[Paper Review] Quantum storage of 1650 modes of single photons at telecom wavelength

Shihai Wei, Bo Jing+11 more|arXiv (Cornell University)|Sep 2, 2022

Photonic and Optical Devices4 citations

TL;DR

This paper demonstrates a 1650-mode photonic quantum memory at telecom wavelength (1532 nm) using the atomic frequency comb (AFC) protocol in a 10-m-long cryogenically cooled erbium-doped silica fiber. By employing five 10 GHz-wide spectral channels, each supporting up to 330 temporal modes, the system achieves simultaneous multimode storage of heralded single photons, marking a critical step toward high-rate, fiber-compatible quantum networks.

ABSTRACT

To advance the full potential of quantum networks one should be able to distribute quantum resources over long distances at appreciable rates. As a consequence, all components in the networks need to have large multimode capacity to manipulate photonic quantum states. Towards this end, a multimode photonic quantum memory, especially one operating at telecom wavelength, remains a key challenge. Here we demonstrate a spectro-temporally multiplexed quantum memory at 1532 nm. Multimode quantum storage of telecom-band heralded single photons is realized by employing the atomic frequency comb protocol in a 10-m-long cryogenically cooled erbium doped silica fibre. The multiplexing encompasses five spectral channels - each 10 GHz wide - and in each of these up to 330 temporal modes, resulting in the simultaneous storage of 1650 modes of single photons. Our demonstrations open doors for high-rate quantum networks, which are essential for future quantum internet.

Motivation & Objective

• To enable high-capacity, long-distance quantum networks compatible with existing telecom infrastructure.
• To overcome the challenge of limited multimode capacity in photonic quantum memories at telecom wavelengths.
• To achieve simultaneous storage of a large number of single-photon modes across spectral and temporal degrees of freedom.
• To demonstrate practical, fiber-compatible quantum memory with high storage capacity and low crosstalk.
• To advance the development of a future quantum internet based on multimode quantum memory.

Proposed method

• Implementation of the atomic frequency comb (AFC) protocol in a 10-m-long cryogenically cooled erbium-doped silica fiber (EDF).
• Spectral channel division into five 10 GHz-wide channels, each separated by 5 GHz, using an optical frequency comb and frequency chirping.
• Use of a 10-m-long EDF with low erbium doping concentration to reduce non-radiative decay and enhance storage lifetime.
• Employment of impedance-matched in-fiber Bragg reflection (DBR) mirrors to form a cavity that enhances light-matter interaction and increases storage efficiency.
• Utilization of Zeeman sublevels in erbium ions as long-lived storage states, with magnetic fields applied to stabilize the persistent holes.
• Optimization of the waiting time before signal photon storage to 200 ms to suppress background noise from spontaneous emission.

Experimental results

Research questions

• RQ1 Can a multimode photonic quantum memory be realized at telecom wavelength with high storage capacity?
• RQ2 Can the atomic frequency comb (AFC) protocol in a long, cryogenically cooled EDF support simultaneous storage of 1650 temporal and spectral modes?
• RQ3 What is the crosstalk level between different spectro-temporal modes in such a system?
• RQ4 How does the use of impedance-matched in-fiber cavities improve storage efficiency and lifetime?
• RQ5 What is the optimal waiting time to minimize noise from spontaneous emission during storage?

Key findings

• The system successfully stores 1650 distinct spectro-temporal modes of heralded single photons at 1532 nm with high fidelity and low crosstalk.
• The crosstalk between different spectral channels is negligible, as confirmed by g(2)(0) measurements across all 1650 modes.
• The lifetime of the Zeeman sublevels used for spectral tailoring reaches 0.278 ± 0.035 s at 0.2 T magnetic field, enabling stable AFC formation.
• The waiting time before photon storage is optimized to 200 ms, minimizing background counts from spontaneous emission.
• The measured g(2)(0) values for all 1650 mode pairs are close to 1, indicating minimal photon bunching and high single-photon character.
• The use of impedance-matched in-fiber DBR cavities enhances light-matter interaction and supports high-efficiency storage in a compact, fiber-integrated platform.