On-Chip Quantum Interference from a Single Silicon Ring-Resonator Source

Letter

On-Chip Quantum Interference from a Single Silicon Ring-Resonator Source

Stefan F. Preble, Michael L. Fanto, Jeffrey A. Steidle, Christopher C. Tison, Gregory A. Howland, Zihao Wang, and Paul M. Alsing

Phys. Rev. Applied 4, 021001 – Published 20 August 2015

Abstract

Here we demonstrate quantum interference of photons on a silicon chip produced from a single-ring-resonator photon source. The source is seamlessly integrated with a Mach-Zehnder interferometer, which path entangles degenerate biphotons produced via spontaneous four-wave mixing in the silicon ring resonator. The resulting entangled N00N state is controlled by varying the relative phase of the integrated Mach-Zehnder interferometer, resulting in high two-photon interference visibilities of $V \sim 96 %$ . Furthermore, we show that the interference can be produced using pump wavelengths tuned to all of the ring resonances accessible with our tunable lasers ( $C + L$ band). This work is a key demonstration towards the simplified integration of multiple photon sources and quantum circuits together on a monolithic chip, in turn, enabling quantum-information chips with much greater complexity and functionality.

Received 9 April 2015

DOI:https://doi.org/10.1103/PhysRevApplied.4.021001

Authors & Affiliations

Stefan F. Preble^1,*, Michael L. Fanto², Jeffrey A. Steidle¹, Christopher C. Tison², Gregory A. Howland², Zihao Wang¹, and Paul M. Alsing²

¹Rochester Institute of Technology, Microsystems Engineering, 168 Lomb Memorial Drive, Rochester, New York 14623, USA
²Air Force Research Laboratory, 525 Brooks Road, Rome, New York 13441, USA

^*Corresponding author. Stefan.Preble@rit.edu

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Vol. 4, Iss. 2 — August 2015

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Images

Figure 1
(a) Microscope image of the quantum circuit that consists of an integrated pump splitting circuit, ring resonator ( $Q$ of 15,000, FSR of 5 nm) entangled biphoton source and MZI analysis circuit. The devices were fabricated using e-beam lithography, with typical waveguide losses of $3 dB / cm$ [27]. (b) Schematic of the complete experimental setup. A pair of tunable lasers are polarized, combined and passed through pump clean-up filters. A short section of High Index fiber (Nufern UHNA-7) was spliced to optical fiber (SMF-28) to efficiently mode match to the Silicon waveguide achieving a total insertion loss of approximately 5 dB [16]. The relative phase ( $θ$ ) in the MZI was controlled by thermal heating of one of the spirals. Photons from the two outputs were filtered to remove noise, the rejected pumps are sent to power meters to measure the classical signatures. The biphotons are detected by InGaAs APDs (idQuantique ID210 – 10% Efficiency, ID230 – 25% Efficiency) and correlated using a time-to-digital converter. (c) Transmission spectrum (when the MZI is tuned for 50/50 splitting) indicating the wavelengths of the two pump lasers as well as the wavelength of the resulting biphotons.
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Figure 2
(a) Classical laser light from the two outputs of the silicon circuit as varying the relative phase of the MZI. The heating power was converted to phase using a fit assuming the phase linearly depends on temperature. The blue- diamond data was scaled by a factor of $\times 1.67$ for ease of comparison. This path experienced a higher loss on the chip because of fabrication imperfections. (b) Coincidences between the two paths measured for ninety-seconds. The coincidences were measured with a 32 ps time resolution and integrated over 224 ps in order to account for the timing jitter of the APDs. The accidentals were obtained by averaging the time correlations far away from the coincidence peak over a time interval of 320 ns. The calculated error is obtained from the standard deviation of the accidentals over the same range. (Incoherent): Coincidence counts when the pumps are tuned asymmetrically about the central resonance, resulting in independent, incoherent, photon pairs.
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Figure 3
(a)–(f) Coincidences for different pump-laser wavelengths. (g),(h) Dependence of the coincidences on the wavelengths of the two pump lasers. The scales are different because the New Focus laser (blue scale with range $- 0.1$ to 0.1 nm) has a very limited fine-tuning range.
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