Relaxation and decoherence of qubits encoded in collective states of engineered magnetic structures

Shakirov, Alexey M.; Rubtsov, A. N.; Lichtenstein, A. I.; Ribeiro, Pedro

doi:10.1103/physrevb.96.094410

Cited by 8 publications

(11 citation statements)

References 63 publications

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“…The definition of T 2 employed in the following has been established in Ref. [23], where some of the subtleties of defining a decoherence timescale in the presence of a spin-polarized environment were addressed. This quantity, dubbed T dec 2 in the following, is determined by the fastest decay rate of information in a system perturbed away from the nonequilibrium steady state that is established in the presence of a static bias V .…”

Section: Resultsmentioning

confidence: 99%

“…( 9) has the same form as the one obtained for the static case in Ref. [23], except for the explicit time dependence of the density matrix and the operators J aa (t) due to the driving. Note that the current obtained in this way assumes that the ac voltage has been turned on in the infinite past and that the system has already attained a periodic regime with the frequency of the drive.…”

Section: Model and Methodsmentioning

confidence: 93%

“…To capture spin-torque effects, we employ a masterequation description for the evolution of the reduced density matrix of the local moment that crucially includes the coherences. Therefore, we generalized the Redfield master equation approach, previously used to model coherent evolution and transport in engineered atomic spin devices [20,23], to deal with the ac driving bias.…”

Section: Model and Methodsmentioning

confidence: 99%

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Spin transfer torque induced paramagnetic resonance

2019

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We show how the spin-transfer torque generated by an ac voltage may be used to excite a paramagnetic resonance of an atomic spin deposited on a metallic surface. This mechanism is independent of the environment of the atom and may explain the ubiquity of the paramagnetic resonance reported by Baumann et al. [Science 350, 417 (2015)]. The current and spin dynamics are modeled by a time-dependent Redfield master equation generalized to account for the periodic driven voltage. Our approach shows that the resonance effect is a consequence of the nonlinearity of the coupling between the magnetic moment and the spin-polarized current which generates a large second-harmonic amplitude that can be measured in the current signal.

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Section: Resultsmentioning

confidence: 99%

Section: Model and Methodsmentioning

confidence: 93%

Section: Model and Methodsmentioning

confidence: 99%

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Spin transfer torque induced paramagnetic resonance

2019

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“…Atoms are individually addressable by a spin-polarized metallic tip. Applying a finite bias voltage between the tip and the surfaces induces an inelastic current that can be used to infer properties of the magnetic state [14][15][16][17][18][19] . For artificial magnetic structures, the most relevant systemenvironment interaction is the magnetic exchange with the itinerant electrons of the metallic substrate 16,20 .…”

Section: Introductionmentioning

confidence: 99%

“…Contrarily to their equilibrium counterparts, a classification of quantum critical phenomena in the presence arXiv:1801.00818v2 [cond-mat.mes-hall] 18 Nov 2019 of dissipation has not yet been accomplished despite the significant body of works devoted to the topic 48,[54][55][56][57][58][59][60][61][62][63] . In particular, dissipative phase transitions have been shown to escape Landau's symmetry breaking paradigm 48,55,57 in some cases but not others 61 .…”

Section: Introductionmentioning

confidence: 99%

Lipkin-Meshkov-Glick model with Markovian dissipation: A description of a collective spin on a metallic surface

Ferreira

Ribeiro

2019

Phys. Rev. B

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Motivated by recent prototypes of engineered atomic spin devices, we study a fully connected system of N spins 1/2, modeled by the Lipkin-Meshkov-Glick (LMG) model of a collective spin s = N/2 in the presence of Markovian dissipation processes. We determine and classify the different phases of the dissipative LMG model with Markovian dissipation, including the properties of the steady-state and the dynamic behavior in the asymptotic long-time regime. Employing variational methods and a systematic approach based on the Holstein-Primakoff mapping, we determine the phase diagram and the spectral and steady-state properties of the Liouvillian by studying both the infinite-s limit and 1/s corrections. Our approach reveals the existence of different kinds of dynamical phases and phase transitions, multi-stability and regions where the dynamics is recurrent. We provide a classification of critical and non-critical Liouvillians according to their spectral and steady-state properties.

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Harnessing the Quantum Behavior of Spins on Surfaces

2022

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out via microwave photons. [4] Spins in solid-state materials constitute another family of individual quantum systems where spin states with naturally quantized energy levels can be manipulated via magnetic fields. Physical realizations of solidstate spin systems include gate-defined quantum dots, single dopants in semiconductors such as phosphorus donors in silicon, and single defects in insulators such as nitrogen-vacancy centers in diamond. [5][6][7] Harnessing quantum resources at the nanoscale gives birth to the discipline of quantum-coherent nanoscience that may bring forth useful quantum nanodevices "at the bottom." [8,9] In this review, we focus on a new class of quantum spin systems, individual atomic and molecular spins on surfaces, which has the potential to produce quantum functionalities at the atomic scale. An STM is used to access this tiny length scale, where a sharp metallic tip is positioned in nanometer proximity to spin carriers on a surface to probe their properties through tunneling electrons. [10] Experiments with single atomic spins on material surfaces date back to the early days of low-temperature STM, when Yu-Shiba-Rusinov states and a Kondo resonance were measured in individual magnetic atoms on bulk superconductors [11] and noble metals, [12,13] respectively. STM has also been extensively used on single molecular spins to characterize molecular structures, [14][15][16] probe and modify their electronic and magnetic properties, [17][18][19] and investigate their classical and quantum applications. [19][20][21] Following early STM experiments on single spins, the desire to further control and magnetically image individual spins has prompted the developments of new local probe techniques such as spinpolarized STM, [22] inelastic-tunneling-based spin-flip spectroscopy, [23] electrical pump-probe measurements, [24] and various innovative forms of force and magnetic microscopy. [25][26][27][28] An exciting development in recent years is the incorporation of coherent spin control in atomic-scale microscopy. The need to coherently manipulate and measure individual spins at this length scale necessitates all-electrical protocols with Angstrom precision. These stringent requirements are met by drawing on powerful methodologies from material and quantum sciences, that is, STM's abilities to build nanostructures atom-by-atom and selectively sense individual spin-carrying atoms, as well as electron spin resonance's (ESR's) ability to coherently control electron spin states via electromagnetic waves. This unique combination has so far enabled the quantum control of single electron spins of atoms [29][30][31][32][33] and molecules, [34] as well as the manipulation of single nuclear spins through hyperfine interactions. [35] Quantum coherence can be increased using singlet-triplet The desire to control and measure individual quantum systems such as atoms and ions in a vacuum has led to significant scientific and engineering developments in the past decades that form the basis of today's quantum infor...

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Relaxation and decoherence of qubits encoded in collective states of engineered magnetic structures

Cited by 8 publications

References 63 publications

Spin transfer torque induced paramagnetic resonance

Spin transfer torque induced paramagnetic resonance

Lipkin-Meshkov-Glick model with Markovian dissipation: A description of a collective spin on a metallic surface

Harnessing the Quantum Behavior of Spins on Surfaces

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