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arXiv:2204.03886 · AVS Quantum Science

Trapping a free-propagating single-photon into an atomic ensemble as a quantum stationary light pulse

U-Shin Kim, Yong Sup Ihn, Chung-Hyun Lee, Yoon-Ho Kim

Published Jun 1, 2022• 7 citations
arXivHTMLPDF

Abstract

Efficient photon–photon interaction is one of the key elements for realizing quantum information processing. The interaction, however, must often be mediated through an atomic medium due to the bosonic nature of photons, and the interaction time, which is critically linked to the efficiency, depends on the properties of the atom–photon interaction. While the electromagnetically induced transparency effect does offer the possibility of photonic quantum memory, it does not enhance the interaction time as it fully maps the photonic state to an atomic state. The stationary light pulse (SLP) effect, on the contrary, traps the photonic state inside an atomic medium with zero group velocity, opening up the possibility of enhanced interaction time. In this work, we report the first experimental demonstration of trapping a free-propagating single-photon into a cold atomic ensemble via the quantum SLP (QSLP) process. We conclusively show that the quantum properties of the single-photon state are preserved well during the QSLP process. Our work paves the way for new approaches for efficient photon–photon interactions, exotic photonic states, and many-body simulations in photonic systems.

DOI
10.1116/5.0093545

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Efficient photon–photon interaction is one of the key elements for realizing quantum information processing. The interaction, however, must often be mediated through an atomic medium due to the bosonic nature of photons, and the interaction time, which is critically linked to the efficiency, depends on the properties of the atom–photon interaction. While the electromagnetically induced transparency effect does offer the possibility of photonic quantum memory, it does not enhance the interaction time as it fully maps the photonic state to an atomic state. The stationary light pulse (SLP) effect, on the contrary, traps the photonic state inside an atomic medium with zero group velocity, opening up the possibility of enhanced interaction time. In this work, we report the first experimental demonstration of trapping a free-propagating single-photon into a cold atomic ensemble via the quantum SLP (QSLP) process. We conclusively show that the quantum properties of the single-photon state are preserved well during the QSLP process. Our work paves the way for new approaches for efficient photon–photon interactions, exotic photonic states, and many-body simulations in photonic systems.
The stationary light pulse (SLP) refers to a zero-group-velocity optical pulse in an atomic ensemble prepared by two counter-propagating driving fields. Despite the uniqueness of an optical pulse trapped within an atomic medium without a cavity, observations of SLP so far have been limited to trapping a single optical pulse due to the stringent SLP phase-matching condition, and this has severely hindered the development of SLP-based applications. Here, we first show theoretically that the SLP process in fact supports two phase-matching conditions and we then utilize the result to experimentally demonstrate simultaneous SLP trapping of two optical pulses for the duration from0.8 μs0.8\ \mu \mathsf{s}0.8 μsto2.0 μs2.0\ \mu \mathsf{s}2.0 μs. The characteristic dissipation time, obtained by the release efficiency measurement, is1.22 μs1.22\ \mu \mathsf{s}1.22 μs, which corresponds to an effective Q-factor of2.9×1092.9\times 10^{9}2.9×109[1]. As our SLP system reports a large effective N-atom cooperativity of8×1068\times 10^{6}8×106, our work is expected to bring forth interesting SLP-based applications, such as, efficient photon-photon interaction, spatially multi-mode coherent quantum memory, creation of exotic photonic gas states, etc.
The stationary light pulse (SLP) refers to a zero-group-velocity optical pulse in an atomic ensemble prepared by two counterpropagating driving fields. Despite the uniqueness of an optical pulse trapped within an atomic medium without a cavity, observations of SLP so far have been limited to trapping a single optical pulse due to the stringent SLP phase-matching condition, and this has severely hindered the development of SLP-based applications. In this Letter, we first show theoretically that the SLP process in fact supports two phase-matching conditions and we then utilize the result to experimentally demonstrate simultaneous SLP trapping of two optical pulses for the duration from 0.8 to 2.0 μs. The characteristic dissipation time, obtained by the release efficiency measurement from the SLP trapping state, is 1.22 μs, which corresponds to an effective Q factor of 2.9×10^{9}. Our Letter is expected to bring forth interesting SLP-based applications, such as, efficient photon-photon interaction, spatially multimode coherent quantum memory, creation of exotic photonic gas states, etc.
We experimentally demonstrate coherent trapping of an arbitrary photonic polarization state as a stationary light pulse (SLP) within a cold 87 Rb atomic ensemble. The input polarization state is separated into two orthogonal polarization components, which are mapped onto two phase-matched path modes and simultaneously trapped as SLPs in a single cold atomic ensemble. After a programmed trapping duration, the two modes are released and recombined to reconstruct the polarization state. We evaluate state preservation of the released polarization state using state tomography, yielding an average fidelity of (98.7±1.1)% and an average release efficiency of (30±4)% for a trapping duration of 1.0 µs. By analyzing the release efficiency for trapping durations from 0.5 µs to 3.0 µs, we obtain an SLP lifetime of (1.34 ± 0.08) µs. These results elucidate the coherent trapping characteristics of arbitrary photonic polarization states in SLP systems, thereby contributing to the expansion of SLP-based applications in photonic quantum information processing.
In Chapter 7 we discussed the interaction between atoms and photons. We found that the coupling between a single atom and a single photon is rather weak, unless the atom and the photon are contained within a small cavity. The only way to significantly affect a free atom with light is to use a state of light with many photons, and in particular we showed how to use classical laser fields to prepare particular atomic states. However, there is another way of enhancing the interaction in a useful way. We can use many atoms rather than a single one. In this chapter, we will show that the interaction between a single photon and an ensemble of atoms can be greatly increased through the phenomenon of collective enhancement. We will show that this gives an atomic ensemble a relatively large susceptibility, and that multilevel atoms can be used to generate large optical nonlinearities. These offer the possibility of slowing, and even stopping, a beam of light; a phenomenon that goes hand in hand with electromagnetically induced transparency. We will discuss how a quantum state of light can be stored in and retrieved from an ensemble of atoms, and how the states of different atomic ensembles can be entangled with one another. We will show that collective states of atoms can even be used as a single qubit or several qubits, and finally, we will show that atomic ensembles can be use to mediate a photon–photon interaction.
In this paper, an optical memory based on an ensemble of cold Cesium atoms interacting with light in the electromagnetically induced transparency (EIT) regime is studied in view of spatially multimode quantum storage. The interfacing protocol involves a control field, generating EIT for the very weak field that carries the quantum signal to be stored and enabling its mapping into the collective hyperfine coherence of the cold atomic ensemble. For the demonstration of multimode storage, the signal pulse at the single photon level is prepared in a mode with (OAM), while the control field is in a TEM00 mode. After the writing process, the information is kept in the memory register. In the retrieval phase, the information is read back from atoms to light and we show that these pulses at the single photon level with OAM can be stored and retrieved with a preserved spatial phase and a good efficiency.