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arXiv 2023年

作者： Liu, He Wang, Ke Gao, Fei Leng, Jin Liu, Yang Zhou, Yu-Chen Cao, Gang Wang, Ting Zhang, Jianjun Huang, Peihao Li, Hai-Ou Guo, Guo-Ping CAS Key Laboratory of Quantum Information University of Science and Technology of China Anhui Hefei230026 China CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics University of Science and Technology of China Anhui Hefei230026 China Institute of Physics CAS Center for Excellence in Topological Quantum Computation Chinese Academy of Sciences Beijing100190 China Shenzhen Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China International Quantum Academy Shenzhen518048 China Guangdong Provincial Key Laboratory of Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China Qilu Institute of Technology Jinan250200 China Hefei National Laboratory University of Science and Technology of China Hefei230088 China Origin Quantum Computing Company Limited Anhui Hefei230026 China

Hole spin qubits based on germanium (Ge) have strong tunable spin orbit interaction (SOI) and ultrafast qubit operation speed. Here we report that the Rabi frequency (fRabi) of a hole spin qubit in a Ge hut wire (HW) double quantum dot (DQD) is electrically tuned through the detuning energy (ϵ) and middle gate voltage (VM ). fRabi gradually decreases with increasing ϵ;on the contrary, fRabi is positively correlated with VM. We attribute our results to the change of electric field on SOI and the contribution of the excited state in quantum dots to fRabi. We further demonstrate an ultrafast fRabi exceeding 1.2 GHz, which evidences the strong SOI in our device. The discovery of an ultrafast and electrically tunable fRabi in a hole spin qubit has potential applications in semiconductor quantum computing. Copyright © 2023, The Authors. All rights reserved.

关键词： Germanium

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Chain rules for quantum channels

Chain rules for quantum channels

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IEEE International Symposium on Information Theory

作者： Mario Berta Marco Tomamichel Department of Computing Imperial College London UK AWS Center for Quantum Computing Pasadena USA California Institute of Technology Pasadena USA Center for Quantum Technologies &amp Department of Electrical and Computer Engineering National University of Singapore Singapore

ISBN: (数字)9781665421591

ISBN: (纸本)9781665421607

Divergence chain rules for channels relate the divergence of a pair of channel inputs to the divergence of the corresponding channel outputs. An important special case of such a rule is the data-processing inequality, which tells us that if the same channel is applied to both inputs then the divergence cannot increase. Based on direct matrix analysis methods, we derive several Rényi divergence chain rules for channels in the quantum setting. Our results simplify and in some cases generalise previous derivations in the literature.

关键词： quantum channels quantum mechanics Entropy Linear matrix inequalities Information theory

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Attainability of quantum state discrimination bounds with collective measurements on finite copies

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Physical Review A 2025年第2期111卷 022438-022438页

作者： Lorcán O. Conlon Jin Ming Koh Biveen Shajilal Jasminder Sidhu Ping Koy Lam Syed M. Assad Institute of Materials Research and Engineering Agency for Science Technology and Research (ASTAR) 2 Fusionopolis Way 08-03 Innovis 138634 Republic of Singapore Institute of High Performance Computing Agency for Science Technology and Research (ASTAR) 1 Fusionopolis Way #16-16 Connexis Singapore 138632 Republic of Singapore Department of Physics Harvard University Cambridge Massachusetts 02138 USA SUPA Department of Physics The University of Strathclyde Glasgow G4 0NG United Kingdom Centre for Quantum Computation and Communication Technology Department of Quantum Science Australian National University Canberra ACT 2601 Australia

One of the fundamental tenets of quantum mechanics is that nonorthogonal states cannot be distinguished perfectly. When distinguishing multiple copies of a mixed quantum state, a collective measurement, which generates entanglement between the different copies of the unknown state, can achieve a lower error probability than nonentangling measurements. The error probability that can be attained using a collective measurement on a finite number of copies of the unknown state is given by the Helstrom bound. In the limit where we can perform a collective measurement on asymptotically many copies of the quantum state, the quantum Chernoff bound gives the attainable error probability. It is natural to ask, then, what strategies can be employed to reach these two bounds—is entanglement across all available modes always necessary or can other, experimentally more simple measurements saturate these bounds? In this work we address this question. We find analytic expressions for the Helstrom bound for arbitrarily many copies of the unknown state in simple qubit examples. Using these analytic expressions, we investigate whether the quantum Chernoff bound can be saturated by repeatedly implementing the M-copy Helstrom measurement. We also investigate the necessary conditions to saturate the M-copy Helstrom bound. It is known that a collective measurement on all M copies of the unknown state is always sufficient to saturate the M-copy Helstrom bound. However, general conditions for when such a measurement is necessary to saturate the Helstrom bound remain unknown. We investigate specific measurement strategies which involve entangling operations on fewer than all M copies of the unknown state. For many regimes we find that a collective measurement on all M copies of the unknown state is necessary to saturate the M-copy Helstrom bound.

关键词： quantum entanglement

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Generation of Tunable Correlated Frequency Comb via Four-Wave-Mixing in Optical fibers

arXiv

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arXiv 2024年

作者： Bhardwaj, Aryan Chatterjee, Debanuj Singh, Ashutosh Kumar Prabhakar, Anil The Centre for Quantum Information Communication and Computing Indian Institute of Technology Madras The Department of Electrical Engineering Indian Institute of Technology Madras Chennai600036 India The Univ. Lille CNRS Laboratoire de Physique des Lasers Atomes et Molécules PhLAM UMR 8523 Lille59000 France

We report an all-fiber-based experimental setup to generate a correlated photon-pair comb using Four Wave Mixing (FWM) in Highly non-linear- fiber (HNLF). Temporal correlations of the generated photons were confirmed through coincidence measurements. We observed a maximum of 32 kcps, with a coincidence to accidental ratio of 17 ± 1. To further understand the underlying processes, we also simulated a generalized FWM event involving the interaction between an arbitrary frequency comb and a Continuous Wave (CW) pump. non-linear dynamics through the HNLF were modelled using Schrödinger propagation equations, with numerical predictions agreeing with our experimental results. © 2024, CC BY.

关键词： Four wave mixing

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Generation of highly-pure single-photon states at telecommunication wavelength

Generation of highly-pure single-photon states at telecommun...

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Frontiers in Optics, FiO 2022

作者： Kawasaki, Akito Takase, Kan Nomura, Takefumi Miki, Sigehito Terai, Hirotaka Yabuno, Masahiro China, Fumihiro Asavanant, Warit Endo, Mamoru Yoshikawa, Jun-Ichi Furusawa, Akira Department of Applied Physics School of Engineering The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo113-8656 Japan Optical Quantum Computing Research Team RIKEN Center for Quantum Computing 2-1 Hirosawa Saitama Wako351-0198 Japan Advanced ICT Research Institute National Institute of Information and Communications Technology 588-2 Iwaoka Nishi-ku Hyogo Kobe651-2492 Japan Graduate School of Engineering Kobe University 1-1 Rokkodai-cho Nada-ku Hyogo Kobe657-0013 Japan

We generate highly-pure single-photon states at the telecommunication wavelength with the best record of the minimum Wigner negativity, paving the way toward the integration of universal quantum computers and construc...

ISBN: (纸本)9781557528209

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Generation of multi-photon Fock states at telecommunication wavelength using picosecond pulsed light

arXiv

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arXiv 2024年

作者： Sonoyama, Tatsuki Takahashi, Kazuma Sano, Tomoki Suzuki, Takumi Nomura, Takefumi Yabuno, Masahiro Miki, Shigehito Terai, Hirotaka Takase, Kan Asavanant, Warit Endo, Mamoru Furusawa, Akira Department of Applied Physics School of Engineering The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo113-8656 Japan Advanced ICT Research Institute National Institute of Information and Communications Technology 588-2 Iwaoka Nishi-ku Hyogo Kobe651-2492 Japan Optical Quantum Computing Research Team RIKEN Center for Quantum Computing 2-1 Hirosawa Saitama Wako351-0198 Japan

Multi-photon Fock states have diverse applications such as optical quantum information processing. For the implementation of quantum information processing, it is desirable that Fock states be generated within the telecommunication wavelength band, particularly in the C-band (1530-1565 nm). This is because mature optical communication technologies can be leveraged for the transmission, manipulation, and detection. Additionally, to achieve high-speed quantum information processing, it is desirable for Fock states to be generated in short optical pulses, as this allows embedding lots of information in the time domain. In this paper, we report the first generation of picosecond pulsed multi-photon Fock states (single-photon and two-photon states) in the C-band with Wigner negativities, which are verified by pulsed homodyne tomography. In our experimental setup, we utilize a single-pixel superconducting nanostrip photon-number-resolving detector (SNSPD), which is expected to facilitate the high-rate generation of various quantum states. This capability stems from the high temporal resolution of SNSPDs (50 ps in our case) allowing us to increase the repetition frequency of pulsed light from the conventional MHz range to the GHz range, although in this experiment the repetition frequency is limited to 10 MHz due to the bandwidth of the homodyne detector. Consequently, our experimental setup is anticipated to serve as a prototype of a high-speed optical quantum state generator for ultrafast quantum information processing at telecommunication wavelength. Copyright © 2024, The Authors. All rights reserved.

关键词： Particle beams

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Stabilizing a Bosonic Qubit Using Colored Dissipation

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Physical Review Letters 2022年第11期128卷 110502-110502页

作者： Harald Putterman Joseph Iverson Qian Xu Liang Jiang Oskar Painter Fernando G. S. L. Brandão Kyungjoo Noh AWS Center for Quantum Computing Pasadena California 91125 USA IQIM California Institute of Technology Pasadena California 91125 USA Pritzker School of Molecular Engineering The University of Chicago Illinois 60637 USA

Protected qubits such as the 0−π qubit, and bosonic qubits including cat qubits and Gottesman-Kitaev-Preskill (GKP) qubits offer advantages for fault tolerance. Some of these protected qubits (e.g., 0−π qubit and Kerr-cat qubit) are stabilized by Hamiltonians which have (near-)degenerate ground state manifolds with large energy gaps to the excited state manifolds. Without dissipative stabilization mechanisms the performance of such energy-gap-protected qubits can be limited by leakage to excited states. Here, we propose a scheme for dissipatively stabilizing an energy-gap-protected qubit using colored (i.e., frequency-selective) dissipation without inducing errors in the ground state manifold. Concretely we apply our colored dissipation technique to Kerr-cat qubits and propose colored Kerr-cat qubits which are protected by an engineered colored single-photon loss. When applied to the Kerr-cat qubits our scheme significantly suppresses leakage-induced bit-flip errors (which we show are a limiting error mechanism) while only using linear interactions. Beyond the benefits to the Kerr-cat qubit we also show that our frequency-selective loss technique can be applied to a broader class of protected qubits.

关键词： quantum error correction quantum information processing with continuous variables quantum information with solid state qubits quantum state engineering Superconducting qubits

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Visualizing quantum Circuit Probability estimating computational action for quantum program synthesis

arXiv

引用

arXiv 2023年

作者： Bach, Bao Gia Kundu, Akash Acharya, Tamal Sarkar, Aritra Faculty of Computer Science and Engineering Ho Chi Minh City University of Technology Viet Nam Viet Nam Joint Doctoral School Silesian University of Technology Gliwice Poland Institute of Theoretical and Applied Informatics Polish Academy of Sciences Gliwice Poland Independent Researcher Bengaluru India Quantum Machine Learning Research group Quantum Computing Division QuTech Netherlands Quantum Intelligence Research team Department of Quantum & Computer Engineering Delft University of Technology Netherlands

This research applies concepts from algorithmic probability to Boolean and quantum combinatorial logic circuits. A tutorial-style introduction to states and various notions of the complexity of states are presented. Thereafter, the probability of states in the circuit model of computation is defined. Classical and quantum gate sets are compared to select some characteristic sets. The reachability and expressibility in a space-time-bounded setting for these gate sets are enumerated and visualized. These results are studied in terms of computational resources, universality and quantum behavior. The article suggests how applications like geometric quantum machine learning, novel quantum algorithm synthesis and quantum artificial general intelligence can benefit by studying circuit probabilities. © 2023, CC BY-NC-SA.

关键词： Machine learning

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Sparse Channel Estimation in Massive MIMO Systems Using Compressed Sensing and Neural Networks

Sparse Channel Estimation in Massive MIMO Systems Using Comp...

引用

Intelligent Signal Processing and Effective Communication Technologies (INSPECT), IEEE International Conference on

作者： Deepak Upadhyay Kunj Bihari Sharma Mridul Gupta Abhay Upadhyay Nookala Venu Dept. of Computer Science and Engineering Graphic Era Hill University Dehradun India Dept. of Computer Science and Engineering Graphic Era deemed to be University Dehradun India Data Science and Quantum Computing ABV Indian Institute of Information Technology and Management Gwalior India

ISBN: (数字)9798350379525

ISBN: (纸本)9798350379532

In this paper, based on compressed sensing and neural networks, we present an intelligent sparse channel estimation technique for Massive MIMO systems. We show that our approach improves considerably the estimation accuracy in terms of Mean Squared Error (MSE) and Normalized Mean Squared Error (NMSE) with respect to classical methods. We demonstrate [Figure: ] that our approach is computationally more efficient, requires less time and resources (memory/disk) compared to the existing literature but for a robustness of performance across distal or low Signal-to-Noise Ratios (SNRs). We also confirm our method exhibits fast convergence and efficiently accommodates a variety of sparsity levels. By visualizing it using heatmaps and ROC curves we show that this method is able to effectively differentiate between signal and noise, asserting our approach as a powerful tool for the contemporary set of problems present in wireless communications.

关键词： Wireless communication Heating systems Accuracy Neural networks Channel estimation Estimation Massive MIMO Robustness Compressed sensing Convergence

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Transfer Learning Approaches for Channel State Prediction in Heterogeneous Fading Networks

Transfer Learning Approaches for Channel State Prediction in...

引用

Intelligent Signal Processing and Effective Communication Technologies (INSPECT), IEEE International Conference on

ISBN: (数字)9798350379525

ISBN: (纸本)9798350379532

In this work, we leverage state-of-the-art machine learning algorithms to predict Channel State Information (CSI), for enhancing performance of wireless communication systems. The simulation and analysis stop with transfer learning to finetune, adaptive domain adaptations, multitasking (MTL) as well a few shot meta-learning models framework under different network packet loss rate scenarios. By generalizing better from one domain to another, transfer learning pushes the performance beyond what traditional methods can obtain. Further, fine-tuning also helps to align the source and target domain distributions in feature space by a partial (or full) reduction of re-stylization error. This work proposes multi-Task learning as a tool to mitigate loses in light of predicting across fading scenarios. Considering multi-task learning also provides benefits from shared learnings, so experience is pooled between the tasks which indirectly improve prediction as well and it helps in training both of these algorithms together. Moreover, the few-shot learning models prove to be highly desirable as they deliver state-of-the-art performance with minimal training data for difficult problems. These results show the potential of AI-based methods to improve CSI prediction, and have implications for improving reliability and throughput when deploying real wireless communication systems.

关键词： Wireless communication Fading channels Machine learning algorithms Transfer learning Training data Predictive models Multitasking Data models Few shot learning Channel state information

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