title: Free Nano-Object Ramsey Interferometry for Large Quantum Superpositions.
abstract: We propose an interferometric scheme based on an untrapped nano-object subjected to gravity. The motion of the center of mass (c.m.) of the free object is coupled to its internal spin system magnetically, and a free flight scheme is developed based on coherent spin control. The wave packet of the test object, under a spin-dependent force, may then be delocalized to a macroscopic scale. A gravity induced dynamical phase (accrued solely on the spin state, and measured through a Ramsey scheme) is used to reveal the above spatially delocalized superposition of the spin-nano-object composite system that arises during our scheme. We find a remarkable immunity to the motional noise in the c.m. (initially in a thermal state with moderate cooling), and also a dynamical decoupling nature of the scheme itself. Together they secure a high visibility of the resulting Ramsey fringes. The mass independence of our scheme makes it viable for a nano-object selected from an ensemble with a high mass variability. Given these advantages, a quantum superposition with a 100 nm spatial separation for a massive object of 10^{9}  amu is achievable experimentally, providing a route to test postulated modifications of quantum theory such as continuous spontaneous localization.
authors.affiliation: QOLS, Blackett Laboratory, Imperial College London, London SW7 2BW, United Kingdom.
authors.forename: C
authors.initials: C
authors.lastname: Wan
authors.affiliation: QOLS, Blackett Laboratory, Imperial College London, London SW7 2BW, United Kingdom.
authors.forename: M
authors.initials: M
authors.lastname: Scala
authors.affiliation: Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, United Kingdom.
authors.forename: G W
authors.initials: GW
authors.lastname: Morley
authors.affiliation: Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, United Kingdom.|Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom.
authors.forename: Atm A
authors.initials: AA
authors.lastname: Rahman
authors.affiliation: Department of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ, United Kingdom.
authors.forename: H
authors.initials: H
authors.lastname: Ulbricht
authors.affiliation: Department of Physics, College of Science, Swansea University, Swansea SA2 8PP, United Kingdom.
authors.forename: J
authors.initials: J
authors.lastname: Bateman
authors.affiliation: Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom.
authors.forename: P F
authors.initials: PF
authors.lastname: Barker
authors.affiliation: Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom.
authors.forename: S
authors.initials: S
authors.lastname: Bose
authors.affiliation: QOLS, Blackett Laboratory, Imperial College London, London SW7 2BW, United Kingdom.
authors.forename: M S
authors.initials: MS
authors.lastname: Kim