"Quantum technologies have potential of changing in not too distant future the way how our everyday-use devices―such as cars, mobiles or laptops―operate. Apart from more renowned and widely announced benefits of quantum communication or computing, a field that is within a closer reach of the current technologies is quantum sensing, more generally termed as quantum metrology. Its main motivation is to design and harness quantum features of light and matter, in order to be able to perform measurements with unprecedented precisions—limited only by the quantum structure of nature, while simultaneously benefiting from its unique properties such as the phenomenon of entanglement. Quantum-enhanced sensing devices have already been successfully demonstrated in many settings, however, the main obstacle that keeps restricting their performance and impedes their commercialisation is the impact of noise that, unfortunately, is much more efficient in destroying the necessary quantum properties. That is why, in recent years, a huge part of both theoretical and experimental research has been devoted to improving quantum sensing protocols by making them noise-robust and, hence, more implementation friendly.
Within this action novel advanced tools of quantum information theory have been used, in order to achieve such goal in proposing a new generation of quantum metrology schemes. In particular, within the project, noise-robust protocols have been identified in atomic magnetometry, atomic spectroscopy and general settings involving fast control and error-correction operations, all of which have been shown to be capable of beating the standard limits imposed on precision by the noise, and fully benefit from the quantum properties of either light or matter. Moreover, within the theoretical part of the action, even more hope has been shed by demonstrating that the phenomenon of quantum-enhancement in sensing is typical in nature―systems prepared in a random manner at the quantum level should typically allow for the classical precision limits to be broken. Finally, by considering the so-called multi-stage architectures in which, e.g. atoms are utilised as sensors of external fields while being constantly measured with the light, it has been demonstrated by an explicit experiment that, thanks to the sophisticated data inference techniques of classical estimation theory, the noisy output signals can be effectively filtered in real-life implementations, in order to recover the underlying features and track in real time signals encoded ""deep inside"" a given device at the quantum level, despite all the noise appearing ""on the top"".
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