We implement an experimental architecture in which a single atom of K is trapped in an optical tweezer, and is immersed in a bath of Rb atoms at ultralow temperatures. In this regime, the motion of the single trapped atom is confined to the lowest quantum vibrational levels. This realizes an elementary and fully controllable quantum impurity system. For the trapping of the K atom, we use a species-selective dipole potential, that allows us to independently manipulate the quantum impurity and the bath. We concentrate on the characterization and control of the interactions between the two subsystems. To this end, we perform Feshbach spectroscopy, detecting several inter-dimensional confinement-induced Feshbach resonances for the KRb interspecies scattering length, that parametrizes the strength of the interactions. We compare our data to a theory for inter-dimensional scattering, finding good agreement. Notably, we also detect a series of p-wave resonances stemming from the underlying free-space s-wave interactions. We further determine how the resonances behave as the temperature of the bath and the dimensionality of the interactions change. Additionally, we are able to screen the quantum impurity from the bath by finely tuning the wavelength of the light that produces the optical tweezer, providing us with a new effective tool to control and minimize the interactions. Our results open a range of new possibilities in quantum simulations of quantum impurity models, quantum information, and quantum thermodynamics, where the interactions between a quantized system and the bath is a powerful yet largely underutilized resource.

中文翻译：

---

控制冷原子量子杂质系统中的相互作用


我们实现了一种实验架构，其中单个 K 原子被光镊捕获，并在超低温下浸入 Rb 原子浴中。在这种情况下，单个被捕获原子的运动被限制在最低的量子振动能级。这实现了基本的、完全可控的量子杂质系统。为了捕获 K 原子，我们使用物种选择性偶极子电势，这使我们能够独立操纵量子杂质和浴。我们专注于两个子系统之间相互作用的表征和控制。为此，我们执行 Feshbach 光谱，检测 KRb 种间散射长度的几个维度间限制引起的 Feshbach 共振，从而参数化相互作用的强度。我们将我们的数据与维度间散射理论进行比较，发现了良好的一致性。值得注意的是，我们还检测到了一系列源自潜在自由空间 s 波相互作用的 p 波共振。我们进一步确定随着浴温和相互作用维度的变化，共振如何表现。此外，我们能够通过微调产生光镊的光的波长来筛选浴中的量子杂质，为我们提供了一种新的有效工具来控制和最小化相互作用。我们的结果为量子杂质模型、量子信息和量子热力学的量子模拟开辟了一系列新的可能性，其中量子化系统和浴之间的相互作用是一种强大但基本上未得到充分利用的资源。