Strong coupling between two quantum dots and a photonic crystal cavity using magnetic field tuning

Abstract

We demonstrate strong coupling between two indium arsenide (InAs) quantum dots (QDs) and a photonic crystal cavity by using a magnetic field as a frequency tuning method. The magnetic field causes a red shift of an exciton spin state in one QD and a blue shift in the opposite exciton spin state of the second QD, enabling them to be simultaneously tuned to the same cavity resonance. This method can match the emission frequency of two QDs separated by detunings as large as 1.35 meV using a magnetic field of up to 7 T. By controlling the detuning between the two QDs we measure the vacuum Rabi splitting (VRS) both when the QDs are individually coupled to the cavity, as well as when they are coupled to the cavity simultaneously. In the latter case the oscillator strength of two QDs shows a collective behavior, resulting in enhancement of the VRS as compared to the individual cases. Experimental results are compared to theoretical calculations based on the solution to the full master equation and found to be in excellent agreement.

Nanophotonic Quantum Interface for a Single Solid-state Spin

“…Tuning compensates for spectral mismatch between the quantum dot exciton energy and the cavity resonant frequency, and also provides control over the interaction strength between the two systems. The quantum dot exciton energy can be tuned by various means such as changing the sample temperature [34,38], applying an AC Stark shift [90], utilizing the quantum confined Stark effect [139], or applying a magnetic field [140][141][142].…”

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].…”

Tuning of emission energy of single quantum dots using phase-change mask for resonant control of their interactions

“…Reversible in situ control of QD emission energy has been achieved using strain [11][12][13], magnetic fields [14,15], electric fields (DC Stark effect) [16,17], optical fields (AC Stark effect) [18], and temperature [19]. Magnetic field tuning is a promising approach due to its wide tunability range.…”