271 research outputs found
Quantum-circuit algorithms for many-body topological invariant and Majorana zero mode
The topological state of matter is a potential resource to realize long-term
fault-tolerant quantum computers beyond the near-term noisy intermediate-scale
quantum devices. To achieve the realization, we need a deep understanding of
topological behaviors in real quantum computers. However, quantum-circuit
algorithms to analyze topological properties have still been insufficient. Here
we propose three quantum-circuit algorithms, (i) to find the ground state in
the selected parity subspace, (ii) to determine the many-body topological
invariant, and (iii) to visualize the zero-energy edge mode. To demonstrate
these algorithms, we adopt the interacting Kitaev chain as a typical model of
many-body topological superconductors in one dimension. The algorithms are
applicable to not only one-dimensional topological superconductors but other
topological states including higher-dimensional systems.Comment: 11 pages, 7 figure
Spin-Spin Correlation Enhanced by Impurities in a Frustrated Two-leg Spin Ladder
We theoretically study a spin-spin correlation enhanced by non-magnetic
impurities in a frustrated two-leg spin ladder. The frustration is introduced
by the next-nearest-neighbor antiferromagnetic interaction in the leg direction
in the antiferromagnetic two-leg spin ladder. The spin-spin correlation
function around impurity site is calculated by the density-matrix
renormalization-group method. We find that the spin-spin correlation is
enhanced around impurity site with the wavenumber reflecting the frustration.
As increasing the frustration, the wavenumber is shifted from commensurate to
incommensurate. We discuss several experimental results on BiCu2PO6 in the
light of our theory.Comment: 5 pages, 4 figure
Quasi-Spin Correlations in a Frustrated Quantum Spin Ladder
The quasi-spin correlations in a frustrated quantum spin ladder with one-half
magnetization are theoretically studied by using the density-matrix
renormalization-group method and the quasi-spin transformation. In this model,
the frustration induces a gapless-to-gapful phase transition with a strong rung
coupling. The gapful state is observed as the one-half magnetization plateau in
the magnetization curve. In the magnetization-plateau state, we find that the
quasi-spin dimer has a large expectation value with long-ranged correlations.
This result does not only comes in useful to clarify the magnetization-plateau
state, but gives a crucial information to understand the magnetization curve of
the real compound BiCuPO, whose effective spin model corresponds to
ours.Comment: 7 pages, 2 figure
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