Nonreciprocal entanglement via Barnett effect in a hybrid quadpartite system

Abstract We present a theoretical scheme for nonreciprocal entanglement in a quadpartite system via the
Barnett effect. Our quadpartite system is based on a microwave (MW) cavity, simultaneously
coupled with phonon, an LC circuit, and magnon via radiation pressure, adjustable capacitance of
the LC circuit, and Kittel magnetostatics, respectively. By changing the magnetic field’s direction,
the Barnett effect produces a Barnett frequency shift that may be efficiently controlled to be either
negative or positive. By controlling system parameters, we show that, by employing a bidirectional
contrast ratio, multipartite entanglements can be non-reciprocally enhanced via the Barnett shift.
In addition, Barnett’s shift also affects the robustness of these entanglements against the bath
temperature. Such a system with a variety of control mechanisms might find a range of applications
in quantum technologies, computation, and information processing.