Abstract:

Bose-Einstein condensates and superfluids of exciton-polaritons have been proposed as building blocks for qubits and quantum gates.    The main challenge on the way towards implementation of the polariton platform for quantum technologies is the demonstration of        quantum entanglement of two polariton condensates. We study two coupled condensates of exciton-polaritons confined in elliptical         traps. Together, they form a superposition of four eigen states of the double trap that can be considered as a qudit (a four-level analogue of a qubit). We initialize and control the system with non-resonantoptical pulses and read out its 4x4 density matrix with time-resolved interferometry, We detect a rise of negativity of the system that is a fingerprint of quantum entanglement.