Upcoming quantum technologies require scalable and cost-efficient technical solutions for widespread functionality. In order to exploit the quantum states of light, single-photon detectors are essential for application. Here, we present a low-footprint plug-and-play multi-channel single-photon detector system featuring integrated photonics that allows for ultra-fast quantum key distribution (QKD). Each channel comprises a superconducting nanowire single-photon detector (SNSPD) patterned from a niobium-titanium nitride (NbTiN) superconducting film atop silicon nitride waveguide structures. Subsequently, the on-chip photonics are interfaced by broadband 3D polymeric fiber-to-chip couplers to the ports of an 8x8 fiber array. The readout electronics allow for individual evaluation of up to 64 channels simultaneously. Integrated to a QKD experiment, a pair of the system's detection channels achieves secret key rates of up to 2.5 Mbit/s employing a coherent one-way protocol.
The integration of nano-scale quantum emitters with nano-photonic circuits is a prerequisite for a broad range of quantum technologies, benefitting quantum communication, quantum sensing or quantum information processing. However, the assembly of single emitters with high positioning accuracy in large-scale arrays and their efficient interfacing with photonic quantum channels constitutes a major challenge. Here, we show how single colloidal core-shell quantum dots (CQDs) are embedded in photonic integrated circuits that allow for individual excitation and photoluminescence collection. By utilizing finite-difference time-domain simulations, we design nanophotonic interfaces with high coupling efficiencies between CQDs and single-mode optical waveguides. Here, we utilize a tantalum pentoxide (Ta2O5) on insulator nanophotonic platform that enables integrated optics experiments at the single-photon level due to low intrinsic material fluorescence and low-loss waveguiding. We employ a PMMA thin film for patterning hundreds of nanoscale apertures that are precisely aligned to prefabricated nanophotonic devices and transfer a solution of CdSeTe/ZnS CQDs diluted in decane into the apertures. The CQDs are positioned with 50 nm accuracy with respect to optical waveguides. Highly efficient 3D fiber-chip interfaces produced from a polymer in direct laser writing allow us to characterize the CQDwaveguide coupling and assess the spectral characteristics of the collected photoluminescence. Moreover, we record the second order autocorrelation function g2(τ) of the photoluminescence signal, which shows photon antibunching indicative of individual quantum emitters. Addressing individual CQDs via independent waveguide channels and a reproducible integration approach that extends to larger numbers of devices provides a novel perspective for realizing quantum technology with solution-processible single-photon emitters.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.