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 -
TY - JOUR
T1 - Laser cooling and optical detection of excitations in a LC electrical circuit
JF - Physical Review Letters
Y1 - 2011
A1 - J. M. Taylor
A1 - A. S. Sørensen
A1 - C. M. Marcus
A1 - E. S. Polzik
AB - We explore a method for laser cooling and optical detection of excitations in a LC electrical circuit. Our approach uses a nanomechanical oscillator as a transducer between optical and electronic excitations. An experimentally feasible system with the oscillator capacitively coupled to the LC and at the same time interacting with light via an optomechanical force is shown to provide strong electro-mechanical coupling. Conditions for improved sensitivity and quantum limited readout of electrical signals with such an "optical loud speaker" are outlined.
VL - 107
UR - http://arxiv.org/abs/1108.2035v1
CP - 27
J1 - Phys. Rev. Lett.
U5 - 10.1103/PhysRevLett.107.273601
ER -
TY - JOUR
T1 - Dynamic Nuclear Polarization in Double Quantum Dots
JF - Physical Review Letters
Y1 - 2010
A1 - Michael Gullans
A1 - J. J. Krich
A1 - J. M. Taylor
A1 - H. Bluhm
A1 - B. I. Halperin
A1 - C. M. Marcus
A1 - M. Stopa
A1 - A. Yacoby
A1 - M. D. Lukin
AB - We theoretically investigate the controlled dynamic polarization of lattice nuclear spins in GaAs double quantum dots containing two electrons. Three regimes of long-term dynamics are identified, including the build up of a large difference in the Overhauser fields across the dots, the saturation of the nuclear polarization process associated with formation of so-called "dark states," and the elimination of the difference field. We show that in the case of unequal dots, build up of difference fields generally accompanies the nuclear polarization process, whereas for nearly identical dots, build up of difference fields competes with polarization saturation in dark states. The elimination of the difference field does not, in general, correspond to a stable steady state of the polarization process.
VL - 104
UR - http://arxiv.org/abs/1003.4508v2
CP - 22
J1 - Phys. Rev. Lett.
U5 - 10.1103/PhysRevLett.104.226807
ER -
TY - JOUR
T1 - Relaxation, dephasing, and quantum control of electron spins in double quantum dots
JF - Physical Review B
Y1 - 2007
A1 - J. M. Taylor
A1 - J. R. Petta
A1 - A. C. Johnson
A1 - A. Yacoby
A1 - C. M. Marcus
A1 - M. D. Lukin
AB - Recent experiments have demonstrated quantum manipulation of two-electron spin states in double quantum dots using electrically controlled exchange interactions. Here, we present a detailed theory for electron spin dynamics in two-electron double dot systems that was used to guide these experiments and analyze experimental results. The theory treats both charge and spin degrees of freedom on an equal basis. Specifically, we analyze the relaxation and dephasing mechanisms that are relevant to experiments and discuss practical approaches for quantum control of two-electron system. We show that both charge and spin dephasing play important roles in the dynamics of the two-spin system, but neither represents a fundamental limit for electrical control of spin degrees of freedom in semiconductor quantum bits.
VL - 76
UR - http://arxiv.org/abs/cond-mat/0602470v2
CP - 3
J1 - Phys. Rev. B
U5 - 10.1103/PhysRevB.76.035315
ER -
TY - JOUR
T1 - Solid-state circuit for spin entanglement generation and purification
JF - Physical Review Letters
Y1 - 2005
A1 - J. M. Taylor
A1 - W. Dür
A1 - P. Zoller
A1 - A. Yacoby
A1 - C. M. Marcus
A1 - M. D. Lukin
AB - We show how realistic charge manipulation and measurement techniques, combined with the exchange interaction, allow for the robust generation and purification of four-particle spin entangled states in electrically controlled semiconductor quantum dots. The generated states are immunized to the dominant sources of noise via a dynamical decoherence-free subspace; all additional errors are corrected by a purification protocol. This approach may find application in quantum computation, communication, and metrology.
VL - 94
UR - http://arxiv.org/abs/cond-mat/0503255v2
CP - 23
J1 - Phys. Rev. Lett.
U5 - 10.1103/PhysRevLett.94.236803
ER -
TY - JOUR
T1 - Long-lived memory for mesoscopic quantum bits
JF - Physical Review Letters
Y1 - 2003
A1 - J. M. Taylor
A1 - C. M. Marcus
A1 - M. D. Lukin
AB - We describe a technique to create long-lived quantum memory for quantum bits in mesoscopic systems. Specifically we show that electronic spin coherence can be reversibly mapped onto the collective state of the surrounding nuclei. The coherent transfer can be efficient and fast and it can be used, when combined with standard resonance techniques, to reversibly store coherent superpositions on the time scale of seconds. This method can also allow for ``engineering'' entangled states of nuclear ensembles and efficiently manipulating the stored states. We investigate the feasibility of this method through a detailed analysis of the coherence properties of the system.
VL - 90
UR - http://arxiv.org/abs/cond-mat/0301323v1
CP - 20
J1 - Phys. Rev. Lett.
U5 - 10.1103/PhysRevLett.90.206803
ER -