Vladimir Pesic

Cryogenic circuits for control and readout placed close to the qubits promise great advantage in scalability compared to conventional room temperature setups. However, cryogenic operation poses very strict requirements on the electronics. In order to understand what signals need to be applied to the qubits and what the specifications for control and readout electronics are, qubit simulation at the level of microwave pulses is necessary. These simulations can be performed using Quantum information processing package of Quantum Toolbox in Python (QuTiP) [1] and from this we can evaluate the effects of the quantum and classical noise in the system, driving signals and other relevant effects that directly give the requirements that cryogenic electronics needs to fulfill. Furthermore, after the circuits are designed and simulated according to these specifications, signals extracted from the SPICE simulation can be applied to the same qubit models from the previous step. In this way already in the circuit design stage we would be able to conclude if the circuit fulfills the requirements and test various trade-offs that may appear, such as power consumption, amount of noise generated by the circuit, gate duration, pulse amplitude etc. This approach is not limited by the qubit platform used and by adapting the effective Hamiltonian used in the simulation it can be applied on different qubit types. Finally, the ability to test the circuit together with the quantum processor before any fabrication is done would result in an improved efficiency and reduced cost of the design process.

[1] B. Li, S. Ahmed, S. Saraogi, N. Lambert, F. Nori, A. Pitchford, and N. Shammah, Pulse-level noisy quantum circuits with QuTiP, Quantum 6, 630 (2022).