For years, scientific journals have been populated with results demonstrating fundamental advances in the control of qubits and the observation of quantum entanglement in a variety of systems, with the prospects of advanced technologies in communication, information, sensing, and more. Fundamental research will certainly continue, but it has now become essential to improve both materials and algorithms to validate the feasibility of quantum technologies. Indeed, funding agencies in the last couple of years have also placed more emphasis on technological developments, as demonstrated by programmes such as the UK National Quantum Technologies Programme (, Dutch Advance Research Centre QuTech ( and the development of centres of excellence such as the Centre for Quantum Computation & Communication Technology in Australia (

In the past few years we have published a number of papers reporting technological advances in quantum systems, and two papers included in this issue follow this trend. On page 242, Andrea Morello and colleagues report a demonstration of Bell's inequality violation for a pair of qubits embedded in silicon. Bell's inequality was introduced by physicist John Stewart Bell during the 1960s. A violation of the inequality by a pair of quantum objects placed far apart from one another is a demonstration of the nonlocal nature of quantum entanglement and of the impossibility of describing such entanglement by classical mechanics. Bell's inequality violation has been demonstrated before, so in this sense the work by Morello and co-workers is not conceptually new. What matters, however, is the degree to which the violation occurs. The amount by which the two qubits (represented by the electron spin and the nuclear spin associated with a single phosphorus donor in silicon) violate Bell's inequality is close to the theoretical limit. The results are, therefore, a direct demonstration that quantum entanglement can be created reliably in silicon solid-state devices, which are the basic components of existing technology.

On page 247, Ronald Hanson and colleagues report the improved magnetic sensing properties of the spin of an electron associated with a nitrogen–vacancy (NV) centre in diamond. The electron spin around an NV centre is protected from environmental magnetic noise and can be used to monitor external magnetic fields. But the sensitivity of these measurements depends on the state of the spin before the measurements take place. Hanson and colleagues applied an adaptive protocol, which uses the results of subsequent measurements to initialize the state of the spin in an iterative way. Once again, the sensing properties of NV centres are known, and so are adaptive protocols. But the results show to what extent the sensitivity can be improved and demonstrate the ability of NV centres to measure fast varying magnetic fields, both important technological achievements.

To be clear, these types of result by themselves do not mean that we are ready for the widespread use of quantum technologies. But they are a testimony of the technological achievements that are essential steps for the realization of realistic technologies. As a journal that aims to report both fundamental and technological advances involving matter at the nanoscale, we cannot but applaud these efforts and will continue to follow them with interest.