Despite an apparent progress in implementing individual solid-state qubits, there have been no experimental reports so far on multi-bit gates required for building a real quantum computer. Here we report a new circuit comprising two coupled charge qubits. Using a pulse technique, we coherently mix quantum states and observe quantum oscillations whose spectrum reflects interaction between the qubits. Our results demonstrate the feasibility of coupling of multiple solid-state qubits and indicate the existence of entangled two-qubit states.
@article{arxiv.cond-mat/0212314,
title = {Quantum oscillations in two coupled charge qubits},
author = {Yu. A. Pashkin and T. Yamamoto and O. Astafiev and Y. Nakamura and D. V. Averin and J. S. Tsai},
journal= {arXiv preprint arXiv:cond-mat/0212314},
year = {2010}
}