Modulation of single-photon-level wave packets with two-component electromagnetically induced transparency

Abstract

Coherent manipulation of single-photon wave packets is essentially important for optical quantum communication and quantum information processing. In this paper, we realize controllable splitting and modulation of single-photon-level pulses by using a tripod-type atomic medium. The adoption of two control beams enable us to store one signal pulse into superposition of two distinct atomic collective excitations. By controlling the time delay between the two control pulses, we observe splitting of a stored wave packet into two temporally-distinct modes. By controlling the frequency detuning of the control beams, we observe both temporal and frequency-domain interference of the retrieval signal pulses, which provides a method for pulse modulation and multi-splitting of the signal photons.PACS numbers: 42.50. Gy, 42.25.Hz, 42.79.Fm, 03.67.Hk Techniques for tailoring the dispersion of materials, especially the electromagnetically induced transparency (EIT) method, enable us to control light propagation better than before and inspire lots of applications in quantum optics and atomic physics [1,2]. The ordinary EIT structure is a three-level atomic system interacting with two laser fields, named the signal and control light. By dynamically decreasing/increasing the control light power, coherent state of the signal photons could be transferred into/from the atoms, described as the atomphoton dark-state polaritons [3,4]. For now, EIT has become an important method for photonic quantum memory -an essential component of quantum information science [5,6]. Furthermore, coherent control of the spinor polaritons would lead to numbers of useful quantum state engineering.Particularly, a tripod-type four-level EIT scheme, which offers more freedom and possibilities for photon storage and manipulation, has drawn significant attentions in the last few years [7][8][9][10][11][12][13][14][15][16][17][18][19]. In the tripod-EIT configuration, three ground atomic levels are coupled with an excited level by two signal fields and one control field [15] or one signal field and two control fields. As there exist a pair of orthogonal dark-state polaritons, whose coherence depends on the amplitude and phase of the control fields, beam splitting of a signal pulse could be achieved based on this tripod-type photon storage [13,17]. In comparison with other beam-splitting methods [20][21][22], the tripod-EIT scheme highlights the simplicity and high degree of controllability. For instance, in a former experiment that using rapid coherence transport in a wallcoated atomic vapor cell [21], ratio of pulse splitting is rather difficult to control effectively. Besides, the tripod-EIT scheme offers a novel way for the modulation of single-photon wave packets [23], which would greatly benefit quantum information processing of the photonic qubits.By now, in the previous tripod-EIT experiments [15,18], constructive and destructive interference of the twocomponent dark-state polaritons has been observed, e.g., experimental demonstration of dual-channel...

Journeys from quantum optics to quantum technology

“…These group velocities can be controlled by varying the Rabi frequencies of the coupling laser fields. These effects have been experimentally observed [197][198][199][200][201] and can be important in quantum information processing [202].…”

Coherent and dynamic beam splitting based on light storage in cold atoms

“…Recently, controllable beam splitting in frequency or time modes has been demonstrated by using the gradient echo memory scheme 15 , with a double-tripod EIT scheme 16 , and with a tripod EIT scheme 17 . Spatial beam splitting has been demonstrated in warm atomic vapor relying on the EIT effect and natural atomic thermal motions in which atoms with light-induced ground state coherence can move freely to another spatial channel at which the ground state coherence is retrieved back to light 18 .…”

Creation of two-photon states via interactions between Rydberg atoms during light storage

“…Previously regeneration of light from an initially unpopulated coherence was implemented using an external detuning in a tripod atom-light coupling scheme [39] (see also a related work [40]). In that case the regenerated light remains classical by storing a classical light.…”