Photon density of states in polarization-entangled laser operation

Antı́a Lamas-Linares, Christian Mikkelsen, John C. Howell +1 more

Inspired by laser operation, we address the question of whether stimulated emission into polarization entangled modes can be achieved. We describe a state produced by stimulated emission of the singlet Bell state and propose a setup for creating it. As a first important step towards an entangled-photon laser we demonstrate experimentally interference-enhanced polarization entanglement.

Antı́a Lamas-Linares, John C. Howell, Dirk Bouwmeester

Li Dong, Yan-Fang Lin, Qingyang Li +3 more

Olivier Pfister, William J. Brown, Michael D. Stenner +1 more

We describe the operating characteristics of a new type of quantum oscillator that is based on a two-photon stimulated emission process. This two-photon laser consists of spin-polarized and laser-driven 39K atoms placed in a high-finesse transverse-mode-degenerate optical resonator and produces a beam with a power of approximately 0.2 microW at a wavelength of 770 nm. We observe complex dynamical instabilities of the state of polarization of the two-photon laser, which are made possible by the atomic Zeeman degeneracy. We conjecture that the laser could emit polarization-entangled twin beams if this degeneracy is lifted.

Christian Kurtsiefer, Markus Oberparleiter, Jürgen Volz +1 more

Dirk Bouwmeester

We introduce the notion of laser-like operation for polarization entangled photons. The proposed device has a two-mode output which contains quantum correlations both between the polarization degree of freedom for particles in separate modes and between the photon numbers in the modes. The proposed device will operate in the new and virtually unexplored regime of many-particle entanglement. We present the design and provide experimental data in support of the main operation mechanism. In particular we show the generation of a rotational symmetric four-photon entangled state obtained by stimulated emission of the familiar antisymmetric two-particle Bell state. The produced states allow for novel quantum cryptography and quantum information protocols and for tests of spin-s Bell inequalities.