Quantum control of hybrid nuclear–electronic qubits

Morley, Gavin W.; Lueders, Petra; Mohammady, M. Hamed; Balian, S. J.; Aeppli, G.; Kay, Christopher W. M.; Witzel, Wayne; Jeschke, Gunnar; Monteiro, T. S.

doi:10.1038/nmat3499

Cited by 60 publications

(48 citation statements)

References 202 publications

(566 reference statements)

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“…A large number of important defects in the solid state possess such mixing, including donors in silicon, [18][19][20] NV centres in diamond, 21 transition metals in II-VI materials 22 and rare-earth dopants in silicates.…”

Section: -13mentioning

confidence: 99%

Quantum-bath-driven decoherence of mixed spin systems

et al. 2014

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The decoherence of mixed electron-nuclear spin qubits is a topic of great current importance, but understanding is still lacking: while important decoherence mechanisms for spin qubits arise from quantum spin bath environments with slow decay of correlations, the only analytical framework for explaining observed sharp variations of decoherence times with magnetic field is based on the suppression of classical noise. Here we obtain a general expression for decoherence times of the central spin system which exposes significant differences between quantum-bath decoherence and decoherence by classical field noise. We perform measurements of decoherence times of bismuth donors in natural silicon using both electron spin resonance (ESR) and nuclear magnetic resonance (NMR) transitions, and in both cases find excellent agreement with our theory across a wide parameter range. The universality of our expression is also tested by quantitative comparisons with previous measurements of decoherence around 'optimal working points' or 'clock transitions' where decoherence is strongly suppressed. We further validate our results by comparison to cluster expansion simulations.

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Section: -13mentioning

confidence: 99%

Quantum-bath-driven decoherence of mixed spin systems

et al. 2014

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“…The dynamical process underlying NMR can be viewed as the manipulation of magnetization vectors (proportional to spin angular momenta) with pulsed magnetic fields in the radio frequency (rf) regime as controls. Quantum control of spin systems has been treated theoretically and experimentally [9][10][11][12][13][14]. More specifically, for coupled two-spin systems the techniques of polarization or coherence transfer have attracted much interest [15][16][17] motivated by the desire of enhancing the signals of a low gyromagnetic ratio nucleus by transferring to it the larger magnetization of a higher gyromagnetic ratio nucleus [18].…”

Section: Introductionmentioning

confidence: 99%

Experimental observation of saddle points over the quantum control landscape of a two-spin system

et al. 2015

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The growing successes in performing quantum control experiments motivated the development of control landscape analysis as a basis to explain these findings. When a quantum system is controlled by an electromagnetic field, the observable as a functional of the control field forms a landscape. Theoretical analyses have predicted the existence of critical points over the landscapes, including saddle points with indefinite Hessians. This paper presents a systematic experimental study of quantum control landscape saddle points. Nuclear magnetic resonance control experiments are performed on acoupled two-spin system in a l3C-labeled chloroform ( I3CHC13) sample. We address the saddles with a combined theoretical and experimental approach, measure the Hessian at each identified saddle point, and study how their presence can influence the search effort utilizing a gradient algorithm to seek an optimal control outcome. The results have significance beyond spin systems, as landscape saddles are expected to be present for the control of broad classes of quantum systems.

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“…This has in particular been investigated for Si:Bi, where, due to the large hyperfine coupling of Bi, the mixing of electron and nuclear spin occurs at relatively large magnetic fields, allowing for conventional X-band EPR. [13][14][15] Conventional EPR however, requires a thermal equilibrium polarization of the spin system, limiting the sensitivity of conventional EPR to about 10 9 spins at X-band frequencies and typical cryogenic temperatures of the order of 5 K, making low-field experiments challenging. However, by using optical and electrical spin-readout schemes, known as optically/electrically detected magnetic resonance (ODMR/EDMR), single electron and nuclear spins can be detected, their spin state determined, [16][17][18] and the toolbox of sophisticated pulse sequences realized in EPR can be adapted to pulsed EDMR and ODMR.…”

Section: Introductionmentioning

confidence: 99%

Pulsed low-field electrically detected magnetic resonance

et al. 2015

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We present pulsed electrically detected magnetic resonance (EDMR) measurements at low magnetic fields using phosphorus-doped silicon with natural isotope composition as a model system. Our measurements show that pulsed EDMR experiments, well established at X-band frequencies (10 GHz), such as coherent spin rotations, Hahn echoes, and measurements of parallel and antiparallel spin pair life times are also feasible at frequencies in the MHz regime. We find that the Rabi frequency of the coupled 31 P electron-nuclear spin system scales with the magnetic field as predicted by the spin Hamiltonian, while the measured spin coherence and recombination times do not strongly depend on the magnetic field in the region investigated. The usefulness of pulsed lowfield EDMR for measurements of small hyperfine interactions is demonstrated by electron spin echo envelope modulation measurements of the P b0 dangling-bond state at the Si/SiO2 interface. A pronounced modulation with a frequency at the free Larmor frequency of hydrogen nuclei was observed for radio frequencies between 38 MHz and 400 MHz, attributed to the nuclear magnetic resonance of hydrogen in an adsorbed layer of water. This demonstrates the high sensitivity of low-field EDMR also for spins not directly participating in the spin-dependent transport investigated.

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Quantum control of hybrid nuclear–electronic qubits

Cited by 60 publications

References 202 publications

Quantum-bath-driven decoherence of mixed spin systems

Quantum-bath-driven decoherence of mixed spin systems

Experimental observation of saddle points over the quantum control landscape of a two-spin system

Pulsed low-field electrically detected magnetic resonance

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