arXiv subjects

Raisei Mizokuchi

Publications and source records attributed to Raisei Mizokuchi.

4 recordsLinked to original sources

arXiv2026

Coherence protection of a silicon hole spin qubit with phase-modulated microwave driving

Hole spins in silicon quantum dots are a promising platform for quantum computing due to their strong intrinsic spin-orbit coupling (SOC), which enables fast, all-electrical control. However, this coupling also increases their susceptibility to charge noise, thereby limiting coherence times. Moreover, holes in silicon are also affected by hyperfine interactions with residual nuclear spins in the silicon substrate, introducing a non-negligible source of low-frequency noise. Here, we implement a phase-modulated concatenated continuous driving (CCD) technique for hole spin qubits to suppress low-frequency noise through microwave phase modulation. This approach stabilizes Rabi oscillations and extends the oscillation decay time compared to the conventional method. Furthermore, by defining a qubit in the CCD frame, we achieve coherent control while simultaneously protecting the qubit from noise, confirming coherence protection during gate operations. These results demonstrate a viable route toward noise-robust hole spin qubits.

cond-mat.mes-hall↗

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↗

arXiv2026

Robust spin-qubit control in a natural Si-MOS quantum dot using phase modulation

Silicon quantum dots are one of the most promising candidates for practical quantum computers because of their scalability and compatibility with the well-established complementary metal-oxide-semiconductor technology. However, the coherence time is limited in industry-standard natural silicon because of the $^{29}$Si isotopes, which have non-zero nuclear spin. Here, we protect an isotopically natural silicon metal-oxide-semiconductor (Si-MOS) quantum dot spin qubit from environmental noise via electron spin resonance with a phase-modulated microwave (MW) drive. This concatenated continuous drive (CCD) method extends the decay time of Rabi oscillations from 1.2 $\mathrm{μs}$ to over 200 $\mathrm{μs}$. Furthermore, we define a protected qubit basis and propose robust gate operations. We find the coherence time measured by Ramsey sequence is improved from 143 ns to 40.7 $μ$s compared to that of the bare spin qubit. The single qubit gate fidelity measured with randomized benchmarking is improved from 95% to 99%, underscoring the effectiveness of the CCD method. The method shows promise for improving control fidelity of noisy qubits, overcoming the qubit variability for global control, and maintaining qubit coherence while idling.

cond-mat.mes-hall↗

arXiv2018

Germanium quantum well Josephson field effect transistors and interferometers

Hybrid superconductor-semiconductor structures attract increasing attention owing to a variety of potential applications in quantum computing devices. They can serve to the realization of topological superconducting systems, as well as gate-tunable superconducting quantum bits. Here we combine a SiGe/Ge/SiGe quantum-well heterostructure hosting high-mobility two-dimensional holes and aluminum superconducting leads to realize prototypical hybrid devices, such as Josephson field-effect transistors (JoFETs) and superconducting quantum interference devices (SQUIDs). We observe gate-controlled supercurrent transport with Ge channels as long as one micrometer and estimate the induced superconducting gap from tunnel spectroscopy measurements in superconducting point-contact devices. Transmission electron microscopy reveals the diffusion of Ge into the aluminum contacts, whereas no aluminum is detected in the Ge channel.

cond-mat.mes-hall↗