The polariton is a quasiparticle formed by the strong coupling to a matter excitation. It is a crucial ingredient of emergent photonic quantum systems ranging from semiconductor nanophotonics to circuit quantum electrodynamics. Using the interaction between polaritons has led to the realization of superfluids of light and strongly correlated phases in the microwave domain, with similar efforts underway for microcavity excitons–polaritons.
Scientists at Stony Brook University, led by Dominik Schneble, report the Formation of matter-wave polaritons in an optical lattice. This discovery allows studies of a central QIST paradigm through direct quantum simulation using ultracold atoms.
The researchers believe that their novel quasiparticles, which resemble strongly interacting photons in materials and electronics while avoiding some inherent problems, may aid the development of QIST platforms. It could potentially revolutionize computing and communication technologies.
Despite being an ideal carrier of quantum information, photons do not typically interact with each other. This becomes a challenge in working with photon-based QIST platforms. The absence of such interaction can stop-controlled the exchange of quantum information between them.
Scientists addressed this problem by coupling the photons to heavier excitations in materials. It, therefore, forms polaritons, chimera-like hybrids between light and matter. Collisions between these heavier quasiparticles cause the interaction between photons, enabling the implementation of photon-based quantum gate operations and, eventually, of an entire QIST infrastructure.
However, these photon-based polaritons have a limited lifetime. It’s because of their radiative coupling to the environment which causes uncontrolled spontaneous decay and decoherence.
This discovery circumvents such limitations caused by spontaneous decay completely. The photon features of their polaritons are carried exclusively by atomic matter waves, which are immune to such undesirable decay processes. This feature gives you access to parameter regimes that photon-based polaritonic systems don’t have (or don’t have yet).
Dominik Schneble from Stony Brook University said, “The development of quantum mechanics has dominated the last century, and a ‘second quantum revolution’ toward the development of QIST and its applications is now well underway around the globe, including at corporations such as IBM, Google, and Amazon.”
“Our work highlights some fundamental quantum mechanical effects that are of interest for emergent photonic quantum systems in QIST ranging from semiconductor nanophotonics to circuit quantum electrodynamics.”
Scientists conducted experiments with a platform that features ultracold atoms in an optical lattice. They then used a dedicated vacuum apparatus featuring various lasers and control fields and operating at nanokelvin temperature to implement a scenario in which the atoms trapped in the lattice “dress’’ themselves with clouds of vacuum excitations made of fragile, evanescent matter waves.
As a result, the polaritonic particles become far more mobile. By gently shaking the lattice, the scientists could directly explore their inner structure, gaining access to the contributions of matter waves and atomic lattice excitation. When left to their own devices, matter-wave polaritons hop through the lattice, interact with one another, and form stable quasiparticle matter phases.
Schneble said, “With our experiment, we performed a quantum simulation of an exciton-polariton system in a novel regime. The quest to perform such ‘analog’ simulations, which in addition are ‘analog’ in the sense that the relevant parameters can be freely dialed in, by itself constitutes an important direction within QIST.”
- Kwon, J., Kim, Y., Lanuza, A. et al. Formation of matter-wave polaritons in an optical lattice. Nat. Phys. (2022). DOI: 10.1038/s41567-022-01565-4