QDev Seminar: Antti Vepsäläinen

Aalto University, Helsinki

Adiabatic control in circuit quantum electrodynamics.

Quantum control by adiabatic pulses presents the advantage of robustness under errors in the control parameters, yet it is inherently slow. Here I present an implementation of the superadiabatic protocol in a three-level system realized with a transmon superconducting circuit, where an additional control pulse is used to cancel the non-adiabatic evolution of the system. This enables the transfer of population from the ground state to the second excited state by stimulated adiabatic Raman passage in only a few tens of nanoseconds, approaching the quantum speed limit. As a bridge between adiabatic and direct methods, superadiabatic concept allows a continuous interpolation between the speed and robustness of the population transfer. As a result, it is possible to choose an optimal protocol speed that meets the given robustness criteria. This is particularly important in the field of circuit quantum electrodynamics, where the acceptable duration of the protocol is limited by the coherence time. Additionally, combination of two superadiabatic passages can be used to form a robust rotation gate in the {|0> - |2>} subspace.