Hidehiro Yonezawa
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View article: Unified formalism and adaptive algorithms for optimal quantum state, detector and process tomography
Unified formalism and adaptive algorithms for optimal quantum state, detector and process tomography Open
Quantum tomography is a standard technique for characterizing, benchmarking and verifying quantum systems/devices and plays a vital role in advancing quantum technology and understanding the foundations of quantum mechanics. Achieving the …
View article: Tracking Quantum Dynamics in an Optical Cavity for Recovering Purity and Squeezing via Quantum State Smoothing
Tracking Quantum Dynamics in an Optical Cavity for Recovering Purity and Squeezing via Quantum State Smoothing Open
Tracking the dynamics of a quantum system is conventionally achieved by monitoring the system continuously in time and filtering the information contained in measurement records via the causal quantum trajectory approach. However, in pract…
View article: Configuration design of multimode Gaussian operations on continuous-variable quad-rail lattice cluster states
Configuration design of multimode Gaussian operations on continuous-variable quad-rail lattice cluster states Open
Continuous-variable quad-rail lattice cluster states enable flexible quantum circuit design on their two-dimensional structure. However, how to combine basic operations on the quad-rail lattice cluster state to realize multimode operations…
View article: Research on Quantum Materials and Quantum Technology at RIKEN
Research on Quantum Materials and Quantum Technology at RIKEN Open
RIKEN covers fundamental research on physics, chemistry, biology, life and medical science, information and mathematical science, and engineering. Here, we outline research activities on quantum materials and quantum technology that includ…
View article: Fast State Stabilization Using Deep Reinforcement Learning for Measurement-Based Quantum Feedback Control
Fast State Stabilization Using Deep Reinforcement Learning for Measurement-Based Quantum Feedback Control Open
The stabilization of quantum states is a fundamental problem for realizing various quantum technologies. Measurement-based-feedback strategies have demonstrated powerful performance, and the construction of quantum control signals using me…
View article: Fast State Stabilization using Deep Reinforcement Learning for Measurement-based Quantum Feedback Control
Fast State Stabilization using Deep Reinforcement Learning for Measurement-based Quantum Feedback Control Open
The stabilization of quantum states is a fundamental problem for realizing various quantum technologies. Measurement-based-feedback strategies have demonstrated powerful performance, and the construction of quantum control signals using me…
View article: A two-stage solution to quantum process tomography: error analysis and optimal design
A two-stage solution to quantum process tomography: error analysis and optimal design Open
Quantum process tomography is a critical task for characterizing the dynamics of quantum systems and achieving precise quantum control. In this paper, we propose a two-stage solution for both trace-preserving and non-trace-preserving quant…
View article: Nonlinear feedforward enabling quantum computation
Nonlinear feedforward enabling quantum computation Open
View article: On the regularization and optimization in quantum detector tomography
On the regularization and optimization in quantum detector tomography Open
View article: Quantum state and detector tomography with known rank
Quantum state and detector tomography with known rank Open
Quantum state tomography and quantum detector tomography are two main problems in quantum system identification. In this paper, we study state tomography and detector tomography with prior knowledge about the true rank of the unknown state…
View article: Nonlinear feedforward enabling quantum computation
Nonlinear feedforward enabling quantum computation Open
Measurement-based quantum computation with optical time-domain multiplexing is a promising method to realize a quantum computer from the viewpoint of scalability. Fault tolerance and universality are also realizable by preparing appropriat…
View article: On the regularization and optimization in quantum detector tomography
On the regularization and optimization in quantum detector tomography Open
Quantum detector tomography (QDT) is a fundamental technique for calibrating quantum devices and performing quantum engineering tasks. In this paper, we utilize regularization to improve the QDT accuracy whenever the probe states are infor…
View article: Amplification of optical Schrödinger cat states with an implementation protocol based on a frequency comb
Amplification of optical Schrödinger cat states with an implementation protocol based on a frequency comb Open
We proposed and analyzed a scheme to generate large-size Schr\\"{o}dinger cat\nstates based on linear operations of Fock states and squeezed vacuum states and\nconditional measurements. By conducting conditional measurements via photon\nnu…
View article: Fault-tolerant <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="d1e529" altimg="si5.svg"> <mml:msup> <mml:mrow> <mml:mi>H</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>∞</mml:mi> </mml:mrow> </mml:msup> </mml:math> control for optical parametric oscillators with pumping fluctuations
Fault-tolerant control for optical parametric oscillators with pumping fluctuations Open
View article: Simultaneous Estimation of Parameters and the State of an Optical Parametric Oscillator System
Simultaneous Estimation of Parameters and the State of an Optical Parametric Oscillator System Open
In this article, we consider the filtering problem of an optical parametric oscillator (OPO). The OPO pump power may fluctuate due to environmental disturbances, resulting in uncertainty in the system modeling. Thus, both the state and the…
View article: Simultaneous estimation of parameters and the state of an optical parametric oscillator system
Simultaneous estimation of parameters and the state of an optical parametric oscillator system Open
In this paper, we consider the filtering problem of an optical parametric oscillator (OPO). The OPO pump power may fluctuate due to environmental disturbances, resulting in uncertainty in the system modeling. Thus, both the state and the u…
View article: Simultaneous estimation of parameters and the state of an optical\n parametric oscillator system
Simultaneous estimation of parameters and the state of an optical\n parametric oscillator system Open
In this paper, we consider the filtering problem of an optical parametric\noscillator (OPO). The OPO pump power may fluctuate due to environmental\ndisturbances, resulting in uncertainty in the system modeling. Thus, both the\nstate and th…
View article: Time-Domain-Multiplexed Measurement-Based Quantum Operations with 25-MHz Clock Frequency
Time-Domain-Multiplexed Measurement-Based Quantum Operations with 25-MHz Clock Frequency Open
Continuous-variable optical quantum computation has seen much progress in recent years. In particular, cluster states - the universal resource for measurement-based quantum computation - have been realized in a scalable fashion using the t…
View article: Two-Stage Estimation for Quantum Detector Tomography: Error Analysis, Numerical and Experimental Results
Two-Stage Estimation for Quantum Detector Tomography: Error Analysis, Numerical and Experimental Results Open
Quantum detector tomography is a fundamental technique for calibrating quantum devices and performing quantum engineering tasks. In this paper, a novel quantum detector tomography method is proposed. First, a series of different probe stat…
View article: Two-step feedback preparation of entanglement for qubit systems with time delay
Two-step feedback preparation of entanglement for qubit systems with time delay Open
View article: One-hundred step measurement-based quantum computation multiplexed in the time domain with 25 MHz clock frequency
One-hundred step measurement-based quantum computation multiplexed in the time domain with 25 MHz clock frequency Open
Among various approaches toward quantum computation, measurement-based quantum computation (MBQC) multiplexed in time domain is currently a promising method for addressing the need for scalability. MBQC requires two components: cluster sta…
View article: Fault-tolerant Coherent H-infinity Control for Linear Quantum Systems
Fault-tolerant Coherent H-infinity Control for Linear Quantum Systems Open
Robustness and reliability are two key requirements for developing practical quantum control systems. The purpose of this paper is to design a coherent feedback controller for a class of linear quantum systems suffering from Markovian jump…
View article: Feasibility study of a coherent feedback squeezer
Feasibility study of a coherent feedback squeezer Open
We investigate a coherent feedback squeezer that uses quantum coherent feedback (measurement-free) control. Our squeezer is simple, easy to implement, robust to the gain fluctuation, and broadband compared to the existing squeezers because…
View article: Coherent H∞ control for Markovian jump linear quantum systems
Coherent H∞ control for Markovian jump linear quantum systems Open
The purpose of this paper is to design a coherent feedback controller for a Markovian jump linear quantum system suffering from a fault signal. The control objective is to bound the effect of the disturbance input on the output for the tim…
View article: Squeezing in lithium niobate waveguides
Squeezing in lithium niobate waveguides Open
Lithium niobate is widely used in photonics applications because of its large second order nonlinearity and the possibility of integrating nonlinear parametric processes and fast electro-optical reconfigurability. Here we show how these pr…
View article: Generation of time-domain-multiplexed two-dimensional cluster state
Generation of time-domain-multiplexed two-dimensional cluster state Open
Generating large-scale cluster states The development of a practical quantum computer requires universality, scalability, and fault tolerance. Although much progress is being made in circuit platforms in which arrays of qubits are addresse…
View article: Feedback preparation of Bell states for two-qubit systems with time delay
Feedback preparation of Bell states for two-qubit systems with time delay Open
Bell states are the maximally entangled states in
\ntwo-qubit quantum systems, and play a significant role in
\nquantum computation and quantum communication. Feedback
\ncontrol of stochastic quantum systems usually suffers from timedelay
…
View article: Time-Domain Multiplexed 2-Dimensional Cluster State: Universal Quantum Computing Platform
Time-Domain Multiplexed 2-Dimensional Cluster State: Universal Quantum Computing Platform Open
Quantum computation promises applications that are thought to be impossible with classical computation. To realize practical quantum computation, the following three properties will be necessary: universality, scalability, and fault-tolera…
View article: Quantum-limited fiber-optic phase tracking beyond 𝜋 range
Quantum-limited fiber-optic phase tracking beyond 𝜋 range Open
We experimentally demonstrate a fiber-based phase tracking system through an adaptive homodyne detection technique. In the experiment, we use a random phase signal as an example. The system works well when the random phase varies between -…
View article: Quantum gate identification: Error analysis, numerical results and optical experiment
Quantum gate identification: Error analysis, numerical results and optical experiment Open