Article
Quantum Science & Technology
Timjan Kalajdzievski, Nicolas Quesada
Summary: Exact decomposition methods have lower gate counts, while approximate techniques cover decompositions for all operations but require significant circuit depth.
Article
Optics
Qi-Ping Su, Yu Zhang, Liang Bin, Chui-Ping Yang
Summary: Compared with a qubit, a qudit provides a larger Hilbert space for information storage and processing. This work proposes a simple method to realize a hybrid quantum controlled-sum gate using a superconducting qutrit and a cat-state qutrit, forming a universal set of ternary logic gates for quantum computing with qutrits. The proposal is based on circuit QED and employs a dispersive coupling between a superconducting ququart and a microwave cavity. The gate operation is simple and does not require classical pulse or measurement. The feasibility of generating a hybrid maximally entangled state and its experimental implementation are also discussed.
Article
Multidisciplinary Sciences
Jan Provaznik, Radim Filip, Petr Marek
Summary: Numerical simulation of continuous variable quantum state preparation is essential for optimizing quantum information processing protocols. This study presents a powerful tool for such simulations using Fock state representation and numerical computation. The accuracy of several methods for computing the truncated coherent displacement operator is analyzed in an approximation of the infinite-dimensional Fock space by finite complex vector spaces. An alternative method with improved accuracy, based on the standard matrix exponential, is proposed. The method is then applied to analyze non-Gaussian state preparation schemes using coherent displacement of a two mode squeezed vacuum and photon counting measurement. Different detection mechanisms, including avalanche photodiodes, their cascades, and photon number resolving detectors, are compared for engineering non-linearly squeezed cubic states and constructing qubit-like superpositions.
SCIENTIFIC REPORTS
(2022)
Article
Quantum Science & Technology
Feiran Wang, Shihao Ru, Yunlong Wang, Min An, Pei Zhang, Fuli Li
Summary: The study proposed and implemented a quantum Fredkin gate, using polarization and photonic orbital angular momentum to achieve SWAP operation with an effective conversion rate of 95.4%. Additionally, a specific type of state similar to Greenberger-Horne-Zeilinger states can be prepared using the quantum Fredkin gate, demonstrating its quantum contextual characteristic.
QUANTUM SCIENCE AND TECHNOLOGY
(2021)
Article
Multidisciplinary Sciences
William P. Livingston, Machiel S. Blok, Emmanuel Flurin, Justin Dressel, Andrew N. Jordan, Irfan Siddiqi
Summary: Continuous quantum error correction using direct parity measurements in a resource-efficient manner is demonstrated, achieving high detection efficiency and increasing the relaxation time of protected logical qubits.
NATURE COMMUNICATIONS
(2022)
Article
Optics
Alfonso Tello Castillo, Elizabeth Eso, Ross Donaldson
Summary: Free-space quantum key distribution (QKD) has gained popularity due to its adaptable nature and potential for global scale encryption key sharing. This paper demonstrates a time-bin QKD system operating at 1 GHz clock frequency, using a free-space channel and receiver. The results highlight the importance of accounting for atmospheric turbulence in free-space QKD modeling.
Article
Optics
Yan Tian, Pu Wang, Jianqiang Liu, Shanna Du, Wenyuan Liu, Zhenguo Lu, Xuyang Wang, Yongmin Li
Summary: Measurement-device-independent quantum key distribution (MDI-QKD) can eliminate all side-channel attacks on detectors. This research successfully demonstrated continuous-variable MDI-QKD over optical fiber and proved its feasibility in practical applications.
Article
Physics, Multidisciplinary
Bartosz Regula, Ludovico Lami, Giovanni Ferrari, Ryuji Takagi
Summary: The study introduces a general method for quantifying resources for continuous-variable quantum systems based on robustness measure, with a direct operational interpretation. It is shown to be a well-behaved resource quantifier applicable to various physically relevant resources, such as optical nonclassicality.
PHYSICAL REVIEW LETTERS
(2021)
Article
Optics
Shaoping Shi, Yajun Wang, Long Tian, Wei Li, Yimiao Wu, Qingwei Wang, Yaohui Zheng, Kunchi Peng
Summary: This article presents a fully connected continuous-variable quantum teleportation network architecture, where a squeezed state of light distributes entangled sideband modes to each communication link, offering potential for various tasks of quantum information processing.
LASER & PHOTONICS REVIEWS
(2023)
Article
Optics
Yan Pan, Heng Wang, Yun Shao, Yaodi Pi, Yang Li, Bin Liu, Wei Huang, Bingjie Xu
Summary: A high-rate continuous-variable quantum key distribution (CV-QKD) system based on high-order discrete modulation is experimentally investigated. The results demonstrate the potential application of the high-rate discrete-modulated CV-QKD system for high-speed security communication under tens of kilometers, achieving transmission results and secret key rates comparable to ideal Gaussian modulation.
Review
Physics, Multidisciplinary
Shuhong Hao, Xiaowei Deng, Yang Liu, Xiaolong Su, Changde Xie, Kunchi Peng
Summary: Measurement-based quantum computation with continuous variables, based on performing measurement and feedforward of measurement results on a large scale Gaussian cluster state, provides a feasible way to implement quantum computation. Quantum error correction is crucial for protecting quantum information in quantum computation and communication. This review introduces the progress in continuous variable measurement-based quantum computation and quantum error correction using Gaussian cluster states, as well as discusses challenges in fault-tolerant measurement-based quantum computation with continuous variables.
Article
Optics
E. R. Zinatullin, S. B. Korolev, T. Yu Golubeva
Summary: Comparing two entangled transformations in quantum teleportation shows that the controlled-Z operation leads to lower transmission errors, which can be reduced further with appropriate weight coefficients. Despite intrinsic noise from the CZ optical scheme, specified parameters can still provide gains compared to traditional teleportation protocols.
News Item
Physics, Multidisciplinary
Simone Gasparinetti
Summary: The emission of light from qubits in a superconducting circuit can be controlled to determine the direction of photon propagation, allowing for information routing in quantum networks.
Article
Optics
Qi-Ping Su, Yu Zhang, Chui-Ping Yang
Summary: This study proposes a one-step implementation of a multi-target qubit controlled-NOT gate, where a superconducting qubit controls multiple cat-state qubits simultaneously. The gate operation is simple, quick, and independent of the number of target qubits.
Article
Quantum Science & Technology
Miller Eaton, Carlos Gonzalez-Arciniegas, Rafael N. Alexander, Nicolas C. Menicucci, Olivier Pfister
Summary: The article presents an algorithm for reliably generating various quantum states critical to quantum error correction and universal continuous-variable (CV) quantum computing from Gaussian CV cluster states. The algorithm utilizes the Photon-counting-Assisted NodeTeleportation Method (PhANTM), which employs standard Gaussian information processing with the addition of local photon-number-resolving measurements. The method can stabilize cat states against Gaussian noise and maintain non-Gaussianity within the cluster. Existing protocols for breeding cat states can be embedded into cluster-state processing using PhANTM.
Article
Physics, Applied
Shunya Konno, Atsushi Sakaguchi, Warit Asavanant, Hisashi Ogawa, Masaya Kobayashi, Petr Marek, Radim Filip, Jun-ichi Yoshikawa, Akira Furusawa
Summary: In this paper, a superposition between a vacuum state and a single-photon state with maximized nonlinear squeezing is generated and observed in real-time quadrature measurements. This work presents an important step in extending continuous-variable quantum information processing from the Gaussian regime to the non-Gaussian regime.
PHYSICAL REVIEW APPLIED
(2021)
Correction
Engineering, Electrical & Electronic
Naoto Takanashi, Takahiro Kashiwazaki, Takushi Kazama, Koji Enbutsu, Ryoichi Kasahara, Takeshi Umeki, Akira Furusawa
IEEE JOURNAL OF QUANTUM ELECTRONICS
(2021)
Article
Computer Science, Information Systems
Yuanlong Wang, Shota Yokoyama, Daoyi Dong, Ian R. Petersen, Elanor H. Huntington, Hidehiro Yonezawa
Summary: 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. The Two-stage Estimation method has computational complexity O(nd(2)M) and is validated through simulation and a quantum optical experiment.
IEEE TRANSACTIONS ON INFORMATION THEORY
(2021)
Article
Physics, Applied
Warit Asavanant, Baramee Charoensombutamon, Shota Yokoyama, Takeru Ebihara, Tomohiro Nakamura, Rafael N. Alexander, Mamoru Endo, Jun-ichi Yoshikawa, Nicolas C. Menicucci, Hidehiro Yonezawa, Akira Furusawa
Summary: Recent progress in continuous-variable optical quantum computation has seen the realization of scalable measurement bases using cluster states through time-domain multiplexing. Demonstrations of quantum operations using time-domain-multiplexed cluster states have been successful, with a proposed method to evaluate and verify continuous-variable operations. These advancements bring the realization of large-scale fault-tolerant universal optical quantum computers closer to reality.
PHYSICAL REVIEW APPLIED
(2021)
Article
Physics, Applied
Takahiro Kashiwazaki, Taichi Yamashima, Naoto Takanashi, Asuka Inoue, Takeshi Umeki, Akira Furusawa
Summary: A low-loss quasi-single-mode periodically poled LiNbO3 (PPLN) waveguide was fabricated using mechanical polishing processes, which allowed for larger squeezing level. This waveguide was utilized to assemble a low-loss fiber-pigtailed OPA module, showing promising results for high-speed large-scale fault-tolerant quantum computing. The waveguide did not exhibit pump-induced optical loss even under high power pumping conditions.
APPLIED PHYSICS LETTERS
(2021)
Article
Physics, Multidisciplinary
Kosuke Fukui, Shuntaro Takeda, Mamoru Endo, Warit Asavanant, Jun-ichi Yoshikawa, Peter van Loock, Akira Furusawa
Summary: Non-Gaussian states are crucial for optical quantum technologies, and the optical quantum state synthesizer (OQSS) is a promising method for their preparation. However, the complexity of simulating state preparation on a classical computer poses a significant challenge. To overcome this, we propose a backcasting approach and show that the requirements for photon-number resolving detectors can be significantly reduced.
PHYSICAL REVIEW LETTERS
(2022)
Article
Automation & Control Systems
Yanan Liu, Daoyi Dong, Ian R. Petersen, Qing Gao, Steven X. Ding, Shota Yokoyama, Hidehiro Yonezawa
Summary: This article aims to design a coherent feedback controller for a class of linear quantum systems suffering from Markovian jumping faults, to achieve fault tolerance and H-infinity disturbance attenuation performance. An H-infinity controller is designed by solving a set of linear matrix inequalities, and a real application to quantum optical systems is proposed.
IEEE TRANSACTIONS ON AUTOMATIC CONTROL
(2022)
Article
Physics, Applied
A. Inoue, T. Kashiwazaki, T. Yamashima, N. Takanashi, T. Kazama, K. Enbutsu, K. Watanabe, T. Umeki, M. Endo, A. Furusawa
Summary: In this work, a real-time amplitude measurement method for continuous-variable optical quantum information processing is developed using a modular optical parametric amplifier (OPA) and a broadband balanced photodiode. This method improves the clock frequency limitation of homodyne detectors and enables the realization of high clock frequency optical quantum computers and multi-core systems.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
Takahiro Kashiwazaki, Taichi Yamashima, Koji Enbutsu, Takushi Kazama, Asuka Inoue, Kosuke Fukui, Mamoru Endo, Takeshi Umeki, Akira Furusawa
Summary: We achieved continuous-wave 8.3 dB squeezed light generation using a terahertz-order-broadband waveguide optical parametric amplifier through improvements in the measurement setup. By reducing optical loss and minimizing phase-locking fluctuations, we were able to optimize the experimental parameters for squeezing levels. This highly squeezed light without loss-correction and circuit-noise correction holds promise for fault-tolerant ultra-fast optical quantum computers.
APPLIED PHYSICS LETTERS
(2023)
Article
Quantum Science & Technology
Kan Takase, Kosuke Fukui, Akito Kawasaki, Warit Asavanant, Mamoru Endo, Jun-ichi Yoshikawa, Peter van Loock, Akira Furusawa
Summary: This article proposes a synthesizer that encodes Gottesman-Kitaev-Preskill (GKP) qubits in propagating light by exploiting the nonlinearity of photon detectors. The synthesizer offers several advantages, including systematic and rigorous synthesis of arbitrary GKP qubits, minimal resource usage, high fidelity and success probability, and robustness against loss.
NPJ QUANTUM INFORMATION
(2023)
Article
Optics
Warit Asavanant, Kosuke Fukui, Atsushi Sakaguchi, Akira Furusawa
Summary: This paper presents an optical quantum computation platform that does not require optical switches. Instead, it is based on continuous-variable measurement-based quantum computation, where the quantum entanglement structure is modified to allow quantum teleportation to replace optical switching and rerouting. The architecture also includes additional modes that enable the teleportation of quantum states along the cluster state, a task typically requiring optical switches.
Article
Optics
Kosuke Fukui, Mamoru Endo, Warit Asavanant, Atsushi Sakaguchi, Jun-ichi Yoshikawa, Akira Furusawa
Summary: This article introduces a method to generate optical GKP qubits using cross-Kerr interaction and validates its feasibility through numerical calculations. The results show that the method is capable of generating GKP qubits with the required quality, achieving high fidelity and success probability.
Article
Optics
Fumiya Hanamura, Warit Asavanant, Kosuke Fukui, Shunya Konno, Akira Furusawa
Summary: This study focuses on the estimation and error correction of displacements in continuous-variable quantum information processing using non-Gaussian states. Analysis of complex GKP states and experimentally feasible single-photon states reveals the importance of non-Gaussianity for displacement estimation, demonstrating that non-Gaussian states can surpass the lower bound achieved with Gaussian operations.
Article
Physics, Multidisciplinary
Shunya Konno, Warit Asavanant, Kosuke Fukui, Atsushi Sakaguchi, Fumiya Hanamura, Petr Marek, Radim Filip, Jun-ichi Yoshikawa, Akira Furusawa
Summary: This paper explores the method of implementing non-Clifford operations on GKP qubits, achieving high-fidelity linear optical implementation by combining nonlinear feedforward and GKP-encoded ancillary states.
PHYSICAL REVIEW RESEARCH
(2021)
Article
Optics
Warit Asavanant, Kan Takase, Kosuke Fukui, Mamoru Endo, Jun-ichi Yoshikawa, Akira Furusawa
Summary: The study introduces a new method to tailor the wave functions of quantum states using non-Gaussian entangled states, allowing for the generation of various classes of quantum states. The results highlight the importance of conditioning using homodyne measurements in complement to photon number detection for generating non-Gaussian states.
