Entanglement and entanglement storage in dipolar coupled diamond defects

Florian Dolde, Ingmar Jakobi, Boris Naydenov +7 more

Chong Zu, Francisco Machado, Bryce Kobrin +5 more

Maarten J. Degen, Suzanne B. van Dam, J. Randall +3 more

Saptarshi Saha, Rangeet Bhattacharyya

Abstract Quantum computation requires efficient long-term storage devices to preserve quantum states. An attractive candidate for such storage devices is qubits connected to a common dissipative environment. The common environment gives rise to persistent entanglements in these qubit systems. Hence these systems act efficiently as a storage device of entanglement. However, the existence of a common environment often requires the physical proximity of the qubits and hence results in direct dipolar coupling between the qubits. In this work, we investigate effects of the secular and the nonsecular part of the dipolar coupling on the environment-induced entanglement using a recently-proposed fluctuation-regulated quantum master equation (Chakrabarti and Bhattacharyya 2018 Phys. Rev. A 97 063837). We show that nonsecular part of the dipolar coupling results in reduced entanglement and hence less efficiency of the storage devices. We also discuss the properties of efficient storage that mitigates the detrimental effects of the dipolar coupling on the stored entanglement.

I Jakobi, S A Momenzadeh, F Fávaro de Oliveira +6 more

Coherently coupled pairs or multimers of nitrogen-vacancy defect electron spins in diamond have many promising applications especially in quantum information processing (QIP) but also in nanoscale sensing applications. Scalable registers of spin qubits are essential to the progress of QIP. Ion implantation is the only known technique able to produce defect pairs close enough to allow spin coupling via dipolar interaction. Although several competing methods have been proposed to increase the resulting resolution of ion implantation, the reliable creation of working registers is still to be demonstrated. The current limitation are residual radiation-induced defects, resulting in degraded qubit performance as trade-off for positioning accuracy. Here we present an optimized estimation of nanomask implantation parameters that are most likely to produce interacting qubits under standard conditions. We apply our findings to a well-established technique, namely masks written in electron-beam lithography, to create coupled defect pairs with a reasonable probability. Furthermore, we investigate the scaling behavior and necessary improvements to efficiently engineer interacting spin architectures.

G. B. Furman, V. Meerovich, Vladimir Sokolovsky