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arXiv:2308.04541 · ACS Photonics

High-Efficiency Single Photon Emission from a Silicon T-Center in a Nanobeam

Chang-Min Lee, Fariba Islam, Samuel Harper, Mustafa Atabey Buyukkaya, Daniel B. Higginbottom, Stephanie Simmons, Edo Waks A

Published Oct 31, 2023• 33 citations
arXivHTMLPDF

Abstract

Color centers in Si could serve as both efficient quantum emitters and quantum memories with long coherence times in an all-silicon platform. Of the various known color centers, the T-center holds particular promise because it possesses a spin ground state that has long coherence times, but this color center exhibits a long excited state lifetime that results in a low-photon emission rate, requiring methods to extract photon emission with high efficiency. We demonstrate high-efficiency single-photon emission from a single T-center using a nanobeam. The nanobeam efficiently radiates light in a mode that is well-matched to a lensed fiber, enabling us to couple over 70% of the photons in the nanobeam directly into a single-mode fiber. This efficiency enables us to directly demonstrate single-photon emission from the zero-phonon line, which represents the coherent emission from the T-center. Our results represent an important step toward silicon-integrated spin–photon interfaces for quantum computing and quantum networks.

DOI
10.1021/acsphotonics.3c01142

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Color centers in Si could serve as both efficient quantum emitters and quantum memories with long coherence times in an all-silicon platform. Of the various known color centers, the T-center holds particular promise because it possesses a spin ground state that has long coherence times, but this color center exhibits a long excited state lifetime that results in a low-photon emission rate, requiring methods to extract photon emission with high efficiency. We demonstrate high-efficiency single-photon emission from a single T-center using a nanobeam. The nanobeam efficiently radiates light in a mode that is well-matched to a lensed fiber, enabling us to couple over 70% of the photons in the nanobeam directly into a single-mode fiber. This efficiency enables us to directly demonstrate single-photon emission from the zero-phonon line, which represents the coherent emission from the T-center. Our results represent an important step toward silicon-integrated spin–photon interfaces for quantum computing and quantum networks.
T centers in silicon could serve as efficient quantum memories based on spin-photon interface. But these emitters have long excited state lifetimes and are therefore dim. We demonstrate high-efficiency single photon emission from the zero-phonon line of a single T center using a nanobeam. The tapered nanobeam features coupling efficiency of 71% into a lensed fiber, enabling an order of magnitude improvement in photon count rates as compared to previously reported values. Consequently, we demonstrate single photon emission from the zero-phonon line, representing the coherent emission from the T center. Our result is an important step towards CMOS-integrated spin-photon interfaces.
Implementation of large-scale quantum networks have the potential to augment the capabilities of existing quantum information technologies. By linking quantum processors over photonic channels, future quantum networks could enable applications such as remote quantum sensing, distributed quantum computing, and secure quantum communication. Atomic defects in solids are readily integrated with photonic structures, making them promising candidates for use in quantum networking devices. In particular, the silicon material platform holds great promise due to the technologically mature silicon electronic and photonic industries. The T center defects in silicon possess telecom O-band optical transitions, as well as long-lived electronic and nuclear spins, making it the focus of particular interest. These spin and optical properties of single T centers, together with their accessibility to the existing integrated electronic and photonic technologies, opening the door to modular long-distance quantum networking technologies built on the T center platform. This work outlines the integration of single T centers with a silicon photonic crystal cavity; we observe cavity-enhanced fluorescence emission, resulting in a decay rate enhancement factor of F = 6.89 compared to the bulk emission rate. Through the use of silicon photonic circuits and an angle-polished fiber for light coupling, we achieve a maximum zero phonon line photon outcoupling rate of 73.3 kHz. The design and fabrication of the nanophotonic cavity used in experiment is detailed. This work represents a major step towards use of the silicon T center as a telecom spin-photon interface in future quantum networking applications.
Silicon G centers show significant promise as single photon sources in a scalable silicon platform. But these color centers have large nonradiative decay and a low Debye-Waller factor, limiting their usability in quantum applications. In this work, we demonstrate bright Purcell-enhanced emission from a silicon G center by coupling it to a nanophotonic cavity. The nanobeam cavity enhances the spontaneous emission rate of a single G center by a factor of 6, corresponding to a Purcell factor greater than 31 when accounting for decay into the phonon sideband. We obtain a spontaneous emission rate of 0.97 ns, which is the fastest single photon emission rate reported in silicon. With this radiative enhancement, we achieve an order of magnitude improvement in emitter brightness compared to previously reported values. These results pave the way for scalable quantum light sources on a silicon photonic chip.
Single photons enable the distribution of quantum information over large distances and thus play a major role in quantum technologies such as communication and computing. Solid-state emitters are practical and efficient sources of single photons that can be manufactured in large numbers. When combined with a spin, the resulting spin-photon interfaces can store quantum states for extended periods and serve as the basis for quantum networks and repeaters. Among the many host materials explored over the past few decades, silicon stands out for its advanced nanofabrication, the maturity of its integrated photonics and microelectronics, and its high isotopic purity, which leads to exceptionally long spin coherence. These properties position silicon single-photon emitters and spin-photon interfaces among the most promising hardware platforms for implementing quantum networks and distributed quantum information processors. This review summarizes the current state of the art and open challenges towards coherent single-photon sources and scalable spin-photon interfaces based on color centers and erbium dopants in nanophotonic silicon structures.
Monolithic integration of single-photon sources into silicon photonics offers a compelling solution for realizing scalable quantum telecommunication architectures. Among the candidate silicon color centers, the C-center features a zero-phonon emission in the telecom L-band, corresponding to the spectral window of minimum transmission loss in optical fibers. Despite this advantage, isolating single C-centers has remained an unrealized challenge in solid-state quantum optics. In this work, we report the isolation of a single silicon C-center. We enhance the spontaneous emission rate of the zero-phonon line by coupling the single emitter to a nanophotonic crystal cavity, observing a fivefold reduction in the excited-state lifetime compared to bulk conditions, which corresponds to a Purcell factor lower bound of 33. Second-order autocorrelation measurements confirm single-photon emission from the investigated defect, obtaining an optical purity of g(2)(0)=0.23g^{(2)}(0) = 0.23g(2)(0)=0.23 without background correction. Our results establish a native telecom L-band quantum light source in silicon, laying the foundation for ultra-low-loss and long-distance quantum applications.
Novel T centers in silicon hold great promise for quantum networking applications due to their telecom band optical transitions and the long-lived ground state electronic spins. An open challenge for advancing the T center platform is to enhance its weak and slow zero phonon line (ZPL) emission. In this work, by integrating single T centers with a low-loss, small mode-volume silicon photonic crystal cavity, we demonstrate an enhancement of the fluorescence decay rate by a factor of F = 6.89. Efficient photon extraction enables the system to achieve an average ZPL photon outcoupling rate of 73.3 kHz under saturation, which is about two orders of magnitude larger than the previously reported value. The dynamics of the coupled system is well modeled by solving the Lindblad master equation. These results represent a significant step towards building efficient T center spin-photon interfaces for quantum information processing and networking applications.