Unitary magnon-mediated operations for quantum computing

Coupled magnonic and photonic resonators with strong coupling rates (> 100 MHz) form a basis of a promising hybrid quantum computing architecture [1-3]. Tunability of magnon resonant frequencies with magnetic field allows one to reconfigure such systems during a quantum computation. Here, we show that dynamic tuning of magnon frequencies at timescales comparable to the magnon-photon energy exchange time allows one to achieve qualitatively new functionalities of such hybrid devices. In particular, we demonstrate theoretically the possibility of realization of several unitary magnon-mediated quantum gates, such as coherent quantum data exchange and entanglement generation. Different gates can be realized in the same physical structure by shaping the profile of the pulsed magnetic field that controls magnon frequency. It should be noted, that decoherence processes in magnonic resonators have a very weak effect on the overall performance of the proposed gates and our estimates show that magnon-mediated operations may have efficiencies better than existing quantum gate designs.
[1] H. Huebl, et al., Phys. Rev. Lett., 111, 127003 (2013).
[2] X. Zhang, et al., Phys. Rev. Lett., 113, 156401 (2014).
[3] Y. Li, et al., Phys. Rev. Lett., 123, 107701 (2019).