We study the nondemolition mapping of collective quantum coherence onto a cavity light field in a superradiant, cold-atom ${}^{87}$ Rb Raman laser. We show theoretically that the fundamental precision of the mapping is near the standard quantum limit on phase estimation for a coherent spin state, $\ensuremath{\Delta}\ensuremath{\phi}=1/\sqrt{N}$, where $N$ is the number of atoms. The associated characteristic measurement time scale ${\ensuremath{\tau}}_{W}\ensuremath{\propto}1/N$ is collectively enhanced. The nondemolition nature of the measurement is characterized by only 0.5 photon recoils deposited per atom due to optical repumping in a time ${\ensuremath{\tau}}_{W}$. We experimentally realize conditional Ramsey spectroscopy in our superradiant Raman laser, compare the results to the predicted precision, and study the mapping in the presence of decoherence, far from the steady-state conditions previously considered. Finally, we demonstrate a hybrid mode of operation in which the laser is repeatedly toggled between active and passive sensing.We study the nondemolition mapping of collective quantum coherence onto a cavity light field in a superradiant, cold-atom ${}^{87}$Rb Raman laser. We show theoretically that the fundamental precision of the mapping is near the standard quantum limit on phase estimation for a coherent spin state, $\ensuremath{\Delta}\ensuremath{\phi}=1/\sqrt{N}$, where $N$ is the number of atoms. The associated characteristic measurement time scale ${\ensuremath{\tau}}_{W}\ensuremath{\propto}1/N$ is collectively enhanced. The nondemolition nature of the measurement is characterized by only 0.5 photon recoils deposited per atom due to optical repumping in a time ${\ensuremath{\tau}}_{W}$. We experimentally realize conditional Ramsey spectroscopy in our superradiant Raman laser, compare the results to the predicted precision, and study the mapping in the presence of decoherence, far from the steady-state conditions previously considered. Finally, we demonstrate a hybrid mode of operation in which the laser is repeatedly toggled between active and passive sensing.

Physical Review AJul 17, 201326 citations

Steady-State Superradiant Laser with an Atomic Beam Source

Haonan Liu, Simon B. Jäger, J. Cooper +3 more

Bulletin of the American Physical SocietyJun 3, 20200 citations

Superradiant Raman laser magnetometer

Joshua M. Weiner, Kevin C. Cox, Justin G. Bohnet +2 more

We demonstrate a proof-of-principle magnetometer that relies on the active oscillation of a cold atom Raman laser to continuously map a field-sensitive atomic phase onto the phase of the radiated light. We demonstrate wideband sensitivity during continuous active oscillation, as well as narrowband sensitivity in passive Ramsey-like mode with translation of the narrowband detection in frequency using spin-echo techniques. The sensor operates with a sensitivity of 190 pT/Hz at 1 kHz and effective sensing volume of 2×10−3 mm3. Fundamental quantum limits on the magnetic field sensitivity of an ideal detector are also considered.We demonstrate a proof-of-principle magnetometer that relies on the active oscillation of a cold atom Raman laser to continuously map a field-sensitive atomic phase onto the phase of the radiated light. We demonstrate wideband sensitivity during continuous active oscillation, as well as narrowband sensitivity in passive Ramsey-like mode with translation of the narrowband detection in frequency using spin-echo techniques. The sensor operates with a sensitivity of 190 pT/Hz at 1 kHz and effective sensing volume of 2×10−3 mm3. Fundamental quantum limits on the magnetic field sensitivity of an ideal detector are also considered.

arXiv:1210.3663Applied Physics LettersDec 24, 201225 citations

A Superradiant Laser: Toward mHZ Linewidth Lasers

James K. Thompson

Abstract : We demonstrated that an optical laser can operate with less than 1 photons on average inside the cavity while also obtaining significant spectral narrowing of the emitted light relative to the single atom transition linewidth. We further explored the power output properties and threshold conditions of this laser. We made direct measurements that showed that the lasing frequency can be made greater than 10000 times less sensitive to the resonance frequency of the optical cavity than is the case for normal lasers or for passive optical reference cavities. Such a large reduction in sensitivity would essentially remove both thermal and technical mirror vibrations as a limitation on laser linewidth. Other studies included how phase information can be stored and manipulated inside of our laser, such that it may be possible to have both an active laser and a passive Ramsey-like sensor in the same setup. We considered the fundamental limits on the atomic quantum information that can be extracted from the laser light and found that it corresponded closely to the fundamental atomic standard quantum limit on phase estimation.Abstract : We demonstrated that an optical laser can operate with less than 1 photons on average inside the cavity while also obtaining significant spectral narrowing of the emitted light relative to the single atom transition linewidth. We further explored the power output properties and threshold conditions of this laser. We made direct measurements that showed that the lasing frequency can be made greater than 10000 times less sensitive to the resonance frequency of the optical cavity than is the case for normal lasers or for passive optical reference cavities. Such a large reduction in sensitivity would essentially remove both thermal and technical mirror vibrations as a limitation on laser linewidth. Other studies included how phase information can be stored and manipulated inside of our laser, such that it may be possible to have both an active laser and a passive Ramsey-like sensor in the same setup. We considered the fundamental limits on the atomic quantum information that can be extracted from the laser light and found that it corresponded closely to the fundamental atomic standard quantum limit on phase estimation.

Dec 3, 20140 citations

We study the nondemolition mapping of collective quantum coherence onto a cavity light field in a superradiant, cold-atom

{}^{87}

Rb Raman laser. We show theoretically that the fundamental precision of the mapping is near the standard quantum limit on phase estimation for a coherent spin state, $\ensuremath{\Delta}\ensuremath{\phi}=1/\sqrt{N}$, where

N

is the number of atoms. The associated characteristic measurement time scale ${\ensuremath{\tau}}_{W}\ensuremath{\propto}1/N$ is collectively enhanced. The nondemolition nature of the measurement is characterized by only 0.5 photon recoils deposited per atom due to optical repumping in a time ${\ensuremath{\tau}}_{W}$. We experimentally realize conditional Ramsey spectroscopy in our superradiant Raman laser, compare the results to the predicted precision, and study the mapping in the presence of decoherence, far from the steady-state conditions previously considered. Finally, we demonstrate a hybrid mode of operation in which the laser is repeatedly toggled between active and passive sensing.