Robust quantum computing via photonic d-level cluster states
By exciting a nonlinear optical resonant element with a coherent set of multiple laser pulses in which the pulse separation is much larger than the photon lifetime in the resonator, researchers from the Institut National de la Recherche Scientifique (INRS-EMT; Varennes, QC, Canada) have prepared and coherently manipulated discrete d-level multipartite quantum systems based on frequency-time hyper-entangled two photon states. To do so, they use integrated photonic chips and fiber-optic telecommunications components. The demonstration is the first experimental realization and characterization of so-called qudit cluster states that are equivalent to the realization of a quantum computer, as well as the first proof-of-concept demonstration of high-dimensional one-way quantum processing.
The photon pairs (signal and idler) are simultaneously generated in a four-wave mixing process as a superposition of several time modes (d = 3, given by the number of pulses) generating a time-based d-level two-photon state. One pulse exciting the nonlinear resonant medium (microring resonator) additionally generates a frequency-based d-level photon state. Together, this creates a d-level hyperentangled multipartite state. Next, frequency-to-time mapping is accomplished using a fiber Bragg grating (FBG) array in a phase-stable loop configuration, transforming the hyperentangled state into a three-level four-partite cluster state using an appropriate phase pattern. These d-level cluster states can tolerate up to 66.6% of incoherent noise compared to only 50% for four- and six-qubit cluster states. Furthermore, the team transformed these cluster states into different orthogonal bi-partite states and confirmed, through quantum interference measurements, that the states are mutually orthogonal and entangled, enabling powerful, noise-tolerant quantum operations using standard optical components. Reference: C. Reimer et al., Nat. Phys. Lett.; https://www.nature.com/articles/s41567-018-0347-x (Dec. 3, 2018).
Gail Overton | Senior Editor (2004-2020)
Gail has more than 30 years of engineering, marketing, product management, and editorial experience in the photonics and optical communications industry. Before joining the staff at Laser Focus World in 2004, she held many product management and product marketing roles in the fiber-optics industry, most notably at Hughes (El Segundo, CA), GTE Labs (Waltham, MA), Corning (Corning, NY), Photon Kinetics (Beaverton, OR), and Newport Corporation (Irvine, CA). During her marketing career, Gail published articles in WDM Solutions and Sensors magazine and traveled internationally to conduct product and sales training. Gail received her BS degree in physics, with an emphasis in optics, from San Diego State University in San Diego, CA in May 1986.