01124nas a2200145 4500008004100000245007500041210006900116260001400185490000800199520068100207100001900888700001800907700001600925856003700941 2013 eng d00aElectrically-protected resonant exchange qubits in triple quantum dots0 aElectricallyprotected resonant exchange qubits in triple quantum c2013/7/310 v1113 aWe present a modulated microwave approach for quantum computing with qubits comprising three spins in a triple quantum dot. This approach includes single- and two-qubit gates that are protected against low-frequency electrical noise, due to an operating point with a narrowband response to high frequency electric fields. Furthermore, existing double quantum dot advances, including robust preparation and measurement via spin-to-charge conversion, are immediately applicable to the new qubit. Finally, the electric dipole terms implicit in the high frequency coupling enable strong coupling with superconducting microwave resonators, leading to more robust two-qubit gates.
1 aTaylor, J., M.1 aSrinivasa, V.1 aMedford, J. uhttp://arxiv.org/abs/1304.3407v201080nas a2200193 4500008004100000245003200041210002800073260001400101490000800115520060900123100001600732700001300748700001900761700001900780700001100799700002000810700001900830856003700849 2013 eng d00aThe Resonant Exchange Qubit0 aResonant Exchange Qubit c2013/7/310 v1113 aWe introduce a solid-state qubit in which exchange interactions among confined electrons provide both the static longitudinal field and the oscillatory transverse field, allowing rapid and full qubit control via rf gate-voltage pulses. We demonstrate two-axis control at a detuning sweet-spot, where leakage due to hyperfine coupling is suppressed by the large exchange gap. A {\pi}/2-gate time of 2.5 ns and a coherence time of 19 {\mu}s, using multi-pulse echo, are also demonstrated. Model calculations that include effects of hyperfine noise are in excellent quantitative agreement with experiment.
1 aMedford, J.1 aBeil, J.1 aTaylor, J., M.1 aRashba, E., I.1 aLu, H.1 aGossard, A., C.1 aMarcus, C., M. uhttp://arxiv.org/abs/1304.3413v201244nas a2200241 4500008004100000245008400041210006900125260001300194300001400207490000600221520055700227100001600784700001300800700001900813700002100832700002000853700001900873700002300892700001100915700002000926700001900946856003700965 2013 eng d00aSelf-Consistent Measurement and State Tomography of an Exchange-Only Spin Qubit0 aSelfConsistent Measurement and State Tomography of an ExchangeOn c2013/9/1 a654 - 6590 v83 aWe report initialization, complete electrical control, and single-shot readout of an exchange-only spin qubit. Full control via the exchange interaction is fast, yielding a demonstrated 75 qubit rotations in under 2 ns. Measurement and state tomography are performed using a maximum-likelihood estimator method, allowing decoherence, leakage out of the qubit state space, and measurement fidelity to be quantified. The methods developed here are generally applicable to systems with state leakage, noisy measurements, and non-orthogonal control axes.
1 aMedford, J.1 aBeil, J.1 aTaylor, J., M.1 aBartlett, S., D.1 aDoherty, A., C.1 aRashba, E., I.1 aDiVincenzo, D., P.1 aLu, H.1 aGossard, A., C.1 aMarcus, C., M. uhttp://arxiv.org/abs/1302.1933v1