  Deconfined quantum critical point was proposed as a second-order quantum
phase transition between two broken symmetry phases beyond the
Landau-Ginzburg-Wilson paradigm. However, numerical studies cannot completely
rule out a weakly first-order transition because of strong violations of
finite-size scaling. We demonstrate that the fidelity is a simple probe to
study deconfined quantum critical point. We study the ground-state fidelity
susceptibility close to the deconfined quantum critical point in a spin chain
using the large-scale finite-size density matrix renormalization group method.
We find that the finite-size scaling of the fidelity susceptibility obeys the
conventional scaling behavior for continuous phase transitions, supporting the
deconfined quantum phase transition is continuous. We numerically determine the
deconfined quantum critical point and the associated correlation length
critical exponent from the finite-size scaling theory of the fidelity
susceptibility. Our results are consistent with recent results obtained
directly from the matrix product states for infinite-size lattices using others
observables. Our work provides a useful probe to study critical behaviors at
deconfined quantum critical point from the concept of quantum information.

Strongly Correlated Electrons