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Volume 595 Issue 7867, 15 July 2021

Quantum motion

The cover shows a glass nanoparticle 150 nanometres in diameter levitating above a microscope objective that forms an optical trap. In this week’s issue, Lorenzo Magrini and his colleagues demonstrate that such a trapped nanoparticle can be cooled from room temperature to near its quantum ground state using measurement-based quantum control. With the nanoparticle held in the trap, the researchers capture light scattered from the particle, which enables them to measure its position continuously while minimizing any measurement-based effects that could disturb the nanosphere. The determined trajectory of the particle is then fed back to the control system, an electric field, adjusting it in real-time in order to lower the particle’s energy, thereby cooling it. In a similar experiment, Lukas Novotny and co-workers achieved the cooling effect using a cryogenic and ultrahigh-vacuum set-up. Both papers could help pave the way to quantum control of macroscopic objects.

Cover image: Lorenzo Magrini/Aspelmeyer Group/Univ. Vienna

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