Sensing dot with high output swing for scalable baseband readout of spin qubits

Abstract

A key requirement for quantum computing, in particular for a scalable quantum computing architecture, is a fast and high-fidelity qubit readout. For semiconductor based qubits, one limiting factor is the output swing of the charge sensor. We demonstrate GaAs and Si/SiGe asymmetric sensing dots (ASDs), which exceed the response of a conventional charge sensing dot by more than ten times, resulting in a boosted output swing of 3 mV. This substantially improved output signal is due to a device design with a strongly decoupled drain reservoir from the sensor dot, mitigating negative feedback effects of conventional sensors. The large output signal eases the use of very low-power readout amplifiers in close proximity to the qubit and will thus render true scalable qubit architectures with semiconductor based qubits possible in the future.

Tailoring potentials by simulation-aided design of gate layouts for spin qubit applications

“…We experimentally benchmark our simulation by probing predicted gate-voltage dependencies of current through the device. By simulating our device layout, we were able to predict the properties of and successfully operate first generation devices [12]. We included a study to make the gate layout robust to unavoidable fabrications imperfections.…”

“…Fig. 1) leads to strongly tilted Coulomb diamonds [12] from which C D can be measured. A large and continuously declining slide region decouples the drain reservoir.…”

“…5c, respectively). In the first case, a significantly lower asymmetry η would be experimentally obtained causing a decrease in sensor gain [12]. In the second case the sensor current might be blocked, since the potential disorder (cf.…”

“…1b). This specific potential is studied as a QD charge sensor with enhanced performance [12]. A double quantum dot (DQD) is added next to it, which can host the spin qubit.…”

“…Demonstrator devices for electron spin qubits have been shown to work with high manipulation [1][2][3][4][5][6][7][8][9] and readout fidelities [9][10][11][12] and indicate a possible path to scaling to a quantum computer [13][14][15][16][17][18]. Gate-layouts of most demonstrator devices are closely related to or copies of previous devices of a research group or of published layouts.…”