Probing macroscopic quantum superpositions with nanorotors

Abstract

Whether quantum physics is universally valid is an open question with far-reaching implications. Intense research is therefore invested into testing the quantum superposition principle with ever heavier and more complex objects. Here we propose a radically new, experimentally viable route towards studies at the quantum-to-classical borderline by probing the orientational quantum revivals of a nanoscale rigid rotor. The proposed interference experiment testifies a macroscopic superposition of all possible orientations. It requires no diffraction grating, uses only a single levitated particle, and works with moderate motional temperatures under realistic environmental conditions. The first exploitation of quantum rotations of a massive object opens the door to new tests of quantum physics with submicron particles and to quantum gyroscopic torque sensors, holding the potential to improve state-of-the-art devices by many orders of magnitude.

Quantum decoherence

“…[371,372]; such experiments may soon become technologically feasible [12,263]. Other promising avenues for testing quantum mechanics include motional superposition states of micromechanical oscillators [373,375], interference of free nanoparticles [376,379] (an approach that offers the prospect of spatial superpositions separated by 100 nm for particles on the order of 10 9 amu [376]), and molecular nanorotors [377]. Ultimately, experiments carried out in space rather than on Earth might be able to push the limit for macroscopic superpositions to objects involving on the order of 10 10 atoms [288].…”

Stability and dynamics of optically levitated dielectric disks in a Gaussian standing wave beyond the harmonic approximation

“…The following example outlines the steps for how a calculation is performed: the disk's symmetry axis is aligned with the axial direction (x axis), the disk is displaced a distance y 0 from the focus of the standing wave, the scattered waves are calculated using the DDA, and the forces and torques are computed using Eqs. (9) and (10). The process is identical for rotations: the disk is initially situated at r 0 = 0, 0, 0 and (α = 0, β = π/2), a rotation is made α = 0 + θ z , the scattered waves are calculated using the DDA, and the forces and torques are calculated.…”

“…Increasing the size of the particle relative to the wavelength of the laser further complicates the motion for any particle shape [7]. Still, terms necessary to describe nanorods and nanodumbbells have been investigated and the motion is also well understood [8][9][10][11].…”

Encoding a qubit in a molecule

“…Nanoparticles may seem to be unlikely candidates for quantum computing, but it would be interesting nonetheless to try to stabilize quantum superpositions of their orientational states (cf. [125]).…”