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arXiv 2021年

作者： Song, Xue-Ke Meng, Fei Liu, Bao-Jie Wang, Dong Ye, Liu Yung, Man-Hong School of Physics and Material Science Anhui University Hefei230601 China Shenzhen Institute for Quantum Science and Engineering Department of Physics Southern University of Science and Technology Shenzhen518055 China QICI Quantum Information and Computation Initiative Department of Computer Science The University of Hong Kong Pokfulam Road Hong Kong Shenzhen Key Laboratory of Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China

The stimulated Raman adiabatic passage (STIRAP) shows an efficient technique that accurately transfers population between two discrete quantum states with the same parity, in three-level quantum systems based on adiabatic evolution. This technique has widely theoretical and experimental applications in many fields of physics, chemistry, and beyond. Here, we present a generally robust approach to speed up STIRAP with invariant-based shortcut to adiabaticity. By controlling the dynamical process, we inversely design a family of Hamiltonians that can realize fast and accurate population transfer from the first to the third level, while the systematic error is largely suppressed in general. Furthermore, a detailed trade-off relation between the population of the intermediate state and the amplitudes of Rabi frequencies in the transfer process is illustrated. These results provide an optimal route toward manipulating the evolution of three-level quantum systems in future quantum information processing. Copyright © 2021, The Authors. All rights reserved.

关键词： Quantum optics

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Emission engineering in monolithically integrated silicon nitride microring resonators

arXiv

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arXiv 2024年

作者： Mandal, Kishor Kumar Singh, Anuj Kumar Kumar, Brijesh Shah, Amit P. Vij, Rishabh Majumder, Amrita Khunte, Janhavi Jayawant Achanta, Venu Gopal Kumar, Anshuman Laboratory of Optics of Quantum Materials Department of Physics Indian Institute of Technology Bombay Mumbai400076 India Department of Condensed Matter Physics and Material Science Tata Institute of Fundamental Research Homi Bhabha Road Mumbai400005 India Centre of Excellence in Quantum Information Computation Science and Technology Indian Institute of Technology Bombay Powai Mumbai400076 India

Monolithic integration of solid-state emitters with photonic elements of the same material is a promising approach to overcome the constraints of fabrication complexity and coupling losses in traditional hybrid integration approaches. A wide band-gap, low-loss silicon nitride (SiN) platform is a mature technology, having CMOS compatibility, widely used in hybrid integrated photonics and optoelectronics. However, it has been shown that certain growth conditions enable the SiN material to host color centers, whose origin is currently under investigation. In this work, we have engineered a novel technique for the efficient coupling of these intrinsic emitters into the whispering gallery modes (WGMs) of the SiN microring cavity – which has not been explored previously. We have engineered a subwavelength-sized notch into the rim of the SiN microring structure, to optimize the collection efficiency of the cavity-coupled enhanced photoluminescence (PL) spectra at room temperature. The platform presented in this work will enable the development of monolithic integration of color centers with nanophotonic elements for application to quantum photonic technologies. Copyright © 2024, The Authors. All rights reserved.

关键词： Silicon nitride

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Universal quantum computation with optical four-component cat qubits

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Physical Review A 2022年第4期106卷 042614-042614页

作者： Daiqin Su Ish Dhand Timothy C. Ralph Xanadu Toronto Ontario Canada M5G 2C8 MOE Key Laboratory of Fundamental Physical Quantities Measurement Hubei Key Laboratory of Gravitation and Quantum Physics and PGMF Institute for Quantum Science and Engineering School of Physics Huazhong University of Science and Technology Wuhan 430074 China Institut für Theoretische Physik Albert-Einstein-Allee 11 Universität Ulm 89069 Ulm Germany Centre for Quantum Computation and Communication Technology School of Mathematics and Physics University of Queensland St. Lucia Queensland 4072 Australia

We propose a teleportation-based scheme to implement a universal set of quantum gates with a four-component cat code, assisted by appropriate entangled resource states and photon-number-resolving detection. The four-component cat code features the ability to recover from single-photon loss. Here we propose a concrete procedure to correct the single-photon loss, including detecting the single-photon-loss event and recovering the initial states. By concatenating with standard qubit error-correcting codes, we estimate the loss threshold for fault-tolerant quantum computation and obtain a significant improvement over the two-component cat code.

关键词： Optical quantum information processing Quantum computation Quantum error correction Quantum information processing with continuous variables Quantum protocols Quantum repeaters Quantum teleportation

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Negative nonlocal vicinity resistance of viscous flow in a two-dimensional electron system

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Physical Review B 2021年第15期104卷 155308-155308页

作者： Wei-Jie Ji Shu-Yu Zheng Li Lu Kai Chang Chi Zhang State Key Laboratory of Superlattices and Microstructures (SKLSM) Institute of Semiconductors Chinese Academy of Science P.O. Box 912 Beijing 100083 China College of Material Science and Opto-Electronic Technology University of Chinese Academy of Sciences Beijing 100190 China Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100190 China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing 100190 China

We perform a quantum transport study of Hall viscous liquid in multiterminal narrow Hallbar devices of a high-mobility two-dimensional electron system (2DES) in GaAs/AlGaAs heterostructure. In the nonlocal transport measurements of vicinity geometry under magnetic fields (B), we observe that the absolute negative magnetoresistance (Rxx) value (Rmin<0) and the corresponding magnetic field (Bmin) are both inversely proportional to the adjacent Hallbar arm distance (L). The occurrence of negative resistance is dependent on the characteristic lengths of the devices and the electron flow direction under B-fields. The minimal resistance Rmin occurs when the cyclotron radius RC approximates L. Multiples of high-order (nth-order) Rmin,n's persist from low to high magnetic fields in a large sample size of L=5μm. Our experimental study reveals the transport behaviors in the vicinity regime, where the negative resistances depict viscous electronic flows in the high-mobility 2DES. In addition, the negative and high-order minimal resistances expand to a magnetic field of several kGs.

关键词： Fractional quantum Hall effect Integer quantum Hall effect Magnetoresistance III-V semiconductors Two-dimensional electron gas Two-dimensional electron system Hall bar Resistivity measurements

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Strong decays of the isovector-scalar D∗D¯∗ hadronic molecule

arXiv

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arXiv 2024年

作者： Deng, Jin-Cheng Wang, Bo College of Physics Science and Technology Hebei University Baoding071002 China Hebei Key Laboratory of High-precision Computation and Application of Quantum Field Theory Baoding071002 China Hebei Research Center of the Basic Discipline for Computational Physics Baoding071002 China

We adopt the effective Lagrangian approach to study the strong decays of the 1−(0++) D∗D¯∗ molecular state [denoted as Tψa0(4010) according to the LHCb naming convention] through triangle diagrams. The decay channels include the open-charm DD¯, and the hidden-charm ηcπ, J/ψρ, and χc1π. The coupling between the Tψa0(4010) and its constituents D∗D¯∗ is obtained by solving for the residue of the scattering T-matrix at the pole. Our calculations yield a total width of few tens MeV for the Tψa0(4010) state using three different form factors, with its main decay channels being ηcπ and χc1π. The X(4100) and X(4050) have similar masses and widths, with both masses being close to the D∗D¯∗ threshold. Additionally, their decay final states are consistent with those of the Tψa0(4010). Therefore, it is likely that they represent the same state and both potentially correspond to the Tψa0(4010). We suggest that future experiments focus on searching for the Tψa0(4010) signal in the final states ηcπ−, χc1π− and D0D− of the B0 → ηcπ−K+, χc1π−K+ and D0D−K+ processes, respectively, as well as further investigating its resonance parameters with Flatté-like formula. © 2024, CC BY.

关键词： Lagrange multipliers

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Joint product numerical range and geometry of reduced density matrices

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science China(physics,Mechanics & Astronomy) 2017年第2期60卷 9-17页

作者： Jianxin Chen Cheng Guo Zhengfeng Ji Yiu-Tung Poon Nengkun YU Bei Zeng Jie Zhou Joint Center for Quantum Information and Computer Science University of Maryland College Park 20740 USA Institute for Advanced Study Tsinghua University Beijing 100084 China Centre for Quantum Computation ＆ Intelligent Systems School of Software Faculty of Engineering and Information Technology University of Technology Sydney Sydney 2007 Australia State Key Laboratory of Computer Science.Institute of Software Chinese Academy of Sciences Beijing 100084 China Department of Mathematics Iowa State University Ames 50011-2140 USA Institute for Quantum Computing University of Waterloo Waterloo N2L 3G1 Canada Department of Mathematics ＆ Statistics University of Guelph Guelph N1G 2 W1 Canada Perimeter Institute for Theoretical Physics Waterloo N2L 2Y5 Canada

The reduced density matrices of a many-body quantum system form a convex set, whose three-dimensional projection is convex in R3. The boundary of may exhibit nontrivial geometry, in particular ruled surfaces. Two physical mechanisms are known for the origins of ruled surfaces： symmetry breaking and gapless. In this work, we study the emergence of ruled surfaces for systems with local Hamiltonians in infinite spatial dimension, where the reduced density matrices are known to be separable as a consequence of the quantum de Finetti＇s theorem. This allows us to identify the reduced density matrix geometry with joint product numerical range II of the Hamiltonian interaction terms. We focus on the case where the interaction terms have certain structures, such that a ruled surface emerges naturally when taking a convex hull of ∏. We show that, a ruled surface on sitting in ∏ has a gapless origin, otherwise it has a symmetry breaking origin. As an example, we demonstrate that a famous ruled surface, known as the oloid, is a possible shape of , with two boundary pieces of symmetry breaking origin separated by two gapless lines.

关键词： reduced density matrices quantum tomography numerical range quantum information oloid ruled surface

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Quantum games of asymmetric information

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Physical Review E 2003年第1期68卷 016124-016124页

作者： Jiangfeng Du Hui Li Chenyong Ju Structure Research Laboratory and Department of Modern Physics University of Science and Technology of China Hefei 230027 People’s Republic of China Department of Physics National University of Singapore Lower Kent Ridge Singapore 119260 Singapore Centre for Quantum Computation Department of Applied Mathematics and Theoretical Physics University of Cambridge Wilberforce Road Cambridge CB3 0WA United Kingdom

We investigate quantum games in which the information is asymmetrically distributed among the players and find that the possibility of the quantum game outperforming its classical counterpart depends strongly on not only the entanglement but also the informational asymmetry. What is more interesting, when the information distribution is asymmetric, is that the contradictive impact of the quantum entanglement on the profits is observed, which is not reported in quantum games of symmetric information.

关键词： Quantum theory

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Quantum emitters in bilayer hexagonal boron nitride

arXiv

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arXiv 2024年

作者： Mehta, Reyhan Kumar, Anshuman Department of Condensed Matter Physics and Materials Science Tata Institute of Fundamental Research Homi Bhabha Road Mumbai400005 India Laboratory of Optics of Quantum Materials Department of Physics Indian Institute of Technology Bombay Mumbai400076 India Centre of Excellence in Quantum Information Computation Science and Technology Indian Institute of Technology Bombay Powai Mumbai400076 India

Hexagonal boron nitride has been experimentally shown to exhibit room-temperature single-photon emission. This emission is attributed to defect states in the wide band-gap of hBN, which allow new optical transitions between these dispersion-less defect levels. In this work, we study the new spectral features introduced by interacting atomic defects in consecutive layers of bilayer hBN. Density Functional theory simulations have been carried out to calculate the energy band structure, frequency-dependent complex dielectric functions, and Kohn-Sham states to demonstrate and understand the cause of the emission enhancements. We found that placing colour centres in the vicinity of each other in bilayer hBN introduces new polarization dependent spectral features, with strong dependence on the distance and relative orientation between atomic defects. Our results provide a pathway to engineering single photon emission in hBN via inter-defect interaction. Copyright © 2024, The Authors. All rights reserved.

关键词： Boron nitride

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Using weak values to experimentally determine “negative probabilities” in a two-photon state with Bell correlations

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Physical Review A 2015年第1期91卷 012113-012113页

作者： B. L. Higgins M. S. Palsson G. Y. Xiang H. M. Wiseman G. J. Pryde Centre for Quantum Dynamics and Centre for Quantum Computation and Communication Technology Griffith University Brisbane 4111 Australia Institute for Quantum Computing and Department of Physics & Astronomy University of Waterloo Waterloo ON N2L 3G1 Canada Key Laboratory of Quantum Information University of Science and Technology of China Hefei 230026 China

Bipartite quantum entangled systems can exhibit measurement correlations that violate Bell inequalities, revealing the profoundly counter-intuitive nature of the physical universe. These correlations reflect the impossibility of constructing a joint probability distribution for all values of all the different properties observed in Bell inequality tests. Physically, the impossibility of measuring such a distribution experimentally, as a set of relative frequencies, is due to the quantum back-action of projective measurements. Weakly coupling to a quantum probe, however, produces minimal back-action, and so enables a weak measurement of the projector of one observable, followed by a projective measurement of a noncommuting observable. By this technique it is possible to empirically measure weak-valued probabilities for all of the values of the observables relevant to a Bell test. The marginals of this joint distribution, which we experimentally determine, reproduces all of the observable quantum statistics including a violation of the Bell inequality, which we independently measure. This is possible because our distribution, like the weak values for projectors on which it is built, is not constrained to the interval [0,1]. It was first pointed out by Feynman that, for explaining singlet-state correlations within “a [local] hidden variable view of nature … everything works fine if we permit negative probabilities.” However, there are infinitely many such theories. Our method, involving “weak-valued probabilities,” singles out a unique set of probabilities, and moreover does so empirically.

关键词： PHONON-phonon interactions BELL'S theorem QUANTUM entanglement QUANTUM information science QUANTUM theory QUANTUM statistics

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Strain Tunable Semimetal–Topological-Insulator Transition in Monolayer 1T′−WTe2

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Physical Review Letters 2020年第4期125卷 046801-046801页

作者： Chenxiao Zhao Mengli Hu Jin Qin Bing Xia Canhua Liu Shiyong Wang DanDan Guan Yaoyi Li Hao Zheng Junwei Liu Jinfeng Jia Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education) Shenyang National Laboratory for Materials Science School of Physics and Astronomy Shanghai Jiao Tong University Shanghai 200240 China Department of Physics Hong Kong University of Science and Technology Hong Kong China Tsung-Dao Lee Institute Shanghai Jiao Tong University Shanghai 200240 China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing 100190 China

A quantum spin hall insulator is manifested by its conducting edge channels that originate from the nontrivial topology of the insulating bulk states. Monolayer 1T′−WTe2 exhibits this quantized edge conductance in transport measurements, but because of its semimetallic nature, the coherence length is restricted to around 100 nm. To overcome this restriction, we propose a strain engineering technique to tune the electronic structure, where either a compressive strain along the a axis or a tensile strain along the b axis can drive 1T′−WTe2 into an full gap insulating phase. A combined study of molecular beam epitaxy and in situ scanning tunneling microscopy or spectroscopy then confirmed such a phase transition. Meanwhile, the topological edge states were found to be very robust in the presence of strain.

关键词： Topological phase transition Topological phases of matter Monolayer films Topological materials Transition metal dichalcogenides First-principles calculations Scanning tunneling microscopy Scanning tunneling spectroscopy

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