Dual-Wavelength Operation of a VCSEL for Cryogenic Communication

The development of quantum computing is progressing rapidly, but there are still important technological and scaling challenges to overcome to reach the expected potential. Generally speaking, one of the main challenges of scaling quantum computers arises from the delicacy of the quantum states. For example, the fact that superconducting-based quantum processors need to be connected to the ambient environment with high-speed (microwave regime) signals, brings in scaling limitations related to the ability of preserving very low operation temperatures [1]. An important step in overcoming this challenge would be replacing traditional microwave connectors between the outside environment and the mK-range processors with optical fibers. This would simultaneously increase the bandwidth available and drastically reduce the thermal load due to heating by minimizing the number of thermal bridges to outside environment [2]. Another intermediate solution is to interface quantum processes with a superconducting processor based on single flux quantum (SFQ) technology, operating at more relaxed cryogenic conditions (4 K instead of mK range) [3]. Such hybrid solution would also need to have bidirectional communication links to external environments, and an optical link exploiting efficient light sources operating at cryogenic temperatures appears to be instrumental to it.