An integrated quantum photonic circuit that can be thermally reconfigured has been fabricated by femtosecond laser micromachining. Thermally reconfigurable quantum photonic circuits would permit quantum protocols to be implemented that require dynamically changing circuit functionality. A team in Italy has used femtosecond laser micromachining to inscribe waveguide Mach–Zehnder interferometers that operate at telecommunication wavelengths on a glass chip and also to pattern gold resistive heaters on the chip surface, which can be used to accurately tune the circuit. The researchers demonstrated high-quality manipulation of single- and two-photon states with fringe visibilities exceeding 95%. They also fully characterized the thermal response of the interferometric circuit and found good agreement with that expected based on the fabrication design. This device could potentially be used as a building block for reconfigurable quantum circuits.
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