Quantum State Manipulation of Atoms and Photons

Valérian Giesz, Niccolò Somaschi, Gaston Hornecker +12 more

In a quantum network based on atoms and photons, a single atom should control the photon state and, reciprocally, a single photon should allow the coherent manipulation of the atom. Both operations require controlling the atom environment and developing efficient atom-photon interfaces, for instance by coupling the natural or artificial atom to cavities. So far, much attention has been drown on manipulating the light field with atomic transitions, recently at the few-photon limit. Here we report on the reciprocal operation and demonstrate the coherent manipulation of an artificial atom by few photons. We study a quantum dot-cavity system with a record cooperativity of 13. Incident photons interact with the atom with probability 0.95, which radiates back in the cavity mode with probability 0.96. Inversion of the atomic transition is achieved for 3.8 photons on average, showing that our artificial atom performs as if fully isolated from the solid-state environment.

National Research Council

Christine A. Muschik, Inés de Vega, Diego Porras +1 more

In a quantum network, transmission of quantum states is performed by photonic channels, which distribute them between remote locations. However, the storage and manipulation of the photons is more problematic. Recently, several schemes have been proposed to store photons efficiently by interfacing the photonic channel with an atomic system, i.e. an atomic ensemble. In those schemes, the photonic input state is transferred to a collective atomic state. But the manipulation of photonic states requires the ability to perform entangling operations. We show how to do this manipulation and perform a deterministic entangling gate between photons. To this order, we interface a system of cold neutral atoms in an optical lattice with the photonic channel, such that now the atoms are not only used to store information, but also to process it by means of cold controlled collisions in the lattice.

Monika Schleier-Smith

Mikhail D. Lukin

Modern optical techniques allow one to accurately control light using atoms and to manipulate atoms using light. In this Colloquium the author reviews several ideas indicating how such techniques can be used for accurate manipulation of quantum states of atomic ensembles and photons. First a technique is discussed that allows one to transfer quantum states between light fields and metastable states of matter. The technique is based on trapping quantum states of photons in coherently driven atomic media, in which the group velocity is adiabatically reduced to zero. Next, possible mechanisms are outlined for manipulating quantum states of atomic ensembles. Specifically, a ``dipole blockade'' technique is considered in which optical excitation of mesoscopic samples into Rydberg states can be used to control the state of ensembles at the level of individual quanta. It is also noted that even simple processes involving atom-photon correlations can be used to effectively manipulate the ensemble states. Potentially these techniques can be used for implementation of important concepts from quantum information science.

Charles H. Holbrow, James N. Lloyd, Joseph C. Amato +2 more