[Paper Review] Single-Photon Switching and Entanglement of Solid-State Qubits in an Integrated Nanophotonic System

Alp Sipahigil, Ruffin E. Evans+14 more|arXiv (Cornell University)|Aug 18, 2016

Diamond and Carbon-based Materials Research1 references297 citations

TL;DR

This paper demonstrates an integrated diamond nanophotonic platform where silicon-vacancy (SiV) centers couple to cavities and waveguides to realize a single-photon switch, tunable Raman-based single-photon source, and heralded entanglement between two SiVs in a diamond nanophotonic waveguide.

ABSTRACT

Efficient interfaces between photons and quantum emitters form the basis for quantum networks and enable nonlinear optical devices operating at the single-photon level. We demonstrate an integrated platform for scalable quantum nanophotonics based on silicon-vacancy (SiV) color centers coupled to nanoscale diamond devices. By placing SiV centers inside diamond photonic crystal cavities, we realize a quantum-optical switch controlled by a single color center. We control the switch using SiV metastable orbital states and verify optical switching at the single-photon level by using photon correlation measurements. We use Raman transitions to realize a single-photon source with a tunable frequency and bandwidth in a diamond waveguide. Finally, we create entanglement between two SiV centers by detecting indistinguishable Raman photons emitted into a single waveguide. Entanglement is verified using a novel superradiant feature observed in photon correlation measurements, paving the way for the realization of quantum networks.

Motivation & Objective

• Demonstrate efficient interfaces between photons and solid-state qubits using SiV centers in diamond nanophotonic devices.
• Realize a quantum-optical switch controlled by a single SiV center.
• Create tunable single-photon sources using Raman transitions to overcome inhomogeneous broadening.
• Generate and verify entanglement between two SiV centers via indistinguishable Raman photons in a waveguide.

Proposed method

• Integrate negatively-charged SiV centers into diamond nanophotonic cavities with small mode volume and high Q.
• Use metastable orbital states of SiV to control cavity transmission and realize a single-photon switch with memory.
• Employ Raman transitions between SiV metastable states to generate tunable single photons in a diamond waveguide.
• Establish entanglement between two SiV centers by detecting indistinguishable Raman photons emitted into a single waveguide.

Experimental results

Research questions

• RQ1 Can a single SiV center provide a robust all-optical switch at the single-photon level?
• RQ2 Can Raman-tuned photons mitigate spectral diffusion to produce tunable, indistinguishable photons for entanglement?
• RQ3 Is it possible to herald entanglement between two solid-state qubits in a nanophotonic waveguide via indistinguishable photons?
• RQ4 What are the observed photon statistics that signal nonlinear, quantum-level interactions in the SiV-cavity system?

Key findings

• A single SiV center in a diamond cavity achieves ~38% extinction of a resonant probe transmission.
• Saturation and nonlinear response of the SiV-cavity system are observed at the single-photon level.
• Autocorrelation measurements show scattered photons antibunching (g(2)SS(0)=0.15(4)) and transmitted photons bunching (g(2)TT(0)=1.50(5)).
• Raman-assisted emission from a single SiV in a diamond waveguide yields tunable photon frequency and subnatural linewidth (<30 MHz) under appropriate detuning and power.
• Indistinguishable Raman photons from two separate SiVs generate entanglement verified by superradiant correlations with g(2)ind(0)=0.98(5).
• A lower bound on conditional entanglement fidelity from interference is F≥82(7)% for events within the interference window.