Open Quantum System Treatment of Ultralight Dark Matter Detection

Obtaining insight into the composition of dark matter (DM) and its couplings to standard model (SM) matter has inspired several cutting-edge experimental efforts. Experiments involving quantum systems are especially relevant to the search for ultralight bosonic dark matter (UBDM), the lowest available mass range of DM candidates. While a classical treatment of UBDM and its detectors is well-justified, future detection strategies would benefit from a quantum treatment of both the field and its interaction with a quantum detector. Additionally, several well-motivated theories suggest that UBDM may itself be a quantum field. Implications of the quantum nature of the field can only be studied through a quantum description of it. Fortunately, the field of quantum optics already provides a rigorous formalism for characterizing bosonic fields. The project will apply quantum optics formalism, specifically the theory of open quantum systems and coherence measures, to characterize the UBDM field and its interaction with a detector. The work done would lay the groundwork for similar treatment of other weak signals, particularly of astrophysical origin. This project provides excellent educational development for researchers of all levels: undergraduate, graduate and postdoctoral. The PI already has experience working with talented scientists at all these levels of development and plans to provide relevant research experience to eager scientists of various skill levels on the proposed project. The PI will develop programs to expand the quantum workforce by involving engineers in coding quantum computers and developing connections to and collaborations with the broader high-energy physics community understand and address the opportunities at the interface of high-energy physics and quantum sensing. There are two interconnected research directions at the interface of high energy physics (HEP) and quantum optics that will be pursued as part of the research program. Modeling ultralight dark matter as a bath: a microscopic, first-principles description of DM SM interaction would involve single quanta exchange between the detector and the UBDM field. Here, the PI focus on modeling this interaction and gain insights into the optimal detection process. Building on early work by the PI's group, this research direction involves building a formal quantum description of the interaction between UBDM and a quantum detector, which involves several atomic, molecular, and optical (AMO) systems. Specifically, this work will involve deriving the effective interaction Hamiltonians and non-Markovian bath descriptions for various UBDM searches involving quantum systems. Characterizing the ultralight dark matter bath: given the estimated large average occupation numbers and multimode nature of the UBDM field, a complete characterization of the field's density matrix is impractical. However, well-established techniques from quantum optics, such as coherence measures, can distinguish between different quantum states of light. The proposed work involves uncovering galactic merger history, squeezing due to self-interactions, or cosmic de coherence channels in the correlation functions of the UBDM field. These calculations will lay the groundwork for measuring our galactic merger history or uncovering signatures of its cosmological production mechanism in the time-delay statistics from a possible dark matter signal. Both areas of research involve adapting tools from quantum optics to address a particle physics problem of increasing interest to the experimental AMO community. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.