Entangled Light Pulses from Single Cold Atoms

Abstract

The coherent interaction between a laser-driven single trapped atom and an optical high-finesse resonator allows one to produce entangled multiphoton light pulses on demand. The mechanism is based on the mechanical effect of light. The degree of entanglement can be controlled through the parameters of the laser excitation. Experimental realization of the scheme is within reach of current technology. A variation of the technique allows for controlled generation of entangled subsequent pulses, with the atomic motion serving as intermediate memory of the quantum state. DOI: 10.1103/PhysRevLett.96.023601 PACS numbers: 42.50.Dv, 03.67.Mn, 32.80.Qk Coherently controlled atom-photon interfaces are the basic building blocks of implementations of quantum information processing and secure telecommunication with quantum optical systems. Experimental efforts towards this goal have reached several remarkable milestones. For instance, in the optical regime quantum correlations between atomic gases and light have been created and explored [1][2][3][4]; entanglement between a single trapped ion and a single photon has been demonstrated [5]; and highly controlled photonic interaction has been achieved with single atoms flying through resonators [6 -9], or with atoms or ions trapped by an external potential inside an optical cavity [10 -14]. The latter experiments have demonstrated, amongst others, the generation of Rabi oscillations between the atomic dipole and the cavity field [7,13], laser action at the level of a single atom [6,10], and the creation of single photons on demand [9,11,14]. In particular, in the experiment of Ref. [14] single-photon wave packets of adjustable shape and emission rate were generated. These realizations access novel regimes of engineering atomphoton interaction and open promising perspectives for implementing controlled nonlinear dynamics with quantum optical systems [15]. Besides its applications, this progress touches on interesting fundamental questions, such as how macroscopic nonlinear phenomena emerge from the dynamics of single quantum systems.In this context, we show here that a single cold trapped atom in a high-finesse resonator can be used for the controlled, quantum-coherent generation of entangled light pulses, by exploiting the mechanical effects of atomphoton interaction. The atom's motional degrees of freedom act as a quantum medium that is used to establish entanglement between two field modes or to store and transmit quantum correlations between subsequent light pulses with variable delay. In all cases, at the end of the process the quantum medium is perfectly decorrelated from the electromagnetic field modes.The specific application that we describe is that after a short coherent excitation pulse from the laser, the cavity will emit a pulse of two-mode squeezed, i.e., entangled, light. We also describe a variation of the scheme that allows for controlled generation of entangled subsequent pulses, with the atomic motion serving as intermediate memory of the quantum state.Our ...

Robust entanglement of a micromechanical resonator with output optical fields

“…[52,76,77,79], which require many driven cavity modes, each associated with the corresponding output mode. In the present case instead, the different output modes originate from the same single driven cavity mode, and therefore it is much simpler from an experimental point of view.…”

Single atom as a macroscopic entanglement source

“…We note that Morigi et al [15,16] have also considered the generation of two-mode squeezing in a single atom. Their situation is however different from ours.…”

“…The entanglement between single atom and its emitted photon has been observed [14]. More recently, Morigi et al [15,16] put forward a scheme where a single trapped atom allows for the generation of entangled light under certain conditions.…”

Influence of Virtual Photon Process on the Generation of Squeezed Light from Atoms in an Optical Cavity

“…A paradigmatic example of quantum light source is the optical parametric amplifier, which is usually realized with nonlinear crystals in resonators [17]. In the recent past, there have been theoretical proposals that a single atom and two atoms in a suitable setup can act as a nonlinear medium to generate squeezed light [18][19][20][21][22][23]. More recently, it was proposed that a Bose-Einstein condensate in an optical cavity also generates squeezed light with the two-body atom-atom interaction appearing as a coherent handle to control this generation [24].…”