日本大学文理学部 物理学科

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タイトル：Tailoring the Phonon Environment of Embedded Rydberg Aggregates

概要：

State-of-the-art experiments can controllably create Rydberg atoms inside a Bose- Einstein condensate (BEC) [1]. The large Rydberg electron orbital volume contains many neutral atoms, resulting in electron-atom scattering events. The number of atoms within the orbit, and hence the Rydberg-BEC interaction, can be tuned by choice of principal quantum number or condensate density [1]. This makes the hybrid system a fascinating platform for quantum simulation. We studied the physics of the interaction and corresponding dynamics of single or multiple Rydberg atoms in two internal electronic states embedded inside a BEC, to assess their utility for controlled studies of decoherence and quantum simulations of excitation transport similar to photosynthetic light-harvesting.

We initially developed a theoretical framework to calculate the open quantum system input parameters like the bath correlation function and the spectral density, initially for a single Rydberg atom, possibly in two internal states with angular momentum quantum numbers l = 0 (|s⟩) and l = 1 (|p⟩) [2], in BEC and then for a chain of Rydberg atoms, forming an aggregate. The electron-atom contact interactions lead to Rydberg-BEC coupling, which creates Bogoliubov excitations (phonons) in the BEC.

Using this spin-boson model with the calculated parameters, we examine the decoherence dynamics of a Rydberg atom in a superposition of |s⟩ and |p⟩ states,  resulting from the interaction with its condensate environment. Further, we investigated the emergence of the non-Markovian features in the system in the presence of a microwave external drive of the Rydberg atom using a stochastic computational technique for non-Markovian open quantum systems [3].

Finally, we extend this to the aggregate case, where one of the atoms in the aggregate is in the state |p⟩, while the rest are in the state |s⟩, resulting in excitation transport via  dipole-dipole interaction [4]. We investigate the effects of non-Markovinity and decoherence on the excitation transport based on an effective model described by a Holstein Hamiltonian, allowing us to set up the dynamics similar to those found in light- harvesting complexes, but at a different time and energy scales.

References:
 1. J. B. Balewski, et. al., ; Nature 502 664 (2013).
 2. S. Rammohan, et. al.,; Phys. Rev. A 103, 063307 (2021).
 3. S. Rammohan, et. al.,; Phys. Rev. A 104, L060202 (2021).
 4. D. W. Schönleber, et. al.,; Phys. Rev. Lett. 114 123005 (2015).

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