Entanglement manipulation with a tunable magnonic beamsplitter

Generation and detection of entanglement by two-photon interference, i.e., a photonic Hong-Ou-Mandel (HOM) effect [1], is central to many quantum technologies [2]. Here, we propose a hybrid magnonic system [3,4] for two-magnon interference, i.e., a magnonic HOM. The system is a set of 2 magnonic resonators with coupling rate κ and frequencies ω₁ and ω₂. A dynamic magnetic field B(t) can tune the frequency separation Δω=│ω₁–ω₂│ of the system.

A magnonic beamsplitter (BS) operation forms when the system is strongly coupled (Δω≪κ) for a time such that the probability for single magnon scattering between resonators is ½. Applying the BS pulse to a two-magnon initially unentangled state │11〉 generates a maximally entangled N00N state (│20〉+e^iθ│02〉)/√2. Shaping the magnetic field profile can tune the sensitivity of the magnonic BS to generate and detect (being a unitary operation) different relative phases θ of the N00N state. Such tunable magnonic BS that can manipulate N00N states could be useful for the quantum metrology of hybrid magnonic systems.

[1] C. K. Hong et al., Phys. Rev. Lett., 59, 2044–2046 (1987)

[2] F. Bouchard et al., Rep. Prog. Phys., 84, 012402 (2021)

[3] Y. Li et al., J. Appl. Phys., 128, 130902 (2020)

[4] D. D. Awschalom et al., IEEE Trans. Quantum Eng., 2, 1-36 (2021)