title: Magnon dark modes and gradient memory.
abstract: Extensive efforts have been expended in developing hybrid quantum systems to overcome the short coherence time of superconducting circuits by introducing the naturally long-lived spin degree of freedom. Among all the possible materials, single-crystal yttrium iron garnet has shown up recently as a promising candidate for hybrid systems, and various highly coherent interactions, including strong and even ultrastrong coupling, have been demonstrated. One distinct advantage in these systems is that spins form well-defined magnon modes, which allows flexible and precise tuning. Here we demonstrate that by dissipation engineering, a non-Markovian interaction dynamics between the magnon and the microwave cavity photon can be achieved. Such a process enables us to build a magnon gradient memory to store information in the magnon dark modes, which decouple from the microwave cavity and thus preserve a long lifetime. Our findings provide a promising approach for developing long-lifetime, multimode quantum memories.
authors.affiliation: Department of Electrical Engineering, Yale University, New Haven, Connecticut 06511, USA.
authors.forename: Xufeng
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Electrical Engineering, Yale University, New Haven, Connecticut 06511, USA.|Department of Applied Physics, Yale University, New Haven, Connecticut 06511, USA.|Key Lab of Quantum Information, University of Science and Technology of China, CAS, Hefei 230026, China.
authors.forename: Chang-Ling
authors.initials: CL
authors.lastname: Zou
authors.affiliation: Department of Electrical Engineering, Yale University, New Haven, Connecticut 06511, USA.
authors.forename: Na
authors.initials: N
authors.lastname: Zhu
authors.affiliation: Institute for Theoretical Physics II, University of Erlangen-Nuremberg, Staudtstrasse 7, 91058 Erlangen, Germany.|Max Planck Institute for the Science of Light, Günther-Scharowsky-Straße 1/Bau 24, 91058 Erlangen, Germany.
authors.forename: Florian
authors.identifier: http://orcid.org/0000-0003-4566-1753
authors.initials: F
authors.lastname: Marquardt
authors.affiliation: Department of Applied Physics, Yale University, New Haven, Connecticut 06511, USA.
authors.forename: Liang
authors.identifier: http://orcid.org/0000-0002-0000-9342
authors.initials: L
authors.lastname: Jiang
authors.affiliation: Department of Electrical Engineering, Yale University, New Haven, Connecticut 06511, USA.
authors.forename: Hong X
authors.initials: HX
authors.lastname: Tang