title: Quantum Effects in Higher-Order Correlators of a Quantum-Dot Spin Qubit.
abstract: We measure time correlators of a spin qubit in an optically active quantum dot beyond the second order. Such higher-order correlators are shown to be directly sensitive to pure quantum effects that cannot be explained within the classical framework. They allow direct determination of ensemble and quantum dephasing times, T_{2}^{*} and T_{2}, using only repeated projective measurements and without the need for coherent spin control. Our method enables studies of purely quantum behavior in solid state systems, including tests of the Leggett-Garg type of inequalities that rule out local hidden variable interpretation of the quantum-dot spin dynamics.
authors.affiliation: Walter Schottky Institut and Physik Department, Technische Universität München, 85748 Garching, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Bechtold
authors.affiliation: Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 USA.|Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: F
authors.initials: F
authors.lastname: Li
authors.affiliation: Walter Schottky Institut and Physik Department, Technische Universität München, 85748 Garching, Germany.|E. L. Ginzton Laboratory, Stanford University, Stanford, California 94305, USA.
authors.forename: K
authors.initials: K
authors.lastname: Müller
authors.affiliation: Walter Schottky Institut and Physik Department, Technische Universität München, 85748 Garching, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Simmet
authors.affiliation: Walter Schottky Institut and Physik Department, Technische Universität München, 85748 Garching, Germany.
authors.forename: P-L
authors.initials: PL
authors.lastname: Ardelt
authors.affiliation: Walter Schottky Institut and Physik Department, Technische Universität München, 85748 Garching, Germany.
authors.forename: J J
authors.initials: JJ
authors.lastname: Finley
authors.affiliation: Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: N A
authors.initials: NA
authors.lastname: Sinitsyn