Abstract We propose a quantum optomechanical method to probe the potential existence of dark matter particles possessing an infinitesimal electric charge, known as milli-charged particles (mCPs), when bound to ordinary matter. In our setup, a charged fused silica nanosphere (NS) is optically levitated within a Fabry–Perot cavity and subjected to an additional electrostatic field produced by a charged metallic ring. If mCPs exist and are embedded in the NS as relics of early Universe matter, their presence would generate a tiny but measurable deviation from a purely thermal output spectrum. Specifically, the output light from the cavity would exhibit quadrature squeezing even at room temperature, and the NS center-of-mass motion could become entangled with the optical field. These quantum effects are absent when there are no residual infinitesimal charges in the NS. We provide a theoretical framework for this proposal, including the system Hamiltonian and linearized quantum Langevin dynamics, and show how measurements of squeezing and entanglement in the cavity output can reveal the presence of bound mCPs.
Asjad et al. (Tue,) studied this question.