Theoretical Study of the Preparation and Manipulation of Dark-Exciton Qubits - RMGS

As a 2D hydrogen-like quasiparticle, excitons in Transition Metal Dichalcogenide (TMDCs) possess an orbital-like electronic structure [Nature Materials 2019, 18(10), 1065-1070], and all orbitals are labeled with different principal and angular quantum numbers [1-5]. Group theory analysis reveals that the dipole transition between ground and exciton states with non-zero angular quantum numbers are forbidden according to the orbital angular momentum (OAM) related optical selection rules [6]. A pertinent example are the 2p and 3p states. Compared to 1s, 2s and 3s excitonic states, these OAM-forbidden dark excitons have considerably longer lifetimes [Nature Physics2010, 6(12), 993-997] and hence would be a suitable candidate as qubits in quantum computing [7-12]. Generally, two-photon absorption spectroscopy is exploited to probe these dark states [13-15], but it suffers from poor optical control and complicated experimental implementation.In this crossing-college collaboration project, we aim to theoretically study the preparation and manipulation of 2p and 3p excitonic dark states with OAM-carrying twisted single photons. The dark-exciton qubits can be prepared through selectively exciting the 2p or 3p states to create a superposed state with an arbitrary phase by two time-spaced pulses with different center frequencies, which can be subsequently manipulated by inducing a continuous wave to trigger their Rabi oscillation and control their phase.