Dephasing-assisted entanglement in a system of strongly coupled qubits

TL;DR

This paper shows that in strongly coupled qubits, high dephasing can surprisingly help create long-lived entangled states, challenging the usual view that dephasing destroys entanglement.

Contribution

It demonstrates that dephasing reservoirs can facilitate the formation of long-lived entangled states in strongly coupled qubits, a novel insight in quantum decoherence.

Findings

Long-lived mixed entangled states with nonzero concurrence are possible.

The lifetime of these states increases exponentially with the ratio of coupling strength to temperature.

High dephasing rates, combined with strong coupling, enhance entanglement longevity.

Abstract

Creation of entangled states of quantum systems with low decoherence rates is a cornerstone in practical implementation of quantum computations. Processes of separate dephasing in each qubit in experimentally feasible systems is commonly accepted to destroy entanglement. In this work, we consider a system of two strongly coupled qubits that interact with dephasing reservoirs. We demonstrate that interaction with dephasing reservoirs can contribute to the formation of a long-lived mixed entangled state with nonzero concurrence. The weight of the subradiant state in this mixed state tends toward unity if the dephasing rate is much larger than the radiative rate and less than the coupling constant between qubits. The lifetime of this state is proportional to the exponent of the ratio of the coupling constant to environmental temperature and can be, by orders of magnitude, larger than the system's characteristic dephasing and dissipation times. Therefore, high dephasing, along with strong coupling, contributes to the creation of an entangled state with a long lifetime. This result paves the way for creation of long-lived entangled states.