Originally published on LinkedIn
Longitudinal coupling of a quantum dot to a resonator, demonstrated
Dec 8, 2023 | Charles Tahan
This is an archived copy of a LinkedIn post. The original is at the link above.
Very happy to see this collaborative work with U. Wisconsin-Madison finally published. The experiment unequivocally demonstrates an enhancement of coupling due to modulation of the longitudinal interaction between a dot and a resonator, which we predicted over 8 years ago:
https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.20.064005
This pairs perfectly with the new paper we posted yesterday (https://arxiv.org/abs/2312.03118) which provides a generalized theory for modulated longitudinal coupling for both spin and superconducting multi-level qubit systems in all experimentally relevant regimes. This “runs to ground”, so to speak, all the ways a solid-state system can couple to a wire, both transverse and longitudinal, modulated or not, and demonstrates how important it is to consider both, especially in dot systems.
Multi-dot encoded spin qubits are especially interesting because one can design systems with zero transverse dipole moment relatively easily and then use modulated readout (https://journals.aps.org/prb/abstract/10.1103/PhysRevB.99.245306) or gates (https://doi.org/10.1103/PhysRevB.103.035301) to enable computation. Plus, spin qubits - like topological qubits - offer a natural joint measurement (one can think of a singlet-triplet qubit either as a single qubit or two separate single spin qubits), offering another tool to make gates more efficient (https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.16.064019).