Photon counter with Rydberg atoms INO - CNR Istituto Nazionale di Ottica www.ino.it 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, 56124 Pisa (I) andrea.fioretti@ino.it

Introduction to Rydberg atoms Experimental procedures Outline Motivations Introduction to Rydberg atoms Experimental procedures Results of past experiments (1996-2008) Some new experimental facts Conclusions and outlook A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

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

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

Introduction to Rydberg atoms Experimental procedures Outline Motivations Introduction to Rydberg atoms Experimental procedures Results of past experiments (1996-2008) Some new experimental facts Conclusions and outlook A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

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

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

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

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

Introduction to Rydberg atoms Experimental procedures Outline Motivations Introduction to Rydberg atoms Experimental procedures Results of past experiments (1996-2008) Some new experimental facts Conclusions and outlook A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

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. 8. 819 (2012) A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

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

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, 033424 (2013) A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

First photon counting results Excitation of 22D of sodium Detection of higher states (DE= 95GHz or higher) N.E.P.: 10-17 W Hz-1/2 @ 14 K From: H. Figger et al., Phys. Rev. A 88, 033424 (2013) A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

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 Hz-1/2 @ 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

Introduction to Rydberg atoms Experimental procedures Outline Motivations Introduction to Rydberg atoms Experimental procedures Results of past experiments (1996-2008) Some new experimental facts Conclusions and outlook A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

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

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

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

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

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

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

Introduction to Rydberg atoms Experimental procedures Outline Motivations Introduction to Rydberg atoms Experimental procedures Results of past experiments (1996-2008) Some new experimental facts Conclusions and outlook A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

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

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

Other approaches: m-wave electrometry Use of Electromagnetic Induced Transparency (EIT) in a room-temperature vapor cell Sensitivity: 30 mV cm-1 Hz-1/2 @ 13.9 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

Other approaches: m-wave electrometry Relatively simple approach: Spectroscopic method at room temperature From :J.A. Sedlacek et al., Nat. Phys. 8. 819 (2012) A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

Introduction to Rydberg atoms Experimental procedures Outline Motivations Introduction to Rydberg atoms Experimental procedures Results of past experiments (1996-2008) Some new experimental facts Conclusions and outlook A. Fioretti, CNR-INO, Workshop on Axion Physics and Experiments, Frascati, 28/3/2017

Thank you for your attention Conclusions and Outlook Rydberg atoms are indeed photomultiplier tubes in the 1-500 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

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