Quantum photonics relies on interfacing different technologies under mutually compatible operating conditions. While integrated optics is typically optimised for room temperature operation, superconducting nanowire single photon detectors (SNSPDs) require cryogenic operating conditions. Recently, we have demonstrated integrated photonic modulators driven by the electrical output of SNSPDs, demonstrating low-power cryogenic opto-electronic signal processing and detector read out [1]. We use titanium in-diffused waveguides in lithium niobate as our nonlinear and electro-optic integration platform, which is very useful for cryogenic prototyping and informs the design of more scalable nonlinear and electro-optic integration platforms, in particular lithium niobate on insulator (LNOI).
In this talk I will discuss our latest results implementing a cryogenic feed-forward opto-electronic circuit, which can selectively manipulate a quantum state based on a desired measurement outcome [2]. The single photon detection with an SNSPD, amplification with CMOS ICs and electro-optic modulation in lithium niobate waveguides is performed entirely within a cryostat at 0.8K. The tight integration allows us to minimize the latency between the measurement result at the single photon level and the modulation.
[1] Thiele et al., Optics Express, 31(20), 32717-32726 (2023)
[2] Thiele et al., arXiv preprint arXiv:2410.08908. (2024)