Experimental study of ballistic fluxon detectors for superconducting qubits

我们想要设计、制造和实验研究用于超导量子比特的非常快和弱微扰读出的新型探测器。该探测原理是基于测量在约瑟夫森传输线中运动的弹道磁通子通过量子比特时的延迟时间。由于量子比特的局域磁通引起的钉扎势，磁通传播延迟依赖于量子比特的状态。与用于超导量子比特的现有读出技术相比，弹道通量探测器的预期优势是低功耗、高时间分辨率和对量子比特的小反向作用。我们将通过(I)检测通量振荡频移，(Ii)测量锁频通量注入的输出相移和(Iii)直接使用通量干涉仪来进行通量延迟测量。弹道荧光探测器应适用于超导量子比特非破坏性测量方案的实现，包括量子非破坏读出和反馈控制方案。

We would like to design, fabricate and experimentally investigate new type of detectors for very fast and weakly perturbing readout of superconducting qubits. The detection principle is based on measuring the delay time of a ballistic fluxon moving in a Josephson transmission line when passing by a qubit. Due to the pinning potential induced by the localized magnetic flux of the qubit, the fluxon propagation delay depends on the state of the qubit. The expected advantage of ballistic fluxon detectors over existing readout techniques used for superconducting qubits are low dissipated power, high time resolution and small back action on the qubit. We will perform fluxon delay measurements by (i) detecting the fluxon oscillation frequency shift, (ii) measuring the output phase shift of the frequency-locked fluxon injection and (iii) directly by using a fluxon interferometer. Ballistic fluxon detectors should be suitable for implementation of non-destructive measurement schemes with superconducting qubits, including quantum non-demolition readout and feedback control schemes.