Unconventional phonon blockade via atom-photon-phonon interaction in hybrid optomechanical systems

Topological phases and non-Hermitian topology in tunable nonreciprocal cyclic three-mode optical systems

We propose a method for simulating a 1D non-Hermitian Su-Schrieffer-Heeger model with modulated nonreciprocal hopping using a cyclic three-mode optical system. The current system exhibits different localization of topologically nontrivial phases, which can be characterized by the winding number. We find that the eigenenergies of such a system undergo a real-complex transition as the nonreciprocal hopping changes, accompanied by a non-Bloch parity-time symmetry breaking. We explain this phase transition by considering the evolution of saddle points on the complex energy plan and the ratio of complex eigenenergies. Additionally, we demonstrate that the skin states resulting from the non-Hermitian skin effect possess higher-order exceptional points under the critical point of the non-Bloch parity-time phase transition. Furthermore, we investigate the non-Hermitian skin phase transition by the directional mean inverse participation ratio and the generalized Brillouin zone. This work provides an alternative way to investigate the novel topological and non-Hermitian effects in nonreciprocal optical systems.

Strong antibunching effect under the combination of conventional and unconventional photon blockade

Photon blockade (PB), an effective method of generating antibunching effect, is a critical way to construct a single photon source. The PB effect can be divided into conventional PB effect (CPB) and unconventional PB effect (UPB). Most studies focus on designing systems to successfully enhance CPB or UPB effect individually. However, CPB extremely depends on the nonlinearity strength of the Kerr materials to achieve strong antibunching effect while UPB relies on quantum interference beset with the high probability of the vacuum state. Here, we propose a method to utilize the relevance and complementarity of CPB and UPB to realize these two types simultaneously. We employ a hybrid Kerr nonlinearity two-cavity system. Because of the mutual assistance of two cavities, CPB and UPB can coexist in the system under certain states. In this way, for the same Kerr material, we reduce the value of the second-order correlation function due to CPB by three orders of magnitude without losing the mean photon number due to the presence of UPB, so the advantages of both PB effects are fully reflected in our system, which is a huge performance boost for single photons.

Optical noise-resistant nonreciprocal phonon blockade in a spinning optomechanical resonator

A scheme of nonreciprocal conventional phonon blockade (PB) is proposed in a spinning optomechanical resonator coupled with a two-level atom. The coherent coupling between the atom and breathing mode is mediated by the optical mode with a large detuning. Due to the Fizeau shift caused by the spinning resonator, the PB can be implemented in a nonreciprocal way. Specifically, when the spinning resonator is driven from one direction, the single-phonon (1PB) and two-phonon blockade (2PB) can be achieved by adjusting both the amplitude and frequency of the mechanical drive field, while phonon-induced tunneling (PIT) occurs when the spinning resonator is driven from the opposite direction. The PB effects are insensitive to cavity decay because of the adiabatic elimination of the optical mode, thus making the scheme more robust to the optical noise and still feasible even in a low-Q cavity. Our scheme provides a flexible method for engineering a unidirectional phonon source with external control, which is expected to be used as a chiral quantum device in quantum computing networks.

Phonon Blockade in Parametrically Pumped Acoustic Cavity at Finite Temperature

In this study, we investigated the phonon blockade effect in a parametrically driven and dissipative acoustic cavity at finite temperature. With the approximated analytical results based on the steady-state density-matrix master equation, we found that a quantum-interference-induced phonon blockade exists at finite temperature. We found a crossover between the quantum and thermal regimes on the curve of the second-order correlation function of the acoustic mode as the temperature increases. This phenomenon implies an asymmetry about the quantum and classic regimes. We also numerically simulated the single-phonon emission using the Monte Carlo wave function method. The results showed that a wide and deep dip around the zero time delay exists on the curve of the time-delayed second-order correlation function, which implies the possibility of observing a strong phonon blockade with pulse driving. Our study outlines a potential candidate for a efficient single-phonon source and applications in quantum information and phononic quantum networks.