In the study published in Nature on 12 January 2023, led by researchers from the University of New South Wales in Australia, demonstrated a technique that allows a switchable interaction among the spins and orbital motion of electrons in silicon quantum dots without using a micromagnet. Fast electrical control was shown in multiple devices and electronic configurations, highlighting the technique’s utility.
The electron spin, formerly described by Pauli as a “classically non-describable two-valuedness,” is a natural resource for long-lived quantum information since it is immune to electric fluctuations and can be duplicated in vast qubit arrays in silicon, providing high-fidelity control. Thus, one of the most convenient control solutions is the incorporation of nanoscale magnets to artificially boost the coupling between spins and electric fields, which reduces the spin’s noise immunity and increases architectural complexity.
Thus, the study’s primary objective is to utilize a switchable interaction between spins and the orbital motion of electrons in silicon quantum dots without using a micromagnet.
Switchability of the electrical dependency
The switchability of the electrical dependency allows us to solve one of the most challenging elements of quantum information: the addressability of a qubit must frequently be traded against its noise robustness. This enables us to manage the degeneracy while harvesting the long intrinsic coherence of Si qubits while idling.
The premise was that consistently attaining this degeneracy in four different devices in this initial demonstration provides confidence that a consistent procedure is doable. They also stressed that improved electric spin driving is only one result of the capacity to construct hybridized wavefunctions with coherent spin states controllably.
The findings show that regulating the energy quantization of electrons in the nanostructure, which enhances orbital motion, improves the naturally modest effects of the relativistic spin-orbit interaction in silicon by more than three orders of magnitude.
Furthermore, utilizing the electrical drive, they achieved T2=50 µs coherence time, fast single-qubit gates, and gate fidelities of 99.93% as measured by randomized benchmarking. Higher gate speeds and improved CMOS manufacturing compatibility afforded by on-demand electric control boost the prospects for achieving scalable silicon quantum processors.
Extensions of the result, according to the researchers, could lead to strategies for coupling spins to photons, as well as long-range two-qubit gates via spin-dependent electric dipolar coupling, similar to strategies such as the Rydberg gates and Mlmer Srensen gates, which have previously been demonstrated in atomic qubits or predicted for electron-nuclear flip-flop qubits in silicon.
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