arXiv subjects

Kimihiko Kato

Publications and source records attributed to Kimihiko Kato.

5 recordsLinked to original sources

arXiv2026

Interplay of Electric Dipole Spin Resonance and Multilevel Landau-Zener Interference in p-Type Silicon Quantum Dots

In this work, we examine microwave responses of the Pauli spin blockade (PSB) leakage current through a p-type silicon double quantum dot. We observe more than the expected two resonance lines with the main resonance line exhibits both positive and negative peaks as a function of the magnetic field, corresponding to enhancement and suppression of the PSB leakage current, respectively. We attribute the observed spectra to the interplay between two spin rotation mechanisms: spin-orbit-mediated electric dipole spin resonance (EDSR) and multilevel Landau-Zener (MLLZ) interference, both of which are present in electrically driven devices with strong spin-orbit coupling (and enhanced in the vicinity of orbital level crossings). A numerical simulation taking into account both mechanisms show agreement with the experimental results. While these unconventional spectral behaviours can be readily suppressed away from the orbital level crossing or in devices with weak spin-orbit coupling, our study showcases the potential complexity of spin-rotating mechanisms for electrically driven spin qubits.

cond-mat.mes-hall↗

arXiv2025

Pauli spin blockade at room temperature in double-quantum-dot tunneling through individual deep dopants in silicon

Pauli spin blockade (PSB) is a spin-dependent charge transport process that typically appears in double quantum dot (QD) devices and is employed in fundamental research on single spins in nanostructures to read out semiconductor qubits. The operating temperature of PSB is limited by that of the QDs and remains below 10 K, limiting wide application development. Herein, we confirm that a single deep dopant in the channel of a silicon field effect transistor functions as a room-temperature QD; consequently, transport through two different deep dopants exhibits PSB up to room temperature. The characteristic magnetoconductance provides a means to identify PSB and enables the PSB device to function as a magnetic sensor with a sensitivity below geomagnetic field. Lifting in PSB caused by magnetic resonance (50 K) and Rabi oscillations (10 K) are also observed. Further development of this unique system may lead to room-temperature quantum technologies based on silicon technology.

cond-mat.mes-hall↗

arXiv2022

Introduction of deep level impurities, S, Se, and Zn, into Si wafers for high-temperature operation of a Si qubit

To realize high-temperature operation of Si qubits, deep impurity levels with large confinement energy, which are hardly thermally excited, have been introduced into Si wafers. Group II impurity Zn and group VI impurities S and Se, which are known to form deep levels, were introduced into the Si substrates by ion implantation. These samples were analyzed for concentration-depth profiles, energy level depths, and absence of defects. To introduce deep impurities into thin channels such as 50-nm-thick Si, we found impurity introduction conditions so that the concentration depth profiles have maximum value at less than 50 nm from the Si surface. Then, the formation of the deep levels and absence of defects were experimentally examined. By using the conditions to introduce deep impurities into Si wafer obtained from the experiments, single-electron transport at room temperature, high-temperature operation of qubit, and room-temperature quantum magnetic sensors are promising.

cond-mat.mtrl-sci↗

arXiv2021

4.2 K Sensitivity-Tunable Radio Frequency Reflectometry of a Physically Defined P-channel Silicon Quantum Dot

We demonstrate the measurement of p-channel silicon-on-insulator quantum dots at liquid helium temperatures by using a radio frequency (rf) reflectometry circuit comprising of two independently tunable GaAs varactors. This arrangement allows observing Coulomb diamonds at 4.2\,K under nearly best matching condition and optimal signal-to-noise ratio. We also discuss the rf leakage induced by the presence of the large top gate in MOS nanostructures and its consequence on the efficiency of rf-reflectometry. These results open the way to fast and sensitive readout in multi-gate architectures, including multi-qubit platforms.

cond-mat.mes-hall↗

arXiv2021

RF Reflectometry for Readout of Charge Transition in a Physically Defined PMOS Silicon Quantum Dot

We have embedded a physically defined p-channel silicon MOS quantum dot (QD) device into an impedance transformer RC circuit. To decrease the parasitic capacitance and surpass the cutoff frequency of the device which emerges in MOS devices that have a top gate and act as RC low-pass filter, we fabricate a new device to reduce the device's top gate area from 400 $\mbox{$μ$m}^2$ to 0.09 $\mbox{$μ$m}^2$. Having a smaller top gate eliminates the cutoff frequency problem preventing the RF signal from reaching QD. We show that we have fabricated a single QD properly, which is essential for RF single-electron transistor technique. We also analyze and improve the impedance matching condition and show that it is possible to perform readout of charge transition at 4.2 K by RF reflectometry, which will get us to fast readout of charge and spin states.

cond-mat.mes-hall↗