Article
Physics, Multidisciplinary
Yosep Kim, Alexis Morvan, Long B. Nguyen, Ravi K. Naik, Christian Junger, Larry Chen, John Mark Kreikebaum, David Santiago, Irfan Siddiqi
Summary: The development of noisy intermediate-scale quantum devices has brought about a wider range of executable high-fidelity single- and two-qubit gates. In this study, a high-fidelity iToffoli gate based on two-qubit interactions is demonstrated using fixed-frequency superconducting qubits. The gate implementation process achieves a fidelity of up to 98.26(2)%. Numerical simulations also show that the gate scheme used can produce more efficient three-qubit gates than the traditional Toffoli and iToffoli gates. This work not only introduces a high-fidelity iToffoli gate to current superconducting quantum processors, but also paves the way for developing multi-qubit gates based on two-qubit interactions.
Article
Quantum Science & Technology
Gary J. Mooney, Gregory A. L. White, Charles D. Hill, Lloyd C. L. Hollenberg
Summary: This study investigates the ability to prepare large-scale entangled quantum states on current superconducting quantum devices, with the application of quantum readout-error mitigation (QREM) to enhance observed entanglement levels. The results show full bipartite entanglement in two of the largest superconducting devices to date, indicating promising progress in generating entanglement in noisy intermediate-scale quantum (NISQ) devices.
ADVANCED QUANTUM TECHNOLOGIES
(2021)
Article
Chemistry, Multidisciplinary
Michael T. Jones, Md Serajum Monir, Felix N. Krauth, Pascal Macha, Yu-Ling Hsueh, Angus Worrall, Joris G. Keizer, Ludwik Kranz, Samuel K. Gorman, Yousun Chung, Rajib Rahman, Michelle Y. Simmons
Summary: This study demonstrates a platform for quantum computing using phosphorus donor atoms in silicon. By adjusting the arrangement and spacing of the donor atoms, the speed and accuracy of qubit gates can be improved without affecting neighboring qubits. This approach provides a new pathway for achieving high fidelity and scalable quantum computing.
Article
Physics, Applied
Maria Hita-Perez, Gabriel Jauma, Manuel Pino, Juan Jose Garcia-Ripoll
Summary: This study investigates the coupling of two flux qubits through a capacitor and Josephson junction, extracting effective Hamiltonians for controlling qubit dynamics. By tuning static charge coupling with capacitors and magnetic-like interactions with Josephson junctions, various qubit Hamiltonians with different interactions can be engineered, including ultrastrongly coupled ones. An exhaustive numerical study on a three-Josephson junctions flux qubit is presented, which can be directly applied in experimental work, and the developed numerical tool can be used to analyze general systems of many qubits and any type of coupling.
APPLIED PHYSICS LETTERS
(2021)
Article
Quantum Science & Technology
N. H. Le, M. Cykiert, E. Ginossar
Summary: We propose a scheme for scalable and robust quantum computing on two-dimensional arrays of qubits with fixed longitudinal coupling. Our approach is based on driving a subarray of qubits, allowing for the decomposition of the total multi-qubit Hamiltonian into commuting few-qubit blocks. Using efficient optimization techniques, we show that it is possible to realize a universal set of quantum gates and arbitrary quantum circuits with high fidelity, even in the presence of parameter uncertainty.
NPJ QUANTUM INFORMATION
(2023)
Article
Physics, Multidisciplinary
Mark A. Johnson, Mateusz T. Madzik, Fay E. Hudson, Kohei M. Itoh, Alexander M. Jakob, David N. Jamieson, Andrew Dzurak, Andrea Morello
Summary: This article presents a method for initializing quantum states with a fidelity beyond the thermal limit using real-time monitoring and negative-result measurement. The experimental results show that this method can reduce initialization errors and improve fidelity by increasing the bandwidth of the amplifier chain or slowing down electron tunneling rates.
Article
Optics
Klee Pollock, Ge Wang, Eric Chitambar
Summary: The paper investigates the entanglement of assistance in the simplest scenario of three qubits, finding that lossless decoupling may be possible under certain conditions. Different measures of entanglement can lead to different outcomes.
Article
Multidisciplinary Sciences
Qingling Zhu, Sirui Cao, Fusheng Chen, Ming-Cheng Chen, Xiawei Chen, Tung-Hsun Chung, Hui Deng, Yajie Du, Daojin Fan, Ming Gong, Cheng Guo, Chu Guo, Shaojun Guo, Lianchen Han, Linyin Hong, He-Liang Huang, Yong-Heng Huo, Liping Li, Na Li, Shaowei Li, Yuan Li, Futian Liang, Chun Lin, Jin Lin, Haoran Qian, Dan Qiao, Hao Rong, Hong Su, Lihua Sun, Liangyuan Wang, Shiyu Wang, Dachao Wu, Yulin Wu, Yu Xu, Kai Yan, Weifeng Yang, Yang Yang, Yangsen Ye, Jianghan Yin, Chong Ying, Jiale Yu, Chen Zha, Cha Zhang, Haibin Zhang, Kaili Zhang, Yiming Zhang, Han Zhao, Youwei Zhao, Liang Zhou, Chao-Yang Lu, Cheng-Zhi Peng, Xiaobo Zhu, Jian-Wei Pan
Summary: To maintain a long-term quantum computational advantage, upgrading quantum hardware is necessary to compete against continuously improved classical algorithms and hardware. Researchers have demonstrated a superconducting quantum computing system, Zuchongzhi 2.1, with 66 qubits in a tunable coupler architecture. The improved readout fidelity and more powerful quantum processor enable larger-scale random quantum circuit sampling, enhancing the quantum computational advantage significantly.
Article
Physics, Multidisciplinary
Patrick Barthel, Patrick H. Huber, Jorge Casanova, Inigo Arrazola, Dorna Niroomand, Theeraphot Sriarunothai, Martin B. Plenio, Christof Wunderlich
Summary: We demonstrate the experimental implementation of a two-qubit phase gate using a radio frequency controlled trapped-ion quantum processor. The gate is generated by applying a pulsed dynamical decoupling sequence to the ions' carrier transitions, allowing for tunable and high-fidelity phase shift. The gate's performance is robust against various sources of error and holds potential for fast gate speeds.
NEW JOURNAL OF PHYSICS
(2023)
Article
Computer Science, Artificial Intelligence
Giovanni Acampora, Ferdinando Di Martino, Alfredo Massa, Roberto Schiattarella, Autilia Vitiello
Summary: This paper introduces the concept of Distributed Noisy-Intermediate Scale Quantum (D-NISQ) as a reference computational model to design innovative frameworks for quantum devices to interact and solve complex problems collaboratively. Through two case studies, a multi-threaded implementation of the D-NISQ model demonstrates greater reliability in solving problems through quantum computation.
INFORMATION FUSION
(2023)
Article
Physics, Multidisciplinary
Xiao Geng, Kaiyong He, Rutian Huang, Jianshe Liu, Wei Chen
Summary: A qubit energy tuner (QET) based on SFQ circuits was proposed for Z control of superconducting qubits. The QET allows the setting of energy levels or frequencies of qubits and performing gate operations requiring Z control. The circuit structure of the QET consists of an inductor loop and flux bias units. Simulations verified the functionality of the QET, demonstrating its efficacy in digital Z control of large-scale superconducting quantum computers.
FRONTIERS IN PHYSICS
(2023)
Article
Physics, Multidisciplinary
Yewei Yuan, Chao Wang, Bei Wang, Zhao-Yun Chen, Meng-Han Dou, Yu-Chun Wu, Guo-Ping Guo
Summary: This paper proposes a quantum-classical comparator based on the quantum Fourier transform, which is used for comparing two quantum integers and modular arithmetic. The proposed algorithms reduce computing resources and make them valuable for noisy intermediate-scale quantum computers.
NEW JOURNAL OF PHYSICS
(2023)
Article
Materials Science, Multidisciplinary
Wenlong Li, Xue Dong, Guofeng Zhang, Re-Bing Wu
Summary: This paper explores various methods for controlling flying qubits using a three-level atom with time-varying tunable couplings. It shows that by tuning the couplings, a single photon can be distributed into two channels with arbitrary shapes, or an arbitrary-shaped distributed single photon can be caught. The paper also demonstrates the transfer of a flying qubit from one channel to another with conversion of both central frequency and photon shape. These results provide useful control protocols for high-fidelity quantum information transmission over complex quantum networks.
Article
Physics, Applied
Hayato Goto
Summary: This article introduces a tunable coupler called a double-transmon coupler, which achieves fast high-fidelity two-qubit gates by controlling the magnetic flux and avoids residual coupling during idle time. This approach offers an alternative solution for improving the performance of superconducting quantum computers.
PHYSICAL REVIEW APPLIED
(2022)
Article
Physics, Multidisciplinary
Feng Bao, Hao Deng, Dawei Ding, Ran Gao, Xun Gao, Cupjin Huang, Xun Jiang, Hsiang-Sheng Ku, Zhisheng Li, Xizheng Ma, Xiaotong Ni, Jin Qin, Zhijun Song, Hantao Sun, Chengchun Tang, Tenghui Wang, Feng Wu, Tian Xia, Wenlong Yu, Fang Zhang, Gengyan Zhang, Xiaohang Zhang, Jingwei Zhou, Xing Zhu, Yaoyun Shi, Jianxin Chen, Hui-Hai Zhao, Chunqing Deng
Summary: Superconducting qubits provide a promising path toward building large-scale quantum computers. Among alternative superconducting qubits, fluxonium exhibits large anharmonicity and long coherence times, making it a particularly promising candidate. In this work, we engineer a fluxonium-based quantum processor that achieves high qubit coherence, fast frequency tunability, and individual-qubit addressability for reset, readout, and gates. With simple and fast gate schemes, we achieve high average fidelity for single-qubit and two-qubit gates, comparable to the highest reported values in literature.
PHYSICAL REVIEW LETTERS
(2022)
Article
Multidisciplinary Sciences
Ming Gong, Xiao Yuan, Shiyu Wang, Yulin Wu, Youwei Zhao, Chen Zha, Shaowei Li, Zhen Zhang, Qi Zhao, Yunchao Liu, Futian Liang, Jin Lin, Yu Xu, Hui Deng, Hao Rong, He Lu, Simon C. Benjamin, Cheng-Zhi Peng, Xiongfeng Ma, Yu-Ao Chen, Xiaobo Zhu, Jian-Wei Pan
Summary: The study successfully demonstrated the experimental realization of the [5, 1, 3] code, verifying key aspects such as error identification and correction, logical operations, and state decoding.
NATIONAL SCIENCE REVIEW
(2022)
Article
Quantum Science & Technology
Tyson Jones, Simon C. Benjamin
Summary: This study explores a method for automatically recompiling a quantum circuit A into a target circuit /3, with the goal of achieving the same behavior on a specific input. This method can be crucial for hybrid, NISQ-era algorithms for dynamical simulation or eigensolving.
Article
Quantum Science & Technology
Richard Meister, Simon C. Benjamin, Earl T. Campbell
Summary: A promising method for simulating complex quantum systems, such as molecules and other many-body systems, using quantum computers is the linear combination of unitaries (LCU) method. This study presents an optimized adaptation of the LCU method for electronic structure calculations with varying magnitude terms in the Hamiltonians. The results show that the adaptive method can significantly improve simulation accuracy.
Review
Physics, Multidisciplinary
Dayue Qin, Xiaosi Xu, Ying Li
Summary: Minimizing noise in quantum computers is crucial, and quantum error mitigation is a promising way to reduce errors on NISQ quantum computers.
Review
Physics, Multidisciplinary
Jules Tilly, Hongxiang Chen, Shuxiang Cao, Dario Picozzi, Kanav Setia, Ying Li, Edward Grant, Leonard Wossnig, Ivan Rungger, George H. Booth, Jonathan Tennyson
Summary: The variational quantum eigensolver (VQE) is a method used to compute the ground state energy of a Hamiltonian, which is important in quantum chemistry and condensed matter physics. It has the advantage of being able to model complex wavefunctions in polynomial time, making it a promising application for quantum computing. However, there are still many open questions regarding optimization, quantum noise, and other challenges, which require further research and exploration.
PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS
(2022)
Article
Physics, Applied
Hamza Jnane, Brennan Undseth, Zhenyu Cai, Simon C. Benjamin, Balint Koczor
Summary: This paper explores the application of interlinked multicore architectures in practical quantum computing and evaluates their performance through analysis and numerical modeling. The study finds that high-fidelity communication can be achieved through optimized entanglement purification, and recently proposed error mitigation schemes can effectively suppress imperfections in the multicore environment.
PHYSICAL REVIEW APPLIED
(2022)
Article
Quantum Science & Technology
Dayue Qin, Yanzhu Chen, Ying Li
Summary: Quantum computing offers advantages over classical computing, but noise in quantum devices hinders most quantum algorithms from achieving their potential. Quantum error mitigation protocols handle this noise using minimal qubit resources. This paper applies statistics principles to analyze the scaling behavior of intrinsic error in quantum error mitigation, finding that error increases linearly before mitigation and sublinearly after mitigation, indicating that error mitigation is more effective in larger circuits. The importance Clifford sampling technique is proposed as a key method for error mitigation in large circuits to achieve this result.
NPJ QUANTUM INFORMATION
(2023)
Article
Multidisciplinary Sciences
Hans Hon Sang Chan, Richard Meister, Tyson Jones, David P. Tew, Simon C. Benjamin
Summary: First-quantized, grid-based methods are a promising approach for chemistry modeling on quantum computers. In this study, we used emulated quantum computers with up to 36 qubits to execute resource-frugal algorithms for modeling atoms. Various tasks were explored, and the grid-based method was found to perform well, supporting the idea that it will be dominant in the era of fault-tolerant quantum computing.
Article
Quantum Science & Technology
Zhenyu Cai, Adam Siegel, Simon Benjamin
Summary: This paper explores the concept of looped pipelines, which allows for the benefits of a three-dimensional lattice in a strictly two-dimensional device. By leveraging qubit shuttling, the looped pipeline architecture can process a stack of qubit arrays, enabling various schemes from error mitigation to fault-tolerant codes. This approach significantly reduces the space-time cost of magic state distillation without impacting the code's threshold.
Article
Physics, Multidisciplinary
Cica Gustiani, Richard Meister, Simon C. Benjamin
Summary: Variational methods are a promising approach for quantum computers to solve chemistry problems. In this study, we use adaptive evolving quantum circuits described in a related paper to solve problems. The results show that this approach can outperform human-designed circuits and we compare them for larger instances up to 14 qubits. Additionally, we propose a novel approach to improve the performance and compactness of circuits by constraining the circuit evolution in the physically relevant subspace. We consider both static and dynamic properties of molecular systems. The emulation environment used is QuESTlink and all resources are open source and linked in this paper.
NEW JOURNAL OF PHYSICS
(2023)
Article
Quantum Science & Technology
Mingxia Huo, Ying Li
Summary: This work proposes an algorithm that combines quantum Monte Carlo with quantum computing to simulate the imaginary-time evolution and solve the ground-state problem. By sampling the real-time evolution operator with a random evolution time according to a modified Cauchy-Lorentz distribution, the expected value of an observable in imaginary-time evolution can be computed. The results show that Monte Carlo quantum simulation is promising even without a fully fault-tolerant quantum computer.
Article
Physics, Multidisciplinary
Anbang Wang, Jingning Zhang, Ying Li
Summary: This study investigates the error-mitigation problem of open systems via digital quantum simulation (DQS). It proves that the deviation in the steady state obtained from DQS depends only on the error in a single Trotter step, and proposes an error-mitigation technique based on the scaling behavior near the critical point of a quantum phase transition.
PHYSICAL REVIEW RESEARCH
(2022)
Article
Optics
Balint Koczor, Simon C. Benjamin
Summary: In this paper, the quantum natural gradient is generalized to consider arbitrary quantum states, incorporating imperfect unitary gates and nonunitary operations. The quantum Fisher information is used as the core metric, and a modification of error suppression and virtual distillation techniques enables an accurate approximation of the QFI. Numerical simulations show that this approach significantly outperforms other variational techniques in noisy quantum circuits.
Article
Physics, Multidisciplinary
Balint Koczor, Simon C. Benjamin
Summary: The article introduces the method of analytic descent to efficiently optimize the energy landscape in local regions, avoiding the difficulties of complex parameter optimizations.
PHYSICAL REVIEW RESEARCH
(2022)
Article
Optics
Mingxia Huo, Ying Li
Summary: The paper introduces a practical protocol for quantum error mitigation by virtually purifying quantum states with reduced errors. By combining dual-state purification and tomography purification, the fidelity of the purified state can be increased. The protocol demonstrates reduced errors on a cloud quantum computer, especially for larger circuits with a decreasing rescaling factor as the number of qubits and circuit depth increases.
