Measurement of Quantum Interference in a Silicon Ring Resonator Photon Source

Summary

Silicon photonic chips have the potential to realize complex integrated quantum systems. Presented here is a method for preparing and testing a silicon photonic chip for quantum measurements.

Abstract

Silicon photonic chips have the potential to realize complex integrated quantum information processing circuits, including photon sources, qubit manipulation, and integrated single-photon detectors. Here, we present the key aspects of preparing and testing a silicon photonic quantum chip with an integrated photon source and two-photon interferometer. The most important aspect of an integrated quantum circuit is minimizing loss so that all of the generated photons are detected with the highest possible fidelity. Here, we describe how to perform low-loss edge coupling by using an ultra-high numerical aperture fiber to closely match the mode of the silicon waveguides. By using an optimized fusion splicing recipe, the UHNA fiber is seamlessly interfaced with a standard single-mode fiber. This low-loss coupling allows the measurement of high-fidelity photon production in an integrated silicon ring resonator and the subsequent two-photon interference of the produced photons in a closely integrated Mach-Zehnder interferometer. This paper describes the essential procedures for the preparation and characterization of high-performance and scalable silicon quantum photonic circuits.

Introduction

Silicon is showing great promise as a photonics platform for quantum information processing^1,2,3,4,5. One of the vital components of quantum photonic circuits is the photon source. Photon-pair sources have been developed from silicon in the form of micro-ring resonators made via a third-order nonlinear process, spontaneous four-wave mixing (SFWM)^6,7,8. These sources are capable of producing pairs of indistinguishab....

Protocol

NOTE: This protocol assumes that the photonic chip has already been fabricated. The chip described here (shown in Figure 1A) was fabricated at the Cornell University NanoScale Science & Technology Facility using standard processing techniques for silicon photonic devices¹¹. These include the use of silicon-on-insulator wafers (composed of a 220 nm-thick silicon layer, a 3-µm layer of silicon dioxide, and a 525 µm-thick silicon substrate), electron-beam lithography to define the strip waveguides (500 nm-wide), and the plasma-enhanced chemical vapor deposition of the silicon dioxide cladding (~3 µm-thick). The micro-ring resonato....

Results

Individual photon counts from each detector, as well as the coincidence counts, were collected as the relative phase between the two paths was tuned. The individual counts (Figure 5A) show the classical interference pattern from an MZI with visibilities of 94.5 ± 1.6% and 94.9 ± 0.9%. The coincidence measurements (Figure 5B) show the quantum interference of the entangled state, as is evident by the oscillation at twice the frequency of the classical inter.......

Discussion

There are multiple challenges for the field of integrated photonics to overcome in order for complex and scalable systems of photonic devices to be feasible. These include, but are not limited to: tight fabrication tolerances, isolation from environmental instabilities, and minimization of all forms of loss. There are critical steps in the above protocol that help to minimize the loss of photonic devices.

One of the most crucial requirements in minimizing loss is closely matching the optical m.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
3-Axis NanoMax Flexure Stage	Thorlabs	MAX312D	Precision 3-axis stages
Three-Hole Fiber Stripping Tool	Thorlabs	FTS4	buffer stripping tool
Three Channel Piezo Controller	Thorlabs	MDT693B	Piezo controllers for NanoMax stages
Fiber Polarization Controller	Thorlabs	FPC562	3-Paddle fiber-based polarization controller
Fiber Cleaver	Thorlabs	XL411	Fiber cleaver
Standard V-Groove Fiber Holder	Thorlabs	HFV001	standard v-groove mount
Tapered V-Groove Fiber Holder	Thorlabs	HFV002	tapered v-groove mount
Right-Angle Top Plate for NanoMax Stage	Thorlabs	AMA011	right-angle bracket
50:50 Fiber Optic Coupler	Thorlabs	TW1550R5F1	50/50 combiner
Optical Fiber Fusion Splicer	Fujikura	FSM-40S	Fusion splicer
MultiPrep Polishing System - 8"	Allied High Tech	15-2100	Chip polisher
GreenLube	Allied High Tech	90-209010	Polishing Lubricant
Cross-Sectioning Paddle with Reference Edge	Allied High Tech	15-1010-RE	Polishing mount
Lightwave Measurement System	Keysight	8164B	Mainframe for tunable laser
Tunable Laser Source	Keysight	81606A	Tunable laser
Optical Power Sensor	Keysight	81634B	Power meter
NIR Single Photon Detector	ID Quantique	ID210	Single photon detectors
NIR Single Photon Detector	ID Quantique	ID230	Low noise, free-running single photon detectors
PicoHarp	PicoQuant	PicoHarp 300	Time-correlated single photon counting
WiDy SWIR InGaAs Camera	NIT	640U-S	IR Camera
WDM Bandpass Filter	JDS Uniphase	30055053-368-2.2	pump cleanup filters
WDM Bandpass Filter	JDS Uniphase	1011787-012	pump rejection filters
Ultra-High Numerical Aperture Fiber	Nufern	UHNA-7	high index fiber
Ultra Optical Single Mode Fiber	Corning	SMF-28	standard single mode fiber