Observation of period doubling and higher multiplicities in a driven single-spin system

TL;DR

This paper reports the experimental observation of period doubling and higher multiplicities in a driven single-spin system, specifically a nitrogen vacancy center in diamond, revealing new insights into quantum subharmonic responses.

Contribution

It demonstrates for the first time the occurrence of period doubling and higher multiplicities in a single-spin system under strong periodic driving.

Findings

Observation of period doubling and higher multiplicities ($k=2$ to 5) in a single-spin system.

Enhanced sensitivity in the driven regime for quantum sensing.

Verification of coherent $k$-tupling oscillations over various parameters.

Abstract

One of the prime features of quantum systems strongly driven by external time-periodic fields is the subharmonic response with integer multiples of the drive period $k\, T_d$. Here we demonstrate experimentally based on a careful theoretical analysis period doubling and higher multiplicities ($k=2,\ldots 5$) for one of the most fundamental systems, namely, an individual spin-$1/2$. Realized as a nitrogen vacancy center in diamond, the particular coherence properties under ambient conditions, strong field sensitivity, and optical addressability allow to monitor coherent $k$-tupling oscillations over a broad set of driving parameters in the vicinity of the ideal manifolds. We verify an enhanced sensitivity within this domain which provides new means for improved sensing protocols.