Southwest Quantum Information and Technology

Quantum-enhanced sensing of displacements and electric fields with large trapped-ion crystals

Presenting Author: Diego Barberena, University of Colorado JILA
Contributing Author(s): Kevin Gilmore, Matthew Affolter, Robert J. Lewis-Swan, Elena Jordan, Ana Maria Rey, John J. Bollinger

In this talk we will describe a protocol that performs quantum enhanced sensing of displacements and electric fields in a large crystal of trapped ions (N=150). The protocol uses the center of mass vibrational mode (COM) of the crystal as a high-Q mechanical oscillator and the ions' collective electronic spin, as the effective measurement device. It is implemented by the use of properly detuned laser beams that entangle the oscillator and the collective spin before applying a weak displacement to the oscillator. After a many-body echo that maps the displacement into a spin rotation while canceling both quantum back-action and thermal noise the collective spin is measured. We derive an effective model of coupled oscillators to describe both the spins and the COM of mode and show that the spin-boson entanglement at the core of the protocol can be understood as the squeezing dynamics of this pair of oscillators. We achieve a sensitivity to displacements of 8.8 ± 0.4 dB below the standard quantum limit and about 19 dB below relevant thermal bounds, and a sensitivity for measuring electric fields of 240 ± 40 nV/m in 1 second (240 nVm-1Hz-1/2). With future improvements, electric field sensitivities below 1 nV/m may be possible, which could enable searches for dark matter.

Read this article online: https://science.sciencemag.org/content/373/6555/673?rss=1

(Session 4 : Friday from 10:50am-11:10am)