Electrical readout of spins in the absence of spin blockade

TL;DR

This paper introduces a novel electrical spin readout method that functions effectively even when spin blockade is lifted by mechanisms like spin-orbit coupling, demonstrated on a silicon quantum dot system.

Contribution

The authors develop a new spin readout technique based on polarizability dependence on energy detuning, enabling high-fidelity measurements despite spin blockade lifting mechanisms.

Findings

Successfully demonstrated spin-selective readout in a silicon quantum dot system.

Determined spin relaxation times ranging from 0.1 to 8 microseconds.

Showed the method's robustness against spin blockade lifting mechanisms.

Abstract

In semiconductor nanostructures, spin blockade (SB) is the most scalable mechanism for electrical spin readout, requiring only two bound spins for its implementation. In conjunction with charge sensing techniques, SB has led to high-fidelity readout of spins in semiconductor-based quantum processors. However, various mechanisms may lift SB, such as strong spin-orbit coupling (SOC) or low-lying excited states, hence posing challenges to perform spin readout at scale and with high fidelity in such systems. Here, we present a method, based on the dependence of the two-spin system polarizability on energy detuning, to perform spin state readout even when SB lifting mechanisms are dominant. It leverages SB lifting as a resource to detect selectively different spin measurement outcomes. We demonstrate the method using a hybrid system formed by a quantum dot (QD) and a Boron acceptor in a silicon p-type transistor and show spin-selective readout of different spin states under SB lifting conditions due to (i) SOC and (ii) low-lying orbital states in the QD. We further use the method to determine the detuning-dependent spin relaxation time of 0.1 - 8 $\mu$s. Our method should help perform projective spin measurements with high spin-to-charge conversion fidelity in systems subject to strong SOC, will facilitate state leakage detection and enable complete readout of two-spin states.