Otto Stern’s Legacy in Quantum Optics: Matter Waves and Deflectometry

Abstract

Otto Stern became famous for molecular beam physics, matter-wave research and the discovery of the electron spin, with his work guiding several generations of physicists and chemists. Here we discuss how his legacy has inspired the realization of universal interferometers, which prepare matter waves from atomic, molecular, cluster or eventually nanoparticle beams. Such universal interferometers have proven to be sensitive tools for quantum-assisted force measurements, building on Stern’s pioneering work on electric and magnetic deflectometry. The controlled shift and dephasing of interference fringes by external electric, magnetic or optical fields have been used to determine internal properties of a vast class of particles in a unified experimental framework.

Expanding wave packets and the quantum to classical transition

“…Diffraction experiments are made nowadays with molecules of mass of several thousand Daltons (roughly 1 Da is the mass of a nucleon) [27]. If σ is equated to the typical slit width of 1 nm, then, for such massive particles, T values of the order of nanoseconds are obtained.…”

Probing Molecular Magnetism Interferometrically

“…Stern and Gerlach's historic experiment involved an intense, collimated atomic beam, a spatially varying magnetic field, and a position-resolving detector that measured the transverse spatial distribution of the outgoing atomic beams. This configuration produced a beam deflection whose magnitude scaled inversely with the mass of the particles, making it difficult to measure the small deflections that heavy particles would undergo [3].…”

“…The new universal Stern-Gerlach matter-wave interferometer should allow researchers to extend matter-wave interferometry to ever larger molecules and to more complex species, including large biological molecules and maybe even living organisms such as bacteria. It should also allow researchers to explore the interface of quantum physics with chemistry, biology, and the macroscopic classical world [3,10]. There is currently much interest in deciphering the role of molecular magnetism in complex animal phenomena, such as the ability of migratory birds to obtain directional information from Earth's magnetic field.…”