Demonstration of an always-on exchange-only spin qubit

TL;DR

This paper demonstrates high-fidelity control of an always-on exchange-only spin qubit using simultaneous exchange pulses in a quantum dot array, achieving nearly 99.86% gate fidelity, which could improve quantum gate efficiency.

Contribution

It introduces the first implementation of an always-on exchange-only spin qubit with simultaneous exchange pulses, enhancing control and fidelity over traditional methods.

Findings

Achieved 99.86% average Clifford gate fidelity.

Demonstrated control of an AEON qubit with simultaneous exchange pulses.

Potential for more efficient two-qubit gates and native Toffoli implementation.

Abstract

In conventional exchange-only (EO) spin qubit demonstrations, quantum gates have been implemented using sequences of individually pulsed pairwise exchange interactions with only one exchange coupling active at a time. Alternatively, multiple non-commuting exchange interactions can be pulsed simultaneously, reducing circuit depths and providing protection against leakage. We demonstrate high-fidelity quantum control of an always-on exchange-only (AEON) qubit, operated using simultaneous exchange pulses in a triangular quantum dot (QD) array. We use blind randomized benchmarking to characterize the performance of the full AEON single-qubit Clifford gate set, achieving an average Clifford gate fidelity $F_{\rm C1}$ = 99.86%. Extensions of this work may enable more efficient EO two-qubit entangling gates as well as the implementation of native $i$-Toffoli gates in Loss-DiVincenzo single-spin qubits.