# Nanoscale Sensing and Quantum Coherence

## TL;DR

This paper reviews nanoscale solid-state qubits, especially single spins, highlighting their quantum coherence properties, sensing capabilities, and recent advancements like dynamical decoupling, with an outlook on future research directions.

## Contribution

It provides a concise overview of quantum coherence, sensitivity limits, and recent improvements in nanoscale quantum sensing using solid-state qubits.

## Key findings

- Quantum coherence enables high-precision sensing at the nanoscale.
- Dynamical decoupling significantly enhances sensor performance.
- The standard quantum limit defines the sensitivity boundary for single-qubit sensors.

## Abstract

Small solid state qubits, most prominently single spins in solids, can be remarkable sensors for various physical quantities ranging from magnetic fields to temperature. They package the performance of their bulk semiconductor counterparts into a nanoscale device, sometimes as small as a single atom. This review is a minimalist introduction into this concept. It gives a brief summary of quantum coherence, Ramsey spectroscopy and a derivation of the "standard quantum limit" of the sensitivity that a single-qubit sensor can reach. It goes on to discuss the surprising improvement that dynamical decoupling has brought about and concludes with an outlook to the major frontiers of the field.