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According to Bell's theorem, any theory that is based on the joint assumption of realism and locality is at variance with certain quantum predictions. Here, theory and experiment agree that a class of such non-local realistic theories is incompatible with experimentally observable quantum correlations, suggesting that giving up the concept of locality is not sufficient to be consistent with quantum experiments, unless certain intuitive features of realism are abandoned.

Commutation relations define the limit to which two complementary properties can be simultaneously known—Heisenberg’s uncertainty principle. Yet it is thought that these canonical relations might be different in the quantum gravity regime. Researchers now show how quantum-optics experiments might provide a direct route for studying these effects.

Nanodiamonds that are levitated by light and are equipped with internal spin provide a new platform for performing quantum and optomechanical experiments with massive, environmentally isolated objects.

A nanomechanical beam coupled to an optical cavity can be operated as a non-volatile memory element.

Using quantum optics to process data could herald a new era of information technology. With the latest semiconductor source of photons, researchers are paving the way towards this enticing goal.

A method for characterizing quantum measurement devices completes the suite of 'tomography techniques', which should enable us to learn all there is to know about a given quantum-physics experiment.

Quantum entanglement comes in a rich variety of types and families if more than two particles are involved. Experiments with photons are opening up fresh ways to systematically study multi-particle entanglement.

Researchers have long wanted to be able to control macroscopic mechanical objects in their smallest possible state of motion. Success in achieving that goal heralds a new generation of quantum experiments.

Optimal quantum control of an optically trapped nanoparticle in its ground state is demonstrated at room temperature, using Kalman filtering to track its quantum trajectory in real time.

By employing monocrystalline semiconductor materials as high-quality optical coatings, the long-standing challenge of minimizing the optical phase noise produced by Brownian motion in a multilayer has been overcome. A thermally limited noise floor consistent with a tenfold reduction in mechanical damping relative to that in the best dielectric multilayers is achieved.

A real-world experiment marks a step towards worldwide quantum communication.

A direct measurement of the gravitational coupling between two 1-mm-radius gold spheres with masses below 100 mg using a torsional pendulum is reported.

Remote quantum entanglement is demonstrated in a micromachined solid-state system comprising two optomechanical oscillators across two chips physically separated by 20 cm and with an optical separation of around 70 m.

Achieving coherent quantum control over massive mechanical resonators via coupling to electrons or photons is a current research goal. Here, unambiguous evidence for strong coupling of cavity photons to a mechanical resonator is reported, paving the way for full quantum optical control of nano- and micromechanical devices.

Cooling optomechanical resonators to their quantum-mechanical ground state could enable the observation of quantum effects in macroscopic objects. The experimental cooling of a 43-ng silicon-nitride beam to a thermal occupancy of just 30 indicates that this ultimate goal is not too far away.

The performance of micromechanical and nanomechanical resonators is often hampered by mechanical damping. In this study, the authors demonstrate a numerical solver for the prediction of support-induced losses in these structures and verify experimentally the fidelity of this method.

Experiments where a tiny mirror, a mechanical microresonator, within an optical cavity undergoes 'self-cooling' is detailed. Under the right, finely tuned conditions, the thermal vibration of the mirror freezes out without outside influence. It cools down by a factor of 30, from room temperature to about 10 kelvin.

Non-classically correlated pairs of single photons and phonons are generated and read out from a nanomechanical resonator, demonstrating that such resonators could be used for light–matter quantum interfaces.

Laser cooling has been a successful technique to cool atoms and diatomic molecules to very low temperatures. Here, using an external cavity for an improved light coupling, Asenbaum et al.achieve the cooling of much larger objects, silicon nanoparticles, and reduce their transverse kinetic energy by up to a factor of 30.

Quantum fluctuations of a laser are transferred onto the motion of a mechanical resonator and interfere with the fluctuations of the light reflected from the resonator, leading to ‘squeezed’ light with optical noise suppressed below the standard quantum limit.