Versatile Chip-Scale Platform for High-Rate Entanglement Generation Using an <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:mi>Al</mml:mi> <mml:mi>Ga</mml:mi> <mml:mi>As</mml:mi> </mml:mrow> </mml:math> Microresonator Array

Abstract

Integrated photonic microresonators have become an essential resource for generating photonic qubits for quantum information processing, entanglement distribution and networking, and quantum communications. The pair-generation rate is enhanced by reducing the microresonator radius, but this comes at the cost of increasing the frequency-mode spacing and reducing the quantum information spectral density. Here, we circumvent this rate-density trade-off in an <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <a:mrow> <a:mi>Al</a:mi> <a:mi>Ga</a:mi> <a:mi>As</a:mi> </a:mrow> </a:math> -on-insulator photonic device by multiplexing an array of 20 small-radius microresonators, each producing a 650-GHz-spaced comb of time-energy entangled-photon pairs. The resonators can be independently tuned via integrated thermo-optic heaters, enabling control of the mode spacing from degeneracy up to a full free spectral range. We demonstrate simultaneous pumping of five resonators with up to <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <d:mn>50</d:mn> </d:math> -GHz relative comb offsets, where each resonator produces pairs exhibiting time-energy entanglement visibilities up to <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <g:mn>95</g:mn> <g:mi mathvariant="normal">%</g:mi> </g:math> , coincidence-to-accidental ratios exceeding <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <k:mn>5000</k:mn> </k:math> , and an on-chip pair rate up to <n:math xmlns:n="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <n:mn>2.6</n:mn> <n:mspace width="0.2em"/> <n:msup> <n:mrow> <n:mrow> <n:mi mathvariant="normal">G</n:mi> <n:mi>Hz</n:mi> </n:mrow> <n:mo>/</n:mo> <n:mi>mW</n:mi> </n:mrow> <n:mn>2</n:mn> </n:msup> </n:math> per comb line—an improvement over prior work by more than a factor of 40. As a demonstration, we generate frequency-bin qubits in a maximally entangled two-qubit Bell state with fidelity exceeding <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <s:mn>87</s:mn> <s:mi mathvariant="normal">%</s:mi> </s:math> ( <w:math xmlns:w="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <w:mn>90</w:mn> <w:mi mathvariant="normal">%</w:mi> </w:math> with background correction) and detected frequency-bin entanglement rates up to 7 kHz (an approximately <ab:math xmlns:ab="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <ab:mn>70</ab:mn> </ab:math> MHz on-chip pair rate) using a pump power of approximately <db:math xmlns:db="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <db:mn>250</db:mn> <db:mspace width="0.2em"/> <db:mtext fontfamily="times">μ</db:mtext> <db:mrow> <db:mi mathvariant="normal">W</db:mi> </db:mrow> </db:math> . Multiplexing small-radius microresonators combines the key capabilities required for programmable and dense photonic qubit encoding while retaining high pair-generation rates, heralded single-photon purity, and entanglement fidelity.

Topics & Concepts