title: Non-classical correlations between single photons and phonons from a mechanical oscillator.
abstract: Interfacing a single photon with another quantum system is a key capability in modern quantum information science. It allows quantum states of matter, such as spin states of atoms, atomic ensembles or solids, to be prepared and manipulated by photon counting and, in particular, to be distributed over long distances. Such light-matter interfaces have become crucial to fundamental tests of quantum physics and realizations of quantum networks. Here we report non-classical correlations between single photons and phonons--the quanta of mechanical motion--from a nanomechanical resonator. We implement a full quantum protocol involving initialization of the resonator in its quantum ground state of motion and subsequent generation and read-out of correlated photon-phonon pairs. The observed violation of a Cauchy-Schwarz inequality is clear evidence for the non-classical nature of the mechanical state generated. Our results demonstrate the availability of on-chip solid-state mechanical resonators as light-matter quantum interfaces. The performance we achieved will enable studies of macroscopic quantum phenomena as well as applications in quantum communication, as quantum memories and as quantum transducers.
authors.affiliation: Vienna Center for Quantum Science and Technology (VCQ), Faculty of Physics, University of Vienna, A-1090 Vienna, Austria.
authors.forename: Ralf
authors.initials: R
authors.lastname: Riedinger
authors.affiliation: Vienna Center for Quantum Science and Technology (VCQ), Faculty of Physics, University of Vienna, A-1090 Vienna, Austria.
authors.forename: Sungkun
authors.initials: S
authors.lastname: Hong
authors.affiliation: Kavli Institute of Nanoscience, Delft University of Technology, 2628CJ Delft, The Netherlands.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Norte
authors.affiliation: Vienna Center for Quantum Science and Technology (VCQ), Faculty of Physics, University of Vienna, A-1090 Vienna, Austria.
authors.forename: Joshua A
authors.initials: JA
authors.lastname: Slater
authors.affiliation: Photon Spot Inc., Monrovia, California 91016, USA.
authors.forename: Juying
authors.initials: J
authors.lastname: Shang
authors.affiliation: Kavli Institute of Nanoscience, Delft University of Technology, 2628CJ Delft, The Netherlands.
authors.forename: Alexander G
authors.initials: AG
authors.lastname: Krause
authors.affiliation: Photon Spot Inc., Monrovia, California 91016, USA.
authors.forename: Vikas
authors.initials: V
authors.lastname: Anant
authors.affiliation: Vienna Center for Quantum Science and Technology (VCQ), Faculty of Physics, University of Vienna, A-1090 Vienna, Austria.
authors.forename: Markus
authors.initials: M
authors.lastname: Aspelmeyer
authors.affiliation: Kavli Institute of Nanoscience, Delft University of Technology, 2628CJ Delft, The Netherlands.
authors.forename: Simon
authors.initials: S
authors.lastname: Gröblacher