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The Review of Laser Engineering

Entangled Photon Generation from a Quantum Dot in Microcavity in a Strong Coupling Regime

Hiroshi Ajiki

Published Jan 1, 2013• 0 citations
Publisher

Abstract

Theoretical study on entangled photon generation from a quantum dot (QD) embedded in microcavity is briefly reviewed within a strong coupling regime. In this system, entangled photon pairs can be generated through the cascade photon emission via dressed states in the cavity quantum electrodynamics (CQED). Excitation levels of a QD are modeled by a V-type three-level system and four-level system including a biexciton. In contrast to the entangled-photon generation until now, all four Bell states can be generated from an identical cavity system by simply selecting applied-field polarizations and frequencies as characteristic features of the CQED. The CQED effects play a crucial role in providing a high degree of entanglement: (i) spectral fi ltering can be used to extract entangled photons due to the vacuum Rabi splitting and (ii) non-entangled co-polarized photons are strongly suppressed due to the photon blockade effect.

DOI
10.2184/lsj.41.7_492

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Theoretical study on entangled photon generation from a quantum dot (QD) embedded in microcavity is briefly reviewed within a strong coupling regime. In this system, entangled photon pairs can be generated through the cascade photon emission via dressed states in the cavity quantum electrodynamics (CQED). Excitation levels of a QD are modeled by a V-type three-level system and four-level system including a biexciton. In contrast to the entangled-photon generation until now, all four Bell states can be generated from an identical cavity system by simply selecting applied-field polarizations and frequencies as characteristic features of the CQED. The CQED effects play a crucial role in providing a high degree of entanglement: (i) spectral fi ltering can be used to extract entangled photons due to the vacuum Rabi splitting and (ii) non-entangled co-polarized photons are strongly suppressed due to the photon blockade effect.
Abstract We theoretically study polarization‐entangled photon generation from a single quantum dot in a microcavity. Entangled‐photon pairs with singlet or triplet Bell states are generated in the resonant‐hyperparametric scattering via dressed states in the cavity QED. Although co‐polarized non‐entangled photons are also generated, the generation is dramatically suppressed in the strong‐coupling limit owing to the photon blockade effect. Finite binding energy of biexciton is also important for the generation of photon pairs with high degree of entanglement. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
We propose a new type of entangled-photon generation from a V-type system in a microcavity. In contrast to the entangled-photon generation until now, all four Bell states can be freely generated from an identical cavity system by simply selecting applied-field polarizations and frequencies due to the excitation of dressed states in cavity quantum electrodynamics (CQED). CQED effects play a crucial role in providing a high degree of entanglement: (i) spectral filtering can be used to extract entangled photons due to the vacuum Rabi splitting and (ii) non-entangled co-polarized photons are strongly suppressed due to the photon blockade effect. The proposed system efficiently generates a high degree of entangled photons by moderately increasing the applied-field intensity.
We theoretically investigate polarization-entangled-photon generation by using a quantum dot embedded in a microcavity. In the absence of a biexciton, two of the four Bell states can be generated by applying cross-circularly polarized laser fields because of a cavity quantum electrodynamics effect [Ajiki et al., New J. Phys. 11, 033033 (2009)]. In the presence of the biexciton state, the generation of these Bell states can be forbidden under specific conditions. Furthermore, another type of Bell state can be generated by applying cross-circularly polarized fields. Our results indicate that one can generate three different types of Bell-state photon pairs just by changing the frequencies of the applied fields.
We theoretically investigate fast and highly efficient entangled-photon generation by irradiating a quantum dot (QD) embedded in a microcavity with short laser pulses. We evaluate the optimized width and field strength of the pulses for achieving a high population of an excited state as an entangled-photon source. We also calculate the emission time of the entangled photon pair as a function of the cavity quality factor QQQ. The shortest emission time reaches 3/(4g)3/(4g)3/(4g) under the condition $Q={\ensuremath{\omega}}_{0}/(4g)$, where ggg is the coupling frequency between the cavity photon and excited states of the QD and ${\ensuremath{\omega}}_{0}$ is the excitation frequency of the QD. The QD-cavity system has a potential for fast and efficient generation of high-quality entangled-photon pairs.
Abstract We propose polarization‐entangled photon generation via resonant hyper‐parametric scattering of a V‐type system in microcavity. Although a bare V‐type system cannot generate entangled photon pairs, microcavity makes the generation possible because of the formation of dressed states. In the strong‐coupling limit, generation of non‐entangled co‐polarized photons is considerably suppressed due to the photon blockade effect. Furthermore, some entangled photons have different frequencies from those of the input fields, and thus, we can utilize spectral filtering in order to extract entangled photons. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Entangled photon pairs are a crucial resource in quantum information processing. However, common sources of entangled photon pairs, such as generation by spontaneous parametric down-conversion, impose a Poisson distribution on the pairs, limiting their applicability to quantum information processing. Therefore, generating entangled photon pairs exhibiting a sub-Poisson distribution (i.e., entangled photon bundle) would be crucial/an important advancement in the current research context. Recently, it has been proposed that antibunched photon pairs can be generated using pulsed excitation of quantum dots based on photon blockade. In this work we propose a scheme to generate entangled photon pairs with strong antibunching properties via continuous driving. Under two-photon resonant continuous pumping, a quantum dot is first excited to a biexciton state and then emits a pair of entangled photons into a two-mode cavity. Owing to the strong coupling between the quantum dot and optical modes of the cavity, at most one pair of left-/right-polarized photons exists at a time in the cavity. Specifically, the antibunching effect, average photon number, and entanglement of the left- or right-polarized photons can be resonantly enhanced when the coupling strengths between the exciton (biexciton) transition and cavity modes are equal. Moreover, our results show that the binding energy of the biexciton substantially affects the antibunching effect, average photon number, and entanglement of the left-/right-polarized photons. With suitable parameters, we can realize photon pairs with strong antibunching, a large average photon number, and deep entanglement. Hence, the studied quantum dot-cavity system is a promising source of antibunched entangled photon pairs.