Quantum-mechanical effects of the driving field on a superconducting qubit*

Heisenberg-like uncertainty in photon-number and phase of the driving field that implements single-qubit gates may lead to significant infidelity of the resulting gate operation. This infidelity scales inversely to the average photon-number in the field [1,2]. We study the effect of quantum fluctuations in the driving field on a superconducting transmon qubit. To observe this quantum-mechanical effect experimentally, we design a single-qubit device with strongly coupled drive line and on-chip filters to suppress the enhanced Purcell decay due to the drive line. We present randomized-benchmarking results characterizing the infidelity due to the quantum fluctuations in the driving field. 

 

[1] Gea-Banacloche, J. & Miller, M. Quantum logic with quantized control fields beyond the 1/n limit: mathematically possible, physically unlikely. Phys. Rev. A 78, 032331 (2008) 

[2] Ikonen, J., Salmilehto, J. & Möttönen, M. Energy-efficient quantum computing. njp Quant. Inf. 3, 17 (2017)