Design of a Lambda system for population transfer in superconducting nanocircuits

  1. G. Falci,
  2. A. La Cognata,
  3. M. Berritta,
  4. A. D'Arrigo,
  5. E. Paladino,
  6. and B. Spagnolo
The implementation of a Lambda scheme in superconducting artificial atoms could allow detec- tion of stimulated Raman adiabatic passage (STIRAP) and other quantum manipulations in the
microwave regime. However symmetries which on one hand protect the system against decoherence, yield selection rules which may cancel coupling to the pump external drive. The tradeoff between efficient coupling and decoherence due to broad-band colored Noise (BBCN), which is often the main source of decoherence is addressed, in the class of nanodevices based on the Cooper pair box (CPB) design. We study transfer efficiency by STIRAP, showing that substantial efficiency is achieved for off-symmetric bias only in the charge-phase regime. We find a number of results uniquely due to non-Markovianity of BBCN, namely: (a) the efficiency for STIRAP depends essentially on noise channels in the trapped subspace; (b) low-frequency fluctuations can be analyzed and represented as fictitious correlated fluctuations of the detunings of the external drives; (c) a simple figure of merit for design and operating prescriptions allowing the observation of STIRAP is proposed. The emerging physical picture also applies to other classes of coherent nanodevices subject to BBCN.