Highly controllable qubit-bath coupling based on a sequence of resonators

  1. P. J. Jones,
  2. J. Salmilehto,
  3. and M. Möttönen
Combating the detrimental effects of noise remains a major challenge in realizing a scalable quantum computer. To help to address this challenge, we introduce a model realizing a controllable
qubit-bath coupling using a sequence of LC resonators. The operating principle is similar to that of a recently proposed coplanar-waveguide cavity (CPW) system, for which our work introduces a complementary and convenient experimental realization. The lumped-element model utilized here provides an easily accessible theoretical description. We present analytical solutions for some experimentally feasible parameter regimes and study the control mechanism. Finally, we introduce a mapping between our model and the recent CPW system.

Tunable electromagnetic environment for superconducting quantum bits

  1. P. J. Jones,
  2. J. A. M. Huhtamäki,
  3. K. Y. Tan,
  4. and M. Möttönen
We introduce a setup which realises a tunable engineered environment for experiments in circuit quantum electrodynamics. We illustrate this concept with the specific example of a quantum
bit, qubit, in a high-quality-factor cavity which is separated from a resistor in another cavity by a capacitor. The temperature of the resistor can be controlled in a well defined manner in order to provide a hot or cold environment for the qubit, as desired. Furthermore, introducing superconducting quantum interference devices (SQUIDs) into the resistor cavity provides control of the coupling strength between this artificial environment and the qubit. We demonstrate that our scheme allows us to couple strongly to the environment enabling rapid initialization of the system, and by subsequent tuning of the magnetic flux of the SQUIDs we may greatly reduce the resistor-qubit coupling, allowing the qubit to evolve unhindered.