Unconventional Photon Blockade Research Articles

Improvement of nonreciprocal unconventional photon blockade by two asymmetrical arranged atoms embedded in a cavity.

We improve the nonreciprocal unconventional photon blockade (UCPB) in an asymmetrical single-mode cavity with two asymmetrical arranged two-level atoms (TLAs) where cavity and atom spatial symmetry breakings are involved in. In order to get direction-dependent UCPB in asymmetrical system, we deduce two restrictions of frequency and intensity through the steady solution of the cavity QED system analytically. The former restriction is exactly the same as that of a single-atom case, and the latter restriction combined with both spatial asymmetries. Controllable UCPB in this model shows an improving nonreciprocal UCPB with wider operating regime which is promoted by two asymmetrical arranged atoms. The most innovation of this work is that the contributions of two spatial symmetry breakings are figured out clearly and they play different roles in nonreciprocal UCPB. The cavity spatial symmetry breaking and weak nonlinearity are essential to quantum nonreciprocity, while the atoms spatial symmetry is not and it only can promote such nonreciprocal UCPB. Our findings show a prospective access to manipulate quantum nonreciprocity by a couple of atoms.

Manipulation of nonreciprocal unconventional photon blockade in a cavity-driven system composed of an asymmetrical cavity and two atoms with weak dipole–dipole interaction

We present a work of manipulating collective unconventional photon blockade (UCPB) and nonreciprocal UCPB (NUCPB) in a cavity-driven system composed of an asymmetrical single-mode cavity and two interacting identical two-level atoms (TLAs). When the atoms do not interact directly, the frequency and intensity restrictions of collective UCPB can be specified, and a giant NUCPB exists due to the splitting of optimal atom–cavity coupling strength in proper parameter regime. However, if a weak atom–atom interaction which provides a new and feeble quantum interference pathway to UCPB is taken into account, two restrictions of UCPB are combined complexly, which are rigorous to be matched simultaneously. Due to the push-and-pull effect induced by weak dipole–dipole interaction, the UCPB regime is compressed more or less. NUCPB is improved as a higher contrast is present when the two complex UCPB restrictions are matched, while it is suppressed when the restrictions are mismatched. In general, whether NUCPB is suppressed or promoted depends on its working parameters. Our findings show a prospective access to produce giant quantum nonreciprocity by a couple of weakly interacting atoms.

Giant nonreciprocal unconventional photon blockade with a single atom in an asymmetric cavity

Inspired by the advantage of unconventional photon blockade (UCPB), we propose a simple cavity-driven quantum electrodynamics model composed of a single two-level atom embedded in an asymmetrical Fabry-Perot cavity. We derive the necessary matching conditions of frequency and intensity required for unconventional photon blockade. In the asymmetric cavity, the optimal atom-cavity coupling strength to get UCPB is related to the driving direction, which causes the equal-time second-order correlation function ${g}^{(2)}(0)$ of the cavity field depending on the driving direction, too. Due to the direction dependent effect, the output photons can be bunched in one direction incident while they are antibunched in the opposite direction incident, which is the so-called nonreciprocal UCPB (NUCPB). A giant NUCPB can be obtained under the appropriate parameter regime, where the output photons are fully antibunching in the opposite driving case. Our findings show a prospective path to producing giant quantum nonreciprocity.

Giant Enhancement of Unconventional Photon Blockade in a Dimer Chain.

Unconventional photon blockade refers to the suppression of multiphoton states in weakly nonlinear optical resonators via the destructive interference of different excitation pathways. It has been studied in a pair of coupled nonlinear resonators and other few-mode systems. Here, we show that unconventional photon blockade can be greatly enhanced in a chain of coupled resonators. The strength of the nonlinearity in each resonator needed to achieve unconventional photon blockade is suppressed exponentially with lattice size. The analytic derivation, based on a weak drive approximation, is validated by wave function MonteCarlo simulations. These findings show that customized lattices of coupled resonators can be powerful tools for controlling multiphoton quantum states.

Photon antibunching in a cavity-QED system with two Rydberg–Rydberg interaction atoms

We propose how to achieve strong photon antibunching effect in a cavity-QED system coupled with two Rydberg–Rydberg interaction atoms. Via calculating the equal time second-order correlation function $$g^{(2)}(0)$$ , we find that the unconventional photon blockade and the conventional photon blockade appear in the atom-driven scheme, and they are both significantly affected by the Rydberg–Rydberg interaction. We also find that under appropriate parameters, one obtains the extremely strong photon antibunching by combining the conventional photon blockade and the unconventional photon blockade, and the mean photon number in the cavity can be improved significantly. In the cavity-driven scheme, the existence of the Rydberg–Rydberg interaction severely destroys the photon antibunching under the unconventional photon blockade mechanism. These results will help to guide the implementation of the single photon emitter in the Rydberg atoms-cavity system.

Nonreciprocal photon blockade and directional amplification in a spinning resonator coupled to a two-level atom

We propose a scheme to realize nonreciprocal photon blockade and directional amplification in a spinning resonator with clockwise and counterclockwise traveling modes coupled to a stationary two-level atom. By manipulating the rotational frequency of the resonator, the two-level atom can be resonant with one of the traveling modes and largely detuned from the other one. Nonreciprocal conventional photon blockade is induced by the difference of the detunings between the two-level atom and the optical modes traveling in different directions. Besides that, nonreciprocal unconventional photon blockade (UPB) based on the quantum interference can also be observed in the system. Based on the mechanism for nonreciprocal UPB, directional amplification of the blockaded photons is predicted by driving the spinning resonator and stationary two-level atom simultaneously. Our proposal will be applicable to achieve highly efficient nonreciprocal single-photon devices for applications in chiral quantum information processing.

Nonreciprocal unconventional photon blockade with spinning atom-cavity

In this work, we propose to manipulate the statistical properties of the photons transport nonreciprocally via rotating nonlinear devices consisting of an atom coupled to a spinning cavity. This nonreciprocal effect allows the flow of light from one side but blocks it from the other with the same driving strength. We show that the nonreciprocal unconventional photon blockade can happen when the cavity is driven by the laser field. Under the weak driving condition, we discuss the physical origins of the nonreciprocal unconventional photon blockade, which originates from the destructive quantum interference between different paths from the ground state to the two-photon state by driving the device from the left side, while the quantum interference paths are broken when the device is driven from the right side, which leads to the occurring of the photon bunching. The optimal conditions for strong photon antibunching are analytically derived, which are in good agreement with those obtained by numerical simulations. Our proposal has potential applications for the on-chip nonreciprocal single-photon devices and provides an effective way for potential applications in solid state quantum computation and quantum information process.

Unconventional Photon Blockade in Quantum‐Well Microcavities with Squeezed Light

The single‐photon blockade effect arising in a cavity containing a quantum well and interacting with squeezed light, resulting from a down‐conversion process through a nonlinear medium, is investigated. Optical parametric oscillator (OPO) materials with positive and negative second‐order susceptibilities are considered. By solving the master equation analytically in the weak‐driving limit and calculating the second‐order equal‐time correlation function, it is found that strong photon antibunching can be achieved in this system with weak excitonic nonlinearity or squeezed light via a destructive quantum interference mechanism. The optimal conditions for the photon blockade are derived analytically and discussed in details. Unlike the excitonic nonlinearity, a strong photon blockade occurs with the squeezed light at total or quasitotal resonance, even in the weak coupling regime, using an OPO material with negative second‐order nonlinear susceptibility. By acting on the driving coherent pump frequency, the control of the cavity output is achieved and the scheme can serve as a tunable single‐photon emission source.

Multi-time correlations in the positive-P, Q, and doubled phase-space representations

A number of physically intuitive results for the calculation of multi-time correlations in phase-space representations of quantum mechanics are obtained. They relate time-dependent stochastic samples to multi-time observables, and rely on the presence of derivative-free operator identities. In particular, expressions for time-ordered normal-ordered observables in the positive-P distribution are derived which replace Heisenberg operators with the bare time-dependent stochastic variables, confirming extension of earlier such results for the Glauber-Sudarshan P. Analogous expressions are found for the anti-normal-ordered case of the doubled phase-space Q representation, along with conversion rules among doubled phase-space s-ordered representations. The latter are then shown to be readily exploited to further calculate anti-normal and mixed-ordered multi-time observables in the positive-P, Wigner, and doubled-Wigner representations. Which mixed-order observables are amenable and which are not is indicated, and explicit tallies are given up to 4th order. Overall, the theory of quantum multi-time observables in phase-space representations is extended, allowing non-perturbative treatment of many cases. The accuracy, usability, and scalability of the results to large systems is demonstrated using stochastic simulations of the unconventional photon blockade system and a related Bose-Hubbard chain. In addition, a robust but simple algorithm for integration of stochastic equations for phase-space samples is provided.

Atom‐Mediated Phonon Blockade and Controlled‐Z Gate in Superconducting Circuit System

AbstractA scheme to generate phonon blockade in a superconducting Josephson junction circuit system is proposed, where the photon, phonon, and artificial two‐level atom are bound into a tripartite interaction. The phonon blockade in the proposal mediated by the two‐level atom differs from the phonon blockade resulting from the single phonon resonance and the destructive interference between different paths, which can be generated within a weak coupling region and a large range of cavity detuning, even with a large optical dissipation rate. In addition, under certain condition, the unconventional photon blockade can be achieved but the phonon blockade is still maintained. Based on the phonon blockade, it is shown that the controlled‐Z gate (CZ) can be implemented with the tripartite interaction.

Realization of the unconventional photon blockade based on a three-wave mixing system.

In this paper, the unconventional photon blockade is studied in a three-wave-mixing system with a non-degenerate parametric amplification. A method of only retaining the Fock-state basis in the interference path is used to calculate the optimal analytic conditions of unconventional photon blockade. The numerical results agree well with the analytic conditions, which verifies the validity of this method. Our calculations indicate that the strong photon antibunching can be obtained in the high-frequency mode of the three-wave mixing. And the influence of system parameters on photon blockade is also discussed.

Photon blockade in a bimode nonlinear nanocavity embedded with a quantum dot

We study the photon antibunching effect in a bimode nano-optical cavity filled with the second-order nonlinear material and embedded with a quantum dot. Analytical results show that both the conventional photon blockade (CPB) induced by the nonlinear interaction between polaritons and the unconventional photon blockade (UCPB) induced by the quantum interference appear in our model. In particular, we find that CPB and UCPB can simultaneously occur in an overlapped parameter regime, which allows one to prepare a single-photon source with high purity and high brightness in the strong-coupling regime. Furthermore, owing to the multipathway interference in this composite model, the photon antibunching effect is significantly enhanced compared to that in the Jaynes-Cummings model and in the degenerate optical parametric amplifier in the weak-coupling regime.

Nonlinear Quantum Optics with Trion Polaritons in 2D Monolayers: Conventional and Unconventional Photon Blockade.

We study a 2D system of trion polaritons at the quantum level and demonstrate that for monolayer semiconductors they can exhibit a strongly nonlinear optical response. The effect is due to the composite nature of trion-based excitations resulting in their nontrivial quantum statistical properties, and enhanced phase space filling effects. We present the full quantum theory to describe the statistics of trion polaritons, and demonstrate that the associated nonlinearity persists at the level of few quanta, where two qualitatively different regimes of photon antibunching are present for weak and strong single photon-trion coupling. We find that single photon emission from trion polaritons becomes experimentally feasible in state-of-the-art transition metal dichalcogenide setups. This can foster the development of quantum polaritonics using 2D monolayers as a material platform.

Emission of single photons in the weak coupling regime of the Jaynes Cummings model

A recently proposed variant of an unconventional photon blockade scheme is studied for a single emitter weakly coupled to a resonator mode. By controlling two weak coherent fields driving the emitter and the resonator mode, a strongly nonclassical output field is obtained, which is not only antibunched, but has vanishing higher photon number coincidences. For a given set of system parameters, the frequencies and strengths of the driving fields that yield such an output are given.

Unconventional photon blockade in a three-mode system with double second-order nonlinear coupling* *Project supported by the National Natural Science Foundation of China (Grant No. 11647054) and the Natural Science Foundation of Jilin Province, China (Grant No. JJKH20181088KJ).

The unconventional photon blockade (UPB) for low-frequency mode is investigated in a three-mode system with double second-order nonlinearity. By analyzing the Hamiltonian of the system, the optimal analytic condition of UPB in low-frequency mode is obtained. The numerical results are calculated by solving the master equation in a truncated Fock space, which agrees well with the analytic conditions. Through the numerical analysis of the system, it is found that the weak driving strength is favorable for the system to realize the UPB effect, and the system is insensitive to the changes of attenuation rate and environmental temperature. The comparison with the two-mode system and another similar three-mode system shows that, under similar system parameters, the UPB effect of this double two-order nonlinear system is more obvious.

Dynamical blockade in a bosonic Josephson junction using optimal coupling

In this paper we use time-dependent Josephson coupling to enhance unconventional photon blockade in a system of two coupled nonlinear bosonic modes which are initially loaded with weakly populated coherent states, so the evolution is restricted to the manifold of up to two field quanta. Using numerical optimal control, we find the optimal coupling which minimizes the two-photon occupation of one mode, which is actually transferred to the other, while maintaining a nonzero one-photon occupation in the same mode. Moreover, we choose for the continuous coupling to vanish after the transfer between the modes such that they are decoupled and one of them is left only with some one-photon population which can be observed upon its decay. We numerically find lower values of the second-order correlation function obtained at earlier times than with constant coupling, with larger one-photon populations and for longer time windows, corresponding thus to higher emission efficiency and easier detection. The presented methodology is not restricted to the system under study, but it can also be transferred to other related frameworks, to find the optimal driving fields which can improve the single-photon emission statistics from these systems.

Conventional and Unconventional Photon Statistics

AbstractThe photon statistics emitted by a large variety of light‐matter systems under weak coherent driving can be understood, to lowest order in the driving, in the framework of an admixture of (or interference between) a squeezed state and a coherent state, with the resulting state accounting for all bunching and antibunching features. One can further identify two mechanisms that produce resonances for the photon correlations: i) conventional photon blockade describes cases that involve a particular quantum level or set of levels in the excitation/emission processes with interferences occurring to all orders in the photon numbers, while ii) unconventional photon blockade describes cases where the driving laser is far from resonance with any level and the interference occurs for a particular number of photons only, yielding stronger correlations but only for a definite number of photons. Such an understanding and classification allows for a comprehensive and transparent description of the photon statistics from a wide range of disparate systems, where optimum conditions for various types of photon correlations can be found and realized.

Enhancement of photon blockade effect via quantum interference.

We study the photon blockade effect in a coupled cavity system, which is formed by a linear cavity coupled to a Kerr-type nonlinear cavity via a photon-hopping interaction. We explain the physical phenomenon from the viewpoint of the conventional and unconventional photon blockade effects. The corresponding physical mechanisms of the two kinds of photon blockade effects are based on the anharmonicity in the eigenenergy spectrum and the destructive quantum interference between two different transition paths, respectively. In particular, we find that the photon blockade via destructive quantum interference also exists in the conventional photon blockade regime and that the unconventional photon blockade occurs in both the weak- and strong-Kerr nonlinearity cases. The photon blockade effect can be observed by calculating the second-order correlation function of the cavity field. This model is general and hence it can be implemented in various experimental setups such as coupled optical-cavity systems, coupled photon-magnon systems, and coupled superconducting-resonator systems. We present some discussions on the experimental feasibility.

Reconfigurable Photon Sources Based on Quantum Plexcitonic Systems.

A single photon in a strongly nonlinear cavity is able to block the transmission of a second photon, thereby converting incident coherent light into antibunched light, which is known as the photon blockade effect. Photon antipairing, where only the entry of two photons is blocked and the emission of bunches of three or more photons is allowed, is based on an unconventional photon blockade mechanism due to destructive interference of two distinct excitation pathways. We propose quantum plexcitonic systems with moderate nonlinearity to generate both antibunched and antipaired photons. The proposed plexcitonic systems benefit from subwavelength field localizations that make quantum emitters spatially distinguishable, thus enabling a reconfigurable photon source between antibunched and antipaired states via tailoring the energy bands. For a realistic nanoprism plexcitonic system, chemical and optical schemes of reconfiguration are demonstrated. These results pave the way to realize reconfigurable nonclassical photon sources in a simple quantum plexcitonic platform.

Nonreciprocal unconventional photon blockade in a driven dissipative cavity with parametric amplification

In this paper, we show that nonreciprocal unconventional photon blockade can be observed in a spinning cavity immersed in a degenerate optical parametric amplifier (OPA) driven by the laser driving with weak Kerr nonlinearities through the Fizeau drag. We analytically derive the optimal conditions for strong antibunching, which are in good agreement with those obtained by numerical simulations. Under the weak driving condition, we discuss the physical origins of the nonreciprocal unconventional photon blockade, which originates from the destructive interference between different paths from the ground state to two-photon states by driving the device from the left side. While the quantum interference paths are broken when the device is driven from the right side, which leads to the occurring of the photon bunching. Moreover, we extend the above results to the general non-Markovian regimes, in which the cavity couples with a thermal reservoir consisting of collection of infinite oscillators (bosonic photonic modes). We show nonreciprocal unconventional photon blockade exhibits a transition from the non-Markovian to Markovian regimes by controlling environmental spectral width regardless of the weakness of OPA gain and driving field.