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- Gavin W Morley, Petra Lueders, +6 authors Tania S Monteiro
- Nature materials
- 2013

Pulsed magnetic resonance allows the quantum state of electronic and nuclear spins to be controlled on the timescale of nanoseconds and microseconds respectively. The time required to flip dilute spins is orders of magnitude shorter than their coherence times, leading to several schemes for quantum information processing with spin qubits. Instead, we… (More)

- Wayne M Witzel, Malcolm S Carroll, Andrea Morello, Lukasz Cywiński, S Das Sarma
- Physical review letters
- 2010

Silicon is promising for spin-based quantum computation because nuclear spins, a source of magnetic noise, may be eliminated through isotopic enrichment. Long spin decoherence times T2 have been measured in isotope-enriched silicon but come far short of the T2=2T1 limit. The effect of nuclear spins on T2 is well established. However, the effect of… (More)

- Richard E George, Wayne Witzel, +4 authors John J L Morton
- Physical review letters
- 2010

Donors in silicon hold considerable promise for emerging quantum technologies, due to their uniquely long electron spin coherence times. Bismuth donors in silicon differ from more widely studied group V donors, such as phosphorous, in several significant respects: They have the strongest binding energy (70.98 meV), a large nuclear spin (I=9/2), and a strong… (More)

- Lukasz Cywiński, Wayne M Witzel, S Das Sarma
- Physical review letters
- 2009

We investigate pure dephasing decoherence (free induction decay and spin echo) of a spin qubit interacting with a nuclear spin bath. While for infinite magnetic field B the only decoherence mechanism is spectral diffusion due to dipolar flip-flops of nuclear spins, with decreasing B the hyperfine-mediated interactions between the nuclear spins become… (More)

- B Lee, W M Witzel, S Das Sarma
- Physical review letters
- 2008

We present a remarkable finding that a recently discovered [G. S. Uhrig, Phys. Rev. Lett. 98, 100504 (2007)10.1103/PhysRevLett.98.100504] series of pulse sequences, designed to optimally restore coherence to a qubit in the spin-boson model of decoherence, is in fact completely model independent and generically valid for arbitrary dephasing Hamiltonians… (More)

- Wayne M Witzel, Andrew Shabaev, C Stephen Hellberg, Verne L Jacobs, Alexander L Efros
- Physical review letters
- 2010

We have shown theoretically that efficient multiple-exciton generation (MEG) by a single photon can be observed in small nanocrystals. Our quantum simulations that include hundreds of thousands of exciton and multiexciton states demonstrate that the complex time-dependent dynamics of these states in a closed electronic system yields a saturated MEG effect… (More)

- W M Witzel, S Das Sarma
- Physical review letters
- 2007

We describe how the spin coherence time of a localized electron spin in solids, i.e., a solid state spin qubit, can be prolonged by applying designed electron spin resonance pulse sequences. In particular, the spin echo decay due to the spectral diffusion of the electron spin resonance frequency induced by the non-Markovian temporal fluctuations of the… (More)

- S J Balian, M B A Kunze, +4 authors T S Monteiro
- Physical review. B, Condensed matter and…
- 2012

We present pulsed electron-nuclear double resonance (ENDOR) experiments which enable us to characterize the coupling between bismuth donor spin-qubits in Si and the surrounding spin-bath of (29)Si impurities which provides the dominant decoherence mechanism (nuclear spin diffusion) at low temperatures (< 16 K). Decoupling from the spin-bath is predicted and… (More)

- W. M. Witzel
- 2007

We theoretically consider the possibility of using solid state nuclear spins in a semiconductor nanostructure environment as long-lived quantum memory. In particular, we calculate, in the limit of a strong applied magnetic field, the quantum coherence time for P donor nuclear spins in random bath environments of Si and GaAs, and the lifetime of excited… (More)

- H. Gerstmann, Hans Diel, W. Witzel
- Programming Methodology
- 1974