arXiv subjects

Aruto Hosaka

Publications and source records attributed to Aruto Hosaka.

9 recordsLinked to original sources

arXiv2025

Perfect impedance matching unlocks sensitive radio-frequency reflectometry in 2D material quantum dots

Two-dimensional (2D) materials are attractive platforms for realizing high-performance quantum bits (qubits). However, radio-frequency (RF) charge detection, which is a key technique for qubits readout, remains challenging in such systems. We demonstrate RF reflectometry with impedance matching for high-resistance quantum dot devices based on bilayer graphene and molybdenum disulfide. By integrating a tunable strontium titanate (SrTiO3) varactor into a resonant circuit, we achieve nearly perfect impedance matching, enabling sensitive charge detection. The demodulated RF signal clearly shows Coulomb oscillations, and the SrTiO3 varactor exhibits robustness against both magnetic fields and voltage noise on the varactor. Our results establish SrTiO3 varactors as effective tunable matching components for RF reflectometry in high-resistance 2D material quantum devices, providing a foundation for high-speed qubits readout.

cond-mat.mes-hall↗

arXiv2025

RFSoC-based radio-frequency reflectometry in gate-defined bilayer graphene quantum devices

Quantum computers require both scalability and high performance for practical applications. While semiconductor quantum dots are promising candidates for quantum bits, the complexity of measurement setups poses an important challenge for scaling up these devices. Here, radio-frequency system-on-chip (RFSoC) technology is exepcted for a promising approach that combines scalability with flexibility. In this paper, we demonstrate RF reflectometry in gate-defined bilayer graphene quantum devices using RFSoC-based measurement architecture. By controlling the confinement strength through gate voltages, we achieve both Fabry-Pérot interferometer and quantum dot operations in a single device. Although impedance matching conditions currently limit the measurement sensitivity, we identify pathways for optimization through tunnel barrier engineering and resonator design. These results represent a step toward integrating high-bandwidth measurements with scalable quantum devices.

cond-mat.mes-hall↗

arXiv2024

Quantum state estimation of multi-partite single photon path entanglement via local measurements

Multipartite entanglement plays a critical role in various applications of quantum internet. In these applications, the entanglement is usually shared by the distant parties. Experimentally, the distributed entanglement should be estimated by only local measurements. Furthermore, for network experiments, it is desirable to employ measurement techniques that are straightforward to implement. In this paper, we propose a method to measure arbitrary multipartite single photon path entangled states by only local measurements. By considering practically reasonable assumptions, our method is relatively easy to implement. We experimentally demonstrate the utility of this method by reconstructing the density matrix of a 3-qubit W-state.

quant-ph↗

arXiv2024

Programmable Quantum Linear Interference with Pulse Shaping of Quantum Light

In this paper, we propose a novel method for interfering frequency-multiplexed photonic quantum states without the use of optical nonlinear effects, and experimentally demonstrate this technique via frequency-domain Hong-Ou-Mandel (HOM) interference. By cascading the generation of quantum states onto arbitrary orthogonal modes, we can induce interference across any desired frequency mode. Following the generation of quantum states onto the frequency modes, performing measurements in independent frequency bands enables the realisation of a frequency-domain linear optical circuit analogous to linear interference in the spatial domain. We successfully demonstrated programmable quantum interference by controlling the spectral mode functions and measurement bases. Our method offers a new approach to harness the full potential of light's temporal-frequency degrees of freedom, providing a path towards scalable and programmable photonic quantum computing architectures without the need for optical nonlinearities or spatial-mode beam splitters.

quant-ph↗

arXiv2024

Efficient Bit Labeling in Factorization Machines with Annealing for Traveling Salesman Problem

To efficiently find an optimum parameter combination in a large-scale problem, it is a key to convert the parameters into available variables in actual machines. Specifically, quadratic unconstrained binary optimization problems are solved with the help of machine learning, e.g., factorization machines with annealing, which convert a raw parameter to binary variables. This work investigates the dependence of the convergence speed and the accuracy on binary labeling method, which can influence the cost function shape and thus the probability of being captured at a local minimum solution. By exemplifying traveling salesman problem, we propose and evaluate Gray labeling, which correlates the Hamming distance in binary labels with the traveling distance. Through numerical simulation of traveling salesman problem up to 15 cities at a limited number of iterations, the Gray labeling shows less local minima percentages and shorter traveling distances compared with natural labeling.

cs.LG↗

arXiv2024

Simplification of tensor updates toward performance-complexity balanced quantum computer simulation

Matrix Product States (MPS) provide a powerful framework for simulating quantum circuits. In practical simulations, tensor updates are typically performed in the canonical form (CF), which corresponds to the Schmidt decomposition and improves approximation accuracy. However, maintaining the canonical form introduces significant computational overhead. An alternative approach, known as the Simple Update (SU), does not enforce the Schmidt decomposition and is expected to reduce computational complexity. In this work, we systematically compare the performance and computational cost of SU and CF in quantum circuit simulations. We benchmark both methods on highly entangled circuits and on a QASM benchmark suite covering a wide range of circuit types. Our results show that SU achieves accuracy comparable to CF while reducing computational complexity, indicating that SU provides an efficient alternative for practical quantum circuit simulations.

quant-ph↗

arXiv2024

Preconditioning for a Variational Quantum Linear Solver

We apply preconditioning, which is widely used in classical solvers for linear systems $A\textbf{x}=\textbf{b}$, to the variational quantum linear solver. By utilizing incomplete LU factorization as a preconditioner for linear equations formed by $128\times128$ random sparse matrices, we numerically demonstrate a notable reduction in the required ansatz depth, demonstrating that preconditioning is useful for quantum algorithms. This reduction in circuit depth is crucial to improving the efficiency and accuracy of Noisy Intermediate-Scale Quantum (NISQ) algorithms. Our findings suggest that combining classical computing techniques, such as preconditioning, with quantum algorithms can significantly enhance the performance of NISQ algorithms.

quant-ph↗

arXiv2024

Application of Tensorized Neural Networks for Cloud Classification

Convolutional neural networks (CNNs) have gained widespread usage across various fields such as weather forecasting, computer vision, autonomous driving, and medical image analysis due to its exceptional ability to extract spatial information, share parameters, and learn local features. However, the practical implementation and commercialization of CNNs in these domains are hindered by challenges related to model sizes, overfitting, and computational time. To address these limitations, our study proposes a groundbreaking approach that involves tensorizing the dense layers in the CNN to reduce model size and computational time. Additionally, we incorporate attention layers into the CNN and train it using Contrastive self-supervised learning to effectively classify cloud information, which is crucial for accurate weather forecasting. We elucidate the key characteristics of tensorized neural network (TNN), including the data compression rate, accuracy, and computational speed. The results indicate how TNN change their properties under the batch size setting.

cs.CV↗

arXiv2024

Multimode Quantum Correlations in Supercontinuum Pulses

Suprecontinuum (SC) light contains complex spectral noise structure and its accurate characterization is important for fundamental understanding of its physics as well as for its applications. Several experimental and theoretical noise characterizations have been performed so far. However, none of them takes into account the quantum mechanical properties. Here, we demonstrate experimental characterisation of quantum noise and its spectral correlations formed in the SC light generated from a photonic crystal fiber. Moreover, by applying an appropriate basis transformation to these correlations, we demonstrate that the SC noise amplitude can be squeezed below the shot-noise limit in some bases, even in the presence of excessively large nonlinearities.

quant-ph↗