Guided magnon transport in spin chains: Transport speed and correcting for disorder

Ahmed, Muhammad H.; Greentree, Andrew D.

doi:10.1103/physreva.91.022306

Cited by 7 publications

(9 citation statements)

References 38 publications

(67 reference statements)

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“…Below τ g the fidelity quickly drops to zero with no noticeable improvement arising from further optimization. This is in accordance with the group velocity being the maximum speed of the magnons [26] and also with the speed limit found in [42] with the numerical Krotov [43] optimization method for the same system but with a different form of spin excitation.…”

Section: Approaching the Group Velocity Speed Limit With ∂Psupporting

confidence: 87%

“…Therefore, an initially localized wave packet will delocalize across the chain as a direct result of the nonlinear dispersion relation [25]. To counteract this spreading it is necessary to guide the magnon transport [11,26] by imposing the external magnetic field B n (t). Various kinds of magnetic traps with different spatial profiles can be used for this, such as, the Pöschl-Teller [27] potential, a square well [25], or a harmonic trap [11].…”

Section: Magnons and The Optimization Objectivementioning

confidence: 99%

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Optimal Control in Disordered Quantum Systems

Coopmans¹,

Kiely²,

Chiara³

et al. 2022

Preprint

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We investigate several control strategies for the transport of an excitation along a spin chain. We demonstrate that fast, high fidelity transport can be achieved using protocols designed with differentiable programming. Building on this, we then show how this approach can be effectively adapted to control a disordered quantum system. We consider two settings: optimal control for a known unwanted disorder pattern, i.e. a specific disorder realisation, and optimal control where only the statistical properties of disorder are known, i.e. optimizing for high average fidelities. In the former, disorder effects can be effectively mitigated for an appropriately chosen control protocol. However, in the latter setting the average fidelity can only be marginally improved, suggesting the presence of a fundamental lower bound.

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Section: Approaching the Group Velocity Speed Limit With ∂Psupporting

confidence: 87%

Section: Magnons and The Optimization Objectivementioning

confidence: 99%

Optimal Control in Disordered Quantum Systems

Coopmans¹,

Kiely²,

Chiara³

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…Taking into account that the spin wave velocity (e.g. [38,39]) is of the order of J, one can see that during the time T the non-equilibrium spin wave propagate from the perturbed bond the distance (in the units of the spin-spin separation) of the order of JT. Therefore, for N?JT, the g(t)− function should be only weakly N-dependent.…”

Section: Discussionmentioning

confidence: 99%

High-fidelity non-adiabatic cutting and stitching of a spin chain via local control

et al. 2018

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We propose and analyze, focusing on non-adiabatic effects, a technique of manipulating quantum spin systems based on local 'cutting' and 'stitching' of the Heisenberg exchange coupling between the spins. This first operation is cutting of a bond separating a single spin from a linear chain, or of two neighboring bonds for a ring-shaped array of spins. We show that the disconnected spin can be in the ground state with a high-fidelity even after a non-adiabatic process. Next, we consider inverse operation of stitching these bonds to increase the system size. We show that the optimal control algorithm can be found by using common numerical procedures with a simple twoparametric control function able to produce a high-fidelity cutting and stitching. These results can be applied for manipulating ensembles of quantum dots, considered as prospective elements for quantum information technologies, and for design of machines based on quantum thermodynamics.

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“…The long spin-coherence times and large Bohr radius of the phosphorus donor electron in silicon make this material an interesting candidate for spin-based devices and other nanoscale electronics [21][22][23][24] . Si:P δ-doped wires might be used as the interconnects between stationary and flying qubits 18,25 , low-resistivity source-drain contacts for nanoelectronics 2,26 , or one-dimensional (1D) spin chains for confined magnon transport [27][28][29] . The modern δ-doped wire is a quasi-1D row of phosphorus atoms oriented in the [110] crystallographic direction, with a width of 1.54 nm in the lateral [110] direction which is equivalent to two dimer rows (2DR) on the reconstructed (001) silicon surface 2,11 .…”

Section: Introductionmentioning

confidence: 99%

Electronic transport in Si:Pδ-doped wires

et al. 2015

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Despite the importance of Si:P delta-doped wires for modern nanoelectronics, there are currently no computational models of electron transport in these devices. In this paper we present a nonequilibrium Green's function model for electronic transport in a delta-doped wire, which is described by a tight-binding Hamiltonian matrix within a single-band effective-mass approximation. We use this transport model to calculate the current-voltage characteristics of a number of delta-doped wires, achieving good agreement with experiment. To motivate our transport model we have performed density-functional calculations for a variety of delta-doped wires, each with different donor configurations. These calculations also allow us to accurately define the electronic extent of a delta-doped wire, which we find to be at least 4.6 nm.

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Guided magnon transport in spin chains: Transport speed and correcting for disorder

Cited by 7 publications

References 38 publications

Optimal Control in Disordered Quantum Systems

Optimal Control in Disordered Quantum Systems

High-fidelity non-adiabatic cutting and stitching of a spin chain via local control

Electronic transport in Si:Pδ-doped wires

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