Measurements of sub photon cavity fields by atom interferometry

Justin Brown, Brian Estey, Paul Hamilton +1 more

S. Haroche, M. Brune, J. M. Raimond

We describe the optimum detection procedure to follow in order to measure by atomic interferometry the number of photons present in a cavity by using a Quantum nondemolition scheme. The method we discuss is the one recently introduced by Brune et al. [1, 2], in which the field intensity is detected by recording atomic interferences in a Ramsey type set up. A succession of two-level atoms interacts with the cavity field which is the analog of a birefringent retarding plate for the atomic wave function. The information is acquired in the form of binary digits (atoms detected in one level or the other). We discuss an optimal strategy which yields the value of the photon number with a number of atoms of the order of the base 2 logarithm of the field photon number dispersion. The procedure described here is the one we intend to use in an experiment in preparation.

Benjamin T. H. Varcoe

Quality factor of up to 4/spl times/10/sup 10/, corresponding to an average lifetime of a photon in the cavity of 0.3 s, are achieved. The photon lifetime is thus much longer than the interaction time of an atom with the maser field. The atoms used are rubidium Rydberg atoms pumped by laser excitation into the upper maser level, 63P/sub 3/2/, the lower maser level is either the 61D/sub 5/2/ or the 61D/sub 3/2/ depending on the cavity frequency. The atom field dynamics is observed by measuring the atoms in the upper or lower maser levels after the cavity. During the interaction the field in the cavity consists only of single or a few photons, nevertheless, it is possible to study the interaction in detail.

Justin Brown, Brian Estey, Holger Müller

Byoung-moo Ann, Younghoon Song, Junki Kim +2 more

Sub-Poisson field with much reduced fluctuations in a cavity can boost quantum precision measurements via cavity-enhanced light-matter interactions. Strong coupling between an atom and a cavity mode has been utilized to generate highly sub-Poisson fields. However, a macroscopic number of optical intracavity photons with more than 3 dB variance reduction has not been possible. Here, we report sub-Poisson field lasing in a microlaser operating with hundreds of atoms with well-regulated atom-cavity coupling and interaction time. Its photon-number variance was 4 dB below the standard quantum limit while the intracavity mean photon number scalable up to 600. The highly sub-Poisson photon statistics were not deteriorated by simultaneous interaction of a large number of atoms. Our finding suggests an effective pathway to widely scalable near-Fock-state lasing at the macroscopic scale.

M. Dovale Álvarez