Enhanced quantum coherence in exchange coupled spins via singlet-triplet transitions

TL;DR

This paper demonstrates that engineering exchange-coupled spin-1/2 atoms to create a singlet-triplet transition significantly enhances their quantum coherence, reducing decoherence from magnetic noise and tunneling electrons, with implications for quantum information processing.

Contribution

The study introduces a method to engineer magnetic interactions between atomically precise spins to create a clock transition, improving spin coherence times in quantum systems.

Findings

Longer spin coherence times achieved with engineered singlet-triplet states.

Reduced decoherence from magnetic field noise and tunneling electrons.

Demonstration of atomically-precise spin structures for quantum coherence enhancement.

Abstract

Manipulation of spin states at the single-atom scale underlies spin-based quantum information processing and spintronic devices. Such applications require protection of the spin states against quantum decoherence due to interactions with the environment. While a single spin is easily disrupted, a coupled-spin system can resist decoherence by employing a subspace of states that is immune to magnetic field fluctuations. Here, we engineered the magnetic interactions between the electron spins of two spin-1/2 atoms to create a clock transition and thus enhance their spin coherence. To construct and electrically access the desired spin structures, we use atom manipulation combined with electron spin resonance (ESR) in a scanning tunneling microscope (STM). We show that a two-level system composed of a singlet state and a triplet state is insensitive to local and global magnetic field noise, resulting in much longer spin coherence times compared with individual atoms. Moreover, the spin decoherence resulting from the interaction with tunneling electrons is markedly reduced by a homodyne readout of ESR. These results demonstrate that atomically-precise spin structures can be designed and assembled to yield enhanced quantum coherence.