Polaritons are quasiparticles formed when photons are strongly coupled to the excitation of matter. These quasiparticles are semi-light and semi-material and underpin the capabilities of a variety of emerging photonic quantum systems, such as semiconductor-based nanophotonic devices and circuit quantum electrodynamic systems.
Researchers at Stony Brook University recently introduced a new polariton system in which the excitation of matter is replaced by atoms in the optical lattice and the photons are replaced by the material waves of the atom. This system Nature PhysicsBrings material wave polaritons and may open up interesting possibilities for the study of polariton quantum materials.
“A few years ago, we were interested in the idea of using ultracold atoms to simulate dynamic behavior. Quantum emitterDr. Dominique Schnebull, head of the team of researchers who conducted the study, told Phys.org. “To construct an artificial atom that spontaneously emits a de Broglie wave, the atom spontaneously emits a photon (as explained in the so-called Weisskopf-Wigner model).
Schneble and his colleagues have shown that there are several advantages to using such artificial atoms instead of “real atoms” to study the dynamic behavior of quantum emitters. Most notably, the man-made system gives researchers the freedom to adjust important parameters such as the excitation energy of the emitter and its coupling to vacuum.
The artificial emitters they first created consisted of microscopic traps (ie, wells in the optical lattice) filled with a single atom. The team implemented a mechanism that allows a single atom to invert its spin and spontaneously emit the trap itself into an embedded material waveguide.
“Importantly, in contrast to traditional quantum emitters, this was the only decay mechanism allowed, and radiation could not escape elsewhere,” Schnebull explained. “of www.nature.com/articles/s41586-018-0348-zPapers that appeared in “> Nature In 2018, we observed that decay under these conditions could have very exotic characteristics. Especially when the excitation energy is set to negative (which may sound strange, but also applies to the “real emitter” of the photonic bandgap material), the emitted material wave radiation with negative energy escapes. Instead, it hovered around the emitter as a coherent cloud of vacuum excitation. “
In their new study, Schnebull and his colleagues took advantage of the fact that the emitters they implemented (ie, wells) were actually part of a periodic lattice that could contain many atoms. .. As a result, the effects of transport and interaction within the grid can be important.
“If you look at the grid, ignoring the emission characteristics for a while, these atoms can tunnel or hop between sites on their own,” Schnebull said. “Whether this happens depends on the strength of the hopping compared to the energy cost of repulsion between two or more atoms on the same lattice site (this is known as the Bose-Hubbard model).”
The main purpose of the researchers’ research was to determine what would happen when the light emitting function of the optical lattice system was turned on, especially with negative energy that radiation cannot escape. Interestingly, they found evidence that waves of hovering material tended to leak into adjacent wells.
In adjacent wells, a reverse decay (ie, absorption) process can cause waves of hovering material to return to the trapped atoms. Through this process, the original wells are emptied at the same time.
“This effectively means that trapped atoms dressed in Matter wave clouds have an additional mechanism for hops between lattice sites,” Schnebull said. “On the other hand, the material wave in the waveguide cannot move freely on its own, it is chained to the atoms in the lattice, so it only needs to hop.”
As a result, in this system, the waves of matter become less mobile or “heavier” and the atoms become more mobile or “lighter”.Matter waves and atoms in the lattice form a complex Quasiparticle It has aspects of both components, called “matter wave polaritons”.
“What makes this system interesting is that the atoms in the lattice (sometimes called” empty lattice excitation “in itself) repel each other on the site,” Schneble explained. “Now, if the matter waves are bonded to those atoms, there is also an effective repulsion between the matter waves. Returning this to a conventional polarization system replaces the matter waves with photons and hopping in the lattice. Atoms can be replaced with excitators. Polaritone (or the excitation of other matter) gives us the freedom to take advantage of the effective repulsive forces between photons. “
By itself, it is known that photons do not interact with each other. Therefore, the strong polariton interactions revealed by researchers are of great interest when extrapolated to traditional systems.
“A unique feature of our platform is that material wave polaritons are lossless, as opposed to photon-based polaritons, whose lifetimes are limited by spontaneous radioactive decay to the environment,” Schnebull said. I am saying.
Similar to previous studies focused on natural decay, recent Polariton studies by this team of researchers open up new possibilities for accessing parameter regimes previously inaccessible to traditional photon-based systems. increase. Therefore, in the future, it may be possible to investigate Polariton physics in detail in the new regime.
“Our research enables us to study polaritonic systems with the flexibility and control of analog quantum simulation,” Schneble added. “It is generally very interesting to explore a radiation system that is strongly coupled to de Broglie waves because there is no uncontrolled radiation loss, and Polariton’s characteristics play an important role in such studies, of course. The Polariton platform itself is highly relevant to applications in QIST, and our work should be interesting in this context as well. ”
Joonhyuk Kwon et al, Formation of Matter Wave Polariton in Optical Lattice, Nature Physics (2022). DOI: 10.1038 / s41567-022-01565-4
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Research introduces lossless Matter wave polaritons into optical lattice systems
Source link Research introduces lossless Matter wave polaritons into optical lattice systems