This project pushes the limits of detection for the weakest radio frequency fields with Rydberg atom-based quantum sensors by using a new three-photon excitation scheme that was discovered by QVIL researchers. Quantum sensors can operate in a regime where radio frequency field strength is measured without the need for costly calibration, unlike conventional methods. Having a signal with a narrower spectral linewidth enables weaker RF fields to be measured in this self-calibrated way.

We achieve narrow spectral linewidths by reducing the Doppler shifts of moving atoms using a three-photon arrangement to better cancel out the laser field wavevectors. Such a scheme also greatly improves sensitivity to microsecond radio frequency field pulses, which are necessary for communications and radar. We have observed spectral linewidths of the cesium Rydberg states of < 200 kHz, which are fully explained by theory. We expect that ~50 kHz spectral linewidths can be experimentally achieved in thermal vapour cells using this method.

In this project we continue to push the sensitivity that we can achieve, as well as simplifying the experiment so that it can be engineered into a fieldable system.

Counterpropagated lasers pass through a cesium vapour cell, eventually reaching a detector. The effect of the lasers on the resulting linewidth is shown.
Fig. 1: An illustration of the three-photon sensing scheme. The 2260 nm and 895 nm lasers are counterpropagated against the 636 nm laser through a Cs vapour cell, and the 895 nm transmission is measured on a photodiode. The improved cancellation of the Doppler shift in this scheme allows for a much narrower linewidth, improving sensitivity.

Representative Publications:

  1. A read-out enhancement for microwave electric field sensing with Rydberg atoms,” J. P. Shaffer and H. Kübler, Proc. SPIE 10674, Quantum Technologies (2018).
  2. Origins of Rydberg-atom electrometer transient response and its impact on radio-frequency pulse sensing,” S.M. Bohaichuk, D. Booth, Kent Nickerson, H. Tai, and J.P Shaffer, Physical Review Applied 18, 034030 (2022).
  3. A Three-Photon Rydberg Atom-Based Radio Frequency Sensing Scheme with Narrow Linewidth,” S. M. Bohaichuk, F. Ripka, V. Venu, F. Christaller, C. Liu, M. Schmidt, H. Kübler and J. P. Shaffer, arXiv:2304.07409 [physics.atom-ph].
  4. Rydberg atom-based radio frequency sensors: amplitude regime sensing,” Rydberg atom-based radio frequency sensors: amplitude regime sensing

Funding agencies:

DARPA logo
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Interested in Collaborating or Joining Our Team?

If you are interested in collaborating with us or becoming a technical staff member, including student internships and postdoctoral training, please contact James Shaffer at [email protected].