Protecting Two-Qubit Quantum States by $\pi$-Phase Pulses

TL;DR

This paper demonstrates that frequent $$-phase pulses effectively protect two-qubit states from decay and errors caused by a common reservoir, outperforming measurement-based methods.

Contribution

It introduces a dynamical decoupling approach using $$-phase pulses to protect two-qubit states, highlighting differences from quantum Zeno effects at finite operation frequencies.

Findings

$$-phase pulses eliminate both decoherence and amplitude errors.

The method outperforms frequent measurement in preserving two-qubit states.

Dynamical decoupling and quantum Zeno effects differ at finite operation frequencies.

Abstract

We study the state decay of two qubits interacted with a common harmonic oscillator reservoir. There are both decoherence error and the error caused by the amplitude change of the superradiant state. We show that frequent $\pi$-phase pulses can eliminate both typpes of errors therefore protect a two-qubit odd-parity state more effectively than the frequent measurement method. This shows that the the methods using dynamical decoupling and the quantum Zeno effects actually can give rather {\em different} results when the operation frequency is finite.