Abstract
Abstract
Quantum speed limit (QSL), the lower bound of the time for transferring an initial state to a target one, is of fundamental interest in quantum information processing. Despite that the speed limit of a unitary evolution could be well analyzed by either the Mandelstam–Tamm or the Margolus–Levitin bound, there are still many unknowns for the QSL in open systems. A particularly exciting result is about that the evolution time can be made arbitrarily small without violating the time-energy uncertainty principle, whenever the dynamics is governed by a parity-time (
P
T
) symmetric Hamiltonian. Here we study the QSLs with both
P
T
and anti-
P
T
Hamiltonians, and pose the QSL as a brachistochrone problem on a non-Hermitian Bloch sphere. We then use dissipative trapped-ion qubits to construct the Hamiltonians, where the state evolutions reach the QSL governed by a generalized Margolus-Levitin bound of the non-Hermitian system. We find that the evolution time monotonously decreases with the increase of the dissipation strength and exhibits chiral dependence on the Bloch sphere. These results enable a well-controlled knob for speeding up the state manipulation in open quantum systems, which could be used for quantum control and simulation with non-unitary dynamics.
Funder
National Natural Science Foundation of China
Key-Area Research and Development Program of Guangdong Province
Natural Science Foundation of Guangdong Province
Guangdong Province Youth Talent Program
Guangdong Science and Technology Project
Shenzhen Science and Technology Program
Science and Technology Program of Guangzhou
Subject
General Physics and Astronomy