U. Vool

Stabilizing a Bell state of two superconducting qubits by dissipation engineering

  1. Z. Leghtas,
  2. U. Vool,
  3. S. Shankar,
  4. M. Hatridge,
  5. S.M. Girvin,
  6. M.H. Devoret,
  7. and M. Mirrahimi
We propose a dissipation engineering scheme that prepares and protects a maximally entangled state of a pair of superconducting qubits. This is done by off-resonantly coupling the two
qubits to a low-Q cavity mode playing the role of a dissipative reservoir. We engineer this coupling by applying six continuous-wave microwave drives with appropriate frequencies. The two qubits need not be identical. We show that our approach does not require any fine-tuning of the parameters and requires only that certain ratios between them be large. With currently achievable coherence times, simulations indicate that a Bell state can be maintained over arbitrary long times with fidelities above 94%. Such performance leads to a significant violation of Bell’s inequality (CHSH correlation larger than 2.6) for arbitrary long times.
arxiv pdf

Cavity-assisted quantum bath engineering

  1. K. W. Murch,
  2. U. Vool,
  3. D. Zhou,
  4. S. J. Weber,
  5. S. M. Girvin,
  6. and I. Siddiqi
We demonstrate quantum bath engineering for a superconducting artificial atom coupled to a microwave cavity. By tailoring the spectrum of microwave photon shot noise in the cavity,
we create a dissipative environment that autonomously relaxes the atom to an arbitrarily specified coherent superposition of the ground and excited states. In the presence of background thermal excitations, this mechanism increases the state purity and effectively cools the dressed atom state to a low temperature.
arxiv pdf