Integrated photon-pair source with monolithic piezoelectric frequency tunability
T. Brydges, A. S. Raja, A. Gelmini, G. Lihachev, A. Petitjean, A. Siddharth, H. Tian, R. N. Wang, S. A. Bhave, H. Zbinden, T. J. Kippenberg, R. Thew
Phys. Rev. A 107, 052602 (2023)
This work was a collaboration between the Quantum Technologies group at the University of Geneva, the Laboratory of Photonics and Quantum Measurements at the EPFL, and OxideMEMS Lab at Purdue University.
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Quantum communication is predicted to be a crucial aspect of future quantum technologies, with a key component being the distribution of entanglement through networks using pairs of entangled photons. However, there are several challenges associated with this, with one of the most significant being that loss in standard fibre links inherently limits direct transmission distances. A solution to this is the quantum repeater architecture, which uses an intermediate repeater node to distribute the entanglement between two end users. 
Our existing integrated micro-ring resonator photon-pair sources, developed in collaboration with EPFL, are a natural solution to this problem. They are well-suited to producing narrow-band photon pairs at telecom wavelengths, with bandwidths compatible with some quantum memory systems. Up until our new Physical Review A publication, however, the frequency of our resonators could only be tuned by altering the temperature of the chip, which is too slow for successful interfacing with an atomic system. To overcome this, the QTech group at the University of Geneva have collaborated with the Laboratory of Photonics and Quantum Measurements group at EPFL and OxideMEMS Labs at Purdue University. Their existing technology processes have allowed us to include a piezoelectric layer on top of our ring resonator structures. By applying a voltage to the piezoelectric layer, the frequency of the micro-ring cavity can be tuned at much faster rates than was previously possible with temperature tuning. This work is the first ever demonstration of fast frequency-tunability of a narrow-band photon-pair source based on micro-ring resonators.
These new capabilities pave the way for interfacing our devices with quantum memoires in the near future, so laying the groundwork for future scalable quantum networks.
Shown in the top image is a photograph of our new device, with each circle corresponding to a micro-ring resonator photon-pair source. The lower image is a microscope image of the electrically wire-bonded piezoelectric layer on top of the micro-ring resonator.