[Paper Review] Indistinguishable photons from an artificial atom in silicon photonics

Lukasz Komza, Polnop Samutpraphoot+9 more|arXiv (Cornell University)|Nov 17, 2022

Photonic and Optical DevicesEngineering54 references17 citations

TL;DR

This paper demonstrates high-fidelity, indistinguishable single-photon emission from a G center—a silicon-based artificial atom—integrated into a silicon photonic waveguide. By achieving a Hong-Ou-Mandel visibility of 88% and an effective two-photon linewidth of 0.4(10) GHz, the work establishes a scalable, on-chip source of coherent telecom-band photons for photonic quantum technologies in silicon.

ABSTRACT

Silicon is the ideal material for building electronic and photonic circuits at scale. Spin qubits and integrated photonic quantum technologies in silicon offer a promising path to scaling by leveraging advanced semiconductor manufacturing and integration capabilities. However, the lack of deterministic quantum light sources, two-photon gates, and spin-photon interfaces in silicon poses a major challenge to scalability. In this work, we show a new type of indistinguishable photon source in silicon photonics based on an artificial atom. We show that a G center in a silicon waveguide can generate high-purity telecom-band single photons. We perform high-resolution spectroscopy and time-delayed two-photon interference to demonstrate the indistinguishability of single photons emitted from a G center in a silicon waveguide. Our results show that artificial atoms in silicon photonics can source highly coherent single photons suitable for photonic quantum networks and processors.

Motivation & Objective

• To address the lack of deterministic, coherent single-photon sources in silicon photonics for scalable quantum technologies.
• To integrate an artificial atom (G center) into a silicon waveguide to enable on-chip, telecom-band photon generation.
• To demonstrate high indistinguishability of emitted photons via time-delayed two-photon interference.
• To quantify spectral stability and coherence properties of the G center emitter under realistic conditions.
• To enable future applications in photonic quantum networks and fault-tolerant quantum computing using silicon-compatible platforms.

Proposed method

• Ion implantation of 12C at 36 keV and 10^12 cm⁻² fluence into a silicon-on-insulator (SOI) wafer, followed by rapid thermal annealing at 1000°C for 20 s to create G centers.
• Integration of the G center into a single-mode silicon photonic waveguide with a broadband Bragg reflector for enhanced photon collection.
• Use of an adiabatic mode converter to couple emitted photons into a lensed fiber with 50% efficiency.
• Employment of pulsed above-bandgap laser excitation to generate single-photon emission from the G center.
• Measurement of time-delayed two-photon interference using a Hong-Ou-Mandel (HOM) interferometer to quantify photon indistinguishability.
• Modeling of spectral diffusion effects using a Lorentzian distribution of emission frequencies and fitting the HOM visibility to extract effective two-photon linewidth (Γ^HOM).

Experimental results

Research questions

• RQ1 Can an artificial atom (G center) in a silicon waveguide generate single photons with high temporal and spectral indistinguishability?
• RQ2 What is the degree of indistinguishability of photons emitted from a G center in a silicon photonic circuit?
• RQ3 How do spectral diffusion and timing jitter affect the visibility of two-photon interference in solid-state emitters?
• RQ4 Can the effective two-photon linewidth be reduced below the single-photon spectral linewidth due to correlated spectral fluctuations?
• RQ5 To what extent can the coherence and indistinguishability of photons from a G center be preserved over nanosecond timescales?

Key findings

• The G center in the silicon waveguide emits single photons at 1278 nm in the telecom O-band with a zero-phonon line (ZPL) and high spectral purity.
• A Hong-Ou-Mandel (HOM) dip visibility of 88% was experimentally measured, indicating high photon indistinguishability.
• The effective two-photon linewidth (Γ^HOM/2π) was measured to be 0.4(10) GHz, which is an order of magnitude smaller than the single-photon linewidth of 2.8 GHz.
• The observed HOM visibility is limited primarily by detector timing jitter (252 ps) and spectral diffusion, with the latter modeled as a Lorentzian frequency fluctuation process.
• The exponential decay in the HOM correlation function at short delays (|τ| < 1 ns) is attributed to uncorrelated spectral diffusion, with a correlation timescale longer than 25 ns.
• The measured photon lifetime (T₁ = 4.6(1) ns) was consistent with the observed decay envelope in the two-photon interference trace.