ETH Zurich Demonstrates 3-D Single-Ion Mapping of Chip Electromagnetic Noise

Researchers at ETH Zurich used a single laser-cooled beryllium ion in a chip-based Penning trap to map electric and magnetic fields three-dimensionally above a quantum-chip surface. By moving the ion arbitrarily, they measured oscillating electric fields as weak as 10 nanovolts per metre in one second and also detected static fields and magnetic fields via ion displacement and Zeeman shifts.

Interesting EngineeringSingle Ion Detector Could Lead to Improvements in Quantum Computers and SensorsHow ETH Zurich Scans Chip Noise With Trapped Ions

Stray electromagnetic noise has limited trapped-ion quantum processors for over three decades, with radio-frequency traps adding background oscillations that mask weak chip-generated disturbances. ETH Zurich replaced RF fields with static electric and magnetic fields in a Penning trap, removing this interference. The project was led by Professor Jonathan Home, with doctoral researchers Tobias Sägesser and Shreyans Jain developing ion positioning and analysis.

Interesting EngineeringSingle Ion Detector Could Lead to Improvements in Quantum Computers and SensorsHow ETH Zurich Scans Chip Noise With Trapped Ions

The ion, cooled to its motional ground state, was positioned 50–450 µm above the chip and scanned a 200 µm × 200 µm area. Ambient electric fields induced incremental ion motion measured by laser-pulse interrogation, achieving a sensitivity of 10 nV m?¹—an order of magnitude better than previous chip-trap results. For reference, a mobile-phone field is about 10 000 times stronger at kilometre distances. Magnetic fields were derived from Zeeman shifts of the ion’s energy levels.

Interesting Engineering

Three-dimensional maps can be compared with noise models to pinpoint material or fabrication sources of interference. Engineers can evaluate surface coatings and processing steps to select those that generate the lowest electric fields, potentially boosting gate fidelity and sensor stability in future trapped-ion quantum computers and quantum-enhanced sensors.

Interesting Engineering

Professor Home said the method resolves a longstanding uncertainty about near-surface electric-field noise, enabling empirical validation of models. Sägesser highlighted the record 10 nV m?¹ sensitivity, and Jain noted that the static-field Penning trap removes background oscillations, making weak chip-generated fields easier to detect.

Single Ion Detector Could Lead to Improvements in Quantum Computers and Sensors

The team will apply the technique to chips with varied metallizations and dielectrics, building a database of material-specific noise signatures, and scale it for larger areas and routine testing.

Interesting Engineering

• “Two years ago, we developed a novel chip trap that allowed to move an ion arbitrarily in three dimensions” — Tobias Sägesser, Doctoral Student, ETH Zurich

Single Ion Detector Could Lead to Improvements in Quantum Computers and Sensors

• “In this way, we have set a new record for the most sensitive measurement of an oscillating electric field in a chip trap” — Tobias Sägesser, Doctoral Student, ETH Zurich

Single Ion Detector Could Lead to Improvements in Quantum Computers and Sensors

• “For more than thirty years, researchers have tried to find out where the electric field noise close to a chip comes from” — Jonathan Home, Professor, ETH Zurich

Single Ion Detector Could Lead to Improvements in Quantum Computers and Sensors