Threshold-independent method for single-shot readout of spin qubits in semiconductor quantum dots

Abstract

The single-shot readout data process is essential for the realization of high-fidelity qubits and fault-tolerant quantum algorithms in semiconductor quantum dots. However, the fidelity and visibility of the readout process is sensitive to the choice of the thresholds and limited by the experimental hardware. By demonstrating the linear dependence between the measured spin state probabilities and readout visibilities along with dark counts, we describe an alternative threshold-independent method for the single-shot readout of spin qubits in semiconductor quantum dots. We can obtain the extrapolated spin state probabilities of the prepared probabilities of the excited spin state through the threshold-independent method. Then, we analyze the corresponding errors of the method, finding that errors of the extrapolated probabilities cannot be neglected with no constraints on the readout time and threshold voltage. Therefore, by limiting the readout time and threshold voltage we ensure the accuracy of the extrapolated probability. Then, we prove that the efficiency and robustness of this method is 60 times larger than that of the most commonly used method. Moreover, we discuss the influence of the electron temperature on the effective area with a fixed external magnetic field and provide a preliminary demonstration for a single-shot readout up to 0.7 K/1.5 T in the future.

Electric field dependence of spin qubit in a Si-MOS quantum dot

“…The SET structure is capacitively coupled to DQD, and is used to monitor the electron tunneling events to realize qubit state readout via Elzerman readout. [41][42][43] Beside the aluminum gates, a rectangular micro-magnet (MM, Ti/Co 10/240 nm) is deposited around the QD structure to provide the magnetic field gradient for EDSR. [12,23,44] An external magnetic field B ext provides Zeeman splitting between electron spin states and fully magnetizes the MM.…”

“…By monitoring the sudden change of I S , the electron spin state can be distinguished. [43] With the ability to operate and read out qubits, we turn to characterize the valley properties of the electric field dependence. When we focus on the electric field dependence of f res , we scan the voltage of the qubit control process (V load ) along the orange dotted line in Fig.…”