Research Fellow Diana A. Chisholm

Quantum non-Gaussian states in massive systems to probe the quantum nature of gravity

Witnessing coherent quantum effects in mesoscopic systems allows to provide answers to foundational questions lying at the interface between quantum and classical physics, such as the quantum-to-classical transition and the quantum nature of gravity. In particular, there is a growing interest in the design of experiments with the goal to witness gravity-induced entanglement between massive systems (e.g. levitated nanoparticles), as this would prove that gravity is fundamentally quantum in nature. Due to the weak nature of gravity, generating a sufficiently high degree of entanglement such that it would be detectable with current experimental setups would require for the nanoparticles to be initially prepared in highly non-classical states, such as coherent non-Gaussian states. Levitated nanoparticles are trapped in a harmonic potential by a laser beam, by modulating the profile of the laser it is possible to change the trapping potential and introduce non-linearities. Doing so allows to drive an initially Gaussian state into one with the necessary degree of non-Gaussianity, even in the presence of detrimental environmental noise. Moreover, in order to generate such states in a sufficiently small time, such that relevant quantum features survive the environmental decoherence, it is necessary to initialise the system in a highly squeezed state: squeezed states with a high uncertainty in position evolve faster under the non-linear Hamiltonian while still retaining the quantum purity required to allow quantum non-classical states to emerge. We will therefore present control protocols for the generation of non-Guassian states, as well as discuss novel techniques for the generation of states with the necessary degree of squeezing in current experimental setups.