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Quenching Spin Decoherence in Diamond through Spin Bath Polarization

Physical Review Letters 2008年第4期101卷 047601-047601页

作者： Susumu Takahashi Ronald Hanson Johan van Tol Mark S. Sherwin David D. Awschalom Department of Physics and Center for Terahertz Science and Technology University of California Santa Barbara California 93106 USA Kavli Institute of Nanoscience Delft University of Technology P.O. Box 5046 2600 GA Delft The Netherlands Department of Physics and Center for Spintronics and Quantum Computation University of California Santa Barbara California 93106 USA National High Magnetic Field Laboratory Florida State University Tallahassee Florida 32310 USA

We experimentally demonstrate that the decoherence of a spin by a spin bath can be completely eliminated by fully polarizing the spin bath. We use electron paramagnetic resonance at 240 GHz and 8 T to study the electron-spin coherence time T2 of nitrogen-vacancy centers and nitrogen impurities in diamond from room temperature down to 1.3 K. A sharp increase of T2 is observed below the Zeeman energy (11.5 K). The data are well described by a suppression of the flip-flop induced spin bath fluctuations due to thermal electron-spin polarization. T2 saturates at ∼250 μs below 2 K, where the polarization of the electron-spin bath exceeds 99%.

关键词： Electrons

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Effect of gauge boson mass on chiral symmetry breaking in three-dimensional QED

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Physical Review D 2003年第6期67卷 065010-065010页

作者： Guo-Zhu Liu Geng Cheng Lab of Quantum Communication and Quantum Computation University of Science and Technology of China Hefei Anhui 230026 People’s Republic of China Department of Astronomy and Applied Physics University of Science and Technology of China Hefei Anhui 230026 People’s Republic of China CCAST (World Laboratory) P.O. Box 8730 Beijing 100080 People’s Republic of China

In three-dimensional quantum electrodynamics (QED3) with a massive gauge boson, we investigate the Dyson-Schwinger equation for the fermion self-energy in the Landau gauge and find that chiral symmetry breaking (CSB) occurs when the gauge boson mass ξ is smaller than a finite critical value ξcv but is suppressed when ξ>ξcv. We further show that the critical value ξcv does not qualitatively change after considering higher order corrections from the wave function renormalization and vertex function. Based on the relation between CSB and the gauge boson mass ξ, we give a field theoretical description of the competing antiferromagnetic and superconducting orders and, in particular, the coexistence of these two orders in high temperature superconductors. When the gauge boson mass ξ is generated via the instanton effect in a compact QED3 of massless fermions, our result shows that CSB coexists with the instanton effect in a wide region of ξ, which can be used to study the confinement-deconfinement phase transition.

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Propagation and Localization of Collective Excitations on a 24-Qubit Superconducting Processor

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Physical Review Letters 2019年第5期123卷 050502-050502页

作者： Yangsen Ye Zi-Yong Ge Yulin Wu Shiyu Wang Ming Gong Yu-Ran Zhang Qingling Zhu Rui Yang Shaowei Li Futian Liang Jin Lin Yu Xu Cheng Guo Lihua Sun Chen Cheng Nvsen Ma Zi Yang Meng Hui Deng Hao Rong Chao-Yang Lu Cheng-Zhi Peng Heng Fan Xiaobo Zhu Jian-Wei Pan Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics University of Science and Technology of China Hefei Anhui 230026 China Shanghai Branch CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics University of Science and Technology of China Shanghai 201315 China Beijing National laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100190 China School of Physical Sciences University of Chinese Academy of Sciences Beijing 100190 China Beijing Computational Science Research Center Beijing 100193 China Theoretical Quantum Physics Laboratory RIKEN Cluster for Pioneering Research Wako-shi Saitama 351-0198 Japan Center of Interdisciplinary Studies Lanzhou University Lanzhou 730000 China CAS Center for Excellence in Topological Quantum Computation UCAS Beijing 100190 China Songshan Lake Materials Laboratory Dongguan 523808 China

Superconducting circuits have emerged as a powerful platform of quantum simulation, especially for emulating the dynamics of quantum many-body systems, because of their tunable interaction, long coherence time, and high-precision control. Here in experiments, we construct a Bose-Hubbard ladder with a ladder array of 20 qubits on a 24-qubit superconducting processor. We investigate theoretically and demonstrate experimentally the dynamics of single- and double-excitation states with distinct behaviors, indicating the uniqueness of the Bose-Hubbard ladder. We observe the linear propagation of photons in the single-excitation case, satisfying the Lieb-Robinson bounds. The double-excitation state, initially placed at the edge, localizes; while placed in the bulk, it splits into two single-excitation modes spreading linearly toward two boundaries, respectively. Remarkably, these phenomena, studied both theoretically and numerically as unique properties of the Bose-Hubbard ladder, are represented coherently by pairs of controllable qubits in experiments. Our results show that collective excitations, as a single mode, are not free. This work paves the way to simulation of exotic logic particles by subtly encoding physical qubits and exploration of rich physics by superconducting circuits.

关键词： Quantum computation Quantum gates Quantum information architectures & platforms Quantum simulation Bose-Hubbard model

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Extended Black Hole Thermodynamics from Extended Iyer-Wald Formalism

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Physical Review Letters 2024年第2期132卷 021401-021401页

作者： Yong Xiao Yu Tian Yu-Xiao Liu Key Laboratory of High-precision Computation and Application of Quantum Field Theory of Hebei Province College of Physical Science and Technology Hebei University Baoding 071002 China Hebei Research Center of the Basic Discipline for Computational Physics Baoding 071002 China School of Physics University of Chinese Academy of Sciences Beijing 100049 China Institute of Theoretical Physics Chinese Academy of Sciences Beijing 100190 China Key Laboratory for Quantum Theory and Applications of the Ministry of Education Lanzhou Center for Theoretical Physics Lanzhou University Lanzhou Gansu 730000 China

In recent years, there has been significant interest in the field of extended black hole thermodynamics, where the cosmological constant and/or other coupling parameters are treated as thermodynamic variables. Drawing inspiration from the Iyer-Wald formalism, which reveals the intrinsic and universal structure of conventional black hole thermodynamics, we illustrate that a proper extension of this formalism also unveils the underlying theoretical structure of extended black hole thermodynamics. As a remarkable consequence, for any gravitational theory described by a diffeomorphism invariant action, it is always possible to construct a consistent extended thermodynamics using this extended formalism.

关键词： Alternative gravity theories Quantum aspects of black holes

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Eightfold fermionic excitation in a charge density wave compound

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Physical Review B 2020年第3期102卷 035125-035125页

作者： Xi Zhang Qiangqiang Gu Haigen Sun Tianchuang Luo Yanzhao Liu Yueyuan Chen Zhibin Shao Zongyuan Zhang Shaojian Li Yuanwei Sun Yuehui Li Xiaokang Li Shangjie Xue Jun Ge Ying Xing R. Comin Zengwei Zhu Peng Gao Binghai Yan Ji Feng Minghu Pan Jian Wang International Center for Quantum Materials School of Physics Peking University Beijing 100871 China School of Physics Huazhong University of Science and Technology Wuhan 430074 China School of Physics and Information Technology Shaanxi Normal University Xi'an 710062 China Electron Microscopy Laboratory School of Physics Peking University Beijing 100871 China Wuhan National High Magnetic Field Center Huazhong University of Science and Technology Wuhan 430074 China Department of Physics Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA Department of Materials Science and Engineering School of New Energy and Materials China University of Petroleum Beijing 102249 China Beijing Academy of Quantum Information Sciences Beijing 100193 China Department of Condensed Matter Physics Weizmann Institute of Science Rehovot 7610001 Israel CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing 100190 China

Unconventional quasiparticle excitations in condensed matter systems have become one of the most important research frontiers. Beyond twofold and fourfold degenerate Weyl and Dirac fermions, threefold, sixfold, and eightfold symmetry protected degeneracies have been predicted. However they remain challenging to realize in solid state materials. Here the charge density wave compound TaTe4 is proposed to hold eightfold fermionic excitation and Dirac point in energy bands. High quality TaTe4 single crystals are prepared, where the charge density wave is revealed by directly imaging the atomic structure and a pseudogap of about 45 meV on the surface. Shubnikov-de Haas oscillations of TaTe4 are consistent with band structure calculation. Scanning tunneling microscopy/spectroscopy reveals atomic step edge states on the surface of TaTe4. This work uncovers that the charge density wave is able to induce new topological phases and sheds new light on the novel excitations in condensed matter materials.

关键词： Charge density waves Dirac fermions Electronic structure First-principles calculations Magnetotransport Shubnikov-de Haas effect Topological materials Single crystal materials Scanning tunneling microscopy

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A Pathway to Er Sites in Si with Long Spin and Optical Coherence Times

A Pathway to Er Sites in Si with Long Spin and Optical Coher...

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Conference on Lasers and Electro-Optics Europe (CLEO EUROPE)

作者： Alexey Lyasota Ian R. Berkman Gabriele G. de Boo John G. Bartholomew Brett C. Johnson Jeffrey C. McCallum Bin-Bin Xu Shouyi Xie Rose L. Ahlefeldt Matthew J. Sellars Chunming Yin Sven Rogge Centre of Excellence for Quantum Computation and Communication Technology School of Physics University of New South Wales Sydney New South Wales Australia Centre for Engineered Quantum Systems School of Physics The University of Sydney Sydney New South Wales Australia The University of Sydney Nano Institute The University of Sydney Sydney New South Wales Australia Centre of Excellence for Quantum Computation and Communication Technology School of Physics University of Melbourne Victoria Australia School of Science RMIT University Melbourne Victoria Australia Centre of Excellence for Quantum Computation and Communication Technology Research School of Physics Australian National University Canberra Australian Capital Territory Australia Hefei National Laboratory for Physical Sciences at the Microscale CAS Key Laboratory of Microscale Magnetic Resonance School of Physical Sciences University of Science and Technology of China Hefei China

ISBN: (纸本)9798350345995

Rare-earth ions in solid-state hosts exhibit low homogeneous broadening and long spin coherence at cryogenic temperatures thus making them a promising candidate for optical quantum memories [1], optical-microwave transducers [2] and single dopant-based devices such as single photon emitters operating at the telecommunication wavelengths [3]. Here, we present an overview of the spin and optical properties of Er ensembles in Si accessed via resonant photoluminescence excitation (PLE) spectroscopy [4]. Samples were positioned directly on top of tailor-fabricated superconducting single photon detectors, placed in a dilution refrigerator unit and resonantly excited using fiber optics. Our method provided high collection efficiency and allowed spectral measurements of low Er density samples. The observed Er PLE spectra were strongly affected by the presence of co-dopants such as O, B or P reflecting their influence on the formation of optically active Er sites and corresponding Er optical transition energies. Higher O densities resulted in especially rich PLE spectra suggesting that a variety of Er-O complexes formed due to O doping. Lowering the O concentration, we achieved PLE spectra dominated by a single Er site in P doped samples. Interestingly, the Er spin relaxation and optical coherence properties were barely affected by the employed co-dopants and mainly depended on the Er concentration. By lowering the Er concentration from relatively high (10 18 cm-3) to low densities (10 16 cm-3), we were able to increase Er spin lifetimes from ~0.1 s to ~30 s. Long spin relaxation times allowed us to identify PLE spectra of new Er sites in Si. In both concentration regimes, we observed sub-MHz transient spectral holes suggesting long optical coherence times. Furthermore, we observed sub-MHz spin transitions in both natural and isotopically purified Si and achieved spin coherence times above 1 ms in isotopically purified Si. Narrow optical linewidths and long transverse and

关键词： Fiber optics Optical properties Photoluminescence Quantum information Quantum memories Silicon

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Dynamics of Topological Excitations in a Model Quantum Spin Ice

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Physical Review Letters 2018年第16期120卷 167202-167202页

作者： Chun-Jiong Huang Youjin Deng Yuan Wan Zi Yang Meng Shanghai Branch National Laboratory for Physical Sciences at Microscale and Department of Modern Physics University of Science and Technology of China Shanghai 201315 China CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics University of Science and Technology of China Hefei Anhui 230026 China CAS-Alibaba Quantum Computing Laboratory Shanghai 201315 China Perimeter Institute for Theoretical Physics Waterloo Ontario N2L 2Y5 Canada Institute of Physics Chinese Academy of Sciences Beijing 100190 China CAS Center of Excellence in Topological Quantum Computation and School of Physical Sciences University of Chinese Academy of Sciences Beijing 100190 China

We study the quantum spin dynamics of a frustrated XXZ model on a pyrochlore lattice by using large-scale quantum Monte Carlo simulation and stochastic analytic continuation. In the low-temperature quantum spin ice regime, we observe signatures of coherent photon and spinon excitations in the dynamic spin structure factor. As the temperature rises to the classical spin ice regime, the photon disappears from the dynamic spin structure factor, whereas the dynamics of the spinon remain coherent in a broad temperature window. Our results provide experimentally relevant, quantitative information for the ongoing pursuit of quantum spin ice materials.

关键词： Frustrated magnetism Quantum spin liquid Spin ice Quantum Monte Carlo

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Experimental Measurement-Device-Independent Quantum Steering and Randomness Generation Beyond Qubits

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Physical Review Letters 2019年第17期123卷 170402-170402页

作者： Yu Guo Shuming Cheng Xiaomin Hu Bi-Heng Liu En-Ming Huang Yun-Feng Huang Chuan-Feng Li Guang-Can Guo Eric G. Cavalcanti CAS Key Laboratory of Quantum Information University of Science and Technology of China Hefei 230026 People’s Republic of China CAS Center For Excellence in Quantum Information and Quantum Physics University of Science and Technology of China Hefei 230026 People’s Republic of China Centre for Quantum Dynamics Griffith University Brisbane Queensland 4111 Australia Centre for Quantum Computation and Communication Technology (Australian Research Council) Centre for Quantum Dynamics Griffith University Gold Coast Queensland 4222 Australia

In a measurement-device-independent or quantum-refereed protocol, a referee can verify whether two parties share entanglement or Einstein-Podolsky-Rosen (EPR) steering without the need to trust either of the parties or their devices. The need for trusting a party is substituted by a quantum channel between the referee and that party, through which the referee encodes the measurements to be performed on that party’s subsystem in a set of nonorthogonal quantum states. In this Letter, an EPR-steering inequality is adapted as a quantum-refereed EPR-steering witness, and the trust-free experimental verification of higher dimensional quantum steering is reported via preparing a class of entangled photonic qutrits. Further, with two measurement settings, we extract 1.106±0.023 bits of private randomness per every photon pair from our observed data, which surpasses the one-bit limit for projective measurements performed on qubit systems. Our results advance research on quantum information processing tasks beyond qubits.

关键词： Nonlocality Quantum information processing Quantum optics

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Searching for long-lived light neutralinos and axionlike particles at the SHiNESS experiment

arXiv

引用

arXiv 2024年

作者： Wang, Zeren Simon Zhang, Yu Liu, Wei School of Physics Hefei University of Technology Hefei230601 China Department of Physics National Tsing Hua University Hsinchu300 Taiwan Center for Theory and Computation National Tsing Hua University Hsinchu300 Taiwan Department of Applied Physics MIIT Key Laboratory of Semiconductor Microstructure and Quantum Sensing Nanjing University of Science and Technology Nanjing210094 China

Recently Soleti et al. [JHEP03(2024)148] proposed a new experiment called SHiNESS at the upcoming European Spallation Source (ESS) facility, making use of the 2-GeV proton beam there impinging on a fixed target, in order to search for hidden sterile neutrinos that could lie in different mass ranges and arise with distinct signatures. Such signatures include excesses in electron-positron pairs that may originate from displaced decays of long-lived particles (LLPs). At the ESS, the dominant sources of such LLPs are decays at rest of π+ mesons and µ+ leptons. We choose to investigate theoretical scenarios of long-lived light neutralinos in the R-parity-violating supersymmetry and long-lived weak-violating electrophilic axionlike particles, as these LLPs can be produced from decays of π+ and µ+. Since the π+’s and µ+’s decay at rest at the ESS, we compute the spectra of the therefrom produced LLPs, and thus estimate the expected sensitivity reach of SHiNESS to the LLPs in these two scenarios. Our calculation shows that in multiple relevant benchmark scenarios, SHiNESS can probe large parameter regions of these models beyond the existing bounds, in just a couple of years of data-collection time. © 2024, CC BY.

关键词： Supersymmetry

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Identifying electronic transitions of defects in hexagonal boron nitride for quantum memories

arXiv

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arXiv 2023年

作者： Cholsuk, Chanaprom Çakan, Aslı Suwanna, Sujin Vogl, Tobias Department of Computer Engineering School of Computation Information and Technology Technical University of Munich Munich80333 Germany Abbe Center of Photonics Institute of Applied Physics Friedrich Schiller University Jena Jena07745 Germany Optical and Quantum Physics Laboratory Department of Physics Faculty of Science Mahidol University Bangkok10400 Thailand

A quantum memory is a crucial keystone for enabling large-scale quantum networks. Applicable to the practical implementation, specific properties, i.e., long storage time, selective efficient coupling with other systems, and a high memory efficiency are desirable. Though many quantum memory systems are developed thus far, none of them can perfectly meet all requirements. This work herein proposes a quantum memory based on color centers in hexagonal boron nitride (hBN), where its performance is evaluated based on a simple theoretical model of suitable defects in a cavity. Employing density functional theory calculations, 257 triplet and 211 singlet spin electronic transitions are investigated. Among these defects, it is found that some defects inherit the Λ electronic structures desirable for a Raman-type quantum memory and optical transitions can couple with other quantum systems. Further, the required quality factor and bandwidth are examined for each defect to achieve a 95% writing efficiency. Both parameters are influenced by the radiative transition rate in the defect state. In addition, inheriting triplet-singlet spin multiplicity indicates the possibility of being a quantum sensing, in particular, optically detected magnetic resonance. This work therefore demonstrates the potential usage of hBN defects as a quantum memory in future quantum networks. Copyright © 2023, The Authors. All rights reserved.

关键词： Boron nitride

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