Abstract
High fidelity universal gates for quantum bits form an essential ingredient of quantum information processing. In particular, geometric gates have attracted attention because they have a higher intrinsic resistance to certain errors. However, their realization remains a challenge because of the need for complicated quantum control on a multi-level structure as well as meeting the adiabatic condition within a short decoherence time. Here, we demonstrate non-adiabatic quantum operations for a two-level system by applying a well-controlled geometric Landau-Zener-Stückelberg interferometry. By characterizing the gate quality, we also investigate the operation in the presence of realistic dephasing. Furthermore, the result provides an essential model suitable for understanding an interplay of geometric phase and Landau-Zener-Stückelberg process which are well explored separately.
Highlights
High fidelity universal gates for quantum bits form an essential ingredient of quantum information processing
For fault-tolerant quantum computation, it is believed that an infidelity or error threshold ranging between 10−4 and 10−2 is required[2,3,4,5]; most experimental implementations far have fallen short of these thresholds[6,7,8,9,10,11]
Universal gates based on geometric phase for a two-level system
Summary
High fidelity universal gates for quantum bits form an essential ingredient of quantum information processing. Geometric gates have attracted attention because they have a higher intrinsic resistance to certain errors Their realization remains a challenge because of the need for complicated quantum control on a multi-level structure as well as meeting the adiabatic condition within a short decoherence time. When the system evolves cyclically, it acquires a geometric phase factor and undergoes a transition between the eigenstates in the degenerate subspace, which constitutes a set of universal unitary transformations for the qubit. In this technique, the system is typically changed adiabatically to guarantee the persistence of the degeneracy. These types of geometric gates can be implemented conveniently in a wide variety of natural or artificial two-level systems
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