Optimal circular dichroism sensing with quantum light: Multiparameter estimation approach

The measurement of circular dichroism (CD) has widely been exploited to distinguish the different enantiomers chiral structures. It applied natural materials (e.g., molecules) as well artificial nanophotonic structures). However, especially for molecules signal level is very low and increasing signal-to-noise ratio paramount importance either shorten necessary time or lower minimum detectable molecule concentration. As one solution this problem, we propose here use quantum states light in CD sensing reduce noise below shot encountered when using coherent light. Through a multiparameter estimation approach, identify ultimate limit precision sensing, allowing general schemes including additional ancillary modes. We show that can be achieved by various optimal schemes. These include pair Fock-state probes direct configuration pairs twin beams an ancilla-assisted configuration, both which photon number-resolved detection shown measurement. offer significant enhancement even presence some system loss. near optimality scheme single beam also cases where actual small. Alternative involving single-photon sources detectors are proposed. This work paves way further investigations metrological techniques chirality sensing.