Collective Storage and Retrieval of Photons

Alexey Vyacheslavovich Gorshkov, Axel André, Michael Fleischhauer +2 more

S. D. Jenkins

In this thesis, we explore the quantum dynamics of light interactions with optically thick collections of atoms. We provide a theoretical description of several recent experiments in which some key operations necessary for the implementation of quantum communication networks are demonstrated. Collective Raman scattering from an atomic ensemble is shown to produce probabilistic entanglement between the polarization of a scattered photon and an associated collective atomic excitation. The predicted correlations agree with experimental observations. We also propose a method to use cascade transitions to produce entanglement between a photon with a frequency in the telecom range (ideal for transmission over optical fibers) and a near infrared photon (ideal for storage in an atomic ensemble), and a description of the experimental demonstration is provided. We also propose and describe the implementation of a deterministic source of single photons.\n\nIn addition, we generalize the theory of dark-state polaritons in ensembles of three level Lambda atoms to account for the nuclear spin degeneracy of alkali atoms. This generalized theory provides a description of the first demonstration of single photon storage and retrieval from atomic ensembles. Additionally, in the presence of a uniform magnetic field, we predict the occurrence of collapses and revivals of the photon retrieval efficiency as a function of storage time within the ensemble. These predictions are in very good agreement with subsequent experimental observations. We also exploit the ability of photon storage to entangle remote atomic qubits.

Lukas Heller, Jan Lowinski, Klara Theophilo +2 more

We demonstrate the storage and retrieval of an on-demand single photon generated by a collective Rydberg excitation in a low-noise Raman quantum memory located in a different cold atomic ensemble. We generate single photons on demand by exciting a cold cloud of rubidium atoms off resonantly to a Rydberg state, with a generation probability up to 15% per trial. We then show that the single photons can be stored and retrieved with a storage-and-retrieval efficiency of 21% and a low noise floor in the Raman quantum memory. This leads to a signal-to-noise ratio ranging from 11 to 26 for the retrieved single photon, depending on the input-photon-generation probability, which allows us to observe significant antibunching. We also evaluate the performance of the Raman memory as a built-in unbalanced temporal beam splitter, tunable by varying the write-in control-pulse intensity. In addition, we demonstrate that the Raman memory can be used to control the single-photon wave shape. These results are a step forward in the implementation of efficient quantum repeater links using single-photon sources.

Hans‐Joachim Lewerenz

Mehmet Fatih Yanik, Shanhui Fan