Nuclear magnetic resonance quantum information processing

Serra, R. M.

doi:10.1098/rsta.2012.0332

Cited by 14 publications

(13 citation statements)

References 12 publications

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“…It is important to state that this Hamiltonian can be signreversed simply by changing the phases x by y and −x by −y in the pulse train, obtaining −H DQ = 1 3 (H xx − H yy ). Note that the nonisotropic dipolar Hamiltonian is the key to obtain the double quantum Hamiltonians and to enable the time-reversal and Loschmidt echo procedures.…”

Section: Le(τmentioning

confidence: 99%

“…Solid-state nuclear magnetic resonance (NMR) represents a unique technique for precise control of nuclear spin dynamics allowing the performance of experimental studies of manybody systems interacting through natural and specifically designed couplings [1,2]. The observation of nonequilibrium many-body dynamics [3,4] and the ability to perform quantum time-reversal experiments [5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

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Clustering and decoherence of correlated spins under double quantum dynamics

et al. 2014

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We present an improved approach for the study of the evolution of spin correlations and decoherence in multiple quantum nuclear magnetic resonance experiments. The infinite system, constituted by the protons of a polycrystalline adamantane sample, evolves under a double quantum Hamiltonian. The distribution of multiple quantum coherence orders is represented by a contribution of spin clusters with different sizes that exchange spins, increasing their size with the evolution time. A cluster with nearly exponential growth at all times is observed, in agreement with previous models. Remarkably, a small cluster that stabilizes in a size corresponding to 18 correlated spins is revealed. In addition, by performing a renormalization of the obtained data with the experimental Loschmidt echo, the contribution of the different clusters to the observable signal is determined. This procedure accounts for the effect of decoherence on the evolution of the system, and allows setting the range of confidence of the experimental data. Our analysis confirms the natural hint that, correlated states involving higher coherence orders are far more sensitive to the uncontrolled decoherent interactions, than those involving lower orders.

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Section: Le(τmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Clustering and decoherence of correlated spins under double quantum dynamics

et al. 2014

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“…At this point, we should recall that in NMR one can often design Hamiltonians by means of the average Hamiltonian theory (AHT) [17]. Thus, the detailed observation of non-equilibrium many-body dynamics [18,19] and the ability to perform echoes in a variety of time reversal experiments [6,7,20] while assessing the loss of coherence [21][22][23][24] have attracted much attention in the last few decades. As decoherence is responsible for the degradation of the information contained in a quantum state, its understanding promises a strong impact on novel technologies.…”

Section: A Brief History Of Time Reversalmentioning

confidence: 99%

Quantum dynamics of excitations and decoherence in many-spin systems detected with Loschmidt echoes: its relation to their spreading through the Hilbert space

Sánchez

Levstein

Buljubasich

et al. 2016

Phil. Trans. R. Soc. A.

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In this work, we overview time-reversal nuclear magnetic resonance (NMR) experiments in many-spin systems evolving under the dipolar Hamiltonian. The Loschmidt echo (LE) in NMR is the signal of excitations which, after evolving with a forward Hamiltonian, is recovered by means of a backward evolution. The presence of non-diagonal terms in the non-equilibrium density matrix of the many-body state is directly monitored experimentally by encoding the multiple quantum coherences. This enables a spin counting procedure, giving information on the spreading of an excitation through the Hilbert space and the formation of clusters of correlated spins. Two samples representing different spin systems with coupled networks were used in the experiments. Protons in polycrystalline ferrocene correspond to an ‘infinite’ network. By contrast, the liquid crystal N -(4-methoxybenzylidene)-4-butylaniline in the nematic mesophase represents a finite proton system with a hierarchical set of couplings. A close connection was established between the LE decay and the spin counting measurements, confirming the hypothesis that the complexity of the system is driven by the coherent dynamics.

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“…We designed these 36 RF pulses to excite square patterns and analysed their robustness towards B 0 and B 1 inhomogeneities. 37 The paper is arranged as follows: the theory section gives a brief description of the function and subtleties 38 of each OC algorithm seen from the MRI RF pulse design viewpoint. The experimental section explains the 39 protocols we used and the details of the measurements.…”

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confidence: 99%

“…In this context, optimal control (OC) is a suitable candidate amongst 23 many numerical approaches or theoretical approximations, since OC can handle multiple constraints and 24 vast controls efficiently [21,22]. Often OC is applied in engineering control tasks [26], but also in optical [36,37], and in quantum information processing [38][39][40]. The first application of OC in RF 27 pulse design for MRI was made more than 25 years ago [21,22].…”

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confidence: 99%