%0 Journal Article
%T Quantum superposition of a single microwave photon in two different 'colour' states
%A Zakka-Bajjani, Eva
%A Nguyen, Franà ois
%A Lee, Minhyea
%A Vale, Leila R.
%A Simmonds, Raymond W.
%A Aumentado, José
%J Nature Physics
%D 2011
%V 7
%N 8
%F Zakka-Bajjani_etal2011
%O exported from refbase (https://db.rplab.ru/refbase/show.php?record=822), last updated on Sat, 12 May 2012 14:59:40 -0500
%X Fully controlled coherent coupling of arbitrary harmonic oscillators is an important tool for processing quantum information. Coupling between quantum harmonic oscillators has previously been demonstrated in several physical systems using a two-level system as a mediating element. Direct interaction at the quantum level has only recently been realized by means of resonant coupling between trapped ions. Here we implement a tunable direct coupling between the microwave harmonics of a superconducting resonator by means of parametric frequency conversion. We accomplish this by coupling the mode currents of two harmonics through a superconducting quantum interference device (SQUID) and modulating its flux at the difference (~7GHz) of the harmonic frequencies. We deterministically prepare a single-photon Fock state and coherently manipulate it between multiple modes, effectively controlling it in a superposition of two different 'colours'. This parametric interaction can be described as a beamsplitter-like operation that couples different frequency modes. As such, it could be used to implement linear optical quantum computing protocols on-chip.
%K fromIPMRAS
%P 599-603