Long-range interactions and entanglement of slow single-photon pulses (4 pages)

Andrew J. Fisher, M. Avellino

Robert Raussendorf

Inbal Friedler, David Petrosyan, Michael Fleischhauer +1 more

We show that very large nonlocal nonlinear interactions between pairs of colliding slow-light pulses can be realized in atomic vapors in the regime of electromagnetically induced transparency. These nonlinearities are mediated by strong, long-range dipole-dipole interactions between Rydberg states of the multilevel atoms in a ladder configuration. In contrast to previously studied schemes, this mechanism can yield a homogeneous conditional phase shift of $\ensuremath{\pi}$ even for weakly focused single-photon pulses, thereby allowing a deterministic realization of the photonic phase gate.

Hong Chen Guo, Rui Guo

Sang-Kyung Choi, Hee Su Park

Sh. Petrosyan, Yu. P. Malakyan

Single-photon coherent optics represents a fundamental importance for the investigation of quantum light-matter interactions. While most work has considered the interaction in the steady-state regime, here we demonstrate that a single-photon pulse shorter than any relaxation time in a medium propagates without energy loss and is consistently transformed into a zero-area pulse. A general analytical solution is found for photon passage through a cold ensemble of $\ensuremath{\Lambda}$-type atoms confined inside a hollow core of a single-mode photonic-crystal fiber. We use the robust far-off-resonant Raman scheme to control the pulse reshaping by an intense control laser beam and show that in the case of cw control field, for exact two-photon resonance, the outgoing photon displays an oscillating temporal distribution, which is the quantum counterpart of a classical field ringing, while for nonzero two-photon detuning a slow photon is produced. We demonstrate also that a train of readout control pulses coherently recalls the stored photon in many well-separated temporal modes, thus producing time-bin entangled single-photon states. Such states, which allow sharing quantum information among many users, are highly demanded for applications in long-distance quantum communication.