Enhanced entanglement and asymmetric EPR steering between magnons

Abstract

The generation and manipulation of strong entanglement and Einstein-Podolsky-Rosen (EPR) steering in macroscopic systems are outstanding challenges in modern physics. Especially, the observation of asymmetric EPR steering is important for both its fundamental role in interpreting the nature of quantum mechanics and its application as resource for the tasks where the levels of trust at different parties are highly asymmetric. Here, we study the entanglement and EPR steering between two macroscopic magnons in a hybrid ferrimagnet-light system. In the absence of light, the two types of magnons on the two sublattices can be entangled, but no quantum steering occurs when they are damped with the same rates. In the presence of the cavity field, the entanglement can be significantly enhanced, and strong two-way asymmetric quantum steering appears between two magnons with equal dissipation. This is very different from the conventional protocols to produce asymmetric steering by imposing additional unbalanced losses or noises on the two parties at the cost of reducing steerability. The essential physics is well understood by the unbalanced population of acoustic and optical magnons under the cooling effect of cavity photons. Our finding may provide a novel platform to manipulate the quantum steering and the detection of bi-party steering provides a knob to probe the magnetic damping on each sublattice of a magnet.

Dissipative generation of significant amount of photon-phonon asymmetric steering in magnomechanical interfaces

“…Recently, the proposal of optomagnonic Bell test is also presented [46]. Apart from to the studies mentioned above, considerable attention has been devoted to the generation of quantum steering [47][48][49][50][51], which is intrinsically distinct from quantum entanglement and Bell nonlocality for its asymmetric characteristics between the parties involved.…”

“…Light-mechanical quantum steering [52][53][54] or steering between two massive mechanical oscillators [55][56][57] have been widely studied in cavity optomechanical systems, suggesting that photon-phonon or phonon-phonon one-way quantum steering can be achieved in such systems [54,56,57]. Primary researches also indicate that asymmetric steering between two magnons [47,49] can be obtained in cavity magnonics and asymmet-ric steering between a macroscopic mechanical oscillator and a magnon mode [50] can be obtained in a microwave-mediated phonon-magnon interface. Nevertheless, whether asymmetric steering can be directly obtained in cavity magnomechanical system is still almost in blank.…”

Implementation and enhancement of nonreciprocal quantum synchronization with strong isolation in antiferromagnet-cavity systems

“…Additionally, cavity spintronics [33][34][35][36][37][38][39][40][41][42][43][44][45][46], a new interdisciplinary subject, which studies a hybrid quantum system, seems to be a potential candidate for quantum information processing. The key element of the system is magnon, the quanta for a collective excitation of spins in a magnetic material, which can strongly interact with microwave photons via magnetic dipole interaction.…”

“…g ab = H ex,a H ex,b cos(kδ) denotes coupling rate between the two magnon modes, g oc = µ 0 ω ± S o N/2V denotes the interaction strength between magnon o and photon mode c with N the number of spins in each sublattice. In the long-wavelength limit (k = 0) [39][40][41], the Hamiltonian reads…”

“…To show NQS more clearly, we draw curves for the degree of quantum synchronization S 12 , S 21 and SIR S iso as a function of external static field H in Fig. 2, where we have chosen experimental parameters [39][40][41]: S a = S b = S because of the sublattice permutation symmetry of AFMs [39][40][41], H an = 0.0163H ex , H sp = H an (H an + 2H ex ) which is called the spin-flop field, ω c /H sp = 0.85, g ac = g bc = g = 0.01H ex , g ab /H ex = 1, κ a = κ b = κ, κ c = 3κ a = 3κ b = 0.003H ex , and ∆ F /H sp = 0.05. It is noted that all parameters chosen above satisfy the requirement of steady conditions, which is guaranteed by the negative real component of eigenvalues of the drift matrix A.…”