Case Study of Decoherence Times of Transmon Qubit

  1. H. Zarrabi,
  2. S. Hajihosseini,
  3. M. Fardmanesh,
  4. and S.I. Mirzaei
In the past two decades, one of the fascinating subjects in quantum physics has been quantum bits (qubits). Thanks to the superposition principle, the qubits can perform many calculations
simultaneously, which will significantly increase the speed and capacity of the calculations. The time when a qubit lives in an excited state is called decoherence time. The decoherence time varies considerably depending on the qubit type and materials. Today, short decoherence times are one of the bottlenecks in implementing quantum computers based on superconducting qubits. In this research, the topology of the transmon qubit is investigated, and the decoherence time caused by noise, flux, and critical current noise is calculated by numerical method.

Bi-stability in a Mesoscopic Josephson Junction Array Resonator

  1. P.R. Muppalla,
  2. O. Gargiulo,
  3. S.I. Mirzaei,
  4. B. Prasanna Venkatesh,
  5. M.L. Juan,
  6. L. Grünhaupt,
  7. I.M. Pop,
  8. and G. Kirchmair
We present an experimental investigation of the switching dynamics of a stochastic bistability in a 1000 Josephson junctions array resonator with a resonance frequency in the GHz range.
As the device is in the regime where the anharmonicity is on the order of the linewidth, the bistability appears for a drive strength of only a few photons. We measure the dynamics of the bistability by continuously observing the jumps between the two metastable states, which occur with a rate ranging from a few Hz down to a few mHz. The switching rate strongly depends on the drive strength, pump strength and the temperature, following Kramer’s law. The interplay between nonlinearity and coupling, in this little explored regime, could provide a new resource for nondemolition measurements, single photon switches or even elements for autonomous quantum error correction.