~Saeki and R.~Katayama and Y.~Iwashita and H.~Tongu and R.~Ito and T.~Nagata and C.~Z.~Antoine}, title = {{L}ower critical field measurement of {N}b{N} multilayer thin film superconductor at {KEK}}, year = {2019}, eprint = {1907.03410}, note = {arXiv:1907.03410v1} }
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The multilayer thin film structure of the superconductor has been proposed by A. Gurevich to enhance the maximum gradient of SRF cavities. The lower critical field Hc1 at which the vortex starts penetrating the superconducting material will be improved by coating Nb with thin film superconductor such as NbN. It is expected that the enhancement of Hc1 depends on the thickness of each layer. In order to determine the optimum thickness of each layer and to compare the measurement results with the theoretical prediction proposed by T. Kubo, we developed the Hc1 measurement system using the third harmonic response of the applied AC magnetic field at KEK. For the Hc1 measurement without the influence of the edge or the shape effects, the AC magnetic field can be applied locally by the solenoid coil of 5mm diameter in our measurement system. ULVAC made the NbN-SiO2 multilayer thin film samples of various NbN thicknesses. In this report, the measurement result of the bulk Nb sample and NbN-SiO2 multilayer thin film samples of different thickness of NbN layer will be discussed.