01080nas 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/1302.1933v101053nas a2200157 4500008004100000245008200041210006900123260001500192490000800207520056400215100001900779700002200798700001900820700001900839856003700858 2011 eng d00aLaser cooling and optical detection of excitations in a LC electrical circuit0 aLaser cooling and optical detection of excitations in a LC elect c2011/12/270 v1073 aWe 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.
1 aTaylor, J., M.1 aSørensen, A., S.1 aMarcus, C., M.1 aPolzik, E., S. uhttp://arxiv.org/abs/1108.2035v101401nas a2200217 4500008004100000245005600041210005600097260001300153490000800166520081300174100002100987700001801008700001901026700001401045700002101059700001901080700001401099700001501113700001801128856003701146 2010 eng d00aDynamic Nuclear Polarization in Double Quantum Dots0 aDynamic Nuclear Polarization in Double Quantum Dots c2010/6/40 v1043 aWe 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.
1 aGullans, Michael1 aKrich, J., J.1 aTaylor, J., M.1 aBluhm, H.1 aHalperin, B., I.1 aMarcus, C., M.1 aStopa, M.1 aYacoby, A.1 aLukin, M., D. uhttp://arxiv.org/abs/1003.4508v201375nas a2200181 4500008004100000245008800041210006900129260001400198490000700212520082100219100001901040700001801059700002001077700001501097700001901112700001801131856004401149 2007 eng d00aRelaxation, dephasing, and quantum control of electron spins in double quantum dots0 aRelaxation dephasing and quantum control of electron spins in do c2007/7/130 v763 aRecent 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.
1 aTaylor, J., M.1 aPetta, J., R.1 aJohnson, A., C.1 aYacoby, A.1 aMarcus, C., M.1 aLukin, M., D. uhttp://arxiv.org/abs/cond-mat/0602470v201053nas a2200181 4500008004100000245007400041210006900115260001400184490000700198520052300205100001900728700001300747700001500760700001500775700001900790700001800809856004400827 2005 eng d00aSolid-state circuit for spin entanglement generation and purification0 aSolidstate circuit for spin entanglement generation and purifica c2005/6/150 v943 aWe 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.
1 aTaylor, J., M.1 aDür, W.1 aZoller, P.1 aYacoby, A.1 aMarcus, C., M.1 aLukin, M., D. uhttp://arxiv.org/abs/cond-mat/0503255v201085nas a2200145 4500008004100000245005000041210004900091260001400140490000700154520067800161100001900839700001900858700001800877856004400895 2003 eng d00aLong-lived memory for mesoscopic quantum bits0 aLonglived memory for mesoscopic quantum bits c2003/5/200 v903 aWe 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.
1 aTaylor, J., M.1 aMarcus, C., M.1 aLukin, M., D. uhttp://arxiv.org/abs/cond-mat/0301323v1