He Sun - Centre for Quantum Computer Technology and Department of Physics, The University of Queensland, Brisbane, Australia

He Sun
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Name
He Sun
Affiliation
Centre for Quantum Computer Technology and Department of Physics, The University of Queensland, Brisbane, Australia
City
Saint Lucia
Country
Australia

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Computer Science - Data Structures and Algorithms (11)
 
Quantum Physics (6)
 
Computer Science - Learning (4)
 
Physics - Mesoscopic Systems and Quantum Hall Effect (4)
 
Computer Science - Discrete Mathematics (4)
 
Mathematics - Probability (4)
 
Mathematics - Combinatorics (3)
 
Computer Science - Distributed; Parallel; and Cluster Computing (3)
 
Mathematics - Differential Geometry (2)
 
Mathematics - Information Theory (1)
 
Mathematical Physics (1)
 
Computer Science - Information Theory (1)
 
Nuclear Theory (1)
 
Computer Science - Computational Engineering; Finance; and Science (1)
 
Mathematics - Spectral Theory (1)
 
Mathematics - Mathematical Physics (1)
 
Computer Science - Computer Science and Game Theory (1)
 
Computer Science - Computational Geometry (1)
 
Computer Science - Computational Complexity (1)

Publications Authored By He Sun

For any undirected and weighted graph $G=(V,E,w)$ with $n$ vertices and $m$ edges, we call a sparse subgraph $H$ of $G$, with proper reweighting of the edges, a $(1+\varepsilon)$-spectral sparsifier if \[ (1-\varepsilon)x^{\intercal}L_Gx\leq x^{\intercal} L_{H} x\leq (1+\varepsilon) x^{\intercal} L_Gx \] holds for any $x\in\mathbb{R}^n$, where $L_G$ and $L_{H}$ are the respective Laplacian matrices of $G$ and $H$. Noticing that $\Omega(m)$ time is needed for any algorithm to construct a spectral sparsifier and a spectral sparsifier of $G$ requires $\Omega(n)$ edges, a natural question is to investigate, for any constant $\varepsilon$, if a $(1+\varepsilon)$-spectral sparsifier of $G$ with $O(n)$ edges can be constructed in $\tilde{O}(m)$ time, where the $\tilde{O}$ notation suppresses polylogarithmic factors. All previous constructions on spectral sparsification require either super-linear number of edges or $m^{1+\Omega(1)}$ time. Read More

Clustering large datasets is a fundamental problem with a number of applications in machine learning. Data is often collected on different sites and clustering needs to be performed in a distributed manner with low communication. We would like the quality of the clustering in the distributed setting to match that in the centralized setting for which all the data resides on a single site. Read More

Graph clustering is a fundamental problem with a number of applications in algorithm design, machine learning, data mining, and analysis of social networks. Over the past decades, researchers have proposed a number of algorithmic design methods for graph clustering. However, most of these methods are based on complicated spectral techniques or convex optimization, and cannot be applied directly for clustering most real-world networks, whose information is often collected on different sites. Read More

We present the first almost-linear time algorithm for constructing linear-sized spectral sparsification for graphs. This improves all previous constructions of linear-sized spectral sparsification, which requires $\Omega(n^2)$ time. A key ingredient in our algorithm is a novel combination of two techniques used in literature for constructing spectral sparsification: Random sampling by effective resistance, and adaptive constructions based on barrier functions. Read More

In this paper we study variants of the widely used spectral clustering that partitions a graph into k clusters by (1) embedding the vertices of a graph into a low-dimensional space using the bottom eigenvectors of the Laplacian matrix, and (2) grouping the embedded points into k clusters via k-means algorithms. We show that, for a wide class of graphs, spectral clustering gives a good approximation of the optimal clustering. While this approach was proposed in the early 1990s and has comprehensive applications, prior to our work similar results were known only for graphs generated from stochastic models. Read More

In this paper, we establish some lower bounds for the sums of eigenvalues of the polyharmonic operator and higher order Stokes operator, which are sharper than the recent results in \cite{CSWZ13, I13}. At the same time, we obtain some certain bounds for the sums of positive and negative powers of eigenvalues of the polyharmonic operator. Read More

We study gossip algorithms for the rumor spreading problem which asks one node to deliver a rumor to all nodes in an unknown network. We present the first protocol for any expander graph $G$ with $n$ nodes such that, the protocol informs every node in $O(\log n)$ rounds with high probability, and uses $\tilde{O}(\log n)$ random bits in total. The runtime of our protocol is tight, and the randomness requirement of $\tilde{O}(\log n)$ random bits almost matches the lower bound of $\Omega(\log n)$ random bits for dense graphs. Read More

We study a natural process for allocating m balls into n bins that are organized as the vertices of an undirected graph G. Balls arrive one at a time. When a ball arrives, it first chooses a vertex u in G uniformly at random. Read More

We present the first streaming algorithm for counting an arbitrary hypergraph $H$ of constant size in a massive hypergraph $G$. Our algorithm can handle both edge-insertions and edge-deletions, and is applicable for the distributed setting. Moreover, our approach provides the first family of graph polynomials for the hypergraph counting problem. Read More

We study the classical rumor spreading problem, which is used to spread information in an unknown network with $n$ nodes. We present the first protocol for any expander graph $G$ with $n$ nodes and minimum degree $\Theta(n)$ such that, the protocol informs every node in $O(\log n)$ rounds with high probability, and uses $O(\log n\log\log n)$ random bits in total. The runtime of our protocol is tight, and the randomness requirement of $O(\log n\log\log n)$ random bits almost matches the lower bound of $\Omega(\log n)$ random bits. Read More

We propose a natural process for allocating n balls into n bins that are organized as the vertices of an undirected graph G. Each ball first chooses a vertex u in G uniformly at random. Then the ball performs a local search in G starting from u until it reaches a vertex with local minimum load, where the ball is finally placed on. Read More

Consider the following toy problem. There are $m$ rectangles and $n$ points on the plane. Each rectangle $R$ is a consumer with budget $B_R$, who is interested in purchasing the cheapest item (point) inside R, given that she has enough budget. Read More

We consider the problem of balancing load items (tokens) in networks. Starting with an arbitrary load distribution, we allow nodes to exchange tokens with their neighbors in each round. The goal is to achieve a distribution where all nodes have nearly the same number of tokens. Read More

In this paper, we investigate eigenvalues of Laplacian on a bounded domain in an $n$-dimensional Euclidean space and obtain a sharper lower bound for the sum of its eigenvalues, which gives an improvement of results due to A. D. Melas [15]. Read More

In this paper, we investigate the Dirchlet eigenvalue problems of poly-Laplacian with any order and quadratic polynomial operator of the Laplacian. We give some estimates for lower bounds of the sums of their first $k$ eigenvalues which improve the previous results. Read More

We consider charge-qubit monitoring (continuous-in-time weak measurement) by a single-electron transistor (SET) operating in the sequential-tunneling regime. We show that commonly used master equations for this regime are not of the Lindblad form that is necessary and sufficient for guaranteeing valid physical states. In this paper we derive a Lindblad-form master equation and a corresponding quantum trajectory model for continuous measurement of the charge qubit by a SET. Read More

We present a new model for the continuous measurement of a coupled quantum dot charge qubit. We model the effects of a realistic measurement, namely adding noise to, and filtering, the current through the detector. This is achieved by embedding the detector in an equivalent circuit for measurement. Read More

We investigate the emission of multimodal polarized light from Light Emitting Devices due to spin-aligned carriers injection. The results are derived through operator Langevin equations, which include thermal and carrier-injection fluctuations, as well as non-radiative recombination and electronic g-factor temperature dependence. We study the dynamics of the optoelectronic processes and show how the temperature-dependent g-factor and magnetic field affect the polarization degree of the emitted light. Read More

2000Jun
Affiliations: 1Centre for Quantum Computer Technology and Department of Physics, The University of Queensland, Brisbane, Australia, 2Centre for Quantum Computer Technology and Department of Physics, The University of Queensland, Brisbane, Australia, 3School of Science, Griffith University, Nathan, Brisbane, Australia, 4Centre for Quantum Computer Technology and Department of Physics, The University of Queensland, Brisbane, Australia

We obtain the finite-temperature unconditional master equation of the density matrix for two coupled quantum dots (CQD) when one dot is subjected to a measurement of its electron occupation number using a point contact (PC). To determine how the CQD system state depends on the actual current through the PC device, we use the so-called quantum trajectory method to derive the zero-temperature conditional master equation. We first treat the electron tunneling through the PC barrier as a classical stochastic point process (a quantum-jump model). Read More

We describe the conditional and unconditional dynamics of two coupled quantum dots when one dot is subjected to a measurement of its occupation number using a single electron transistor (SET). The measurement is made when the bare tunneling rate though the SET is changed by the occupation number of one of the dots. We show that there is a difference between the time scale for the measurement-induced decoherence between the localized states of the dots and the time scale on which the system becomes localized due to the measurement. Read More

1999Dec
Affiliations: 1Nanjing U., 2Nanjing U., 3Nanjing U.
Category: Nuclear Theory

$d^*$ dibaryon study is a critical test of hadron interaction models. The electro production cross sections of $ed\to ed^*$ have been calculated based on the meson exchange current model and the cross section around 30 degree of 1 GeV electron in the laboratory frame is about 10 nb. The implication of this result for the $d^*$ dibaryon search has been discussed. Read More

We present a method for measuring single spins embedded in a solid by probing two electron systems with a single electron transistor (SET). Restrictions imposed by the Pauli Principle on allowed two electron states mean that the spin state of such systems has a profound impact on the orbital states (positions) of the electrons, a parameter which SET's are extremely well suited to measure. We focus on a particular system capable of being fabricated with current technology: a Te double donor in Si adjacent to a Si/SiO2 interface and lying directly beneath the SET island electrode, and we outline a measurement strategy capable of resolving single electron and nuclear spins in this system. Read More