Storing polarization entangled qubits at a telecom wavelength in a cold rubidium atomic ensemble via a quantum interface
Amandine Issautier, Florian Kaiser, Jim Liljekvist, Anthony Martin, Olivier Alibart, Virginia D’Auria, Anders Kastberg, Laurent Labonté, Sébastien Tanzilli
Quantum communication aims at generating and distributing entangled pairs of photonic qubits (or flying qubits) at a telecom wavelength between distant sites, in order to implement quantum information protocols, such as quantum key distribution, quantum teleportation and quantum processing. For many quantum protocols, and especially for quantum repeaters, which make quantum communication over long distances much more efficient, storing of entangled states is necessary and represents a crucial step towards the realization of a real quantum network. A current outstanding challenge is thus to implement quantum memories for entangled qubits, carried by telecom photons, that combine high efficiency, long storage time and near-perfect fidelity between the input and output states. With this project, our goal is to merge the techniques of telecom wavelengths qubit distribution with quantum storage at shorter wavelength (typically for atomic transitions). Our idea is to map, via a quantum interface, polarization entangled qubits at a telecom wave- length onto a cold atomic ensemble, serving as a quantum memory device.
Quantum communication aims at generating and distributing entangled pairs of photonic qubits (or flying qubits) at a telecom wavelength between distant sites, in order to implement quantum information protocols, such as quantum key distribution, quantum teleportation and quantum processing. For many quantum protocols, and especially for quantum repeaters, which make quantum communication over long distances much more efficient, storing of entangled states is necessary and represents a crucial step towards the realization of a real quantum network. A current outstanding challenge is thus to implement quantum memories for entangled qubits, carried by telecom photons, that combine high efficiency, long storage time and near-perfect fidelity between the input and output states. With this project, our goal is to merge the techniques of telecom wavelengths qubit distribution with quantum storage at shorter wavelength (typically for atomic transitions). Our idea is to map, via a quantum interface, polarization entangled qubits at a telecom wave- length onto a cold atomic ensemble, serving as a quantum memory device.
Quantum communication aims at generating and distributing qubits between distant sites, in order to implement quantum information protocols, such as quantum key distribution, quantum teleportation and quantum processing. For many quantum protocols, and especially for quantum repeaters, which make quantum communication over long distances much more efficient, storage of photonic states is necessary and represents a crucial step towards the realisation of a quantum network. An outstanding challenge of quantum communication is to implement quantum memories for photonic qubits, combining long storage time with high fidelity between the input and output states, and good efficiency. Moreover, to be compatible with quantum network applications, such as quantum repeaters, these memories have to enable heralded storage and on-demand read-out. Cold atomic ensembles hold promise for satisfying both these prerequisites, and are therefore a good candidate as storage medium, offering a compromise between different benchmarks. We are setting up an experiment intended to map polarisation qubits onto an optically pumped cold atomic ensemble of rubidium serving as our quantum memory device.
Quantum communication aims at generating and distributing qubits between distant sites, in order to implement quantum information protocols, such as quantum key distribution, quantum teleportation and quantum processing. For many quantum protocols, and especially for quantum repeaters, which make quantum communication over long distances much more efficient, storage of photonic states is necessary and represents a crucial step towards the realisation of a quantum network. An outstanding challenge of quantum communication is to implement quantum memories for photonic qubits, combining long storage time with high fidelity between the input and output states, and good efficiency. Moreover, to be compatible with quantum network applications, such as quantum repeaters, these memories have to enable heralded storage and on-demand read-out. Cold atomic ensembles hold promise for satisfying both these prerequisites, and are therefore a good candidate as storage medium, offering a compromise between different benchmarks. We are setting up an experiment intended to map polarisation qubits onto an optically pumped cold atomic ensemble of rubidium serving as our quantum memory device.
Quantum communication aims at generating and distributing qubits between distant sites, in order to implement quantum information protocols, such as quantum key distribution, quantum teleportation and quantum processing. For many quantum protocols, and especially for quantum repeaters, which make quantum communication over long distances much more efficient, storage and/or emission of photonic states is necessary and represents a crucial step towards the realisation of a quantum network. An outstanding challenge of quantum communication is to implement quantum memories for photonic qubits, combining long storage time with high fidelity between the input and output states, and good efficiency. Moreover, to be compatible with quantum network applications, such as quantum repeaters, these memories have to enable heralded storage and on-demand read-out. Cold atomic ensembles hold promise for satisfying both these prerequisites, and are therefore a good candidate as storage medium, offering a compromise between different benchmarks. We are setting up an experiment intended to map polarisation qubits onto an optically pumped cold atomic ensemble of rubidium serving as our quantum memory device. In a first development, our quantum memory device will be operated in the single photon emission regime so as to implement, together with an entangled photon-pair source based on guided-wave optics, the quantum teleportation scheme.
Quantum communication aims at generating and distributing qubits between distant sites, in order to implement quantum information protocols, such as quantum key distribution, quantum teleportation and quantum processing. For many quantum protocols, and especially for quantum repeaters, which make quantum communication over long distances much more efficient, storage of photonic states is necessary and represents a crucial step towards the realisation of a quantum network. An outstanding challenge of quantum communication is to implement quantum memories for photonic qubits, combining long storage time with high fidelity between the input and output states, and good efficiency. Moreover, to be compatible with quantum network applications, such as quantum repeaters, these memories have to enable heralded storage and on-demand read-out. Cold atomic ensembles hold promise for satisfying both these prerequisites, and are therefore a good candidate as storage medium, offering a compromise between different benchmarks. We are setting up an experiment intended to map polarisation qubits onto an optically pumped cold atomic ensemble of rubidium serving as our quantum memory device.
Polarization-encoded photons at telecommunication wavelengths provide a compelling platform for practical realizations of photonic quantum information technologies due to the ease of performing single qubit manipulations, the availability of polarization-entangled photon-pair sources, and the possibility of leveraging existing fiber-optic links for distributing qubits over long distances. An optical quantum memory compatible with this platform could serve as a building block for these technologies. Here we present the first experimental demonstration of an atomic quantum memory that directly allows for reversible mapping of quantum states encoded in the polarization degree of freedom of a telecom-wavelength photon. We show that heralded polarization qubits at a telecom wavelength are stored and retrieved with near-unity fidelity by implementing the atomic frequency comb protocol in an ensemble of erbium atoms doped into an optical fiber. Despite remaining limitations in our proof-of-principle demonstration such as small storage efficiency and storage time, our broadband light-matter interface reveals the potential for use in future quantum information processing.
Quantum memory is an essential building block for quantum communication and scalable linear quantum computation. Storing two-color entangled photons with one photon being at the telecommunication (telecom) wavelength while the other photon is compatible with quantum memory has great advantages toward the realization of the fiber-based long-distance quantum communication with the aid of quantum repeaters. Here, we report an experimental realization of storing a photon entangled with a telecom photon in polarization as an atomic spin wave in a cold atomic ensemble, thus establishing the entanglement between the telecom-band photon and the atomic-ensemble memory in a polarization degree of freedom. The reconstructed density matrix and the violation of the Clauser-Horne-Shimony-Holt inequality clearly show the preservation of quantum entanglement during storage. Our result is very promising for establishing a long-distance quantum network based on cold atomic ensembles.