1. Photon counter with Rydberg atoms
INO - CNR
Istituto
Nazionale di
Ottica
Photon counter with Rydberg atoms
(an outsider overview)
Andrea Fioretti
Istituto Nazionale di Ottica, CNR-INO, S.S. «A. Gozzini», Pisa
28 marzo 2017
Laboratori Nazionali di Frascati, INFN
Via Moruzzi 1, Pisa (I)

2. Introduction to Rydberg atoms Experimental procedures
Outline
Motivations
Introduction to Rydberg atoms
Experimental procedures
Results of past experiments ( )
Some new experimental facts
Conclusions and outlook
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

3. Motivations Proposals to use Rydberg atoms as detectors start around
1980 (Kleppner, Walther, Haroche …….)
Rydberg atoms are strong absorbers in the m-wave domain, electric dipole mat. el. between neighboring levels ≈(n*)2
Frequency can be tuned by choosing n and electric field F
Detection is very efficient (Field Ionization) and can be state- selective (states with DE > 20 Mhz can be discriminated).
Quantum noise limit can be reached
Theory can calculate Rydberg atom properties (dipole moments, level shifts, state mixing) to very high precision
Johannes Rydberg
(1854 –1919)
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

4. Motivations
Problems
Rydberg atoms have limited lifetime re-excitation necessary
Blackbody radiation induces transitions between Rydberg states very low temperatures required
Inhomogeneity and fluctuations of the electric field induce state mixing
State selectivity in field ionization is not perfect
Johannes Rydberg
(1854 –1919)
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

5. Introduction to Rydberg atoms Experimental procedures
Outline
Motivations
Introduction to Rydberg atoms
Experimental procedures
Results of past experiments ( )
Some new experimental facts
Conclusions and outlook
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

6. Rydberg atoms
Picture credit: Dr. Joshua Gurian
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

7. Rydberg atoms
Picture credit: Dr. Joshua Gurian
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

8. Rydberg atoms Electric Field Ionization
Picture credit: Dr. Joshua Gurian
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

9. Stark diagram of Rydberg atoms
Pictures credit: T.F. Gallagher “Rydberg atoms”
Temporal (ramp) or spatial Field gradients
can discriminate neighboring states
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

10. Introduction to Rydberg atoms Experimental procedures
Outline
Motivations
Introduction to Rydberg atoms
Experimental procedures
Results of past experiments ( )
Some new experimental facts
Conclusions and outlook
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

11. Experimental setups for Rydberg atoms
Cold trapped atoms
Atomic beam
m-wave cavity
Electrodes
Laser beams
Picture credit: Dr. Joshua Gurian
Vapor cell
Picture credit: P.Pillet’s group, Orsay (Fr))
From: J.A. Sedlacek et al., Nat. Phys (2012)
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

12. Rydberg excitation Optical excitation, low l
Optical + rf, high l (circular states)
From: Ryabtsev et al, Physics Uspekhi 59, 196 (2016)
From: Molander et al, J. Phys. B 19, L461 (1986)
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

13. Rydberg detection Spatial field gradient Temporal field gradient
From: Ryabtsev et al, Physics Uspekhi 59, 196 (2016)
From: L. Kime et al., Phys. Rev. A 88, (2013)
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

14. First photon counting results
Excitation of 22D of sodium
Detection of higher states
(DE= 95GHz or higher)
N.E.P.: W 14 K
From: H. Figger et al., Phys. Rev. A 88, (2013)
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

15. First photon counting results
From :M. Gross et al.,Phys. Rev. Lett. 43, 343 (1979)
Maser action is trigger by blackbody radiation in a resonant cavity
N.E.P.: 3x10-17 W 300 K @ 108 GHz (l=2.8 mm)
Quantum-noise limit : QNL = 6x10-19 W Hz-1/2
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

16. Introduction to Rydberg atoms Experimental procedures
Outline
Motivations
Introduction to Rydberg atoms
Experimental procedures
Results of past experiments ( )
Some new experimental facts
Conclusions and outlook
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

17. Axion search with Rydberg atoms
Original proposal:
From: S. Matsuki and K. Yamamoto, Phys. Lett. B 263, 523 (1991)
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

18. Axion search with Rydberg atoms
CARRACK I and II experiments, Kyoto (Japan)
Axion to photon conversion in a cavity with magnetic field
Photon detection via Rydberg atoms in a resonant cavity
Conversion cavity
Detection cavity
From: M. Tada et al.,
Nucl. Phys. B 72, 164 (1999)
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

19. Axion search with Rydberg atoms
CARRACK I and II experiments, Kyoto (Japan)
Frequency range around ~ 2.4 𝐺𝐻𝑧
Qcavity: 5x104 ; Tcavity: 10 mK
Sensitivity depends on atom-photon coupling
Frequency scan by tuning of cavity and Rydberg resonances
Expected count rate
Axion photons
BBR photons
From: S. Matsuki et al.,
Nucl. Phys. B 51B, 213 (1996)
From: M. Tada et al., Nucl. Phys. B 72, 164 (1999)
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

20. Axion search with Rydberg atoms
CARRACK I and II experiments, Kyoto (Japan)
From: M. Tada et al., Nucl. Phys. B 72, 164 (1999)
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

21. Axion search with Rydberg atoms
CARRACK I and II experiments: RESULTS
Detection of BBR in a single-mode cavity
(l=60cm, diam.=9cm ,Q=3,1x014)
SQL limit: 121mK
From :M. Tada et al., Phys. Lett.. A 349, 488 (2006)
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

22. Axion search with Rydberg atoms
CARRACK I and II experiments: LIMITS
Limited state selectivity (state mixing) due to stray electric fields
Possible solutions: changing atom species (K instead of Rb)
guiding electrodes in the cavity
Too complex for a systematic search?
From: M. Shibata et al., J. Low Temp. Phys. 151, 1043 (2008)
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

23. Introduction to Rydberg atoms Experimental procedures
Outline
Motivations
Introduction to Rydberg atoms
Experimental procedures
Results of past experiments ( )
Some new experimental facts
Conclusions and outlook
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

24. A single photon stored in a cavity for 0.5 s,
QND photon counting
A single photon stored in a cavity for 0.5 s,
observed non-destructively by many atoms
Serge Haroche
Nobel Prize 2012
From :S. Gleyzes et al., Nature 446, 297 (2007)
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

25. Cavity: freq= 51 GHz, Q= 4.6x109 , T= 0.8 K
QND photon counting
Cavity: freq= 51 GHz, Q= 4.6x109 , T= 0.8 K
Serge Haroche
Nobel Prize 2012
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

26. Other approaches: m-wave electrometry
Use of Electromagnetic Induced Transparency (EIT) in a room-temperature vapor cell
Sensitivity: 30 mV cm GHz
Field measured: 8 mV cm-1 but 100 nV cm-1 possible
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

27. Other approaches: m-wave electrometry
Relatively simple approach:
Spectroscopic method at
room temperature
From :J.A. Sedlacek et al., Nat. Phys (2012)
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

28. Introduction to Rydberg atoms Experimental procedures
Outline
Motivations
Introduction to Rydberg atoms
Experimental procedures
Results of past experiments ( )
Some new experimental facts
Conclusions and outlook
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

29. Thank you for your attention
Conclusions and Outlook
Rydberg atoms are indeed photomultiplier tubes in the GHz range
Experiments (Kyoto) technically successful (below SQL limit) but (probably) too complex
Interest and use of Rydberg atoms still growing (quantum information and simulation, many-body physics, metrology ...)
Technology and theory are still progressing (cold Rydberg, lasers …)
Photon search in different frequency domains with Rydberg atoms may be interesting
Thank you for your attention
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

30. Axion search with Rydberg atoms
From: I. Kishimoto et al.,.Phys. Lett. A 303, 279 (2002)
A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017