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arXiv:1809.10081 · Applied Physics Letters

High-resolution error detection in the capture process of a single-electron pump

S. P. Giblin, P. See, A. Petrie, T. J. B. M. Janssen, I. Farrer, J. P. Griffiths, G. A. C. Jones, D. A. Ritchie, M. Kataoka

Published Jan 11, 2016• 18 citations
arXivHTMLPDF

Abstract

The dynamic capture of electrons in a semiconductor quantum dot (QD) by raising a potential barrier is a crucial stage in metrological quantized charge pumping. In this work, we use a quantum point contact (QPC) charge sensor to study errors in the electron capture process of a QD formed in a GaAs heterostructure. Using a two-step measurement protocol to compensate for 1/f noise in the QPC current, and repeating the protocol more than 106 times, we are able to resolve errors with probabilities of order 10−6. For the studied sample, one-electron capture is affected by errors in ∼30 out of every million cycles, while two-electron capture was performed more than 106 times with only one error. For errors in one-electron capture, we detect both failure to capture an electron and capture of two electrons. Electron counting measurements are a valuable tool for investigating non-equilibrium charge capture dynamics, and necessary for validating the metrological accuracy of semiconductor electron pumps.

DOI
10.1063/1.4939250

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Japanese Journal of Applied Physics•Apr 1, 2006•3 citations
The dynamic capture of electrons in a semiconductor quantum dot (QD) by raising a potential barrier is a crucial stage in metrological quantized charge pumping. In this work, we use a quantum point contact (QPC) charge sensor to study errors in the electron capture process of a QD formed in a GaAs heterostructure. Using a two-step measurement protocol to compensate for 1/f noise in the QPC current, and repeating the protocol more than 106 times, we are able to resolve errors with probabilities of order 10−6. For the studied sample, one-electron capture is affected by errors in ∼30 out of every million cycles, while two-electron capture was performed more than 106 times with only one error. For errors in one-electron capture, we detect both failure to capture an electron and capture of two electrons. Electron counting measurements are a valuable tool for investigating non-equilibrium charge capture dynamics, and necessary for validating the metrological accuracy of semiconductor electron pumps.
The dynamic capture of electrons in a semiconductor quantum dot (QD) by raising a potential \nbarrier is a crucial stage in metrological quantized charge pumping. In this work, we use a quantum \npoint contact (QPC) charge sensor to study errors in the electron capture process of a QD formed in \na GaAs heterostructure. Using a two-step measurement protocol to compensate for 1/f noise in the \nQPC current, and repeating the protocol more than 106 times, we are able to resolve errors with \nprobabilities of order 106. For the studied sample, one-electron capture is affected by errors in \n30 out of every million cycles, while two-electron capture was performed more than 106 times \nwith only one error. For errors in one-electron capture, we detect both failure to capture an electron \nand capture of two electrons. Electron counting measurements are a valuable tool for investigating \nnon-equilibrium charge capture dynamics, and necessary for validating the metrological accuracy \nof semiconductor electron pumps.
We measure the average number of electrons loaded into an electrostatically-defined quantum dot (QD) operated as a tunable-barrier electron pump, using a point-contact (PC) charge sensor 1 micron away from the QD. The measurement of the electron number probes the QD loading dynamics even in the limit of slow gate voltage rise-times, when the pumped current is too small to measure. Using simulations we show that, with optimised QD-PC coupling, the experiment can make single-shot measurements of the number of electrons in the QD with sufficiently high fidelity to test the error rate of the electron pump with metrological precision.
We present time-resolved charge-sensing measurements on a GaAs double quantum dot with two proximal quantum point-contact (QPC) detectors. The QPC currents are analyzed with cross-correlation techniques, which enable us to measure dot charging and discharging rates for significantly smaller signal-to-noise ratios than required for charge detection with a single QPC. This allows us to reduce the current level in the detector and therefore the invasiveness of the detection process and may help to increase the available measurement bandwidth in noise-limited setups.
We present time-domain electron counting studies on charge fluctuations in a mesoscopic system. In this measurement, a radio-frequency single-electron transistor (RF-SET) acting as a fast electrometer is capacitively coupled to a quantum dot (QD) electrostatically defined in a GaAs/AlGaAs heterostructure. Random telegraph signals (RTSs) were observed on the RF-SET and were interpreted as resulting from individual electrons tunneling into/out of the QD hence switching the QD charge state between N and N+1 electrons near the charge degeneracy point. Periodic behavior of the switching events is observed as the number of average electrons in the electron box is decreased one by one. The occupation time of the excess electron is directly measured and changes from a few microseconds to a few milliseconds as the tunneling resistance of the QD is increased. Histogram of the occupation time obtained from the time-domain electron counting measurements agrees well with the frequency-domain power spectrum analysis, both suggesting a Poissonian process at the charge degenerate point, in agreement with a model consisting of two charge states. Real time electron counting techniques can play a powerful role in studies on temporal electronic correlations, as well as quantum information processing schemes. Techniques that will improve the charge sensitivity of the RF-SET will also be discussed.
Charge sensing with quantum point-contacts (QPCs) is a technique widely used in semiconductor quantum-dot research. Understanding the physics of this measurement process, as well as finding ways of suppressing unwanted measurement back-action, are therefore both desirable. In this article, we present experimental studies targeting these two goals. Firstly, we measure the effect of a QPC on electron tunneling between two InAs quantum dots, and show that a model based on the QPC’s shot-noise can account for it. Secondly, we discuss the possibility of lowering the measurement current (and thus the back-action) used for charge sensing by correlating the signals of two independent measurement channels. The performance of this method is tested in a typical experimental setup.
We performed real-time observation of charge states in a double quantum dot (QD) by monitoring the current passing through an adjacent quantum point contact (QPC). The position of the QPC was chosen in such a way that the Coulomb coupling of the QPC to one QD is made stronger than to the other QD, so that the QPC current can clearly resolve the charge states of the double QD. With a response time of ∼200 µs, we also investigated the energy relaxation time T 1 of the double QD by applying rectangular voltage pulses to the double QD. We confirmed that T 1 can be made sufficiently longer than the response time of the QPC.