Towards a quantum representation of the ampere using single electron pumps

Abstract

Electron pumps generate a macroscopic electric current by controlled manipulation of single electrons. Despite intensive research towards a quantum current standard over the last 25 years, making a fast and accurate quantized electron pump has proved extremely difficult. Here we demonstrate that the accuracy of a semiconductor quantum dot pump can be dramatically improved by using specially designed gate drive waveforms. our pump can generate a current of up to 150 pA, corresponding to almost a billion electrons per second, with an experimentally demonstrated current accuracy better than 1.2 parts per million (p.p.m.) and strong evidence, based on fitting data to a model, that the true accuracy is approaching 0.01 p.p.m. This type of pump is a promising candidate for further development as a realization of the sI base unit ampere, following a redefinition of the ampere in terms of a fixed value of the elementary charge.

Partitioning of on-demand electron pairs

“…3b by black dashed lines, with energy E 0 = 48.4 meV and the detected energy broadening Δ b = 1.8 meV of the emitted electrons as fit parameters and consistent with the normalization of the probabilities to unity. A monotonic energy dependence of the barrier yields good agreement with the measurement, and at T = 0.5 the maximum probability for splitting the electron pair is p 1 = 50%.A particular advantage of single-parameter charge pumps operated far from equilibrium is the possibility to separately control loading from the source and emission into the drain by appropriate tuning of the driving waveform 29 . We now employ a sharp ejection pulse for the emission part of the cycle, aiming to reduce the time delay between the electrons and to preserve the energy difference imposed by the confinement in the quantum dot in the emission spectrum of ballistically propagating electrons (Supplementary Section A3).…”

“…A particular advantage of single-parameter charge pumps operated far from equilibrium is the possibility to separately control loading from the source and emission into the drain by appropriate tuning of the driving waveform 29 . We now employ a sharp ejection pulse for the emission part of the cycle, aiming to reduce the time delay between the electrons and to preserve the energy difference imposed by the confinement in the quantum dot in the emission spectrum of ballistically propagating electrons (Supplementary Section A3).…”

“…Coincidence correlation measurements allow the reconstruction of the full counting statistics, revealing regimes of statistically independent, distinguishable or correlated partitioning, and have been envisioned as a source of information on the quantum state of the electron pair [22][23][24][25][26] . The high pair-splitting fidelity opens a path to future on-demand generation of spin-entangled electron pairs from a suitably prepared two-electron quantum-dot ground state.The few-electron source is based on a single-parameter non-adiabatic quantized charge pump [27][28][29] , which enables the deterministic generation of single electrons and electron pairs with tunable emission energy 12,30 . Non-equilibrium electrons propagate along the edge of a quantum Hall sample with minimal inelastic scattering.…”

Feedback Control in Quantum Transport

“…This effect was also shown to hold for higher-dimensional models, in particular the single-electron transistor. One potential application of this effect might be in the control of singleelectron current sources [17], where reduction of the fluctuations in electron current is essential for the realisation of a useful quantum-mechanical definition of the ampere [18]. In this context, Fricke et al have demonstrated the current locking of two electron pumps through a feedback mechanism based on the charging an mesoscopic island between them [19].…”

Scheme for topological single electron pumping assisted by Majorana fermions

“…If one can control electrons one by one at given instants, a single electron bit may be achieved, which reduces the energy consumption to the limit. This technology is also important for forming the metrology triangle of Ohm's law: the quantum Hall effect discovered by von Klitzing works as the conductance standard [1], and the Josephson effect provides the voltage standard [2], while realization of precise current standard remains to be a challenge [3].…”