Phase-controlled dual-variable quantum nonreciprocity
Phys. Rev. A 114, 053707 – Published 6 November, 2026
DOI: https://doi.org/10.1103/m7jz-mtqt
Abstract
Continuous-variable quadrature squeezing and discrete-variable sub-Poissonian statistics represent complementary nonclassical signatures, manifested respectively as reducing quadrature noise and suppressing number fluctuations, which may be mutually exclusive in some scenarios. Here, we put forward a win-win scheme for the simultaneous and nonreciprocal control of the optimal quadrature squeezing and pronounced sub-Poissonian magnon-number statistics based on the non-Hermitian anharmonicity engineered by the Barnett effect. Such a scheme can be considered in a magnon-qubit-waveguide quantum electrodynamics system, where a rotating ferromagnetic yttrium iron garnet (YIG) sphere and a transmon-type superconducting qubit are coupled to a common one-dimensional semi-infinite waveguide. Physically, the mirror-terminated waveguide naturally induces unequal Lamb shifts for the magnon mode and the qubit, which can be compensated by the Barnett shift, thereby producing non-Hermitian anharmonicity. Furthermore, our approach is not restricted to the purely dissipative-coupling condition, but remains feasible when coherent and dissipative couplings coexist. With realistic experimental parameters, the numerical simulations are well captured by the analytically derived optimal parameter conditions and clearly show that reversing the rotation direction switches the optimal nonclassical signals between opposite phase regions, thus yielding a significant rotation-reversal quantum response. The nonreciprocal dual-variable quantum response also exhibits robustness within an experimentally accessible temperature range, and its realization avoids the need for pump modulation and complex device engineering, which facilitates experimental implementation. This work offers guidance for designing and regulating multifunctional nonreciprocal resources integrating continuous- and discrete-variable nonclassicality in macroscopic YIG spin systems, which may serve as useful building blocks for quantum communication and precision metrology.
