Mesoscopic Spin Systems as Quantum Entanglers

TL;DR

This paper presents a method to entangle two remote spin qubits via an intermediate mesoscopic spin system using indirect measurements, highlighting robustness to imperfections and potential for connecting microscopic and mesoscopic quantum systems.

Contribution

It introduces a novel entanglement scheme utilizing mesoscopic spin systems as quantum entanglers with experimentally feasible control, and establishes the link to micro-macro entanglement.

Findings

Entanglement can be achieved with low-resolution collective measurements.

The scheme is robust against imperfections in MSS preparation.

It provides a new approach for connecting microscopic and mesoscopic spin systems.

Abstract

We quantify the resources required for entangling two uncoupled spin qubits through an intermediate mesoscopic spin system (MSS) by indirect joint measurement. Indirect joint measurement benefits from coherent magnification of the target qubits' state in the collective magnetization of the MSS; such that a low-resolution collective measurement on the MSS suffices to prepare post-selected entanglement on the target qubits. A MSS consisting of two non-interacting halves, each coupled to one of the target qubits is identified as a geometry that allows implementing the magnification process with experimentally available control tools. It is proved that the requirements on the amplified state of the target qubits and the MSS perfectly map to the specifications of micro-macro entanglement between each target qubit and its nearby half of the MSS. In the light of this equivalence, the effects of experimental imperfections are explored; in particular, bipartite entanglement between the target qubits is shown to be robust to imperfect preparation of the MSS. Our study provides a new approach for using an intermediate spin system for connecting separated qubits. It also opens a new path in exploring entanglement between microscopic and mesoscopic spin systems.