Anisotropic Stark Effect and Electric-Field Noise Suppression for Phosphorus Donor Qubits in Silicon

TL;DR

This paper investigates the anisotropic Stark effect in phosphorus donor qubits in silicon, demonstrating how electric-field noise can be suppressed by tuning magnetic fields to counteract strain-induced effects.

Contribution

It introduces novel CPW resonators to measure Stark shifts and proposes a method to suppress electric-field noise in donor qubits by exploiting anisotropic Stark effects.

Findings

Valley repopulation causes anisotropic Stark shifts depending on field orientation.

Strain in samples contributes to effective electric fields affecting decoherence.

Predicted magnetic field conditions can cancel hyperfine Stark effects, reducing noise.

Abstract

We report the use of novel, capacitively terminated coplanar waveguide (CPW) resonators to measure the quadratic Stark shift of phosphorus donor qubits in Si. We confirm that valley repopulation leads to an anisotropic spin-orbit Stark shift depending on electric and magnetic field orientations relative to the Si crystal. By measuring the linear Stark effect, we estimate the effective electric field due to strain in our samples. We show that in the presence of this strain, electric-field sources of decoherence can be non-negligible. Using our measured values for the Stark shift, we predict magnetic fields for which the spin-orbit Stark effect cancels the hyperfine Stark effect, suppressing decoherence from electric-field noise. We discuss the limitations of these noise-suppression points due to random distributions of strain and propose a method for overcoming them.