Witnessing quantum correlations in a nuclear ensemble via an electron spin qubit

Abstract

A coherent ensemble of spins interfaced with a proxy qubit is an attractive platform to create many-body coherences and probe the regime of collective excitations. An electron spin qubit in a semiconductor quantum dot can act as such an interface to the dense nuclear spin ensemble within the quantum dot consisting of multiple high-spin atomic species. Earlier work has shown that the electron can relay properties of its nuclear environment through the statistics of its mean-field interaction with the total nuclear polarisation, namely its mean and variance. Here, we demonstrate a method to probe the spin state of a nuclear ensemble that exploits its response to collective spin excitations, enabling a species-selective reconstruction beyond the mean field. For the accessible range of optically prepared mean fields, the reconstructed populations indicate that the ensemble is in a non-thermal, correlated nuclear state. The sum over reconstructed species-resolved polarisations exceeds the classical prediction threefold. This stark deviation follows from a spin ensemble that contains inter-particle coherences, and serves as an entanglement witness that confirms the formation of a dark many-body state.

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• Simultaneous measurements of nuclear spin heat capacity, temperature and relaxation in GaAs microstructures
• A many-body singlet prepared by a central spin qubit
• Time-crystalline behavior in central-spin models with Heisenberg interactions
• Wavelet-resolved coherence beats in the Overhauser field of a thermal nuclear spin ensemble
• Laser Cooling of Nuclear Magnons
• Two-photon Interface of Nuclear Spins Based on the Opto-Nuclear Quadrupolar Effect
• Suppression of Pulsed Dynamic Nuclear Polarization by Many-Body Spin Dynamics
• The formation of a nuclear-spin dark state in silicon
• Proximal quantum control of spin and spin ensemble with highly localized control field from skyrmions
• Slowly generated anomalously large nuclear field in bulk n-AlGaAs
• Dynamical nuclear spin polarization in a quantum dot with an electron spin driven by electric dipole spin resonance
• Quantifying electron-nuclear spin entanglement dynamics in central-spin systems using one-tangles
• Nuclear spin polaron-formation: anisotropy effects and quantum phase transition