Scientists use matter waves to reveal new collective behavior in quantum optics

A research team led by Dr. Dominique Schnaebel, professor in the Department of Physics and Astronomy, has discovered a new regime for cooperative radiation phenomena, a set of conditions within the system, shedding new light on a 70-year-old global phenomenon. I guessed it. An old problem in quantum optics.

The results of a study of previously unseen collective spontaneous emission effects in a set of synthetic (artificial) atoms were published in Nature Physics along with a theoretical paper in Physical Review Research.

Spontaneous emission is a phenomenon in which an excited atom falls to a lower energy state and spontaneously emits quantum electromagnetic radiation in the form of a single photon. When a single excited atom decays and releases a photon, the probability of finding an atom in the excited state decreases exponentially to zero over time.

In 1954, Princeton physicist RH Dicke considered what happens when a second, unexcited atom is placed in close proximity to it. He claimed that the probability of finding an excited atom was surprisingly reduced by only half. The excited system consists of two simultaneous scenarios. One scenario is where the atoms are in phase, resulting in stronger emission (called superradiance), and the other is where the atoms are out of phase and no radiation occurs (subradiation). When both atoms are excited initially, the decay is always superradiative.

Using a platform of ultracold atoms in a one-dimensional optical lattice geometry, Schneble and colleagues implemented an array of synthetic quantum emitters that collapse by emitting slow atomic matter waves. In contrast, traditional processes emit photons that travel at the speed of light. This difference gave them access to collective radiation phenomena in the new regime.

By preparing and manipulating arrays of emitters hosting weakly interacting many-body phases of excitation and strongly interacting many-body phases of excitation, the researchers demonstrated directional collective emission, producing delayed and superfluous We studied the interaction between radiative and subradiative dynamics.

“Dicke’s ideas are of great importance in quantum information science and technology (QIST). For example, intense efforts are being made to exploit super- and sub-radiations in arrays of quantum emitters coupled to one-dimensional waveguides. ” said fellow member Schnebel. Stony Brook’s Center for Distributed Quantum Processing (CDQP).

“In our research, we are able to prepare and manipulate sub-radiation conditions with unprecedented control. We are able to block spontaneous emissions and observe where the radiation is hiding in the array. To the best of our knowledge, this is the first such demonstration,” says Schnebel.

The study is the result of a Stony Brook team that includes two former Ph.D. Students Youngshin Kim and Alfonso Lanuza provide new insights into some fundamental concepts of quantum optics.

Schnabel explains that in Dicke’s theory, photons do not play an active role because they move quickly between nearby emitters on the decay timescale. However, there are situations where this assumption can break down, such as channels in long-range quantum networks. In this case, a guided photon escaping from a decaying emitter may take a long time to reach an adjacent emitter. This unexplored territory is exactly what the researchers were able to access because the waves of matter emitted in their system are billions of times slower than photons.

“We now see how it takes time for collective decay to form from a superradiant state containing a single excitation,” says co-author Kim. “This only happens when neighboring emitters are able to communicate.”

The researchers note that keeping track of slow radiation within a system of emitters is a theoretical challenge.

Co-author Lanuza likens the challenge to a complex game of catch and release. “A photon emitted by an atom may be caught back or bonded to the atom several times before escaping. When multiple photons are present, the rules of the game become complex.” Atoms and Photons Atoms exchanging photons, photons reflecting off excited atoms, and photons being trapped between atoms are just some of the processes involved. ”

Despite this complex photon-atom interaction, he was able to find a mathematical solution for the case of two emitters with up to two excitations and an arbitrary vacuum coupling. This aspect of the study may lead to the elucidation of other complex or unexpected collective atomic decay behaviors in future experiments.

“Overall, our results on collective radiation dynamics establish ultracold matter waves as a versatile tool for studying many-body quantum optics in spatially extended and ordered systems,” Schnebel said. I concluded.