August 18, 2022

New boost in quantum technologies

New boost in quantum technologies Quantum bit in a two-dimensional layer consisting of the elements boron and nitrogen. Credit: University of Stuttgart

Researchers at the University of Stuttgart were able to detect qubits in two-dimensional materials for the first time. 

Quantum computers or quantum sensors consist of materials that are completely different to their classical predecessors. These materials are faced with the challenge of combining contradicting properties that quantum technologies entail, as for example good accessibility of qubits with maximum shielding from environmental influences. In this regard, so-called two-dimensional materials, which only consist of a single layer of atoms, are particularly promising.

The team succeeded in identifying promising quantum bits in these materials. They were able to show that the qubits can be generated, read out and coherently controlled in a very robust manner.

As a matter of fact, a plethora of single-photon emitters have been identified in the atomic layers of two-dimensional van der Waals materials. The team has reported on a set of isolated optical emitters embedded in hexagonal boron nitride that exhibit optically detected magnetic resonance. The defect spins showed an isotropic ge-factor of ~2 and zero-field splitting below 10 MHz. The photokinetics of one type of defect is compatible with ground-state electron-spin paramagnetism. The narrow and inhomogeneously broadened magnetic resonance spectrum differs significantly from the known spectra of in-plane defects.

They determined a hyperfine coupling of ~10 MHz. Its angular dependence indicates an unpaired, out-of-plane delocalized π-orbital electron, probably originating from substitutional impurity atoms. They extracted spin–lattice relaxation times T1 of 13–17 μs with estimated spin coherence times T2 of less than 1 μs.

These results provide further insight into the structure, composition and dynamics of single optically active spin defects in hexagonal boron nitride.

The paper has been published in Nature Materials.