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Quantum Nano Optomechanics

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Measuring photons pushing on a nanowire

Studying interactions between light and matter can elicit answers to some of the most fundamental open questions in physics. Ground-breaking experiments on the quantum scale have shed light on new forms of coupling certain to shake up the field.

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Cavity optomechanics is an exciting new field exploring the interaction between electromagnetic radiation and nano- or micromechanical motion. Practitioners manipulate photons with mirrors and mechanical resonators in table-top experiments, exploiting radiation pressure. Radiation pressure is essentially the force per unit area of light or photons, the pressure exerted on any surface exposed to radiation. Scientists pushed the frontiers of this pioneering field with EU-funding of the project 'Quantum nano optomechanics' (QNAO). They demonstrated the ability to optically probe the nanoscale motion of sub-wavelength oscillators with sensitivities approaching the standard quantum limit. With ultra-low mass nanoresonators, they made force measurements with sensitivities at the attoNewton (1x10-18 Newtons) level in a room temperature experiment. Quantum back-action is the quantum analogy of Newton’s third law stating that for every action there is an equal and opposite reaction. Scientists observed the optical back-action exerted by the light beam onto the nanoresonator indicative of strong coupling between oscillation modes of the resonator. In separate experiments, the team investigated the phenomenon in reverse with the first realisation of a hybrid spin-nanomechanical system. Researchers attached a single nitrogen-vacancy qubit (a diamond-based model system to study electron-spin related phenomena) to the end of a freely hanging nanowire. The latter is the nanoresonator. Using spin spectroscopy in this completely new experimental system, scientists demonstrated that the nanowire motion is imprinted on the spin state. Researchers began a new line of research where spin is automatically locked onto the resonator opening the door to even more advanced measurement protocols in hybrid systems. Explorations with cavity optomechanics can be used to test fundamental hypotheses about light-matter interactions such as gravitational theories. They are also paving the way to many near-term and future applications such as ultra-sensitive acceleration and force sensors, microwave oscillators, optical signal processing technology and silicon photonics. The pioneering experiments of QNAO have made a valuable contribution to an important field.

Keywords

Photons, nanowire, quantum, coupling, cavity optomechanics, radiation pressure, nanoresonator, back-action, entanglement, qubit, spin spectroscopy

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