Aidar Sultanov

Measuring coherent dynamics of a superconducting qubit in an open waveguide

  1. Aidar Sultanov,
  2. Evgeniya Mutsenik,
  3. Matthias Schmelz,
  4. Leonie Kaczmarek,
  5. Gregor Oelsner,
  6. Uwe Huebner,
  7. Ronny Stolz,
  8. and Evgeni Il'ichev
We measured the relaxation and decoherence rates of a superconducting transmon qubit in a resonator-free setting. In our experiments, the qubit is coupled to an open coplanar waveguide
such that the transmission of microwaves through this line depends on the qubit’s state. To determine the occupation of the first excited qubit energy level, we introduced a two-pulse technique. The first applied pulse, at a frequency close to the eigenfrequency of the qubit, serves to excite the qubit. A second pulse is then used for probing the transition between the first and second excited energy levels. Utilizing this measurement technique allowed for the reconstruction of the relaxation dynamics and Rabi oscillations. Furthermore, we demonstrate the consistency between the extracted parameters and the corresponding estimations from frequency-domain measurements.
arxiv pdf

Protocol for temperature sensing using a three-level transmon circuit

  1. Aidar Sultanov,
  2. Marko Kuzmanović,
  3. Andrey V. Lebedev,
  4. and Gheorghe Sorin Paraoanu
We present a method for in situ temperature measurement of superconducting quantum circuits, by using the first three levels of a transmon device to which we apply a sequence of π
gates. Our approach employs projective dispersive readout and utilizes the basic properties of the density matrix associated with thermal states. This method works with an averaging readout scheme and does not require a single-shot readout setup. We validate this protocol by performing thermometry in the range of 50 mK – 200 mK, corresponding to a range of residual populations 1%−20% for the first excited state and 0.02%−3% for the second excited state.
arxiv pdf