A sensitive electrometer based on a Rydberg atom in a Schrödinger-cat state

Abstract

Fundamental quantum fluctuations caused by the Heisenberg principle limit measurement precision. If the uncertainty is distributed equally between conjugate variables of the meter system, the measurement precision cannot exceed the standard quantum limit. When the meter is a large angular momentum, going beyond the standard quantum limit requires non-classical states such as squeezed states or Schrödinger-cat-like states. However, the metrological use of the latter has been so far restricted to meters with a relatively small total angular momentum because the experimental preparation of these non-classical states is very challenging. Here we report a measurement of an electric field based on an electrometer consisting of a large angular momentum (quantum number J ≈ 25) carried by a single atom in a high-energy Rydberg state. We show that the fundamental Heisenberg limit can be approached when the Rydberg atom undergoes a non-classical evolution through Schrödinger-cat states. Using this method, we reach a single-shot sensitivity of 1.2 millivolts per centimetre for a 100-nanosecond interaction time, corresponding to 30 microvolts per centimetre per square root hertz at our 3 kilohertz repetition rate. This highly sensitive, non-invasive space- and time-resolved field measurement extends the realm of electrometric techniques and could have important practical applications: detection of individual electrons in mesoscopic devices at a distance of about 100 micrometres with a megahertz bandwidth is within reach.

Magnetic Resonance with Squeezed Microwaves

“…While the fundamental limitations to this scheme deserve further study, our results could likely be improved using present-day technologies to gain up to a factor of 5 in measurement time, reaching the point at which the method becomes practically relevant for magnetic resonance measurements. Besides improving the degree of squeezing, future work could investigate the use of other nonclassical states, such as Schrödinger-cat states in magnetic resonance, which might bring even larger sensitivity gains [52,53].…”

C6 coefficients for interacting Rydberg atoms and alkali-metal dimers

“…The latter is due to their giant dipole moment and electric polarizability. These exotic features have made Rydberg atoms a widely studied platform for fundamental studies and applications such as quantum information processing [1], quantum nonlinear optics [2], and precision measurements [3]. Ultracold Rydberg atoms can be trapped with high densities [4], enabling studies of long-range interactions [5,6] and resonant excitation exchange (Föster) processes [7].…”

Assessment of Rydberg atoms for wideband electric field sensing

“…Atoms are best described in the language of quantum mechanics, and Rydberg sensors can rightfully be considered "quantum sensors", particularly as they have performed at the standard quantum (shot noise) limit [8,21]. Their sensitivity to electric fields relies on large electric dipole moments and the corresponding energy shifts to the atomic spectroscopy that are detected optically [22].…”