Nonlinearity at the single-photon level is important in both fundamental research and applications of quantum optics. Strong single-photon nonlinearity is usually hard to achieve with a single atom coupled to a cavity mode. Unfortunately, stronger nonlinearity cannot be achieved by coupling more atoms straightforwardly because of the gradual homogeneity of the system energy levels. Here we propose two proposals to realize deeper photon blockade with the increase of the atom number with the help of quantum Zeno dynamics. The single-photon blockade that manifests single-photon nonlinearity is achieved with high single-photon efficiency and purity. We developed a hybrid method by partitioning the system states into two subsets with one computed via a master equation and the other via a non-Hermitian Hamiltonian. This method significantly reduces computational resource requirements and enables simulations of systems with up to thousands of atoms. The results show that our proposals are robust against the inhomogeneity of atom frequency and coupling strength, which is favorable in experiments.
Nonlinearity at the single-photon level is important in both fundamental research and applications of quantum optics. Strong single-photon nonlinearity is usually hard to achieve with a single atom coupled to a cavity mode. Unfortunately, stronger nonlinearity cannot be achieved by coupling more atoms straightforwardly because of the gradual homogeneity of the system energy levels. Here we propose two proposals to realize deeper photon blockade with the increase of the atom number with the help of quantum Zeno dynamics. The single-photon blockade that manifests single-photon nonlinearity is achieved with high single-photon efficiency and purity. We developed a hybrid method by partitioning the system states into two subsets with one computed via a master equation and the other via a non-Hermitian Hamiltonian. This method significantly reduces computational resource requirements and enables simulations of systems with up to thousands of atoms. The results show that our proposals are robust against the inhomogeneity of atom frequency and coupling strength, which is favorable in experiments.
Photon blockade is a phenomenon where the presence of system nonlinearity causes the output to consist of single photons, which has been extensively studied in point atom systems, but it is barely explored in giant atom ones. In this paper, we propose giant atom-mediated photon blockade scheme based on two cavities and three cavities systems with driving field applied to the first cavity. We show that simultaneous unconventional photon blockades (UPBs) can not occur in the point atom system (the atom coupling only to the leftmost cavity) due to there always existing a cavity to have a single path. In contrast, the spatially extended nature of giant atom enables coupling to multiple cavities and allows for the introduction of a phase and coupling strength. Consequently, simultaneous UPBs in multiple cavities can be obtained due to the multipath destructive interference. Moreover, by manipulating the detuning, we observe simultaneous conventional photon blockades (CPBs) in multiple cavities. Finally, we study simultaneous two-photon blockades (2PBs) in point atom multiple cavities system.
A two-level system interacting with a cavity field is an important model for investigating the photon blockade (PB) effect. Most work on this topic has been based on the assumption that the atomic transition frequency is resonant with the fundamental mode frequency of the cavity. We relax this constraint and reexamine PB in a more general atom--cavity system with arbitrary atomic and cavity detunings from a driving field. The results show that when the signs of the atomic and cavity detunings are the same, PB occurs only in the strong-coupling regime, but for opposite signs of the atomic and cavity detunings, strong photon antibunching is observed in both the weak- and strong-coupling regimes and a better PB effect is achieved compared with the case when the signs are the same. More interestingly, we find that this PB arises from quantum interference for both weak and strong nonlinearities. These results deepen our understanding of the underlying mechanism of PB and may be help in the construction of single-photon sources with higher purity and better flexibility using atom--cavity systems.
The most simple and seemingly straightforward application of the photon blockade effect, in which the transport of one photon prevents the transport of others, would be to separate two incoming indistinguishable photons to different output ports. We show that time-energy uncertainty relations inherently prevent this ideal situation when the blockade is implemented by a two-level system. The fundamental nature of this limit is revealed in the fact that photon blockade in the strong coupling regime of cavity QED, resulting from the nonlinearity of the Jaynes-Cummings energy level structure, exhibits efficiency and temporal behavior identical to those of photon blockade in the bad cavity regime, where the underlying nonlinearity is that of the atom itself. We demonstrate that this limit can be exceeded, yet not avoided, by exploiting time-energy entanglement between the incident photons. Finally, we show how this limit can be circumvented completely by using a three-level atom coupled to a single-sided cavity, enabling an ideal and robust photon routing mechanism.
Analogous to Coulomb blockade for electrons, photon blockade is a key quantum optical effect in which the presence of one photon prevents the transmission of subsequent ones through a nonlinear medium. Beyond its fundamental interest, photon and multi-photon blockade are actively studied as mechanisms for generating technologically-relevant quantum states of light. Although photon blockade typically requires achieving strong light-matter coupling, increasing the number of atoms fails to enhance antibunching. Here, we analyze the optical transmission properties of a quantum resonator that embeds a two-photon-coupled ensemble of emitters, combining an approximate analytical approach with full quantum numerical simulations. We show that when light and matter are coupled via a two-photon interaction, both single- and multi-photon blockade can benefit from a collective enhancement. We propose different driving schemes in which the second or third-order correlation functions are strongly suppressed with increasing atom number. Differently from established methods, this collective enhancement of non-classical properties occurs with unitary transmission and is ultimately constrained only by decoherence. This demonstrates that collective two-photon couplings are a powerful mechanism for realizing photon blockade even in platforms where individual strong coupling is not achievable.
The photon blockade (PB) effect represents a quintessential manifestation of quantum optical nonlinearity, where the presence of a single photon within an optical cavity prevents the entry of a second one, thereby realizing a single-photon source. This effect underpins numerous applications in quantum information processing, secure communication, and quantum computation. Nevertheless, the intrinsic nonlinearity of practical optical systems is often too weak to produce a strong blockade, making the enhancement and controllability of the PB effect a persistent challenge. To overcome this limitation, we investigate a two-cavity quantum system incorporating two-photon dissipation as an alternative mechanism for realizing photon blockade. In contrast to conventional schemes that primarily consider single-photon loss, the proposed configuration introduces a second-order nonlinear dissipation channel, through which the correlated loss of photon pairs fundamentally modifies the photon statistics and strengthens the blockade effect. Based on quantum master equation theory, we constructed a model of a two-cavity system incorporating two-photon dissipation and analyzed the effect of different parameters on the photon blockade effect through numerical simulations.
Abstract The unconventional photon blockade, which relies on the physical mechanism of quantum interference, is primarily investigated using a general master equation, where a weak nonlinearity must be presented in the system to achieve photon antibunching. In this study, we explore the unconventional photon blockade using an alternative master equation known as the two-photon absorption master equation, which is derived from the system and environment interaction via two-photon absorption. Specifically, we find that the unconventional photon blockade can be triggered in two-coupled cavities, where each cavity interacts with a two-photon absorption environment. Different from unconventional photon blockade via the general master equation, we show that the two-photon absorption acts as the weak nonlinearity, and this photon blockade corresponds to a large average photon number. To derive optimal conditions for achieving this blockade, we propose a non-Hermitian Hamiltonian method to describe the mode loss caused by the two-photon absorption. In addition, we highlight the distinctions between our proposal and other approaches for generating single-photon states based on two-photon absorption.