After a long wait, our paper has been published in Physical Review Applied (see more information below). The paper describes how the performance of the interface electronics affects the performance of the whole quantum computer. The analysis is extremely relevant to derive the exact specification for the electronics so that we can design electronics good enough for the task but not overdesigned. This allows cutting unnecessary margins int eh electronics and enable to push further the optimization of the electronics. For example, we have used those techniques to design circuits that can consume much less power. This is extremely relevant when designing cryogenic circuits, for which the power consumption is strictly limited by the cooling power of existing refrigerators.
The paper is available here:
Impact of Classical Control Electronics on Qubit Fidelity
Phys. Rev. Applied 12, 044054 (2019) – Published 24 October 2019
Brief summary A quantum computer comprises both qubits and their classical electronic interface. While much research is currently devoted solely to qubits, an efficient electronic controller is also urgently needed for a scalable quantum computer. This study uses analytical techniques to expose the effect of nonideal circuit blocks in a classical controller on qubit fidelity, for all required operations, and how fidelity is affected by the limited performance of the general-purpose, room-temperature equipment typically used with the few qubits types available today. Tailor-made controllers can achieve significantly lower cost, power consumption, and size, as required for scaling up.
Abstract Quantum processors rely on classical electronic controllers to manipulate and read out the state of quantum bits (qubits). As the performance of the quantum processor improves, nonidealities in the classical controller can become the performance bottleneck for the whole quantum computer. To prevent such limitation, this paper presents a systematic study of the impact of the classical electrical signals on the qubit fidelity. All operations, i.e., single-qubit rotations, two-qubit gates, and readout, are considered, in the presence of errors in the control electronics, such as static, dynamic, systematic, and random errors. Although the presented study could be extended to any qubit technology, it currently focuses on single-electron spin qubits, because of several advantages, such as purely electrical control and long coherence times, and for their potential for large-scale integration. As a result of this study, detailed electrical specifications for the classical control electronics for a given qubit fidelity can be derived. We also discuss how qubit fidelity is affected by the limited performance of the general-purpose room-temperature equipment typically employed to control the few qubits available today. Ultimately, we show that tailor-made electronic controllers can achieve significantly lower power, cost, and size, as required to support the scaling up of quantum computers.