Quantum Metrology with a Scanning Probe Atom Interferometer

TLDR

Quantum metrology with entangled atoms enables high‑resolution measurements of microwave near fields, which are essential for developing integrated microwave circuits for quantum information processing and communication, despite atom‑number limits imposed by collisional loss. We employ a small Bose‑Einstein condensate on an atom chip as a scanning‑probe interferometer to map microwave fields near the chip surface with micrometer resolution. Using atom‑atom entanglement, the interferometer surpasses the standard quantum limit by 4 dB, achieving a microwave magnetic‑field sensitivity of 77 pT/√Hz in a 20 μm³ probe volume for interrogation times up to 10 ms.

Abstract

We use a small Bose-Einstein condensate on an atom chip as an interferometric scanning probe to map out a microwave field near the chip surface with a few micrometers resolution. With the use of entanglement between the atoms, our interferometer overcomes the standard quantum limit of interferometry by 4 dB and maintains enhanced performance for interrogation times up to 10 ms. This corresponds to a microwave magnetic field sensitivity of 77 pT/√Hz in a probe volume of 20 μm(3). Quantum metrology with entangled atoms is useful in measurements with high spatial resolution, since the atom number in the probe volume is limited by collisional loss. High-resolution measurements of microwave near fields, as demonstrated here, are important for the development of integrated microwave circuits for quantum information processing and applications in communication technology.