Feedback control of quantum mechanical systems is rapidly attracting attention not only due to fundamental questions about quantum measurements, but also because of its novel applications in many fields in physics. Quantum control has been studied intensively in quantum optics but progress has recently been made in the control of solid-state qubits as well. In quantum transport only a few active and passive feedback experiments have been realized on the level of single electrons, although theoretical proposals exist. Here we demonstrate the suppression of shot noise in a single-electron transistor using an exclusively electronic closed-loop feedback to monitor and adjust the counting statistics. With increasing feedback response we observe a stronger suppression and faster freezing of charge current fluctuations. Our technique is analogous to the generation of squeezed light with in-loop photodetection as used in quantum optics. Sub-Poisson single-electron sources will pave the way for high-precision measurements in quantum transport similar to optical or optomechanical equivalents.

No abstract

Quantum technologies involving qubit measurements based on electronic interferometers rely critically on accurate single-particle emission. However, achieving precisely timed operations requires exquisite control of the single-particle sources in the time domain. Here, we demonstrate accurate control of the emission time statistics of a dynamic single-electron transistor by measuring the waiting times between emitted electrons. By ramping up the modulation frequency, we controllably drive the system through a crossover from adiabatic to nonadiabatic dynamics, which we visualize by measuring the temporal fluctuations at the single-electron level and explain using detailed theory. Our work paves the way for future technologies based on the ability to control, transmit, and detect single quanta of charge or heat in the form of electrons, photons, or phonons.

No abstract

A high level of tunability and control over arrays of quantum dots are key ingredients toward the goal of scalable-based qubit architectures. Increasing array size simultaneously increases the parameter space and therefore the tuning complexity. The electron reconfiguration behavior of quantum dot arrays isolated from the electron reservoirs is studied experimentally. Isolating a quantum dot array from the reservoirs does not only enable a high degree of control over the tunnel couplings but at the same time drastically simplifies the stability diagrams for small numbers of electrons trapped in the array. Experimental results on double, triple, and quadruple quantum dot arrays are presented and complementary model calculations allow the identification of all transitions observed in the experiment. Highly tunable long-range transitions are observed in isolated triple quantum dots and evidence of higher-order cotunneling is found for the quadruple quantum dot array.