Qubit-Photon Bound States: Crossover from Waveguide to Cavity Regime

Physical Review Applied, vol. 20

Abstract

When the energy of a quantum emitter aligns with the photonic bandgap of the waveguide, variety of distinct quantum optical phenomena emerges. The paradigmatic example of such nontrivial interaction results in the formation of a qubit-photon bound state (QPBS) where a single photon is exponentially localized around the qubit position. Superconducting quantum circuits has been extensively used for studying QPBS where the photonic band gaps are generated in two-dimensional periodic structures such as photonic crystals and metamaterials. Nonetheless, in all the experiments reported so far, the exponential nature of the bound state wave function is justified by making two assumptions (1) that the waveguide is infinite in length and (2) the coupling to the external ports are absent. These assumptions are difficult to achieve for a physical device and the transition from an experimentally realizable finite-size system to the theoretically assumed infinite device size has never been thoroughly understood. Here, we have realized an alternative platform based on a three-dimensional (3D) rectangular waveguide that has a naturally occurring low-frequency cutoff for generating QPBS as proposed in Shahmoon and Kurizki [Phys. Rev. A 87, 033831 (2013)]. In its theoretical description, we explicitly take into consideration the finite nature of the 3D waveguide arising due to its metallic boundaries and coupling to microwave ports and demonstrate how the infinite waveguide limit arises in such a finite system.

Authors 6

1. N. Pradeep Kumar

   The University of Queensland · ARC Centre of Excellence for Engineered Quantum Systems

   Affiliation as printed

   ARC Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, Saint Lucia, Queensland 4072, Australia

2. Andrés Rosario Hamann

   The University of Queensland · ETH Zurich · ARC Centre of Excellence for Engineered Quantum Systems

   Affiliation as printed

   ARC Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, Saint Lucia, Queensland 4072, Australia

   Department of Physics, ETH Zürich, Zürich CH-8093, Switzerland

3. Rohit Navarathna

   The University of Queensland · ARC Centre of Excellence for Engineered Quantum Systems

   Affiliation as printed

   ARC Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, Saint Lucia, Queensland 4072, Australia

4. Maximilian Zanner

   Austrian Academy of Sciences · Universität Innsbruck · Institute for Quantum Optics and Quantum Information Innsbruck

   Affiliation as printed

   Center for Quantum Physics, and Institute for Experimental Physics, University of Innsbruck, Innsbruck A-6020, Austria

   Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, Innsbruck A-6020, Austria

5. Mikhail Pletyukhov Aachen Institute for Theory of Statistical Physics

   RWTH Aachen University

   Affiliation as printed

   Institute for Theory of Statistical Physics, RWTH Aachen University, Aachen 52056, Germany

6. Arkady Fedorov corresponding

   The University of Queensland · ARC Centre of Excellence for Engineered Quantum Systems

   Affiliation as printed

   ARC Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, Saint Lucia, Queensland 4072, Australia