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Multipartite-to-bipartite entanglement transformations and polynomial identity testing

Physical Review A 2010年第5期81卷 052310-052310页

作者： Eric Chitambar Runyao Duan Yaoyun Shi Physics Department University of Michigan 450 Church Street Ann Arbor Michigan 48109-1040 USA Centre for Quantum Computation and Intelligent Systems (QCIS) Faculty of Engineering and Information Technology University of Technology Sydney New South Wales 2007 Australia and State Key Laboratory of Intelligent Technology and Systems Tsinghua National Laboratory for Information Science and Technology Department of Computer Science and Technology Tsinghua University Beijing 100084 People’s Republic of China Department of Electrical Engineering and Computer Science University of Michigan 2260 Hayward Street Ann Arbor Michigan 48109-2121 USA

We consider the problem of deciding if some multiparty entangled pure state can be converted, with a nonzero success probability, into a given bipartite pure state shared between two specified parties through local quantum operations and classical communication. We show that this question is equivalent to the well-known computational problem of deciding if a multivariate polynomial is identically zero. Efficient randomized algorithms developed to study the latter can thus be applied to our question. As a result, a given transformation is possible if and only if it is generically attainable by a simple randomized protocol.

关键词： Quantum entanglement

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Scattering-Free Optical Levitation of a Cavity Mirror

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Physical Review Letters 2013年第18期111卷 183001-183001页

作者： G. Guccione M. Hosseini S. Adlong M. T. Johnsson J. Hope B. C. Buchler P. K. Lam Centre for Quantum Computation and Communication Technology Research School of Physics and Engineering The Australian National University Canberra ACT 0200 Australia Department of Quantum Science Research School of Physics and Engineering The Australian National University Canberra ACT 0200 Australia Key Laboratory of Optoelectronics Information College of Precision Instrument and Opto-electronics Engineering Technology of Ministry of Education Tianjin University Tianjin 300072 China

We demonstrate the feasibility of levitating a small mirror using only radiation pressure. In our scheme, the mirror is supported by a tripod where each leg of the tripod is a Fabry-Perot cavity. The macroscopic state of the mirror is coherently coupled to the supporting cavity modes allowing coherent interrogation and manipulation of the mirror motion. The proposed scheme is an extreme example of the optical spring, where a mechanical oscillator is isolated from the environment and its mechanical frequency and macroscopic state can be manipulated solely through optical fields. We model the stability of the system and find a three-dimensional lattice of trapping points where cavity resonances allow for buildup of optical field sufficient to support the weight of the mirror. Our scheme offers a unique platform for studying quantum and classical optomechanics and can potentially be used for precision gravitational field sensing and quantum state generation.

关键词： SCATTERING (physics) MAGNETIC suspension MIRRORS RADIATION pressure QUANTUM states LATTICE dynamics

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Biased Gottesman-Kitaev-Preskill repetition code

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Physical Review A 2023年第5期108卷 052428-052428页

作者： Matthew P. Stafford Nicolas C. Menicucci Quantum Engineering Technology Labs H. H. Wills Physics Laboratory and Department of Electrical and Electronic Engineering University of Bristol Bristol United Kingdom Quantum Engineering Centre for Doctoral Training H. H. Wills Physics Laboratory and Department of Electrical and Electronic Engineering University of Bristol Bristol United Kingdom Centre for Quantum Computation and Communication Technology School of Science RMIT University Melbourne Victoria 3000 Australia

Continuous-variable quantum computing architectures based upon the Gottesman-Kitaev-Preskill (GKP) encoding have emerged as a promising candidate because one can achieve fault tolerance with a probabilistic supply of GKP states and Gaussian operations. Furthermore, by generalizing to rectangular-lattice GKP states, a bias can be introduced and exploited through concatenation with qubit codes that show improved performance under biasing. However, these codes (such as the XZZX surface code) still require weight-four stabilizer measurements and have complex decoding requirements to overcome. In this work, we study the code-capacity behavior of a rectangular-lattice GKP encoding concatenated with a repetition code under an isotropic Gaussian displacement channel. We find a numerical threshold of σ=0.599 for the noise's standard deviation, which outperforms the biased GKP planar surface code with a trade-off of increased biasing at the GKP level. This is all achieved with only weight-two stabilizer operators and simple decoding at the qubit level. Furthermore, with moderate levels of bias (aspect ratio ≤2.4) and nine or fewer data modes, significant reductions in logical error rates can still be achieved for σ≤0.3, opening the possibility of using biased GKP repetition codes as a simple low-level qubit encoding for further concatenation.

关键词： Optical quantum information processing Quantum error correction Quantum information processing with continuous variables

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Plaquette Singlet Transition, Magnetic Barocaloric Effect, and Spin Supersolidity in the Shastry-Sutherland Model

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Physical Review Letters 2023年第11期131卷 116702-116702页

作者： Junsen Wang Han Li Ning Xi Yuan Gao Qing-Bo Yan Wei Li Gang Su Center of Materials Science and Optoelectronics Engineering College of Materials Science and Opto-electronic Technology University of Chinese Academy of Sciences Beijing 100049 China CAS Key Laboratory of Theoretical Physics Institute of Theoretical Physics Chinese Academy of Sciences Beijing 100190 China Kavli Institute for Theoretical Sciences University of Chinese Academy of Sciences Beijing 100190 China School of Physics Beihang University Beijing 100191 China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing 100190 China Hefei National Laboratory University of Science and Technology of China Hefei 230088 China

Inspired by recent experimental measurements [Guo et al., Phys. Rev. Lett. 124, 206602 (2020); Jiménez et al., Nature (London) 592, 370 (2021)] on frustrated quantum magnet SrCu2(BO3)2 under combined pressure and magnetic fields, we study the related spin-1/2 Shastry-Sutherland model using state-of-the-art tensor network methods. By calculating thermodynamics, correlations, and susceptibilities, we find, in zero magnetic field, not only a line of first-order dimer-singlet to plaquette-singlet phase transition ending with a critical point, but also signatures of the ordered plaquette-singlet transition with its critical end point terminating on this first-order line. Moreover, we uncover prominent magnetic barocaloric responses, a novel type of quantum correlation induced cooling effect, in the strongly fluctuating supercritical regime. Under finite fields, we identify a quantum phase transition from the plaquette-singlet phase to the spin supersolid phase that breaks simultaneously lattice translational and spin rotational symmetries. The present findings on the Shastry-Sutherland model are accessible in current experiments and would shed new light on the critical and supercritical phenomena in the archetypal frustrated quantum magnet SrCu2(BO3)2.

关键词： Frustrated magnetism Antiferromagnets Density matrix renormalization group Tensor network renormalization

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Tuning anionic/cationic redox chemistry in a P2-type Na0.67Mn0.5Fe0.5O2 cathode material via a synergic strategy

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science China Materials 2020年第9期63卷 1703-1718页

作者： Weijin Kong Wenyun Yang De Ning Qingyuan Li Lirong Zheng Jinbo Yang Kai Sun Dongfeng Chen Xiangfeng Liu Center of Materials Science and Optoelectronics Engineering College of Materials Science and Optoelectronic TechnologyUniversity of Chinese Academy of SciencesBeijing 100049China State Key Laboratory for Mesoscopic Physics School of PhysicsPeking UniversityBeijing 100871China Helmholtz-Center Berlin for Materials and Energy Hahn-Meitner-Platz 1Berlin 14109Germany Beijing Synchrotron Radiation Facility Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China Department of Nuclear Physics China Institute of Atomic EnergyBeijing 102413China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of SciencesBeijing 100190China

The anionic redox chemistry(O^2-→O^-)in P2-type sodium-ion battery cathodes has attracted much ***,determining how to tune the anionic redox reaction is still a major ***,we tune the activity and reversibility of both the anionic and cationic redox reactions of Na0.67Mn0.5Fe0.5O2 though an integrated strategy that combines the advantages of Li2SiO3 coating,Li doping and Si doping,and the initial capacity,rate performance and cycling stability are significantly *** in-depth modulation mechanism is revealed by means of neutron diffraction,X-ray absorption spectroscopy,in situ X-ray diffraction,electron paramagnetic resonance spectroscopy,first-principles calculations and so *** Li2SiO3 coating alleviates the side reactions and enhances the cycling ***^4+doping lowers the Na^+diffusion barrier due to the expanded interlayer ***,Si^4+doping improves the structural stability,oxygen redox activity and ***^+doping in Na sites further increases the structure *** electron density maps confirm the greater activity of Na and O in the modified *** density maps and bond-valence energy landscapes identify the Na^+migration pathway from Nae site to Naf site(the positions of the Na ions in the crystal structure).The proposed insights into the modulation mechanism of the anionic and cationic redox chemistry are also instructive for designing other oxide-based cathode materials.

关键词： sodium-ion battery P2-type cathode anion redox electron density nephogram Li2SiO3 coating

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Van Hove singularity–induced negative magnetoresistance in Dirac semimetals

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Physical Review B 2023年第24期108卷 245158-245158页

作者： Kai-He Ding Zhen-Gang Zhu Department of Physics and Electronic Science Changsha University of Science and Technology Changsha 410076 China School of Electronic Electrical and Communication Engineering University of Chinese Academy of Sciences Beijing 100049 China Theoretical Condensed Matter Physics and Computational Materials Physics Laboratory College of Physical Sciences University of Chinese Academy of Sciences Beijing 100049 China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing 100190 China

Negative magnetoresistance (NMR) is a marked feature of Dirac semimetals, and may be caused by multiple mechanisms, such as the chiral anomaly, the Zeeman energy, the quantum interference effect, and the orbital moment. Recently, an experiment on Dirac semimetal Cd3As2 thin films revealed a new NMR feature that depends strongly on the thickness of the sample [T. Schumann et al., Phys. Rev. B 95, 241113(R) (2017)]. Here, we introduce a mechanism of inducing NMR via the presence of the Van Hove singularity (VHS) in the density of states. A theoretical fitting of the experimental data on magnetoconductivity and magnetoresistance shows good agreement, indicating that the observed NMR in thin films of Cd3As2 can be attributed to the VHS. This work provides insights into the underlying Dirac semimetals.

关键词： Electrical properties Magnetotransport Transport phenomena 2-dimensional systems Topological materials

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Topological Spin Texture of Chiral Edge States in Photonic Two-Dimensional Quantum Walks

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Physical Review Letters 2022年第4期129卷 046401-046401页

作者： Chao Chen Xing Ding Jian Qin Jizhou Wu Yu He Chao-Yang Lu Li Li Xiong-Jun Liu Barry C. Sanders Jian-Wei Pan Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics University of Science and Technology of China Shanghai Branch Shanghai 201315 China CAS-Alibaba Quantum Computing Laboratory CAS Centre for Excellence in Quantum Information and Quantum Physics Shanghai 201315 China National Laboratory of Solid State Microstructures School of Physics Nanjing University Nanjing 210093 China Shenzhen Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen 518055 China International Center for Quantum Materials and School of Physics Peking University Beijing 100871 China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing 100190 China Institute for Quantum Science and Technology University of Calgary Alberta T2N 1N4 Canada

Topological insulators host topology-linked boundary states, whose spin and charge degrees of freedom could be exploited to design topological devices with enhanced functionality. We experimentally observe that dissipationless chiral edge states in a spin-orbit coupled anomalous Floquet topological phase exhibit topological spin texture on boundaries, realized via a two-dimensional quantum walk. Our experiment shows that, for a walker traveling around a closed loop along the boundary in real space, its spin evolves and winds through a great circle on the Bloch sphere, which implies that edge-spin texture has nontrivial winding. This topological spin winding is protected by a chiral-like symmetry emerging for the low-energy Hamiltonian. Our experiment confirms that two-dimensional anomalous Floquet topological systems exhibit topological spin texture on the boundary, which could inspire novel topology-based spintronic phenomena and devices.

关键词： Edge states Photonics Quantum walks Spin texture Topological phases of matter

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Exotic Cooper pairing in multiorbital models of Sr2RuO4

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Physical Review B 2019年第13期100卷 134506-134506页

作者： Wen Huang Yi Zhou Hong Yao Shenzhen Institute for Quantum Science and Engineering and Department of Physics Southern University of Science and Technology Shenzhen 518055 China Institute for Advanced Study Tsinghua University Beijing 100084 China Center for Quantum Computing Peng Cheng Laboratory Shenzhen 518005 China Beijing National Laboratory for Condensed Matter Physics & Institute of Physics Chinese Academy of Sciences Beijing 100190 China Kavli Institute for Theoretical Sciences & CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing 100190 China State Key Laboratory of Low Dimensional Quantum Physics Tsinghua University Beijing 100084 China

The unconventional superconductivity in Sr2RuO4 continues to defy a unified interpretation. In this paper, we focus on some novel aspects of its superconducting pairing by exploiting the orbital degree of freedom in this material. The multiorbital nature, combined with the symmetry of the orbitals involved, leads to a plethora of exotic Cooper pairings not accessible in single-orbital systems. Essential physics is illustrated first using a two-orbital model with dxz and dyz orbitals. We classify the gap functions according to the underlying lattice symmetries, analyze the effective theories of a few representative pairings, and make connections to Sr2RuO4 in the course. In particular, we show how spin-orbit coupling may entangle spin-triplet and spin-singlet pairings. For completeness, the classification is generalized to the three-orbital model involving the dxy orbital as well. The orbital-basis approach distinguishes from the itinerant-band description for Sr2RuO4 and hence offers an alternative perspective to investigate its enigmatic superconducting state.

关键词： Pairing mechanisms Spin-singlet pairing Spin-triplet pairing Superconducting order parameter Superconductivity Topological materials Topological phases of matter Topological superconductors

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Sub-megahertz homogeneous linewidth for Er in Si via in situ single photon detection

arXiv

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arXiv 2021年

作者： Berkman, Ian R. Lyasota, Alexey de Boo, Gabriele G. Bartholomew, John G. Johnson, Brett C. McCallum, Jeffrey C. Xu, Bin-Bin Xie, Shouyi Ahlefeldt, Rose L. Sellars, Matthew J. Yin, Chunming Rogge, Sven Centre of Excellence for Quantum Computation and Communication Technology School of Physics University of New South Wales SydneyNSW2052 Australia Centre for Engineered Quantum Systems School of Physics University of Sydney SydneyNSW2006 Australia University of Sydney Nano Institute University of Sydney SydneyNSW2006 Australia Centre of Excellence for Quantum Computation and Communication Technology School of Physics University of Melbourne VIC3010 Australia Centre of Excellence for Quantum Computation and Communication Technology School of Engineering RMIT University VIC3001 Australia Centre of Excellence for Quantum Computation and Communication Technology Research School of Physics Australian National University CanberraACT0200 Australia Hefei National Laboratory for Physical Sciences at the Microscale CAS Key Laboratory of Microscale Magnetic Resonance and School of Physical Sciences University of Science and Technology of China Hefei230026 China

We studied the optical properties of a resonantly excited trivalent Er ensemble in Si accessed via in situ single photon detection. A novel approach which avoids nanofabrication on the sample is introduced, resulting in a highly efficient detection of 70 excitation frequencies, of which 63 resonances have not been observed in literature. The center frequencies and optical lifetimes of all resonances have been extracted, showing that 5 % of the resonances are within 1 GHz of our electrically detected resonances and that the optical lifetimes range from 0.5 ms up to 1.5 ms. We observed inhomogeneous broadening of less than 400 MHz and an upper bound on the homogeneous linewidth of 1.4 MHz and 0.75 MHz for two separate resonances, which is a reduction of more than an order of magnitude observed to date. These narrow optical transition properties show that Er in Si is an excellent candidate for future quantum information and communication applications. Copyright © 2021, The Authors. All rights reserved.

关键词： Photons

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Twisted hyperbolic van der Waals crystals for chip-scale full Stokes mid-infrared polarization detection

arXiv

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arXiv 2024年

作者： Sahoo, Nihar Ranjan Prasath, S.S. Jatin Kumar, Brijesh Kumar, Anshuman Laboratory of Optics of Quantum Materials Physics Department 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 Indian Institute of Technology Bombay Mumbai400076 India

Investigating the polarization properties of light in the mid-infrared (mid-IR) spectrum is crucial for molecular sensing, biomedical diagnostics, and IR imaging system technologies. Traditional methods, limited by bulky size and complicated fabrication process, utilize large rotating optics for full Stokes polarization detection, impeding miniaturization and *** occurring hyperbolic van der Waals (vdW) material based devices can address these challenges due to their lithography-free fabrication, ease of integration with chip-scale platforms and room-temperature operation. This study designs a chip-integrated polarimeter by performing multi-objective optimization for efficient exploration of the design parameter space. The spatial division measurement scheme used incorporates six precisely designed linear and circular polarization filters, achieving high extinction ratios exceeding 30 dB and transmittance surpassing 50%, with fabrication tolerance of film thickness up to 100 nm. The proposed device represents a significant advancement in polarimetric detection, providing a compact, cost-effective solution and opens new avenues for on-chip mid-IR polarimetric detection in next-generation ultra-compact optical systems. Copyright © 2024, The Authors. All rights reserved.

关键词： Van der Waals forces

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