Shortcuts to adiabatic cat-state generation in bosonic Josephson junctions

We propose a quantum speedup method for adiabatic generation of cat states in bosonicJosephson junctions via shortcuts to adiabaticity. We apply approximated counter-diabaticdriving to a bosonic Josephson junction using the Holstein–Primakoff transformation. In orderto avoid the problem of divergence in counter-diabatic driving, we take finite-size correctionsinto account. The resulting counter-diabatic driving is well-defined over whole processes.Schedules of the counter-diabatic driving consist of three steps; the counter-diabatic drivingin the disordered phase, smoothly and slowly approaching the critical point, and the counter-diabatic driving in the ordered phase. Using the counter-diabatic driving, adiabatic generationof cat states is successfully accelerated. The enough large quantum Fisher informationensures that generated cat states are highly entangled.

The author is grateful to Professor Seiji Miyashita and Dr Takashi Mori for useful comments on the manuscript. This work is supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan through the Elements Strategy Initiative Center for Magnetic Materials. The author is supported by the Japan Society for the Promotion of Science (JSPS) through the Program for Leading Graduate Schools: Material Education program for the future leaders in Research, Industry, and Technology (MERIT) of the University of Tokyo.