Frequency Control of Single Quantum Emitters in Integrated Photonic Circuits

Abstract

Generating entangled graph states of qubits requires high entanglement rates, with efficient detection of multiple indistinguishable photons from separate qubits. Integrating defect-based qubits into photonic devices results in an enhanced photon collection efficiency, however, typically at the cost of a reduced defect emission energy homogeneity. Here, we demonstrate that the reduction in defect homogeneity in an integrated device can be partially offset by electric field tuning. Using photonic device-coupled implanted nitrogen vacancy (NV) centers in a GaP-on-diamond platform, we demonstrate large field-dependent tuning ranges and partial stabilization of defect emission energies. These results address some of the challenges of chip-scale entanglement generation. 19 NV centers within ∼ 15 nm of the diamond surface, created via implantation and annealing, couple evanescently with the GaP layer. As a result of the static dipole moment of the defect's excited state, there is variation in emission energy both between different defects, due to variation in the local environment caused by implantation and processing damage, and in the emission energy of a single defect over time due to electric field fluctuations. However, this dipole moment also enables electric field control of the defect's emission energy. 6,15,20,21 We provide this control through the addition of Ti/Au electrodes to this GaP-on-diamond photonics platform.In the photonic devices used in these experiments, 22Measurements were performed between 12-14 K in a closed-cycle He cryostat. A 532 nm laser was used for optical excitation, focused onto the sample with a 0.7 NA microscope objective. Photoluminescence (PL) was collected from the grating coupler using the same objective, coupled into a grating spectrometer, and detected by a CCD camera (Figure 1(a)).The input and collection optical paths were separated by a 562 nm dichoric beamsplitter.Bias voltages were applied using a computer-controlled piezocontroller in the range of 0-100 V.We first demonstrate electric-field tuning of a waveguide-coupled NV center. Exciting We also electrically control the emission energy of a resonator-coupled NV center. We first tune the cavity mode of a waveguide-coupled disk resonator onto NV ZPL resonance via Xe gas deposition, while collecting the PL emission from the waveguide grating coupler.The Xe gas deposition results in a redshift of the resonator cavity mode. Figure 2 (b, left) shows the resulting Xe gas tuning curve for one disk resonator. Xe gas flow is halted from t ∼ 15 minutes to t ∼ 45 minutes to perform two voltage experiments and then resumed.NV centers that couple with the cavity mode are bright when in resonance with the cavity mode and not visible otherwise.19 There are several NV centers that couple to the cavity mode for this particular disk resonator. With the cavity mode tuned to resonance with two NV centers, we apply a square wave bias voltage (Figure 2(b)), and we see the two ZPL emission lines moving in response to the applied ...

Quantum nanophotonic and nanoplasmonic sensing: towards quantum optical bioscience laboratories on chip

“…NV centres are compatible with integrated photonic circuits; the study by Faraon et al [173] demonstrates coupling of NV centre fluorescence to diamond-on-silicon waveguides and grating couplers, and the study by Gould et al [174] shows coupling to waveguides via GaP microdisks. Further to this, the GaP system has been modified to allow the single photon emission frequency to be tuned by an applied bias voltage ( Figure 7) [175]. This could compensate for the natural variation in emission frequencies from different NV centres.…”

“…Pink: GaP microdisks and waveguides; Yellow: Ti/Au electrodes for applying bias voltage;Grey: diamond substrate. Reprinted with permission from the study by Schmidgall et al[175]. Copyright (2018) American Chemical Society.…”

Advances in quantum light emission from 2D materials

“…While resonant excitation was used to stabilize the ZPL for few tens of seconds [36], anti-Stokes excitation of quantum emitters in hBN was also used to suppress the spectral wandering [37]. Improving material quality [38] and/ or active electrical [39][40][41] or strain-based feedback can further help to minimize unwanted spectral wandering.…”

Diamond as a Platform for Integrated Quantum Photonics

“…Electrical tuning and stabilization of NV centers in an integrated optical circuit has been recently demonstrated in ref. [] on the hybrid GaP‐on‐diamond photonic platform (see Figure d,e).…”