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Generation of a CW anti-bunched photon field from a thin-film PPLN waveguide by two-photon interference with a weak coherent state
Authors:
Yue Li,
Haochuan Li,
Yuhang Lei,
Xiaoting Li,
Jianmin Wang,
Xuan Tang,
Mu Ku Chen,
E. Y. B. Pun,
Cheng Wang,
Z. Y. Ou
Abstract:
An anti-bunched photon field is produced from a thin-film ppln waveguide by mixing the on-chip two-photon state with a weak but matched coherent state. This is achieved by taking out the two-photon part of the coherent state via a destructive two-photon interference with the on-chip two-photon state. We achieve a photon rate of 100 kHz with a g2-value of 0.35. This anti-bunched light field will ha…
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An anti-bunched photon field is produced from a thin-film ppln waveguide by mixing the on-chip two-photon state with a weak but matched coherent state. This is achieved by taking out the two-photon part of the coherent state via a destructive two-photon interference with the on-chip two-photon state. We achieve a photon rate of 100 kHz with a g2-value of 0.35. This anti-bunched light field will have applications in high-resolution quantum imaging such as long baseline quantum telescopy for enhancing the signal-to-noise ratio.
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Submitted 13 August, 2025;
originally announced August 2025.
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Universal quantum homomorphic encryption based on $(k, n)$-threshold quantum state sharing
Authors:
Haoyun Zhang,
Yu-Ting Lei,
Xing-bo Pan
Abstract:
Quantum homomorphic encryption integrates quantum computing with homomorphic encryption, which allows calculations to be performed directly on encrypted data without decryption on the server side. In this paper, we explore distributed quantum homomorphic encryption, focusing on the coordination of multiple evaluators to achieve evaluation tasks, which not only ensures security but also boosts comp…
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Quantum homomorphic encryption integrates quantum computing with homomorphic encryption, which allows calculations to be performed directly on encrypted data without decryption on the server side. In this paper, we explore distributed quantum homomorphic encryption, focusing on the coordination of multiple evaluators to achieve evaluation tasks, which not only ensures security but also boosts computational power. Notably, we propose a $(k, n)$-threshold universal quantum homomorphic encryption scheme based on quantum state sharing. Each server is capable of executing a universal gate set, including the Clifford gates $\{X,Y,Z,H,S,CNOT\}$ and a non-Clifford T gate. The scheme provides that k evaluation servers chosen from $n$ $(0 < k \leq n)$ cooperate to complete the quantum homomorphic encryption so that the client can get the evaluated plaintext after decryption. Several concrete examples are presented to provide clarity to our solution. We also include security analysis, demonstrating its security against eavesdroppers.
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Submitted 26 February, 2025;
originally announced February 2025.
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Efficient Pumping of Spectral Holes in a Tm$^{3+}$: YAG Crystal for Broadband Quantum Optical Storage
Authors:
Yisheng Lei,
Zongfeng Li,
Mahdi Hosseini
Abstract:
Quantum memory devices with high storage efficiency and bandwidth are essential elements for future quantum networks. Here, we report a storage efficiency greater than 28% in a Tm$^{3+}$: YAG crystal in elevated temperatures and without compromising the memory bandwidth. Using various pumping and optimization techniques, we demonstrate multi-frequency window storage with a high memory bandwidth of…
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Quantum memory devices with high storage efficiency and bandwidth are essential elements for future quantum networks. Here, we report a storage efficiency greater than 28% in a Tm$^{3+}$: YAG crystal in elevated temperatures and without compromising the memory bandwidth. Using various pumping and optimization techniques, we demonstrate multi-frequency window storage with a high memory bandwidth of 630 MHz. Moreover, we propose a general method for large-bandwidth atomic-frequency memory with non-Kramers rare-earth-ion (REI) in solids enabling significantly higher storage efficiency and bandwidth. Our study advances the practical applications of quantum memory devices based on REI-doped crystals.
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Submitted 16 December, 2024;
originally announced December 2024.
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Efficient Storage of Multidimensional Telecom Photons in a Solid-State Quantum Memory
Authors:
Zongfeng Li,
Yisheng Lei,
Trevor Kling,
Mahdi Hosseini
Abstract:
Efficient storage of telecom-band quantum optical information represents a crucial milestone for establishing distributed quantum optical networks. Erbium ions in crystalline hosts provide a promising platform for telecom quantum memories; however, their practical applications have been hindered by demanding operational conditions, such as ultra-high magnetic fields and ultra-low temperatures. In…
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Efficient storage of telecom-band quantum optical information represents a crucial milestone for establishing distributed quantum optical networks. Erbium ions in crystalline hosts provide a promising platform for telecom quantum memories; however, their practical applications have been hindered by demanding operational conditions, such as ultra-high magnetic fields and ultra-low temperatures. In this work, we demonstrate the storage of telecom photonic qubits encoded in polarization, frequency, and time-bin bases. Using the atomic frequency comb protocol in an Er$^{3+}$-doped crystal, we developed a memory initialization scheme that improves storage efficiency by over an order of magnitude under practical experimental conditions. Quantum process tomography further confirms the memory's performance, achieving a fidelity exceeding 92%.
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Submitted 6 December, 2024;
originally announced December 2024.
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Collective field theory of gauged multi-matrix models: Integrating out off-diagonal strings
Authors:
Suddhasattwa Brahma,
Robert Brandenberger,
Keshav Dasgupta,
Yue Lei,
Julia Pasiecznik
Abstract:
We study a two-matrix toy model with a BFSS-like interaction term using the collective field formalism. The main technical simplification is obtained by gauge-fixing first, and integrating out the off-diagonal elements, before changing to the collective field variable. We show that the resulting (2+1)-dimensional collective field action has novel features with respect to non-locality, and that we…
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We study a two-matrix toy model with a BFSS-like interaction term using the collective field formalism. The main technical simplification is obtained by gauge-fixing first, and integrating out the off-diagonal elements, before changing to the collective field variable. We show that the resulting (2+1)-dimensional collective field action has novel features with respect to non-locality, and that we need to add a mass term to get a time-local potential. As is expected, one recovers the single matrix quantum mechanical collective field Hamiltonian in the proper limit.
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Submitted 16 November, 2024;
originally announced November 2024.
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Efficient Quantum Repeater with Single Atoms in Cavities
Authors:
Yisheng Lei
Abstract:
Efficient quantum repeaters are needed to combat photon losses in fibers in future quantum networks. Single atom coupled with photonic cavity offers a great platform for photon-atom gate. Here I propose a quantum repeater scheme with efficient entanglement generation and entanglement swapping based on photon-atom gates. It can be implemented with various types of atomic systems and requires much l…
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Efficient quantum repeaters are needed to combat photon losses in fibers in future quantum networks. Single atom coupled with photonic cavity offers a great platform for photon-atom gate. Here I propose a quantum repeater scheme with efficient entanglement generation and entanglement swapping based on photon-atom gates. It can be implemented with various types of atomic systems and requires much less experimental complexity compared to other repeater protocols. With current available experimental techniques and reasonable improvements, high entanglement distribution rates can be achieved. A multiplexing configuration of 10 single atoms in cavities, secret key rates in order of a few Hz to 100s Hz can be achieved for communication distance of 1000 km. This proposal paves the way for the demonstration of an efficient entanglement distribution with quantum repeaters in the near future.
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Submitted 15 August, 2025; v1 submitted 23 September, 2024;
originally announced September 2024.
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Topological phases of extended Su-Schrieffer-Heeger-Hubbard model
Authors:
Pei-Jie Chang,
Jinghui Pi,
Muxi Zheng,
Yu-Ting Lei,
Dong Ruan,
Gui-Lu Long
Abstract:
Despite extensive studies on the one-dimensional Su-Schrieffer-Heeger-Hubbard (SSHH) model, the variant incorporating next-nearest neighbour hopping remains largely unexplored. Here, we investigate the ground-state properties of this extended SSHH model using the constrained-path auxiliary-field quantum Monte Carlo (CP-AFQMC) method. We show that this model exhibits rich topological phases, charac…
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Despite extensive studies on the one-dimensional Su-Schrieffer-Heeger-Hubbard (SSHH) model, the variant incorporating next-nearest neighbour hopping remains largely unexplored. Here, we investigate the ground-state properties of this extended SSHH model using the constrained-path auxiliary-field quantum Monte Carlo (CP-AFQMC) method. We show that this model exhibits rich topological phases, characterized by robust edge states against interaction. We quantify the properties of these edge states by analyzing spin correlation and second-order Rényi entanglement entropy. The system exhibits long-range spin correlation and near-zero Rényi entropy at half-filling. Besides, there is a long-range anti-ferromagnetic order at quarter-filling. Interestingly, an external magnetic field disrupts this long-range anti-ferromagnetic order, restoring long-range spin correlation and near-zero Rényi entropy. Furthermore, our work provides a paradigm studying topological properties in large interacting systems via the CP-AFQMC algorithm.
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Submitted 19 June, 2024; v1 submitted 16 May, 2024;
originally announced May 2024.
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Single-photon phase spectrum recovery from the Hong-Ou-Mandel dip
Authors:
Yuhang Lei,
Wen Zhao,
Liang Cui,
Xiaoying Li
Abstract:
Characterizing the temporal-spectral profile of single photons is essential for quantum information protocol utilizing temporal mode for encoding. Based on the phase retrieval algorithm, we present a method to reconstruct the phase spectrum difference between two wave packets from their Hong-Ou-Mandel dip, and intensity spectra. Our confirmatory experiment with weak coherent wave packets demonstra…
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Characterizing the temporal-spectral profile of single photons is essential for quantum information protocol utilizing temporal mode for encoding. Based on the phase retrieval algorithm, we present a method to reconstruct the phase spectrum difference between two wave packets from their Hong-Ou-Mandel dip, and intensity spectra. Our confirmatory experiment with weak coherent wave packets demonstrated the accuracy of the reconstructed phase spectrum difference to within plus or minus 0.1 rad. This method is generalizable to the measurement of unknown single-photon wave packets with the aid of a reference wave packet, requiring only the collection of one-dimensional data, which simplifies and expedites the process.
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Submitted 14 August, 2024; v1 submitted 16 May, 2024;
originally announced May 2024.
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One-Way Quantum Repeater with Rare-Earth-Ions Doped in Solids
Authors:
Yisheng Lei
Abstract:
Quantum repeaters are proposed to overcome exponential photon loss over distance in fibers. One-way quantum repeaters eliminate the need for two-way classical communications, which can potentially outperform quantum memory based quantum repeaters. I propose that rare-earth-ions doped in solids and coupled with nano-cavity can be used to generate photonic cluster state efficiently, which serve as g…
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Quantum repeaters are proposed to overcome exponential photon loss over distance in fibers. One-way quantum repeaters eliminate the need for two-way classical communications, which can potentially outperform quantum memory based quantum repeaters. I propose that rare-earth-ions doped in solids and coupled with nano-cavity can be used to generate photonic cluster state efficiently, which serve as good platforms for one-way quantum repeater nodes. In addition, I propose a multiplexed scheme of photonic tree cluster state generation with multiple quantum emitters. With less than 100 quantum emitters, secret key rates can reach the order of MHz over a few thousand kilometers. This proposal is especially useful for generating large scale photonic cluster state, which is essential for correcting operational errors during processing in quantum repeater nodes.
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Submitted 13 April, 2024;
originally announced April 2024.
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Machine-Learning-Enhanced Quantum Optical Storage in Solids
Authors:
Yisheng Lei,
Haechan An,
Zongfeng Li,
Mahdi Hosseini
Abstract:
Quantum memory devices with high storage efficiency and bandwidth are essential elements for future quantum networks. Solid-state quantum memories can provide broadband storage, but they primarily suffer from low storage efficiency. We use passive optimization and machine learning techniques to demonstrate nearly a 6-fold enhancement in quantum memory efficiency. In this regime, we demonstrate coh…
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Quantum memory devices with high storage efficiency and bandwidth are essential elements for future quantum networks. Solid-state quantum memories can provide broadband storage, but they primarily suffer from low storage efficiency. We use passive optimization and machine learning techniques to demonstrate nearly a 6-fold enhancement in quantum memory efficiency. In this regime, we demonstrate coherent and single-photon-level storage with a high signal-to-noise ratio. The optimization technique presented here can be applied to most solid-state quantum memories to significantly improve the storage efficiency without compromising the memory bandwidth.
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Submitted 5 April, 2024;
originally announced April 2024.
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Recovery of phase constant from two-photon interference pattern by phase retrieval algorithm
Authors:
Yuhang Lei,
Wen Zhao,
Liang cui,
Xiaoyin Li
Abstract:
For a HOM interferometer with two independent incident pulses, the interference pattern can be affected by adding a dispersion medium on one of the incident directions, but there hasn't been a method to reconstruct the phase constant of the medium from the interference pattern. To solve it, we adapted two phase retrieval algorithms and used them to recover the phase difference function between the…
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For a HOM interferometer with two independent incident pulses, the interference pattern can be affected by adding a dispersion medium on one of the incident directions, but there hasn't been a method to reconstruct the phase constant of the medium from the interference pattern. To solve it, we adapted two phase retrieval algorithms and used them to recover the phase difference function between the two incident fields, from which the phase constant can be derived. Through simulations, we verified the convergence, accuracy, and robustness of the algorithms, indicating that this phase recovery process can be completed well with negligible error. Our research finds a new application direction for the phase recovery algorithm, provides an algorithmic tool for high-order dispersion measurement using two-photon interference, and paves the way for a higher resolution and phase-sensitive quantum tomography.
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Submitted 14 October, 2023; v1 submitted 11 October, 2023;
originally announced October 2023.
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Quantum Optical Memory for Entanglement Distribution
Authors:
Yisheng Lei,
Faezeh Kimiaee Asadi,
Tian Zhong,
Alexander Kuzmich,
Christoph Simon,
Mahdi Hosseini
Abstract:
Optical photons are powerful carriers of quantum information, which can be delivered in free space by satellites or in fibers on the ground over long distances. Entanglement of quantum states over long distances can empower quantum computing, quantum communications, and quantum sensing. Quantum optical memories can effectively store and manipulate quantum states, which makes them indispensable ele…
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Optical photons are powerful carriers of quantum information, which can be delivered in free space by satellites or in fibers on the ground over long distances. Entanglement of quantum states over long distances can empower quantum computing, quantum communications, and quantum sensing. Quantum optical memories can effectively store and manipulate quantum states, which makes them indispensable elements in future long-distance quantum networks. Over the past two decades, quantum optical memories with high fidelity, high efficiencies, long storage times, and promising multiplexing capabilities have been developed, especially at the single photon level. In this review, we introduce the working principles of commonly used quantum memory protocols and summarize the recent advances in quantum memory demonstrations. We also offer a vision for future quantum optical memory devices that may enable entanglement distribution over long distances.
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Submitted 18 April, 2023;
originally announced April 2023.
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Superradiant phase transition with cavity assisted dynamical spin-orbit coupling
Authors:
Ying Lei,
Shaoliang Zhang
Abstract:
Superradiant phase transition represents an important quantum phenomenon that shows the collective excitations based on the coupling between atoms and cavity modes. The spin-orbit coupling is another quantum effect which induced from the interaction of the atom internal degrees of freedom and momentum of center-of-mass. In this work, we consider the cavity assisted dynamical spin-orbit coupling wh…
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Superradiant phase transition represents an important quantum phenomenon that shows the collective excitations based on the coupling between atoms and cavity modes. The spin-orbit coupling is another quantum effect which induced from the interaction of the atom internal degrees of freedom and momentum of center-of-mass. In this work, we consider the cavity assisted dynamical spin-orbit coupling which comes from the combination of these two effects. It can induce a series of interesting quantum phenomena, such as the flat spectrum and the singularity of the excitation energy spectrum around the critical point of quantum phase transition. We further discuss the influence of atom decay and nonlinear coupling to the phase diagram. The atom decay suppresses the singularity of the phase diagram and the nonlinear coupling can break the symmetric properties of the phase transition. Our work provide the theoretical methods to research the rich quantum phenomena in this dynamic many-body systems.
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Submitted 18 December, 2020;
originally announced December 2020.
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Tensor network and ($p$-adic) AdS/CFT
Authors:
Arpan Bhattacharyya,
Ling-Yan Hung,
Yang Lei,
Wei Li
Abstract:
We use the tensor network living on the Bruhat-Tits tree to give a concrete realization of the recently proposed $p$-adic AdS/CFT correspondence (a holographic duality based on the $p$-adic number field $\mathbb{Q}_p$). Instead of assuming the $p$-adic AdS/CFT correspondence, we show how important features of AdS/CFT such as the bulk operator reconstruction and the holographic computation of bound…
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We use the tensor network living on the Bruhat-Tits tree to give a concrete realization of the recently proposed $p$-adic AdS/CFT correspondence (a holographic duality based on the $p$-adic number field $\mathbb{Q}_p$). Instead of assuming the $p$-adic AdS/CFT correspondence, we show how important features of AdS/CFT such as the bulk operator reconstruction and the holographic computation of boundary correlators are automatically implemented in this tensor network.
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Submitted 25 January, 2018; v1 submitted 15 March, 2017;
originally announced March 2017.
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Quantum correlations in bulk properties of solids obtained from neutron scattering
Authors:
Ben-Qiong Liu,
Lian-Ao Wu,
Guo-Mo Zeng,
Jian-Ming Song,
Wei Luo,
Yang Lei,
Guang-Ai Sun,
Bo Chen,
Shu-Ming Peng
Abstract:
We demonstrate that inelastic neutron scattering technique can be used to indirectly detect and measure the macroscopic quantum correlations quantified by both entanglement and discord in a quantum magnetic material, VODPO4 . 1D2O. The amount of quantum correlations is obtained 2 by analyzing the neutron scattering data of magnetic excitations in isolated V4+ spin dimers. Our quantitative analysis…
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We demonstrate that inelastic neutron scattering technique can be used to indirectly detect and measure the macroscopic quantum correlations quantified by both entanglement and discord in a quantum magnetic material, VODPO4 . 1D2O. The amount of quantum correlations is obtained 2 by analyzing the neutron scattering data of magnetic excitations in isolated V4+ spin dimers. Our quantitative analysis shows that the critical temperature of this material can reach as high as Tc = 82.5 K, where quantum entanglement drops to zero. Significantly, quantum discord can even survive at Tc = 300 K and may be used in room temperature quantum devices. Taking into account the spin-orbit (SO) coupling, we also predict theoretically that entanglement can be significantly enhanced and the critical temperature Tc increases with the strength of spin-orbit coupling.
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Submitted 2 July, 2014;
originally announced July 2014.
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CSCO Criterion for Entanglement and Heisenberg Uncertainty Principle
Authors:
Jinyan Zeng,
Yian Lei,
S. Y. Pei,
X. C. Zeng
Abstract:
We show that quantum entanglement and the Heisenberg uncertainty principle are inextricably connected. Toward this end, a complete set of commuting observables (CSCO) criterion for the entanglement is developed. Assuming (A1,A2,...) and (B1,B2,...) being two CSCO's for a given system, and C being the matrix, Cij = i [Bi,Aj], for each given row i (i=1,2,...) if at least one matrix element Cij (j=1,…
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We show that quantum entanglement and the Heisenberg uncertainty principle are inextricably connected. Toward this end, a complete set of commuting observables (CSCO) criterion for the entanglement is developed. Assuming (A1,A2,...) and (B1,B2,...) being two CSCO's for a given system, and C being the matrix, Cij = i [Bi,Aj], for each given row i (i=1,2,...) if at least one matrix element Cij (j=1,2,...) is nonzero, then for the simultaneous eigenstates |ψ)=|A1',A2',...) of (A1,A2,...), the simultaneous measurements of (B1,B2,...) are, in general,entangled. The only exception is when all the simultaneous eigenstates |ψ)= A1', A2',...), (ψ|C|ψ)=0. This CSCO criterion may be considered as an extension of the Heisenberg uncertainty principle to quantum systems with either two (or more) particles or multi-degrees of freedom (MDF).
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Submitted 14 June, 2013;
originally announced June 2013.
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Quantum query complexity of graph connectivity
Authors:
Christoph Durr,
Mehdi Mhalla,
Yaohui Lei
Abstract:
Harry Buhrman et al gave an Omega(sqrt n) lower bound for monotone graph properties in the adjacency matrix query model. Their proof is based on the polynomial method. However for some properties stronger lower bounds exist. We give an Omega(n^{3/2}) bound for Graph Connectivity using Andris Ambainis' method, and an O(n^{3/2} log n) upper bound based on Grover's search algorithm. In addition we…
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Harry Buhrman et al gave an Omega(sqrt n) lower bound for monotone graph properties in the adjacency matrix query model. Their proof is based on the polynomial method. However for some properties stronger lower bounds exist. We give an Omega(n^{3/2}) bound for Graph Connectivity using Andris Ambainis' method, and an O(n^{3/2} log n) upper bound based on Grover's search algorithm. In addition we study the adjacency list query model, where we have almost matching lower and upper bounds for Strong Connectivity of directed graphs.
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Submitted 5 April, 2003; v1 submitted 27 March, 2003;
originally announced March 2003.