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Search Results: 1 - 10 of 34587 matches for " Su-Peng Kou "
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Topological Quantum Computation by Manipulating Quantum Tunneling Effect of the Toric Codes
Su-Peng Kou
Physics , 2008,
Abstract: Quantum computers are predicted to utilize quantum states to perform memory and to process tasks far faster than those of conventional classical computers. In this paper we show a new road towards building fault tolerance quantum computer by tuning quantum tunneling effect of the degenerate quantum states in topological order, instead of by braiding anyons. Using a designer Hamiltonian - the Wen-Plaquette model as an example, we study its quantum tunneling effect of the toric codes and show how to control the toric code to realize topological quantum computation (TQC). In particular, we give a proposal to the measurement of TQC. In the end the realization of the Wen-Plaquette model in cold atoms is discussed.
Realization of Topological Quantum Computation with surface codes
Su-Peng Kou
Physics , 2009, DOI: 10.1103/PhysRevA.80.052317
Abstract: In this paper, the degenerate ground states of Z2 topological order on a plane with holes (the so-called surface codes) are used as the protected code subspace to build a topological quantum computer by tuning their quantum tunneling effect. Using a designer Hamiltonian - the Kitaev toric-code model as an example, we study quantum tunneling effects of the surface codes and obtain its effective theory. Finally, we show how to do topological quantum computation including the initialization, the unitary transformation and the measurement.
Spin-charge Separation in Nodal Antiferromagnetic Insulator
Su-Peng Kou
Physics , 2008, DOI: 10.1103/PhysRevB.78.233104
Abstract: In this paper, by using two dimensional (2D) Hubbard models with pi-flux phase and that on a hexagonal lattice as examples, we explore spin-charge-separated solitons in nodal antiferromagnetic (AF) insulator - an AF order with massive Dirac fermionic excitations (see detail in the paper). We calculate fermion zero modes and induced quantum numbers on solitons (half skyrmions) in the continuum limit, which are similar to that in the quasi one-dimensional conductor polyacetylene (CH)x and that in topological band insulator. In particular, we find some novel phenomena : thanks to an induced staggered spin moment, a mobile half skyrmion becomes a fermionic particle; when a hole or an electron is added, the half skyrmion turns into a bosonic particle with charge degree of freedom only. Our results imply that nontrivial induced quantum number on solitons may be a universal feature of spin-charge separation in different systems.

Kou Su-peng,

中国物理 B , 2001,
Topological edge states in spin 1 bilinear-biquadratic model
Peng Li,Su-Peng Kou
Physics , 2012, DOI: 10.1088/0953-8984/24/44/446001
Abstract: The spin 1 bilinear-biquadratic model on square lattice in the region $0<\phi<\pi/4$ is studied in a fermion representation with a p-wave pairing BCS type mean-field theory. Our results show there may exist a non-trivial gapped spin liquid with time-reversal symmetry spontaneously breaking. This exotic state manifests its topological nature by forming chiral states at the edges. To show it more clear, we set up and solved a ribbon system. We got a gapless dispersion representing the edge modes beneath the bulk modes. The edge modes with nonzero longitudinal momentum ($k_{x}\neq0$) convect in opposite directions at the two edges, which leads to a two-fold degeneracy. While the zero longitudinal momentum ($k_{x}=0$) modes turn out to be Majorana fermion states. The edge spin correlation functions are found to decay in a power law with the distance increasing. We also calculated the contribution of the edge modes to the specific heat and obtained a linear law at low temperatures.
Macroscopic Quantum Tunneling Effect of Z2 Topological Order
Jing Yu,Su-Peng Kou
Physics , 2009, DOI: 10.1103/PhysRevB.80.075107
Abstract: In this paper, macroscopic quantum tunneling (MQT) effect of Z2 topological order in the Wen-Plaquette model is studied. This kind of MQT is characterized by quantum tunneling processes of different virtual quasi-particles moving around a torus. By a high-order degenerate perturbation approach, the effective pseudo-spin models of the degenerate ground states are obtained. From these models, we get the energy splitting of the ground states, of which the results are consistent with those from exact diagonalization method
Self-localization of holes in a lightly doped Mott insulator
Su-Peng Kou,Z. Y. Weng
Physics , 2004, DOI: 10.1140/epjb/e2005-00300-7
Abstract: We show that lightly doped holes will be self-trapped in an antiferromagnetic spin background at low-temperatures, resulting in a spontaneous translational symmetry breaking. The underlying Mott physics is responsible for such novel self-localization of charge carriers. Interesting transport and dielectric properties are found as the consequences, including large doping-dependent thermopower and dielectric constant, low-temperature variable-range-hopping resistivity, as well as high-temperature strange-metal-like resistivity, which are consistent with experimental measurements in the high-T$_c$ cuprates. Disorder and impurities only play a minor and assistant role here.
The road from one hole to the stripe phase
Fan Yang,Su-peng Kou
Physics , 2004,
Abstract: In this paper, it is shown how a single stripe and a stripe phase grow from individual holes in low doping regime. In an effective low-energy description of the t-J model, {\em i.e.,} the phase string model, a hole doped into the spin ordered phase will induce a dipolar distortion in the background [Phys. Rev. B{\bf 67}, 115103 (2003)]. We analyze the hole-dipole configurations with lowest energy under a dipole-dipole interaction and show that these holes tend to arrange themselves into a regular polygon. Such a stable polygon configuration will turn into a stripe as the number hole-dipoles becomes thermodynamically large and eventually a uniform stripe state can be formed, which constitutes an energetically competitive phase at low doping. We also briefly discuss the effect of Zn impurities on individual hole-dipoles and stripes.
Anomalous Spin Dynamics of Hubbard Model on Honeycomb Lattices
Gao-Yong Sun,Su-Peng Kou
Physics , 2009, DOI: 10.1088/0953-8984/23/4/045603
Abstract: In this paper, the honeycomb Hubbard model in optical lattices is investigated using O(3) non-linear sigma model. A possible quantum non-magnetic insulator in a narrow parameter region is found near the metal-insulator transition. We study the corresponding dynamics of magnetic properties, and find that the narrow region could be widened by hole doping.
Emergence of Topological Fermi Liquid from a Strongly Correlated Bosonic System in Optical Superlattices
Bo-lun Chen,Su-peng Kou
Physics , 2009,
Abstract: Recent experiments on quantum degenerate gases give an opportunity for simulating strongly-correlated electronic systems in optical lattices. It may shed light on some long-standing puzzles in condensed-matter physics, like the nature of high-temperature superconductivity in cuprates that had baffled people over two decades. It is believed that the two-dimensional fermionic Hubbard model, or t-J model, contains the key to this problem; but the difficulty of unveiling the mystery of a strongly-interacting fermionic system is also generally acknowledged. Here, as a substitute, we systematically analyze the property of bosonic t-J model simulated in optical superlattices near unit-filling. In particular, we show the emergence of a strange topological Fermi liquid with Fermi surfaces from a purely bosonic system. We also discuss the possibility of observing these phenomena in ultracold atom experiments. The result may provide some crucial insights into the origin of high-T_{c} superconductivity.
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