Many-body singlets by dynamic spin polarization

TL;DR

This paper demonstrates a method to generate many-body singlet states in spin ensembles via dynamic spin polarization, reducing entanglement variance and unentangled spins, with implications for quantum information and noise reduction.

Contribution

It introduces a novel approach to produce many-body singlets in spin ensembles using collective spin operators, applicable to nuclear spins via dynamic nuclear polarization.

Findings

Achieved reduction of collective spin variance to O(1)

Occupied many-body singlets with ~20% population independent of ensemble size

Enhanced quantum information resources and reduced environmental noise

Abstract

We show that dynamic spin polarization by collective raising and lowering operators can drive a spin ensemble from arbitrary initial state to many-body singlets, the zero-collective-spin states with large scale entanglement. For an ensemble of $N$ arbitrary spins, both the variance of the collective spin and the number of unentangled spins can be reduced to O(1) (versus the typical value of O(N)), and many-body singlets can be occupied with a population of $\sim 20 %$ independent of the ensemble size. We implement this approach in a mesoscopic ensemble of nuclear spins through dynamic nuclear spin polarization by an electron. The result is of two-fold significance for spin quantum technology: (1) a resource of entanglement for nuclear spin based quantum information processing; (2) a cleaner surrounding and less quantum noise for the electron spin as the environmental spin moments are effectively annihilated.