Sandia Labs FY21 LDRD Annual Report


Sandia has designed a faster, more accurate style of test for quantum computers, such as the one pictured here. (Photo by Bret Latter)

A fast-cycle charge noise measurement for better qubits. The spins of electrons localized in quantum dots are prime candidates for quantum bits (qubits) in a solid- state quantum computer. Quantum dots are fabricated using standard semiconductor fabrication techniques on silicon substrates. However, defects such as charge traps and dangling bonds are always present at materials interfaces and are also introduced during many fabrication steps. Defects cause charge noise leading to qubit decoherence. Characterization of this noise, traditionally performed with qubits themselves, is accurate but slow, hindering progress towards better devices. Through this LDRD project, researchers developed a noise spectroscopy technique to measure charge noise based on superconducting resonators. The technique leverages the high-quality factor resonators possible with superconductors, achieving sensitivity to noise in the stock material used to fabricate a qubit at the ultra-low temperatures and power levels encountered in qubit research. It also permits rapid testing of qubit fabrication processes. This research is expected to benefit not only spin-based quantum dot qubits, but also superconductor-based qubits such as the transmon (PI: Rupert Lewis)



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