Kavli Affiliate: John E. Bowers
| First 5 Authors: Yiming Pang, Joshua E. Castro, Trevor J. Steiner, Liao Duan, Noemi Tagliavacche
| Summary:
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 AlGaAs-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 $50$ GHz relative comb offsets, where
each resonator produces pairs exhibiting time-energy entanglement visibilities
up to 95$%$, coincidence-to-accidental ratios exceeding 5,000, and an on-chip
pair rate up to 2.6 GHz/mW$^2$ per comb line — more than 40 times improvement
over prior work. As a demonstration, we generate frequency-bin qubits in a
maximally entangled two-qubit Bell state with fidelity exceeding 87$%$ (90$%$
with background correction) and detected frequency-bin entanglement rates up to
7 kHz ($sim 70$ MHz on-chip pair rate) using $sim 250$ $mu$W pump power.
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.
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