RSFQ Programmable Digital Multi-Tone Generator for Quantum Circuits Control

Many control architectures have been proposed to scale up quantum systems such as quantum computers or sensor arrays. To make use of the their full capabilities, the control and readout systems required to operate them need to be able to manipulate thousands of basic information/processing units (i.e., qubits, SNSPDs, ...) without overloading the cryogenic system with an impractical number of bulky and expensive electronic components and wiring. In this regard, Single Flux Quantum (SFQ) based electronics has been established as a promising candidate, not only due to the easy cryogenic integration with very low power dissipation and operating at closer temperatures to qubit devices, but also because of its operating clock frequencies which may go up to hundreds of GHz.

In this work I present a novel device with the potential to be used for the control of frequency multiplexed arrays of qubits or SNSPDs using well established Rapid Single Flux Quantum (RSFQ) technology. Using RSFQ circuitry, this device generates digital multi-tone signals (complex pulse trains), based on a preloaded pattern which is programmed beforehand into a Circular Shift Register (CSR). Adding a Comb Filtering stage, it is further possible to shift the relative powers of the output tones by tuning a current bias in the system. By being able to control and understand the frequency spectrum of any type of SFQ pulse train, a better and more scalable control of superconducting qubits could be achieved using this device, integrated in a SFQ co-processor like mentioned in previous literature.