Superconducting quantum computing is one of the most promising second-generation quantum technologies, promising exponential advantages over classical computing with major adoption by industrial players such as Google and IBM. Such quantum computers are realized by cryogenic superconducting circuits, where qubits are manipulated by microwave signals with carrier signals typically ranging from 4 to 12 GHz. However, the microwave signals are generated outside of the cryostat and are fed into the quantum circuit via coaxial cables. With increased scaling of the number of qubits – a key requirement for quantum advantage – simultaneous scaling of the microwave signals is severely impeded by heat dissipation in the electrical feedthrough and the limited performance of dilution refrigerators.

The BMFTR project “KRYOWAVE” aims to solve this critical scaling problem of controlling superconducting qubits by using photonic microwaves generated directly at the superconducting circuit. This alternative approach not only promises a significant reduction in phase noise of the microwave with a resulting strong improvement on qubit coherence time, but also strongly reduces heat dissipation in the cryostat with a simultaneous reduction in overall form factor per qubit – thereby providing an ideal and scalable key-enabling technology for qubit control with significant performance improvements for superconducting quantum computers.

In this project, Menlo Systems is developing an application-specific photonic microwave generator, representing the next generation of our Ultrastable Microwaves product line, which will be applied directly in a suitable testbed on superconducting qubits.