TY - JOUR
T1 - Electrically-protected resonant exchange qubits in triple quantum dots
JF - Physical Review Letters
Y1 - 2013
A1 - J. M. Taylor
A1 - V. Srinivasa
A1 - J. Medford
AB - We 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.
VL - 111
UR - http://arxiv.org/abs/1304.3407v2
CP - 5
J1 - Phys. Rev. Lett.
U5 - 10.1103/PhysRevLett.111.050502
ER -
TY - JOUR
T1 - The Resonant Exchange Qubit
JF - Physical Review Letters
Y1 - 2013
A1 - J. Medford
A1 - J. Beil
A1 - J. M. Taylor
A1 - E. I. Rashba
A1 - H. Lu
A1 - A. C. Gossard
A1 - C. M. Marcus
AB - We 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.
VL - 111
UR - http://arxiv.org/abs/1304.3413v2
CP - 5
J1 - Phys. Rev. Lett.
U5 - 10.1103/PhysRevLett.111.050501
ER -
TY - JOUR
T1 - Self-Consistent Measurement and State Tomography of an Exchange-Only Spin Qubit
JF - Nature Nanotechnology
Y1 - 2013
A1 - J. Medford
A1 - J. Beil
A1 - J. M. Taylor
A1 - S. D. Bartlett
A1 - A. C. Doherty
A1 - E. I. Rashba
A1 - D. P. DiVincenzo
A1 - H. Lu
A1 - A. C. Gossard
A1 - C. M. Marcus
AB - We 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.
VL - 8
U4 - 654 - 659
UR - http://arxiv.org/abs/1302.1933v1
CP - 9
J1 - Nature Nanotech
U5 - 10.1038/nnano.2013.168
ER -