Discovery of Matter-Wave Polaritons Sheds New Light on Photonic Quantum Technologies

Simulating Polaritons with Ultracold Atoms. In a paper published online on March 31, 2022 in the journal Nature Physics, a research team led by Dominik Schneble, a professor in the Department of Physics and Astronomy at Stony Brook University, reports the realization of novel quasiparticles made entirely out of ultracold atomic matter.

An artistic rendering of the  findings in the polariton study shows the atoms in an optical lattice forming an insulating phase (left); atoms turning into matter-wave polaritons via vacuum coupling mediated by microwave radiation represented by the green color (center); polaritons becoming mobile and forming a superfluid phase for strong vacuum coupling (right). Photo by Alfonso Lanuza/Schneble Lab/Stony Brook University.

The new quasiparticles are direct analogues of polaritons, chimera-like hybrids between photons (i.e. quanta of electromagnetic radiation) and material excitations that are essential ingredients in modern quantum information science and technology (QIST). The new research allows for studies of such polaritonic systems with the high flexibility and control of an analog quantum simulation, promising new experimental insights into the physics underlying some of the most important QIST platforms.

Working at nano-Kelvin temperature with a dedicated vacuum apparatus featuring various lasers and control fields, the Stony Brook researchers engineered an optical lattice, i.e. an egg-crate like potential landscape formed by standing waves of light. They then implemented a scenario in which ultracold atoms, normally observed as sluggishly hopping from lattice site to lattice site, were seen to surround or "dress" themselves with clouds of vacuum excitations made of fragile, evanescent matter waves. The team found that the atoms in the lattice become much more mobile. The price for the enhanced mobility is that the atoms cease their existence as hopping atoms and are instead transformed into composite quasiparticles with an inner structure that incorporates the aspects of both constituents, typical of a polariton. The researchers were able to directly probe this structure by gently shaking the lattice. When left alone, the matter-wave polaritons hop through the lattice, interact with each other, and form stable phases of quasiparticle matter, which the Stony Brook team accessed.

A major limitation of conventional QIST systems, in which the wave aspects of a polariton arise from photons is the short lifetime of the polariton due to uncontrolled spontaneous decay into the environment. The Stony Brook work circumvents this limitation completely, since the wave aspects of their polaritons are entirely carried by matter waves, for which such decay processes do not exist. This opens up access to parameter regimes that are not, or not yet, accessible with conventional polariton systems.

The university press release may be read here, and an article by Phys.org may be read here.

The NSF-funded work at Stony Brook University led by Prof. Schneble included graduate students Joonhyuk Kwon (now a postdoc at Sandia National Lab), Youngshin Kim, and Alfonso Lanuza. Additional support was provided through funds from the SUNY Center for Quantum Information Science on Long Island. Publication: J. Kwon, Y. Kim, A. Lanuza, and D. Schneble, “Formation of matter-wave polaritons in an optical lattice”, Nature Physics (March 31, 2022) https://www.nature.com/articles/s41567-022-01565-4 Associated publication: A. Lanuza, J. Kwon, Y. Kim, and D. Schneble, “Multiband and array effects on matter-wave based waveguide QED”, Phys. Rev. A 105, 23703 (2022).