Magnetic field tuning of a quantum dot strongly coupled to a photonic crystal cavity

Abstract

We apply magnetic fields of up to 7 T to an indium arsenide quantum dot (QD) strongly coupled to a photonic crystal cavity. The field lifts the degeneracy of QD exciton spin states, and tune their emission energy by a combination of diamagnetic and Zeeman energy shifts. We use magnetic field tuning to shift the energies of the two exciton spin states to be selectively on resonance with the cavity. Strong coupling between the cavity and both states is observed. Magnetic field tuning enables energy shifts as large as 0.83 meV without significant degradation of the QD-cavity coupling strength.

Optical nonlinearity in a quantum dot–microcavity system under an external magnetic field

“…Nevertheless, in micropillar cavity systems, the ellipticity of the micropillar lifts the degeneracy of the two orthogonally linearly polarized modes, causing mode splitting [26,29]. As the excitonic fine structure splitting is neglected, the excitonic eigenstate jσ i (jσ − i) is formed by an electron of spin −1∕2 (1∕2) and a hole of spin 3∕2 (−3∕2) and has right (left) circular polarization [20,[22][23][24]. In the linearly polarized basis, if we define the excitonic states jXi jσ i jσ − i∕ 2 p and jY i jσ i − jσ − i∕ 2 p i [30], the coupling between the excitonic spin states and bimodal cavity could be effectively treated with coupling between the linearly polarized excitonic states and cavity modes with corresponding linear polarization [31].…”

“…Introducing an external magnetic field provides an approach to manipulate the QD excitonic spin states due to the Zeeman effect [19,20], and the coupling constant of QD-cavity system as well [21]. Excitonic Zeeman splitting gives rise to spin-selective coupling of an exciton and a cavity mode in both strong coupling [22] and weak coupling regimes [23], as well as collective coupling of two QDs to a single cavity mode intermediated by a magnetic field [24]. Recently, high fidelity and high speed spin initialization and manipulation using a single charged QD in a bimodal cavity with an external magnetic field was reported [25], and interaction between the excitonic spin states and the polarized modes of a bimodal cavity under a magnetic field has been experimentally implemented [26].…”

Deterministic generation of entanglement between a quantum-dot spin and a photon

“…We also assume that the transition |↑ ↔ |⇑ is resonant with the cavity mode, while the other transition is detuned. In a real experiment, a variety of methods can exist to tune the desired quantum-dot transition to the cavity, including varying temperature [28,29], changing the magnetic field [30], applying strain [31], or tuning the cavity resonance [32,33].…”

Selective coupling of quantum dot exciton spin states to a photonic crystal cavity using magnetic field tuning

“…Magnetic field lifts the degeneracy of QD exciton spin states due to the Zeeman effect, providing access to the individual QD spin states. In addition, a magnetic field can be useful as a method to tune QD emission frequency, which can be used to control the interaction between quantum emitters and an optical cavity [3][4][5]. We apply a magnetic field to photonic crystal cavity devices with embedded InAs QDs, and demonstrate strong coupling between individual QD exciton spin states and a photonic crystal cavity.…”