Integrated quantum polariton interferometry

Exciton-polaritons are hybrid radiation-matter elementary excitations that, thanks to their strong nonlinearities, enable a plethora of physical phenomena ranging from room temperature condensation to superfluidity. While polaritons are usually exploited in a high-density regime, evidence for quantum correlations at the level of few excitations has been recently reported, thus suggesting the possibility of using these systems for quantum information purposes. Here we show that integrated circuits of propagating single polaritons can be arranged to build deterministic quantum logic gates in which the two-particle interaction energy plays a crucial role. Besides showing their prospective potential for photonic quantum computation, we also show that these systems can be exploited for metrology purposes, as for instance to precisely measure the magnitude of the polariton-polariton interaction at the two-body level. Our results will motivate the development of practical quantum polaritonic devices in prospective quantum technologies. Recently, observation of low-density polaritons in the quantum regime has prompted interest beyond their collective behavior. Here, an integrated quantum logic device that relies on two-body polaritonic interaction is proposed theoretically.