Superconducting qubit manipulated by fast pulses: experimental observation of distinct decoherence regimes

TL;DR

This paper experimentally investigates a superconducting qubit manipulated by fast flux pulses, revealing a crossover between two decoherence regimes and identifying an optimal point with minimal noise sensitivity.

Contribution

It demonstrates the observation of distinct decoherence regimes in a double SQUID qubit manipulated by fast pulses, highlighting the existence of an optimal operating point.

Findings

Observation of non-exponential decay of coherent oscillations

Identification of a crossover between two decoherence regimes

Existence of an optimal point with reduced noise sensitivity

Abstract

A particular superconducting quantum interference device (SQUID)qubit, indicated as double SQUID qubit, can be manipulated by rapidly modifying its potential with the application of fast flux pulses. In this system we observe coherent oscillations exhibiting non-exponential decay, indicating a non trivial decoherence mechanism. Moreover, by tuning the qubit in different conditions (different oscillation frequencies) by changing the pulse height, we observe a crossover between two distinct decoherence regimes and the existence of an "optimal" point where the qubit is only weakly sensitive to intrinsic noise. We find that this behaviour is in agreement with a model considering the decoherence caused essentially by low frequency noise contributions, and discuss the experimental results and possible issues.