Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Symmetry-adapted variational quantum eigensolver   We propose a scheme to restore spatial symmetry of Hamiltonian in the
variational-quantum-eigensolver (VQE) algorithm for which the quantum circuit
structures used usually break the Hamiltonian symmetry. The symmetry-adapted
VQE scheme introduced here simply applies the projection operator, which is
Hermitian but not unitary, to restore the spatial symmetry in a desired
irreducible representation of the spatial group. The entanglement of a quantum
state is still represented in a quantum circuit but the nonunitarity of the
projection operator is treated classically as postprocessing in the VQE
framework. By numerical simulations for a spin-$1/2$ Heisenberg model on a
one-dimensional ring, we demonstrate that the symmetry-adapted VQE scheme with
a shallower quantum circuit can achieve significant improvement in terms of the
fidelity of the ground state and has a great advantage in terms of the
ground-state energy with decent accuracy, as compared to the
non-symmetry-adapted VQE scheme. We also demonstrate that the present scheme
can approximate low-lying excited states that can be specified by symmetry
sectors, using the same circuit structure for the ground-state calculation.

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The categories of this paper are: supr-con
16
The categories of this paper are: stat
20
The categories of this paper are: acc-phys
19
The categories of this paper are: eess
32
The categories of this paper are: atom-ph
25
The categories of this paper are: patt-sol
30
The categories of this paper are: q-alg
35
The categories of this paper are: mtrl-th
14
The categories of this paper are: math-ph
23
The categories of this paper are: solv-int
1
The categories of this paper are: cs
5
The categories of this paper are: gr-qc
22
The categories of this paper are: chao-dyn
3
The categories of this paper are: physics
7
The categories of this paper are: hep-th
21
The categories of this paper are: adap-org