Realizing quantum speed limit in open system with a PT-symmetric trapped-ion qubit

TL;DR

This paper experimentally demonstrates that in a PT-symmetric non-Hermitian quantum system, the evolution time of a qubit can be significantly reduced by tuning dissipation, effectively tightening the quantum speed limit and enabling faster quantum operations.

Contribution

The study confirms experimentally that dissipation in PT-symmetric systems can control and accelerate qubit evolution times, surpassing Hermitian limits.

Findings

Evolution time decreases with increased dissipation in PT-symmetric qubits.

Reversal operation time increases with dissipation.

Tighter quantum speed limit bounds are achieved in non-Hermitian systems.

Abstract

Evolution time of a qubit under a Hamiltonian operation is one of the key issues in quantum control, quantum information processing and quantum computing. It has a lower bound in Hermitian system, which is limited by the coupling between two states of the qubit, while it is proposed that in a non-Hermitian system it can be made much smaller without violating the time-energy uncertainty principle. Here we have experimentally confirmed the proposal in a single dissipative qubit system and demonstrate that the evolution time of a qubit from an initial state to an arbitrary state can be controlled by tuning the dissipation intensity in a non-Hermitian Parity-Time-Symmetric ($\mathcal{P T}$-symmetric) quantum system. It decreases with increasing dissipation intensity and also gives a tighter bound for quantum speed limit (QSL). We also find that the evolution time of its reversal operation increases with the increasing dissipation intensity. These findings give us a well-controlled knob for speeding up the qubit operation, and pave the way towards fast and practical quantum computation, opening the door for solving sophisticated problems with only a few qubits.