Synopsis: A Tractor Beam from Matter Waves

Theory shows that the quantum-mechanical wave of a beam of particles can exert a pulling force on a small particle, just as other waves do.
Synopsis figure
Adapted from A. Gorlach et al., Phys. Rev. Lett. (2017)

It was a surprise a few years ago that a steady light beam or sound wave hitting a small object could exert a pulling force on it. Now a team of theorists has analyzed such a “tractor beam” made from another kind of wave—the quantum-mechanical matter wave of a beam of particles such as electrons. Andrey Novitsky of the Technical University of Denmark and his colleagues found the conditions under which a matter wave would produce a pulling force.

A tractor beam works when the waves receive a boost in forward momentum as they interact with the object. This beam acceleration results in the object receiving an opposite recoil momentum that pushes it back toward the tractor beam’s source. Often the beam is a so-called Bessel beam, whose rays spread out like a cone. Novitsky and his colleagues analyzed the effects of parameters such as the cone’s apex angle, the beam energy, and the details of the electromagnetic interaction force between the object and the beam.

The team found that there is a wide range of parameters for which a matter wave forms a tractor beam, but the beam-object interaction matters—a Coulomb field cannot lead to a pulling force, whereas a Yukawa field can. The matter-wave case is surprisingly similar to classical tractor beams, the authors note, despite the fact that matter waves have a probabilistic interpretation and are not a physical wave in the classical sense.

This research is published in Physical Review Letters.

–David Ehrenstein

David Ehrenstein is the Focus editor for Physics.


More Features »


More Announcements »

Subject Areas

Quantum Physics

Previous Synopsis

Energy Research

Protons in the Fast Lane

Read More »

Related Articles

Viewpoint: The Thermodynamic Cost of Measuring Time
Quantum Physics

Viewpoint: The Thermodynamic Cost of Measuring Time

A simple model of an autonomous quantum clock yields a quantitative connection between the clock’s thermodynamic cost and its accuracy and resolution. Read More »

Synopsis: Quantum Sensing of Magnetic Fields
Quantum Physics

Synopsis: Quantum Sensing of Magnetic Fields

A new design for an atomic magnetometer utilizes so-called quantum nondemolition measurements to detect very weak magnetic-field signals. Read More »

Viewpoint: Inducing Transparency with a Magnetic Field

Viewpoint: Inducing Transparency with a Magnetic Field

A magnetic field applied to an atomic sample in an optical cavity generates optical transparency that could be used to enhance the frequency stability of lasers. Read More »

More Articles