RIKEN Center for Quantum Computing

Temporal-Mode Engineering for Multiplexed Microwave Photons and Mode-Selective Quantum State Transfer

Keika Sunada, Takeaki Miyamura, Kohei Matsuura +4

Quantum communication between distant superconducting qubits on separate chips using itinerant microwave photons has been studied to realize distributed quantum information process…

Focusing Surface-Acoustic-Wave Resonators on Thin-Film Lithium Niobate with Transverse-Mode Suppression

Ryo Sasaki, Ryusuke Hisatomi, Rekishu Yamazaki +3

Surface-acoustic-wave (SAW) resonators are a promising platform for constructing hybrid quantum systems, where confined acoustic waves enable strong interaction with various physic…

Control the qubit-qubit coupling with double superconducting resonators

Hui Wang, Rui Wang, Daichi Sugiyama +5

We experimentally studied the switching off processes in the double-resonator coupler superconducting quantum circuit. In both frequency and time-domain, we observed the variation…

Dissipative ground-state preparation of a quantum spin chain on a trapped-ion quantum computer

Kazuhiro Seki, Yuta Kikuchi, Tomoya Hayata +1

We demonstrate a dissipative protocol for ground-state preparation of a quantum spin chain on a trapped-ion quantum computer. As a first step, we derive a Kraus representation of a…

Deterministic Quantum Communication Between Fixed-Frequency Superconducting Qubits via Broadband Resonators

Takeaki Miyamura, Zhiling Wang, Kohei Matsuura +5

Quantum communication between remote chips is essential for realizing large-scale superconducting quantum computers. For such communication, itinerant microwave photons propagating…

Single-shot conditional displacement gate between a trapped atom and traveling light

Seigo Kikura, Hayato Goto, Fumiya Hanamura +1

We propose a single-shot conditional displacement gate between a trapped atom as the control qubit and a traveling light pulse as the target oscillator, mediated by an optical cavi…

Subsystem many-hypercube codes: High-rate concatenated codes with low-weight syndrome measurements

Ryota Nakai, Hayato Goto

Quantum error-correcting codes (QECCs) require high encoding rate in addition to high threshold unless a sufficiently large number of physical qubits are available. The many-hyperc…

Quantum Error Correction with Superpositions of Squeezed Fock States

Yexiong Zeng, Fernando Quijandría, Clemens Gneiting +1

Bosonic codes, leveraging infinite-dimensional Hilbert spaces for redundancy, offer great potential for encoding quantum information. However, the realization of a practical contin…

Nontrivial multi-product commutation relation toward reducing T-count in sequential Pauli-based computation

Yusei Mori, Hideaki Hakoshima, Keisuke Fujii

Quantum compilers that reduce the number of T gates are essential for minimizing the overhead of fault-tolerant quantum computation. Achieving further T-count reduction calls for i…

quant-ph2025★ 3 cited

Edge-of-chaos enhanced quantum-inspired algorithm for combinatorial optimization

Hayato Goto, Ryo Hidaka, Kosuke Tatsumura

Nonlinear dynamical systems with continuous variables can be used for solving combinatorial optimization problems with discrete variables. Numerical simulations of them are also us…

Generation of frequency-bin-encoded dual-rail cluster states via time-frequency multiplexing of microwave photonic qubits

Zhiling Wang, Takeaki Miyamura, Yoshiki Sunada +4

Cluster states are a class of multi-qubit entangled states with broad applications such as quantum metrology and one-way quantum computing. Here, we present a protocol to generate…

On the commutator scaling in Hamiltonian simulation with multi-product formulas

Kaoru Mizuta

A multi-product formula (MPF) is a promising approach for Hamiltonian simulation efficiently both in the system size $N$ and the inverse allowable error $1/ ε$ by combinin…

Scalable Simulation of Quantum Many-Body Dynamics with Or-Represented Quantum Algebra

Lukas Broers, Rong-Yang Sun, Seiji Yunoki

High-performance numerical methods are essential not only for advancing quantum many-body physics but also for enabling integration with emerging quantum computing platforms. We pr…

Comparison of spin-qubit architectures for quantum error-correcting codes

Mauricio Gutiérrez, Juan S. Rojas-Arias, David Obando +1

We investigate the performance of two quantum error-correcting codes, the surface code and the Bacon-Shor code, for implementation with spin qubits in silicon. In each case, we con…

Flux-Trapping Fluxonium Qubit

Kotaro Hida, Kohei Matsuura, Shu Watanabe +1

In pursuit of superconducting quantum computing, fluxonium qubits have recently garnered attention for their large anharmonicity and high coherence at the sweet spot. Towards the l…

quant-ph2025★ 5 cited

Trotterization is substantially efficient for low-energy states

Kaoru Mizuta, Tomotaka Kuwahara

Trotterization is one of the central approaches for simulating quantum many-body dynamics on quantum computers or tensor networks. In addition to its simple implementation, recent…

Preparing the Gutzwiller wave function for attractive SU(3) fermions on a quantum computer

Han Xu, Kazuhiro Seki, Seiji Yunoki

We implement the Gutzwiller wave function for attractive SU(3) fermion systems on a quantum computer using a quantum-classical hybrid scheme based on the discrete Hubbard-Stratonov…

Non-demolition fluorescence readout and high-fidelity unconditional reset of a fluxonium qubit via dissipation engineering

Shu Watanabe, Kotaro Hida, Kohei Matsuura +1

Non-demolition readout and high-fidelity unconditional reset of qubits are key requirements for practical quantum computation. For superconducting qubits, readout and reset are typ…

quant-ph2025★ 2 cited

Logical channel for heralded and pure loss with the Gottesman-Kitaev-Preskill code

Tom B. Harris, Takaya Matsuura, Ben Q. Baragiola +1

Photon loss is the dominant source of noise in optical quantum systems. The Gottesman-Kitaev-Preskill (GKP) bosonic code provides significant protection; however, even low levels o…

Quantum conditional mutual information as a probe of measurement-induced entanglement phase transitions

Yuichi Otsuka, Kazuhiro Seki, Seiji Yunoki

We propose that the quantum conditional mutual information (QCMI), computed with a suitably chosen partition of the system, serves as a powerful probe for detecting measurement-ind…

quant-ph2025★ 4 cited

Capacitively Shunted Double-Transmon Coupler Realizing Bias-Free Idling and High-Fidelity CZ Gate

Rui Li, Kentaro Kubo, Yinghao Ho +4

A high-fidelity CZ gate utilizing a double-transmon coupler (DTC) has recently been demonstrated as a building block for superconducting quantum processors. Like many other kinds o…

quant-ph2025★ 4 cited

Generation of Frequency-Tunable Shaped Single Microwave Photons Using a Fixed-Frequency Superconducting Qubit

Takeaki Miyamura, Yoshiki Sunada, Zhiling Wang +3

Scaling up a superconducting quantum computer will likely require quantum communication between remote chips, which can be implemented using an itinerant microwave photon in a tran…

High-Rate Four Photon Subtraction from Squeezed Vacuum: Preparing Cat State for Optical Quantum Computation

Mamoru Endo, Takefumi Nomura, Tatsuki Sonoyama +12

Generating logical qubits, essential for error detection and correction in quantum computation, remains a critical challenge in continuous-variable (CV) optical quantum information…