Controlling the movement of objects at the nanoscale holds immense promise for both fundamental science and future technologies, and researchers are increasingly focused on harnessing rotational motion. Stephan Troyer, Florian Fechtel, and Lorenz Hummer, all from the University of Vienna, alongside colleagues including Henning Rudolph from the University of Duisburg-Essen and Benjamin A. Stickler from Ulm University, now demonstrate a significant advance in this field. The team successfully cools the rotational motion, known as libration, of silica nanorotors to their ground state using a combination of optical trapping and coherent scattering within a high-finesse cavity. This achievement allows for precise alignment of the nanorotors, reaching a precision better than 20 radians, and opens new avenues for exploring nonlinear dynamics and building advanced nanoscale devices.
Quantum ground-state cooling of two librational modes of a nanorotor Researchers investigate the quantum ground-state cooling of two librational modes within a nanorotor, employing a carefully designed feedback scheme to manipulate its motion. This approach leverages quantum measurement and feedback to reduce thermal energy, bringing the nanorotor closer to its quantum ground state. The experiment demonstrates cooling to an average occupancy of 0. 78 photons, showcasing precise control over the nanorotor’s quantum state and opening avenues for exploring quantum phenomena in complex mechanical systems. This represents a step towards creating macroscopic quantum superpositions and investigating the boundary between quantum and classical behaviour.
Rotational Nanoresonators and Single Microwave Photons
Researchers are exploring the quantum behaviour of nanoscale objects, specifically rotational motion, using nanomechanical resonators. They aim to achieve strong coupling between the resonator’s rotational mode and a single microwave photon, allowing for the exploration of quantum effects, such as squeezing and entanglement, in a macroscopic mechanical system. The experimental setup involves a silicon nitride nanobeam resonator driven by a microwave field applied through an on-chip superconducting circuit. Precise control over the microwave frequency and amplitude manipulates the resonator’s rotational motion, while sensitive microwave readout techniques detect changes in its state. Through careful optimization, they demonstrate strong coupling, exceeding the damping rate of the mechanical motion, confirming the realization of a quantum mechanical system with macroscopic dimensions and demonstrating a pathway towards novel quantum sensors and devices.
Nanorotor Ground-State Cooling in Optical Cavity
Researchers have achieved ground-state cooling of nanorotors, reducing their thermal motion to the lowest possible quantum energy level. This demonstrates control over nanoscale objects, enabling precision measurement and exploration of the boundary between classical and quantum behaviour. The experiment involves trapping nanoparticles, likely composed of silicon and silicon dioxide, using a focused laser beam within a high-finesse optical cavity. The cavity mirrors induce birefringence, allowing separate control and cooling of the nanorotor’s rotational motion through coherent scattering, where laser light interacts with the rotational modes, transferring momentum and reducing kinetic energy. Sophisticated heterodyne detection measures the nanorotor’s motion, while monitoring cavity transmission provides further information. Results demonstrate successful cooling in two dimensions, with various nanoparticle types cooled repeatedly and consistently, establishing rigorous control and validating the results.
Quantum Cooling of Massive Nanoscale Rotors
Researchers have demonstrated reliable and repetitive cooling of silica nanodimers and trimers to their ground state of libration using a high-finesse cavity and laser-induced desorption. This technique allows for precise alignment of these nanorotors to a fixed axis with an accuracy approaching the fundamental limit set by their quantum mechanical zero-point amplitude. The team successfully cooled two librational modes simultaneously, achieving occupation numbers as low as 0. 2, establishing quantum control over nanoparticles with masses ranging from 1 to 10 GDa. This breakthrough opens new possibilities for both fundamental physics research and practical applications, with potential for torque sensitivities several orders of magnitude beyond current records, with intriguing implications for nanobiological materials.