Efficient Toffoli Gate in Circuit Quantum Electrodynamics

The fidelity of quantum gates in circuit quantum electrodynamics is typically limited by qubit decoherence. As such, significant improvements can be realized by shortening gate duration [1, 2]. The three-qubit Toffoli gate, also called the controlled-controlled NOT, is an important operation in basic quantum error correction. We report a scheme for a Toffoli gate that exploits interactions with non-computational excited states of transmon qubits which can be executed faster than an equivalent construction using one- and two-qubit gates. The application of this gate to efficient measurement-free quantum error correction will be discussed. \\[4pt] [1] DiCarlo, et al. Nature 467, 574 (2010). \\[0pt] [2] Chow, et al. Phys. Rev. Lett. 102, 090502 (2009).